When talking to friends it became clear that there was a surprising amount of confusion about what a tiny house actually is.
Tiny house on a trailer
Living in Scotland, and rarely watching TV, I was only vaguely aware of the phenomenon of the USA style tiny houses which are built on trailers and can be towed around.
When people talk about tiny houses, I suspect it is this sort of house which people now think of.
I sometimes find it helpful to refer to my tiny house as a cabin. It’s easier than saying “tiny house” all the time and people know, more or less, what I am talking about. Though while cabins could be lived in full time and may be even quite large and comfortable, I think they are generally perceived as being somewhat rudimentary.
Wooden Chalet
In France, when I talked about my project to the neighbours, they would say “oh, like a chalet?”. They mean a small alpine or Scandanavian style building typically with from interlocking wooden walls. These are quite a common sight and people would often assume I was going to buy such a house in kit form.
Typical summerhouse
In the UK people are quite familiar with the idea of a summerhouse. As the name implies, these are small buildings (probably at the bottom of the garden) that would typically be enjoyed during the summer. Perhaps somewhere to read or relax when the weather is nice. Construction wise, they are likely to be made from wood and unlikely to be insulated. As they are something of a feature, they look a bit prettier than a garden shed.
In his introduction to “The tiny book of tiny houses”, Lester Walker said the book began when he wanted to illustrate “affordable build it yourself vacation homes”.
OK, so here is my take on it …
My definition is that a tiny house must be:
Tiny
A house!
By that I mean, yes, it is very small but it must also be a real house too. In other words you should be able to live in it all year round, just like any other house. So that means good insulation and glazing, some means of cooking and washing and somewhere to sleep and sit.
It could be on wheels (though mine is not) and could be made of any material. It could be cheap or expensive, self-built or built by others. It could be used for holidays or lived in full time.
My own tiny house looks a bit like a garden shed because, according to my planning application, it is! (more of this later). But it does have (or will have) the previously mentioned features of a real house.
So that’s it. Tiny House = Real House but smaller. Simple!
This was a question I had to answer before even submitting a planning application. In fact, the local planning regulations dictated that the roof should be a certain angle and it must be tiled (traditional roman canal tiles or similar). Even though the tiny house would officially be classed as a garden shed, it had to have the same visual impact as a house.
Dordogne tobacco barn
So that was the first design constraint. Furthermore I didn’t want it to look like a log cabin (or chalet, as the French call them). Instead I wanted vertical weatherboarding (aka batten on board cladding or siding). My inspiration for this was the typical tobacco drying barn that is still a common sight in the Dordogne.
So, what were the chances of finding a kit that met my requirements?
Kits
No chance, is the short answer.
From an aesthetic point of view, I couldn’t find anything that was small (less than 20m2), simple, with vertical weatherboarding and a proper tiled roof.
Budget chalet from a kit
Yes, I guess I could have got something custom made and shipped from who knows where, but at what cost? Even the most basic standard ‘chalet’ is surprisingly expensive. For example, the cheapest sold by euro-chalet.fr (pictured) costs 3990 Euros for 19m2. But for that price you only get 44mm uninsulated wooden walls and an imitation slate roof (which I can’t even use). If I just wanted to upgrade to double skinned walls, the price jumps to 7900 Euros.
It’s a similar story with other manufacturers. Often the price seems low but soon goes up with unavoidable ‘extras’. Typically they have a lightweight roof of corrugated steel or bitumen shingles. The insulation (if there is any) won’t necessarily be great and I suspect the timber is treated because it isn’t naturally very durable. It all seems a bit flimsy and not really what I’d call ‘house quality’.
The advantage of a kit should be a faster build time as all the parts are pre-cut. Personally, I’m not too sure about how to fit windows and doors, so having this worked out by somebody else would have been a bonus.
But there just didn’t seem to be an affordable kit that suited my needs.
Plans
To be honest, I didn’t spend a great deal of time considering this option.
Tiny House built from plans
A google search for tiny house plans came up with some which were ‘trailer style’ – no good to me.
After this I found some rather expensive plans ($600!) on offer from houseplans.com in the USA. The resulting tiny house looks quite good but, again, not exactly what I wanted.
Some sites had free plans but broken links when I attempted to download the PDF files.
Eventually I got fed up trawling the internet for the holy grail of a perfect tiny house plan. I was going to have to design and build my house myself.
Building from scratch
By designing my own house I could get exactly what I wanted. That meant a proper, durable tiled roof, good insulation and weatherboarding that was in keeping with the local style.
Hopefully, the money that wasn’t going to be spent on somebody else’s profit margin could be used on better quality materials. In theory I would have a better house for the same price. The materials could also be sourced locally, which would be good for the environment and the local economy.
Then there was the satisfaction of knowing that I did it all myself, from conception to execution. For someone who once wanted to be a design engineer, this held some appeal!
I had some experience of building timber stud walls in house renovations and I had read about similar techniques for building entire houses. Basically I would be building a big box with timber walls and a simple roof. The finer points of the design were still to be worked out but I had the basic idea and that was good enough to get started …
According to the World Green Building Council (WGBC), there are a number of features which can make a building ‘green’, including:
Efficient use of water, energy and other resources
Use of renewable energy, such as solar energy
Pollution and waste reduction measures and the enabling of re-use and recycling
Good indoor environmental air quality
Use of materials that are non-toxic, ethical and sustainable
Consideration of the environment in design, construction and operation
Consideration of the quality of life of occupants in design, construction and operation
A design that enables adaptation to a changing environment
Admittedly, I designed and built my hemp tiny house without ever having heard of the World Green Building Council and its list of features.
I had, however, read several books on ecological building design. My starting point was The Whole House book by Cindy Harris and Pat Borer (now out of print, but worth picking up a used copy). I was also a keen reader of the French eco building magazine La Maison Ecologique. It wasn’t all theory though. At a local eco-centre I took practical courses on building with lime and earth. Later I worked with a French eco-builder for about six months on renovation and new build housing projects.
So, how does my hemp tiny house stack up? Is it really green?
1. Efficient use of water, energy and other resources
Water
In order to help save water I chose to use a compost toilet rather than a normal flushing toilet. This alone would reduce water consumption by about 20%.
Rainwater harvesting for washing and possibly even drinking was considered but rejected as being too expensive and complicated. Besides, I needed a good supply of water in order to build the tiny house (for the hempcrete insulation and concrete foundations). So I got the water authority to put a mains water connection on the site.
I would probably store rainwater for watering the garden, if I lived in the tiny house full time.
Energy
Using hempcrete to insulate the floor, walls and ceiling was my way of finding a good compromise between insulation and thermal inertia. Hempcrete may not be the absolute best insulator per cm of wall thickness but it does have some thermal mass which helps smooth out the daily fluctuations in temperature. It’s also good for getting into the nooks and crannies of the structure and so reducing draughts. Combined with the wooden external cladding I thought the tiny house would be quite energy efficient, from a heating point of view.
Other resources
The tiny house 2 ring gas hob.
I decided on a two ring kitchen hob for cooking which uses a small, refillable gas bottle. As a fossil fuel, this isn’t very green. However, I also plan to use scavenged wood to cook and heat water outdoors as much as possible. It may also be possible to cook on a wood burning stove in winter months.
Petrol (gasoline) is another fossil fuel resource that I use, specifically for the small generator. This was mainly to provide electricity for the power tools involved in building the house. I wouldn’t expect to use it very often in future, perhaps to charge batteries, run tools or maybe a washing machine. Weekly consumption would not be very high.
All in all, I think the hemp tiny house will use resources efficiently, at least in comparison to a conventional home.
2. Use of renewable energy
Tiny house solar panel being tested prior to installation
Electrical energy
My tiny house was conceived from the outset to have a minimal electrical system running from a solar panel. The photo opposite shows the actual panel I used being tested prior to installation on the roof. I also decided to use an inverter and conventional 240v sockets. A small fridge would be the largest power consumer. Otherwise I only need enough spare power for some lights and to charge a phone or laptop.
Heating and hot water from wood
Another source of renewable energy that I plan to make use of is wood. Besides the few trees in my garden, there are many woodland walks nearby and it would be easy to scavenge a bundle of fallen sticks in the course of a daily walk. Should this prove impractical I could buy local firewood or purchase a small piece of woodland for the purpose of harvesting wood for fuel.
With this wood, I plan to heat both the tiny house living space and hot water for washing.
For space heating I’d like a wood burning fire of some type. At the moment I’m inclined towards a highly efficient rocket stove/mass heater, although it may not be practical to build one small enough to work properly. Failing that, I’ll plump for a normal wood burning stove, perhaps from a recycled gas bottle.
For the moment though I am using a small paraffin heater, shown below.
Tiny house paraffin heater
Again, this isn’t ideal from an ecological viewpoint (fossil fuel) but it is at least quite cheap (50 Euros), simple and efficient. Heat output is up to 2.2kw and, as it uses a wick, doesn’t need electricity to run. It can also be used to heat a pot of food or boil a kettle of water. I bought mine from a French company who deal in marine products (people apparently use them in boats!). Paraffin heaters are fairly common in France and most supermarkets sell 20 litre bottles during the colder months.
In order to generate hot water for washing, I plan to build an experimental wood fired water heater. This would be installed outside, but nearby, the tiny house. Cold mains pressure water would be piped to the heater and hot water leaving the heater would be piped back to the house.
Sketch of wood fired water heater
The heater consists of a steel hot water reservoir that is heated by burning wood in a firebox below it. Inside the hot water reservoir is a copper coil that acts as a heat exchanger. Cold water flows through the coil picking up heat on its way back to the house’s hot water system. As the system is outside it can use a cheap single skin flue and provide hot water in the summer without causing overheating inside the house. Hopefully a small firing of 20 or 30 minutes using scavenged wood will provide enough hot water for one or two showers.
To conclude – most of the energy used by the tiny house will come from renewable sources. Solar energy for electricity and wood for heating and hot water. A comparatively small amount of energy from non-renewable sources (bottled gas and petrol) will be used for cooking and occasionally running a generator.
3. Pollution and waster reduction, re-use and recycling
Wood, hemp, lime and terracotta tiles are the main materials used in the construction of the tiny house. I think these are relatively good in terms of the pollution caused by their manufacture and use. The lime and terracotta requires firing in a kiln which needs a fair amount of energy (possibly from non-renewable sources). The hemp and timber would have relatively low energy needs for processing. All materials had to be delivered to site, unfortunately using fossil fuels and causing some pollution. I did, however, try to buy locally where possible.
The tiny house used very little cement (which requires more energy than lime to produce). Had I built my walls from concrete blocks, I’m sure the ’embodied energy’ and likely pollution would have been higher.
Other ways I tried to reduce building material pollution was by using un-treated timber (most of which was not kiln dried either) and by avoiding synthetic, petrochemical based paints and varnishes.
Some compromises were made though. For reasons of time and conveniences, I bought some kitchen cabinets from a DIY store. These were made from chipboard and have some kind of ‘plasticky’ coating. Likewise PVC waste pipe was used. I also bought a 2nd hand sofa bed which has a PVC covering. In defense of that purchase, the damage had been done 30 years ago when the item was made. At least by buying an old sofa I wasn’t causing any additional pollution.
Compared to the ideal situation of using wood, earth and stone sourced from the actual building site (impossible in my case), my tiny house probably caused a fair amount of pollution. However, I’m sure that this was less than that caused by more conventional materials such as concrete and plastics.
As for re-use and recycling, I think the hemp tiny house scores fairly well too. Were the house to be demolished, the structural timbers, roof tiles and wooden floor could be re-used. I’m not quite so sure what would be done with the hempcrete. It’s much easier to break up than normal concrete, so could potentially be crushed and mixed with more lime to make new hempcrete. Failing that, as it is non-toxic, it could be buried or left to degrade without any risk to the environment.
4. Good indoor environmental air quality
The air quality inside the tiny house should be excellent for the following reasons.
A lime and hemp plaster was used to finish the inside surfaces of the walls and this in turn was coated with a white limewash (lime diluted in water). So there were no modern, synthetic paints with their VOCs (volatile organic compounds) that could have added to indoor pollution.
The ceiling consists of limewashed timber planks (again no paints) whereas the chestnut floor was treated with linseed oil rather than polyurethane varnish.
Meanwhile, the vintage PVC sofa, while not ideal, probably stopped off-gassing several decades ago!
Besides the lack of pollutants, the indoor air quality is helped by the ability of lime and hemp to regulate interior humidity. It does this by absorbing water vapour when relative humidity is high (perhaps after cooking or taking a shower) and releasing it when relative humidity drops.
Lastly, the hempcrete walls have a good thermal mass and so can store heat. This means that the house can be frequently ventilated by opening windows and doors while maintaining comfort (due to the heat being slowly released by the walls).
5. Use of non toxic, ethical and sustainable materials
It should be clear enough by now that the tiny house uses mainly non-toxic materials. But are they ethical and sustainable?
I admit that I never really considered this in detail when designing the tiny house, I just assumed that they were.
By all accounts, industrial hemp is not an environmentally damaging plant to grow. Ethically, I’d suggest it was a responsible use of land to make a very useful product.
Wood is a potentially ethical and sustainable material. The structural timber I used was douglas fir and it was supplied by a local sawmill. I assumed it would sourced from sustainably managed European forests, but I didn’t ask. Likewise, the chestnut floor came from another local sawmill and I assume the timber was locally sourced. In both cases I should perhaps have made sure where the timber came from.
For the roof, I didn’t have much choice in the materials used as the local planning rules dictated I use terracotta tiles. The tiles I chose were an inexpensive Spanish brand stocked by the local builders. Perhaps, in the interests of ethics and sustainability, I should have bought some from the nearest French manufacturer. Regardless of that, they are certainly non-toxic and long lasting. I don’t know how sustainable terracotta tiles are. I don’t think they can be recycled but, at worst, they will eventually become harmless dust!
6. Consideration of the environment in design, construction and operation
Again, I think I’ve shown that the tiny house was designed to be kind on the environment regarding it’s construction methods, at least in comparison to modern, conventional buildings.
It’s also designed to blend in visually with the local environment. Firstly, it is very small and certainly not a huge eyesore. Secondly, the vertical exterior weatherboarding, left to age naturally, is similar to that used on the old tobacco drying barns that are still to be found in the local area.
A black mark against the project is the fact that I need to travel about 1000 miles from Scotland to get to the tiny house in France. Obviously this has an environmental impact. In future this could be lessened by using public transport (train or bus) or even travelling by bicycle if I had the time and fitness! Should I decide to move to France full time, I would make a trip back to Scotland at least once per year, so the environmental impact remains. From another point of view, this is no different from anyone taking a yearly foreign holiday and doesn’t really relate to how green the tiny house is. It could even be argued that the environmental impact of any foreign trips I make is offset by the swapping a normal house for an eco-friendly tiny house.
7. Consideration of the quality of life of occupants in design, construction and operation
As the designer and constructor of the tiny house, I have obviously given careful consideration to the quality of life that I will have as the occupant! This is very different to a commercial property developer who is unlikely to live in one of his/her buildings.
I’m satisfied that the quality of life in my tiny house will be very high, according to my own criteria.
That means that the tiny house will be comfortable, with a good thermal performance. It will also be healthy (good indoor air quality) and economic to heat.
By virtue of it’s low build and maintenance costs, it will give me a sense of security. That is to say, I will be able to live in my own place and not be dependent on a landlord.
8. A design that enables adaptation to a changing environment
To be honest, I’m not sure exactly how much the local environment of my tiny house will change in my lifetime.
Should it be necessary, the tiny house can be easily modified thanks to it’s construction method. It would not be difficult to add an extra room, porch, or whatever (just screw the new bits to the existing wooden frame).
More generally, the tiny house is well placed to adapt to changes in the global environment. It will hardly be affected by rises in the costs of electricity or fossil fuels, for example.
It could also be argued that the ‘low tech’, low cost and simple lifestyle afforded by the tiny house will be increasingly sought after by those who are weary of an increasingly busy, precarious or unsatisfying ‘normal’ lifestyle.
In this article I will describe how I found and bought some land in the Dordogne area of France for my hemp tiny house project and the costs involved.
Finding the land
This was the easy part! Actually, it still took a bit of doing. My plan was to identify a dozen or so possible building plots and then arrange to see them over the course of a few days while I was on holiday in France with the kids.
I used a French website called leboncoin to find land for sale. This is a free ads type website, like Gumtree (UK) or Craigslist (USA) and they have all sorts of ads, not just land. Anyway, should you want to check it out yourself, look for land (terrain) in the real estate category (ventes immobilières).
The search criteria for my ideal bit of land were as follows:
Budget
My budget was roughly €10,000, which is about as low as you can get. I hoped to find something that didn’t appeal to most other buyers, perhaps because it was too small, wasn’t flat enough or needed clearing of trees or bushes.
With my tiny house, I didn’t need or want lots of ground. I also thought that a small timber framed house, raised up on piers, would be quite easy to build, even on a slope.
No estate agents
I specifically excluded land that was being sold through estate agents (agents immobiliers) in order to avoid their fees, which could have been up to 10%.
Instead I looked for land that was being sold by individuals (particuliers).
The transaction and all the legal stuff would be handled by a notaire, who does charge a fee, but that was unavoidable.
Cerificat d’Urbanisme (CU)
I restricted my search to land that already had a CU. This meant that, in principle, the land could be built upon. Each community has a PLU (plan local d’urbanisme) within which the local area is divided into development, agricultural and protected zones. Obviously I didn’t want to buy land in, say, a protected zone and find that it was impossible to construct anything later.
It should be noted that a CU is not the same as planning permission (permis de construire). You can apply for planning permission if you have a CU first, but it won’t necessarily be granted. The project still has to comply with, for example, local regulations regarding the house’s appearance.
Location
I chose to look for land near the town of Périgueux, which I knew fairly well. For those who haven’t visited, it’s a charming place with all the best French features: great market, cafés; restaurants, nice architecture and a friendly, relaxed feel. When I lived in France I would often visit the town as I lived about an hour to the north in the neighbouring département of the Haute-Vienne.
Bearing all of the above in mind, I found a dozen or so building plots to visit and contacted the owners before leaving Scotland.
As it turned out, time constraints meant I didn’t see all of them. Of those I did see, most were OK, some were poor but – as luck would have it – the last site site was perfect. It was small (540m2), had some trees, was 40km from Périgueux and Bergerac, was reasonably flat and was away from the main road in a little hamlet. Previously, it had been used by the proprietor’s family for growing grapes (as some of the neighbours still did). Best of all it ‘felt’ right – it’s just a pleasant place to be. The old couple selling it were very nice and the price was right too. At €7,000, it was a handy €3,000 under budget.
The buying process
This process consists of two steps, the Compromis de Vente and the Acte de Vente.
Compromis de Vente
The Compromis de Vente is a contract of sale agreement which binds the seller and buyer. In a nutshell, I promised to buy the land and gave a 10% deposit. The deposit would be forfeited if I didn’t go through with the deal. However, I did insert a clause which meant that, should planning permission be refused, I wouldn’t have to buy the land and I wouldn’t lose my deposit. This is called a “clause suspensive” and is often used to protect the buyer in case they can’t get a mortgage.
So my next task was to get planning permission before I could sign the Acte de Vente. In all honesty, this was quite a challenge – especially as I was in Scotland at the time. Most people would use the services of an architect but this is only compulsory for houses over 150m2. It’s perfectly legal to submit your own application for houses under this size.
While not being especially complicated, there is quite a large ‘dossier’ that needs to be prepared. A form has to be filled in which is supported with drawings and other documents. The worst of these was getting approval for the proposed drainage system from the water authority, which in itself needed a survey by one of their recommended experts.
Anyway, it all got done eventually and my planning permission was granted. Actually, I asked for permission to build two houses. A ‘proper’ wooden house (43m2) and a ‘large garden shed’ (17m2). The ‘garden shed’ was actually the hemp tiny house!
My reasoning was that the shed/tiny house would be a good test run before building the larger house. It would also then provide somewhere to live while the larger house is being built. I don’t feel too sneaky about living in the ‘shed’. I couldn’t find anywhere saying it is forbidden. Furthermore, it gets taxed per square metre just the same as the house does. Whether I will actually get around to building the main house is another matter …
Acte de Vente
The sellers were no doubt very glad to finally conclude the sale after the months it took me to get planning permission.
I transferred the remainder of the money to the notaire prior to the acte being signed. Then we all met again in the notaire’s office and the formalities were concluded, followed by a visit to the seller’s house for a celebratory aperitif!
Regarding costs, the notaire’s fees came to €1,459.
I also had to pay for the services of a “géomètre-expert” who is a kind of surveyor who sorts out the property boundaries. Practically speaking, the final result is that he drives plastic markers into the ground defining the four corners of the land. The cost was shared with the seller and my part came to €561.
The soil survey that was needed to get planning permission cost €580.
So the final cost to buy the land and get planning permission was €9600. Just under my €10,000 budget. So far, so good!
In this post I’ll describe how I managed to build my tiny house from scratch in 6 weeks. Admittedly, the 6-week period didn’t include the internal fitting out, so you can call me a cheat if you like! Even so, starting from a bare piece of land and having the shell of a house, roof and all, in 6-weeks (mostly on my own) is pretty good going.
If you have ever tackled a major DIY project, you might have found that it took longer and cost more than you thought it would. There are lots of reasons why this can happen, such as:
underestimating the time needed for certain tasks
inefficient organisation of work
running out of materials
having to buy unforeseen items.
These are the sorts of problems that can be avoided by effective project management. If you have a large building project, I would recommend learning some project management techniques (buy a good book) and getting some software to help create and manage the project plan. I have used Microsoft Project (many years ago!) and it was excellent, though it isn’t free. More recently I have used the free software Ganttproject which is quite basic but works ok. No doubt there are other software tools available.
My tiny house project wasn’t very big. I didn’t have other contractors to manage (just a carpenter friend who would give me a hand). From experience, I knew the correct sequence of work. As I was doing the work myself, my ‘plan’ was more of a to-do list. However, I still had to be sure all the tasks on the list could be completed in six weeks.
Here are some pointers on how I managed to achieve that.
Materials
I had to make sure I had enough materials and that they were on site at the right time. There’s no way I could stop work while waiting for a delivery. The project would be sunk.
The biggest item that had to be planned in advance was the timber. I used a local sawmill that had been recommended to me. I didn’t quibble over the price (which I knew was reasonable anyway) and sent them a deposit when they asked for one. Having established a good relationship, I got good service in return. To be sure I had enough timber, I added roughly 10% to the all of the quantities. That way I didn’t have to worry about wastage or the occasional cutting mistake.
It was a similar story for the driveway materials and digger hire. These were ordered several weeks before work started and were ready when I needed them.
A top tip, for any building project, is to try to establish a good relationship with the local builders’ merchant. They can supply a range of materials, will likely have good stocks and can deliver for a reasonable price. In my case, I found a local merchant who was able to supply the lime and hemp (by special order) as well as the sand, cement, gravel, roof tiles, breathable membrane and OSB. This was supplied in one big delivery and saved a lot of time and hassle.
I almost came unstuck with the windows. I had assumed (wrongly) that the standard, off the shelf items that I wanted would be in stock. That wasn’t the case and I had to order them. Luckily, they arrived fairly quickly and I was able to have them fitted with time to spare.
It’s also worth making sure you gather together the tools you need in advance as well as the bits of hardware like brackets and screws. I bought my joist hangers, joist hanger twist nails, heavy duty angle brackets and various screws in the UK and brought them with me. This was to avoid running to the shops mid-build only to find they didn’t sell what I needed or that they didn’t have enough in stock.
Simplicity of design
With my ‘garden shed’ design, I wouldn’t be winning any architectural awards. But it was simple and that was important to keep the build time down.
I knew that the lime and hemp insulation would be time consuming in itself and so I couldn’t afford to complicate things further.
Avoiding construction mistakes
I have some building experience but I’m not confident about everything. To reduce the chances of making costly and time consuming mistakes, I employed a friend of mine who is a first rate carpenter and general builder to help out for one day per week. He was able to direct the construction of the frame and the roof (something I was unsure of) and the installation of the windows and doors. He also gave advice on other parts of the build.
I am very glad I got outside expertise to ‘plug the gaps’ in my own knowledge. It was crucial to getting the project finished on time and well worth the extra expense.
Time Planning
Most of the tasks were sequential i.e. foundations – floor – walls – roof etc. So it was quite easy to add up the estimated time for each task to check the total estimated time for the build. This came to less than six weeks but not by much. From memory, I think I had 4 or 5 days ‘slack’.
With more complicated projects (and with more people involved) it is likely that some tasks could be done ‘in parallel’ i.e. one person is working on task A, another on task B and both tasks need to be completed before task C can begin. In this case the shortest time for project completion (the “critical path”) is not so obvious but can be calculated with the help of the project planning software.
Choice of construction methods
This sounds obvious, but I did need to think in advance about how I was going to complete each phase of the build. Not necessarily every tiny detail, but I had to have a good idea of how things would be made. Clearly, this was necessary in order to know which materials to buy and in what quantities. It was also desirable so that I wouldn’t waste too much time on site trying to figure out how to build the next bit.
Be focused
For the build I lived on site in a tent. I could get up, have some breakfast (while it was still nice and cool!), get a quick wash and start work. Being away from home, without the usual distractions, I was able to be highly focused on the job in hand. This might not be possible for everyone but in my case it was a positive factor in getting the house finished on time.
Be lucky
The six week build period coincided with a French heatwave. Working in 35-40 degrees centigrade was a real challenge but I was very lucky that it only rained 3 or 4 times during the whole period. Had it rained for longer it would have certainly been much more difficult to complete the build. Not allowing for bad weather was an oversight on my part, but thankfully I got away with it!
According to The Hempcrete Book by William Stanwix and Alex Sparrow, hempcrete is a “hemp-lime composite construction material … comprising the chopped stalk of the industrial hemp plant mixed with a lime-based binder”.
The authors go on to say that “hempcrete provides a natural, healthy, sustainable, local, low-embodied-energy building material that can truly claim to be better than zero carbon”.
Hempcrete ingredients
In practical terms, the chopped hemp stalk is something like a cross between straw and wood chips. It is a dry, fibrous material and is typically packed into plastic bales. In the image to the left, some hemp has been put into buckets ready for mixing.
The “lime based binder” comes in a bag, just like a bag of cement and indeed the lime powder looks much like cement.
In my case, I used a lime binder that was specially formulated for hempcrete. The trade name is Batichanvre and the half opened bag can be seen at the top right of the photo.
The hemp I used is sold under the name Isocanna and is again meant specifically for use in hempcrete.
When mixed together with water, the lime and hemp make a kind of lightweight concrete. By varying the composition of the mix a variety of densities can be achieved, depending on the intended purpose. For instance, roof insulation requires a less dense mix than that used in wall construction.
The wet hempcrete can be used in a variety of ways within the building process. When used in walls, for example, it is often hand placed into shuttering that has been fixed over a timber frame. When it has set, the shuttering is removed, leaving the rigid hempcrete in place, as shown below.
Cast hempcrete
Once dry, the hempcrete is surprisingly tough, rigid and fire resistant.
The advantages and disadvantages of hempcrete will be discussed in detail elsewhere on this site but I chose it mainly because of its thermal performance, simplicity, versatility and environmental credentials.
In my view, the advantages of hempcrete far outweigh the disadvantages. If your priority is to build a house as quickly, cheaply and easily as possible, then hempcrete will may not be your material of choice. If you value things like comfort, a healthy home and environmental sustainability, then hempcrete is worthy of serious consideration.
It’s also worth pointing out that a prospective house builder and owner will naturally consider the pros and cons of hempcrete with regard to their own building project. There is however a ‘bigger picture’ which concerns the impact of hempcrete on the wider environment and indeed at a global level.
In compiling this list, I consulted the following books as well as drawing on my personal experience:
The Hempcrete Book, by William Stanwix and Alex Sparrow,
The Whole House Book, by Pat Borer and Cindy Harris, and
The Green Self-Build Book, by Jon Broome.
Advantages of hempcrete as a building material
Feel good factor
I have found that hempcrete buildings naturally exude a ‘feel good factor’ which is difficult to put into words and really needs to be experienced. I would say that they promote feelings of well being, comfort, health and even calmness. The first time I felt this was at French Ecocentre where I visited a small octagonal building made from cast hempcrete. There was nothing inside the building, just bare walls, but I had an instant feeling of “wow, this is amazing”. The reaction of the other visitors suggested they felt something similar.
(I am 100% sure that, if the building been made from concrete blocks, my reaction would have been completely different.)
Years later, my step-daughter’s reaction, upon entering my hemp tiny house after the walls had been built, was the same. Surprise, a big smile and words (in French) to the effect of “oh, this is very pleasant!”
Whether this ‘hempcrete effect’ is due to the hempcrete’s thermal, acoustic or vapour regulating effects, or because it’s a free from synthetic chemicals, or something else – I don’t know. Perhaps one could feel similarly in a house made from straw bales, cob, raw earth bricks or timber.
Thermal performance
Hempcrete was described to me (by a French Eco Builder) as a good compromise between thermal insulation and thermal mass. By varying the amount of lime, relative to the hemp, the insulation value can be adjusted. The greater the proportion of lime, the denser the mix becomes and the poorer it becomes as an insulator. Unlike lightweight insulation, the thermal mass of hempcrete helps smooth out daily temperature fluctuations.
In theory, hempcrete does not insulate as well as some other materials of an equivalent thickness. For example, I found a UK hempcrete block supplier who stated that their 15cm blocks had a U-value (thermal transmittance) of 0.43 w/m2k. By way of comparison I read that a 14cm exterior timber stud wall with mineral wool insulation has a U-value of just 0.29 w/m2k.
In practice however, hempcrete tends to perform better than it should. This is partly due to hempcrete’s combination of thermal mass and insulation and partly due to the effect of water vapour as it moves into, through and out of the hempcrete.
As long ago as 2001, as part of a Suffolk Housing Society development, 2 hempcrete houses were built alongside 2 conventional brick houses and the constructions were monitored and compared. They found that the hempcrete houses maintained an inside air temperature 1-2 deg C higher than the brick built houses.
My own experience of living in the hempcrete tiny house last summer was also positive. After days of hot weather (30-35deg C) the house did get warm inside (but never to the point of being uncomfortable). I remember one evening it was 29 deg C inside the house and in the morning it had descended all the way to … 25 deg C! (the outside temperature would probably have been about 15 deg C). The thermal mass of the hempcrete acted a bit like a storage heater – absorbing the heat during the day and releasing it slowly during the night.
Acoustic performance
The previously mentioned Suffolk Housing study found that hempcrete wasn’t quite as good as a cavity block wall at sound attenuation (I.e. at blocking sound) . Hempcrete was, however, a very good sound absorber. The helped create a comfortable acoustic environment inside the house.
In the Hempcrete Book the acoustic quality of hempcrete is described as “unusual and distinct from that of conventional building materials” and depends on hempcrete’s porosity. It is suggested that the acoustic performance can be varied by the amount and type of binder (lime or cement) in the mix and how tightly the hempcrete is compacted.
It seems to me that hempcrete buildings do have good acoustics but this hasn’t been properly quantified or explained yet.
Vapour permeability
Thanks to it’s porosity, hemp is permeable to water vapour. It is also hygroscopic I.e. it can store and release moisture in the surrounding atmosphere. This is due to the microscopic structure of the cell walls.
The lime binder used in hempcrete is also permeable and hygroscopic (to varying degrees, depending on the lime used).
These characteristics are beneficial to the indoor air quality by helping to maintain a steady humidity and inhibiting the formation of condensation and mould on the surface of walls.
Fire resistance
Hempcrete and concrete rocket stove
According to The Hempcrete Book, the French manufacturer Isochanvre has produced test results that indicate hempcrete is a “non-flammable material”.
I can confirm that this is true. As an experiment, I cast hempcrete around some hollow concrete blocks to make a basic wood stove. Despite being in contact with burning wood, the hempcrete didn’t catch fire. Instead it just became progressively more charred and eventually crumbled away.
If you still need to be convinced, there are several videos on youtube of fire tests being conducted on hempcrete, such as this one:
Mechanical strength
Considered as an insulation material, hempcrete is tough and rigid. Compared to regular concrete, hempcrete is significantly less strong (about 1/20 the compressive strength).
However, if a low density hempcrete mix is cast around a load bearing timber frame, the hempcrete itself doesn’t need to have a great compressive strength. However, when fully set, the hempcrete does have a structural role in that it provides racking strength. I.e. it helps the building resist lateral movements. This has the advantage that the number of diagonal braces and horizontal noggins can be reduced or even eliminated completely.
I wish I had known this when I built the tiny house. My carpenter, who helped me frame the building, did a great job. This included diagonal bracing to make the structure nice and rigid. For good measure, I added horizontal noggins right around the building. However, these braces were a real pain when it came to casting the hempcrete around the frame. When I saw how rigid the fully hardened hempcrete was I realised that the braces were unnecessary. If I were to do it again I would suggest some kind of temporary bracing that could be removed in stages as the hempcrete was cast.
Tiny house frame showing diagonal braces and horizontal noggins
Resistance to moisture damage
I already mentioned that hempcrete is vapour permeable and can also store and release moisture. This is significant, as water does not get ‘trapped’ in a building’s walls (as it could do in, for example, a timber framed house with a faulty vapour barrier and glass fibre insulation). So, with no trapped water, the timber frame will not rot and the hempcrete can go on absorbing and releasing water vapour indefinitely.
As regards exposure to rain on exterior surfaces, hempcrete is normally protected by a lime render or timber cladding. However, in The Hempcrete Book the authors describe how hempcrete test panels were left outside, unprotected, for several years without deterioration. My own experience backs this up. At a French Ecocentre, while doing a training course, I saw some hempcrete that had been applied externally as an experiment. A few years later, it was still in good condition.
Non-toxic
Hempcrete produces no toxic emissions during the use of the building and does not pollute the indoor environment.
Furthermore, as it regulates humidity and reduces condensation, hempcrete promotes a healthy indoor air quality and restricts the growth of potentially harmful moulds.
Finally, the thermal mass of hempcrete (heat energy stored in the walls) means that building can be well ventilated without cooling down to any great degree. This again contributes to a good indoor air quality.
Environmental and societal advantages of hempcrete
Sustainability
The use of hempcrete, rather than concrete, is preferable in terms of environmental sustainability. To quote Jon Broome from the Green Self Build Book:
”An extremely low amount of energy is required to produce the hemp material, and the emissions of CO2 from the manufacture and curing of lime are very much less than Portland cement, which is now one of the principle sources of greenhouse gases in the earth’s atmosphere.”
The authors of The Hempcrete Book go further and point out that hempcrete is a natural material that is actually “Carbon Negative”. This means using hempcrete in construction will lock up more CO2 in the building than is emitted during the hempcrete’s production, transportation and disposal.
Contribution to rural economy
Greater use of hempcrete in the construction industry would require more hemp to be grown. Although I am not an expert on agriculture or rural economics, from what I have read and watched, this looks like a positive development. The video below goes into more detail on wider benefits of planting hemp on a larger scale for various uses.
Better health of individuals and benefits to society
There is no doubt in my mind that a house made with hempcrete, using natural finishes, is healthier and more pleasant than a conventional new build using highly processed, synthetic materials.
It stands to reason that living in a hempcrete house would have a beneficial effect on physical and mental health. If hempcrete were more widely used in construction, it would mean less pressure on health services and a positive effect on people’s wellbeing.
If this sounds too much like a hippy dream, consider the negative effect of poor housing. It’s well known that damp and mould in houses can be very bad for the respiratory systems of their occupants. Now imagine all of these people lived in hempcrete buildings with no mould and excellent air quality – I’m sure their health and happiness would be much improved!
Disadvantages of Hempcrete
Cost?
Does a hempcrete building cost more than a conventional building?
Referring back to the Suffolk Housing Society test build, they estimated that the additional cost of their hempcrete buildings was 10% more than the equivalent brick built houses. This was attributed to the increased labour, cost of the materials and the learning process of the contractor. Even so, 10% premium doesn’t seem like much to pay when you consider the thermal performance and comfort obtained.
In The Hempcrete Book, the authors suggest that the construction cost of a hempcrete building should be “broadly similar” to that of a conventional construction. They also make the point about comparing like with like. I.e. the hempcrete building must be compared with a conventional building with high-spec insulation. They also say that there are non-monetary benefits of hempcrete that may be important to the owners e.g. a healthy indoor environment and a low carbon emission construction.
When designing my own timber framed tiny house, I considered other environmentally friendly insulation materials such as wood fibre batts (which I had used before). They are good (but not particularly cheap) and they are not ‘monolithic’ in the same way that hempcrete is. In other words they have to be used as part of a wall system with extra layers (plasterboard, vapour barrier), which adds to the cost and complexity. Hence the reason why I chose hempcrete – it was simpler and no more costly.
To conclude, it’s by no means certain that a hempcrete build will be more expensive than the equivalent conventional construction, especially when you include the long term benefits of living there. As with any big project, you would need to seek quotes from various contractors and be sure that they are comparable.
Availability
Hemp shiv and lime binders are not common building materials. You could probably drive into any builder’s merchants and be able to buy foam, glass fibre or mineral wool insulation off the shelf. They almost certainly wont have any hemp in their warehouse.
However, even here in the UK, a quick google search turned up several suppliers of hemp shiv suitable for use in hempcrete. In France, I was able to order both the hemp and lime quite easily from my local builders merchant. So, in Europe at least, the materials are available but you will need to plan ahead and order them from specialists.
Unfamiliarity
As a ‘novel‘ construction technique, it’s safe to say that there are relatively few contractors who have the skills and knowledge required to build with hempcrete (that’s not to say that they could not acquire them for a particular project).
I guess that, for a hempcrete building, the options are:
Find a hempcrete specialist
Persuade a ‘normal’ building company to do the job (perhaps via a trusted architect)
Build it yourself (or at least the hempcrete part).
Drying time
Cast hempcrete walls must be allowed to dry sufficiently before a finish, such as lime plaster can be applied. This takes at least 6-8 weeks, possibly longer if the weather is cold and wet.
Obviously this factor will have to be incorporated into the building schedule.
Clearly, using hempcrete is much less convenient in this respect than using lightweight insulation and plasterboard (drywall).
Safety
The main drawback of hempcrete with regard to safety is the alkaline and irritant nature of the hemp binder (lime). Care should be taken to avoid inhaling the dust and getting it onto the skin and into the eyes. The mixed hempcrete is also an irritant and gloves should be worn when working with it. So, as common sense would suggest, make sure to use the correct protective equipment (goggles, gloves, masks) and have eye wash or clean water to hand.
The YouTube video below shows hempcrete being mixed in a small drum mixer, similar to the one I used.
I’ll assume that, as you read this, the video is still on YouTube and I’ll also assume that you have watched it.
The question for me then is “is it worth writing the rest of this article?’
Well, yes, probably … because I will give my own experience of mixing and using hempcrete to build an actual tiny house
Mixing Hempcrete
The process
As demonstrated, the mixing process consists of combining the water and binder to make a slurry, to which is added the dry hemp shiv.
I would suggest using the lime binder manufacturer’s instructions as a starting point. I think that every sack of lime or cement that I have ever used has had the mixing information printed on the sack. Failing that, there should be some information on the manufacturer’s website. In the case of St Astier, they provide lots of useful information on how to use their product for different applications.
Depending on your mixing equipment you’ll probably have to convert the mixing quantities provided by the manufacturer into something that makes sense for your situation. For example, St Astier recommends using 1 sack of binder with 100 litres of hemp and 30 litres of water for a hempcrete wall insulation mix. If you have a normal, small, drum type concrete mixer then you probably won’t be able to mix this amount of material in one batch. Instead you might try 1/2 sack of binder to 50 litres of hemp and so on, until you get a batch size that suits the mixer.
You will then want to convert these quantities into ‘buckets’ for convenience of measuring. I.e. your mix may work out as 2 buckets of water + 1 bucket of binder + 3 buckets of hemp (note: this isn’t a real recipe, I’m just illustrating the point!).
To recap: add the lime binder to the water and mix until you have a consistent slurry. St Astier recommend a mixing time of 3-5 minutes. The hemp is then added and the whole lot mixed together until the hemp shiv is uniformly coated with the slurry.
It’s simple enough, but there are a few things too watch out for. If you mix for too long, part of the hempcrete batch can form little balls. It’s best to stop the mixer as soon as you notice this happening. Another potential problem is lime forming a clump on wall of the mixer drum after it has been added to the water. If this happens, the slurry effectively becomes less rich in lime and so does the resulting hempcrete. To combat this it’s best to keep an eye on the drum as it spins around mixing the slurry. If you see a clump of lime on the back of the drum, stop the mixer and scrape the lime off with a trowel or a shovel. Start the mixer and let it run for long enough to incorporate the dislodged lime into the slurry.
I should point out that this is an abbreviated explanation of how to correctly mix hempcrete. Glancing through The Hempcrete Book, I realise that there is much more to the subject than I have written here. I wish I had read the book before beginning my tiny house! So if you are reading this blog post, and are seriously thinking about building with hempcrete, I would say that The Hempcrete Book is indispensable.
The equipment
1. Plasterer’s mixer/whisk..
For small quantities you could get away with using a plasterer’smixer like the one shown below.
Whisk type power mixer
I have used this method to mix up some hempcrete ‘plaster’ to insulate a stone wall in a loft conversion. It was quite handy to be able to mix the material right next to the job rather than go up and down stairs to a cement mixer.
Large rigid plastic mixing bucket
For a bucket I used a large polypropylene type from an agricultural co-operative (I think it was intended to be used for animal feed). Similar buckets are available online.
I would strongly recommend this type of rigid bucket as opposed the the flexible ‘gorilla’ type buckets that are used for mixing plaster. I have found them to be much more durable.
While using this method for a relatively thin coat of hempcrete plaster (5cm) is OK, you really need a bigger mixing system if you want to make enough hempcrete to be able to construct walls and floors.
2. Drum or bell type cement mixer
I used a ‘DIY’ type electrically powered concrete mixer to build the tiny house. It has a capacity of 160 litres and cost 270 Euros.
My 160L electric cement mixer
I was lucky that, in France, every DIY store seems to have similar types of reasonably priced mixers. In the UK they are less readily available and a bit more expensive. For instance, this 160L model from Machine Mart costs £359 (about €416).
160L cement mixer
Larger, industrial quality, drum mixers have much greater mixing capacities but also cost a great deal more. E.g. with a much greater mixing volume (280L), the model below costs more than £2600.
Industrial drum cement mixer
Of course, you could hire a larger machine rather than buy one. This might be worth it if you were confident of completing all the hempcrete work in a relatively short space of time. Other options are to buy a machine (new or second hand) and recoup most of the money by selling it at the end of the job.
If you are on a tight budget, but have a team of people to help with your build, I would suggest buying 2 small electric mixers. By running both mixers at the same time, you get a decent output. I would think that 4 people would be ideal: 2 to operate the mixers and 2 to use the hempcrete.
Pan Mixer
800L Pan Mixer
This is the type of mixer that is best suited to making the large volumes of hempcrete necessary for a ‘normal’ sized house.
As I was building a tiny house (on a tiny budget) on my own, it was too big and expensive for my needs. Having never used one, I can’t say I know much about them.
The picture to the left shows the type of 800L hydraulically powered pan mixer mentioned in The Hempcrete Book. It currently costs £320 per week to hire it and presumably you also have to hire the telehandler (and driver?) needed to make it function
The same company who hire out the above mixer (Kilworth Machinery) recently sold a used stand alone electrically powered pan mixer (shown below) for £7850. Not exactly a budget option!
Pan mixer with electric drive
I also found brand new hydraulically driven Pan Mixers for a relatively affordable £2,350 (Agitrend UK). See below.
Agritrend Pan Mixer
These machines are obviously specialised pieces of kit that are beyond my level of experience. Clearly though, they are the largest, fastest but also most expensive option.
Safety considerations
Given the alkali and highly irritant nature of lime, some safety precautions should be followed.
Firstly, avoid inhaling the dust by wearing a mask when handling the dry lime. This is especially necessary when tipping the lime into the mixer. It’s at this point that a puff of powdered lime tends to be released upwards (into your face!).
Secondly, safety goggles or glasses should be worn as it’s quite common for small amounts of hempcrete to splash out of the mixer as it turns. You don’t want this to get into your eye. If it does, then wash the eye out with eye wash or clean water and seek medical assistance if necessary.
Thirdly, wear thick chemical resistant gloves to protect your skin from wet hempcrete. I found that flock lined gloves were the most comfortable. Another thing I recommend is having a cup of olive oil nearby to use as a cheap and effective moisturiser/barrier. Long sleeved tops and trousers are advisable too. I found that, when wearing shorts, the little ‘chips’ of dry hemp tended to get into the tops of my shoes and get stuck in my socks. This soon became incredibly scratchy and annoying. You have been warned!
Using Hempcrete
Casting around timber frame
In this case, hempcrete is formed (cast) around a load bearing timber frame using shuttering.
For my tiny house I chose to have the exterior of the frame exposed to allow the weatherboarding to be easily fixed in place. The exterior shuttering was therefore screwed directly to the timber studs.
On the inside face of the wall, I wanted the hempcrete to completely cover the timber studs (giving a continuous surface for the finish coat of lime-hemp plaster). In order to do this, I spaced the shuttering back by about 5 cm. This was easily achieved driving long wood screws part way into the studs before attaching the shuttering. I left 5cm sticking out, thereby spacing the shuttering 5cm from the studs. When the shuttering was removed, so were the long woodscrews (they were reused for the next shuttering ‘lift’). The sketch below illustrates this system.
Spacing hempcrete shuttering from timber studs
The photo below shows one of my walls during this process, with the outer shuttering removed and the inner shuttering still in place. Note: you can also see the pieces of scrap timber that were fixed to the sides of the studs to provide a mechanical key for the cast hempcrete. With these in place, it’s impossible for the set hempcrete to move relative to the studs.
Cast hempcrete
You can choose to have the frame exposed, or not, on either or both sides, depending on how you will finish the wall (cladding, plaster, render, etc). Obviously, if the frame was completely covered with hempcrete, that would give the best results in terms of insulation and timber protection.
After some experiments, I settled on 12mm thick OSB (Oriented Strand Board) for the shuttering material, cut to a height of about 60cm. OSB is fairly strong and cheap and the tongue and grooved boards can be fitted together end to end for long runs of shuttering.
I tended to leave the shuttering on overnight and the hempcrete was always solid enough when it was removed the following day.
When it came to placing the hempcrete in the shuttering I’m afraid that I did compact it quite firmly using tamping sticks. I probably made it fairly wet too. It was only later that I learned that the hempcrete should be fairly dry and only pressed down by hand.
Consequently, I have reduced the insulation value of my tiny house walls but have gained a little in thermal mass. That’s perhaps not such a problem in warm and sunny France. Another point in my favour is that the timber weatherboarding is bound to add a little to the overall insulation of the walls.
Roof and floor insulation
Insulating the roof and floor or the tiny house was more straightforward than the walls. The hempcrete mix was less dense (50% less lime) and the shuttering was less complicated.
You can read how I insulated the roof here and how I insulated the floor here.
Hempcrete render (lime and hemp plaster)
My plan was to cover up the rough inside face of the cast hempcrete with a relatively smooth lime and hemp plaster. I had some experience of doing this from my eco-building days many years ago. From memory, we used the Tradical binder, to which we added some weakly hydraulic binder (possibly NHL2) in order to improve the creaminess and stickiness of the mix. Using this method it was possible to get a reasonably smooth (if undulating) wall that was a kind of oatmeal colour.
Fast forward to my tiny house. The house had been built in the summer and I came back in October to plaster the walls. I had about a week to complete the task.
Regarding the lime, I had lots of Batichanvre left so I decided to use that. The manufacturer’s website advised on the correct mixture to use and stated that it should be done in two coats, 2 or 3 cm per coat, with 20-90 minutes between coats.
I thought about adding some NHL2 or CL90 lime to improve the plaster’s workability but I didn’t want to take the risk. Had I had more time, I could have experimented a little.
Anyway, I applied the plaster as directed. It was hard work as the cement-like mix didn’t flow very well and I had to use a lot of muscle to get it on the wall! The grey colour wasn’t very attractive but I knew I would be coating it with white lime wash later, so it didn’t matter.
I didn’t try very hard to make the walls perfectly flat. Having worked as a professional plasterer in ‘conventional’ building, I took some pleasure in making my own walls a bit wibbly-wobbly 😉
Unfortunately, I had to lock up the tiny house and head back to Scotland after a week. This meant the wet plaster would not be very well ventilated. I hoped that the released water vapour would be able to leave the building to some extent via the ‘breathable’ floor and roof, but it was not as good as leaving the windows open for a few weeks.
When I came back the next summer, the plaster was dry but the cabin had obviously been very damp inside. Some clothing had become mouldy, for example. The pitfalls of building abroad and having to leave in a hurry!
I was surprised to see that there were no cracks in the plaster (I had expected some in the corners of the walls or at the edges). Strangely though, numerous cracks did develop over the next few weeks. I don’t know if this was due to some more drying as the building was aired and the temperature inside increased. It may also be due to the movement of the building as it was being occupied and work was carried out inside. Perhaps if I had added some ‘softer’ lime to the mix and let it dry properly, the cracking would have been reduced.
Annoying as it was, I knew that the cracks were only superficial and the the timber frame meant the house was still structurally sound.
We’re I to plaster with lime and hemp again I would (1) use a finer grade of hemp (2) use a less hydraulic lime (3) put on a thinner coat and (4) make sure it can dry properly.
Sprayed Insulation
I know that hempcrete can be sprayed on but I have no experience or knowledge of the process. It’s not a technique that I was ever going to consider for a tiny house in rural France. However, if you were building a larger house and had access to a contractor who specialised in this method, then I guess it would be worth investigating. Although it wouldn’t be cheap, it would be quick and these time savings could be important to you.
Precast Hempcrete
Hempcrete is available as precast blocks, which might be convenient in some situations. I did not look into the possibility of using these for my tiny house. However, I have permission to build a larger house on my piece of land and I will certainly consider using them for that build (if and when it ever happens!). When I have dome some more research on these products I’ll make them the subject of a separate blogpost.
First a word about my tool budget. Actually, I didn’t have a tool budget as such. I did have an overall build budget of about £15,000 (not including the land, which was already paid for). All the tools would have to come out of the £15k. The more I spent on tools, the less I had for materials …
So my philosophy was to buy tools of an appropriate quality for the job in hand but also to get good deals wherever possible.
Given the tight timescale for construction, I didn’t have time to go chasing around trying to buy second-hand stuff. Likewise, I couldn’t afford project delays due to old equipment breaking down.
I was able to take some things with me but space was limited. Travelling in a Ford Mondeo hatchback, even with a roofbox, most of the room was taken up with people, luggage and camping gear. The remaining tools were going to have to be purchased when I got to France.
So here is a list of the essential tools and equipment that I bought or borrowed in order to build the tiny house.
Nail Gun
Building a timber framed house, it was obvious that a gas powered nail gun was going to be invaluable for saving time and making the job easier.
I had used a Paslode nail gun for roofing before and it was OK but had a few niggles. I had heard that the quality was better now but I chose to go with a different brand anyway. My parents had owned Hitachi electrical products and they lasted for years so I reckoned their nail guns might be worth a punt..
In the end I purchased a Hikoki NR90GC2/J8 First Fix Nailer (Hikoki is the new name for Hitachi). This can fire up to 90mm nails. Shopping around, I got the best deal from powertoolworld.co.uk. The total price was £274.99, including delivery. The gun comes in a hard case with charger., two batteries, safety glasses and a bottle of machine oil.
Hikoki NR90GC2 Nail Gun
At the time of writing, the price has gone up to £295 and this seems to be the same in various UK outlets. It’s also £295 on Amazon and on Toolstop.
But this is much cheaper than buying in France. A quick search showed the best price for the same model was €425 (about £370) from the online retailer Racetools.fr (who I had never heard of).
Anyway, I am happy with my choice. The nailer worked perfectly for the length of the build, and was still in great condition at the end. I used it with 90mm and 65mm galvanized nails, which came with gas cartridges included.
All of these guns are quite heavy and take some getting used to, until your arm muscles get bigger!
Sliding Mitre Saw
Clearly, I was going to be cutting lots of timber and needed a decent saw. I didn’t have room in the car to take one from the UK, so I ended up buying one in France from the large DIY and building products store Leroy Merlin.
I pushed the boat out and bought a Metabo KGS254M, which was 1800w and came with a spare blade. The 10″ blade was a good size and Metabo are a trusted brand, so I thought it would do the job.
Metabo KGS254M mitre saw
The cost was €350, which wasn’t cheap (for me at least) and I later found that it would have cost much less in the UK. In fact online sellers such as FFX and Powertoolmate are offering the saw at less than £200, which I think is a bargain.
I can’t complain about the saw’s performance. Virtually all the timber for the house was cut with it and it coped absolutely fine. I had never used this type of saw before, so it was a good learning experience for me. As a bonus, the inclining saw head feature came in handy when I had to join some weatherboarding lengthwise on the gable ends.
Mitre Saw Stand
Evolution Power Tools mitre saw stand
My Metabo mitre saw and stand combination.
I didn’t want to be scrabbling around on the ground when cutting timber, so I invested in a mitre saw stand (for the sake of my back!).
Again it came from Leroy Merlin and was made by Evolution Power Tools. The cost was €90 (about £78). They are available from Screwfix and Amazon in the UK for a similar price.
It isn’t the cheapest stand (or the most expensive) but it is very sturdy and easy to use. Once you have used one, you wouldn’t want to be without it. The telescopic arms are good for longer pieces of timber and the end stops are dead handy for repeated cuts without having to measure every time.
Portable Generator
As the tiny house would be off grid (except for the water supply) I was going to have to run all my power tools off a generator.
It would have to be quite powerful to cope with the electrical loads on it (power tools can pull a high load on start up, apparently). I thought about hiring one but, at over €40 per day for a 2.5kw machine, it would have been far too expensive, even if I had managed to negotiate a discount for a 5 week hire period.
So I looked around for a reasonably priced but powerful generator to take with me to France.
I opted for a Bohmer-AG 3800K 3000w. At only £300 and with 4.5 stars from 250 reviews it seemed like a good bet. It was powerful enough and also had wheels to cart it around the building site.
Bohmer AG 3kw Generator
To be fair, the Bohmer did the job (just about!). It got the house built and saved me a lot of money on hire costs. However, there were a few problems with it. Firstly, the fuel cap seal wasn’t very good. So it was better not to fill the tank completely to the brim or it could leak a little when moving it around. The second problem was that the fuel pipe popped off the carburetor after a few weeks use. The pipe clip wasn’t great but the problem was easily solved with a new bit of (better fitting) rubber hose from the local DIY shop.
Unfortunately the Bohmer stopped working right at the end of the build. Luckily, the house was wind and waterproof and I was at the internal plastering stage, so it didn’t matter too much, but it was still disappointing. The problem was that the generator would still start but when under load it would falter and cut out rather than revving up to supply the required output. So I think there was a problem in the control system rather than the engine itself. Nevertheless, it became unusable after 5 weeks work. Not great.
Had I been in the UK I could have sent it back for a repair or refund but as I was in France, it would have been a bigger hassle. Perhaps it would still have been financially worth doing, but I didn’t have the time to spare and needed another generator quick.
SDMO 3kw generator with Honda engine
This time I did buy second hand but it was actually a machine that had never been used. The owner had bought it in case of a power cut but realised after a few years that he had never needed it. It was made by Robin, which is part of Subaru, and cost €250. It was obviously a better quality unit, it started and ran very well, with enough power and a simple throttle rather than a complicated control system. Sadly, it seems that this model is discontinued now. The nearest I can find to it is a similar open framed machine by SDMO which has a Honda engine www.screwfix.com/p/sdmo-hx3000-3000w-generator-115-230v/84152.
At nearly £550 for the SDMO/Honda generator, it’s a fair old chunk of cash. But that seems to be the price you have to pay if you want something durable. If you did build an off grid tiny house then a good generator would be good for topping up solar electric batteries (if the weather is very cloudy) or to run, say, a washing machine.
In conclusion, I would advise going for a Japanese engined generator (or at least a well known brand). A new machine with a guarantee would be ideal, if you have the money. But buying a good condition used Japanese machine might be a better idea than a brand new, but potentially troublesome, budget brand.
Cordless Drill
I actually completed the entire build with a cheap cordless drill that I got from ALDI! It is18v, has two Li-Ion batteries and works well enough. As the timber house frame was nailed together, the main use for the cordless drill was to fix and unfix the hempcrete shuttering.
18V ALDI Cordless Drill
Having left the ALDI drill in France, I looked around for a replacement when I got home to Scotland (I had a few jobs to do). This time I went for a DeWalt drill to see if they were really that much better.
DeWalt 18v Cordless Drill
The model I bought was the DCD776S2T-GB 18v, £99.99 from Screwfix. This still a budget item but you can tell that it’s a bit of a step up from the ALDI drill. It’s faster, has higher torque, is lighter and has a better case. The batteries didn’t seem to last quite as long, but with two of them and a charger it doesn’t really matter.
I’m sure all of the ‘premium’ brands such as Makita, Bosch and Hitachi make excellent cordless drills. As it’s something that gets a lot of use, you could probably justify getting something high end. My experience has been, however, that even for £100 or less you can get something perfectly adequate.
Cordless Drill Accessories
Makita cordless drill accessory set
If you have a drill you will need (at the very least) a screwdriver bit holder, preferably magnetic, as well as some drill bits (for pilot holes and holes for cables etc) and screwdriver bits (mainly size 2 posidriv for normal woodscrews and philips head for plasterboard screws). Buying all this stuff separately soon adds up and the bits and pieces will be rattling around inside your toolbox.
I bought this Makita accessory set for £25 from Screwfix. It was cheaper than buying stuff separately and it also kept everything organised. Well worth the money.
Electric Chainsaw
Cheap electric chainsaw
In order to build the tiny house I had to remove a lot of branches from an adjacent apple tree and cut down one or two other smaller dead trees. I have owned a Stihl petrol chainsaw in the past and it was fine, but I didn’t want to spend hundreds of euros again for something that I would use very little.
As I already had a generator, I reasoned that an electric chainsaw might do the job. I took a chance on this €50 cheapo from Leroy Merlin and it worked great.
Apart from being much lighter than a petrol model there was no fiddling around with 2-stroke oil mixing, it was quiet, simple and also surprisingly powerful. Just the job!
Similar cheap chainsaw
Oddly enough, a similar spec model on Amazon UK is more expensive, at just over £70.
Cement Mixer
I needed a cement mixer for mixing up the hempcrete and a small quantity of concrete for the foundations. Again, it would have been very expensive to hire one for the duration of the build, so I bought this 160 litre mixer. It came from Leroy Merlin (I got loads of things there while I had the hire van) and it cost €270. You can get similar models at similar prices in any of the big DIY chains in France as they are a very popular item (more so than in the UK, I suspect).
The cement mixer I used for hempcrete
It’s electric, quite low power consumption, and worked well throughout the build. By using a long extension lead, I sited the generator a good distance from the mixer so that the noise was reduced.
160 litres is the biggest I could get at this price. I could have bought a petrol powered mixer with twice the capacity but at a cost of €1650. As I was working on my own, there was a limit to the amount of hempcrete I could use anyway.
If I were to build another hempcrete house I would ideally need at least three helpers and a second mixer. With two people per mixer, progress would be much faster and a second mixer wouldn’t add greatly to the overall cost. Of course, if funds allowed, a single large petrol mixer could be used instead.
Jigsaw
A jigsaw is one of things you wont be using constantly but you will probably need it for something. In my case I needed it for cutting the tops of the weatherboarding planks to fit around the rafter ends. I also used it for cutting holes in the ends of the gutters.
WORX 750w Jigsaw
As an ‘occasional use’ tool, I went for a 750w jigsaw from the budget brand WORX. This cost €89.99 from Leroy Merlin. You can get them from Amazon in the UK for less than £60.
For the price, I’m happy with the performance. It did what I wanted and is light and easy to use with a quick change blade system. I will also use it when I fit out the interior of the tiny house.
With hindsight, it would have been ‘nice’ to have something a bit better, such as a Makita, but I couldn’t justify spending twice as much for a machine with a similar specification.
Circular saw
Erbauer ECS2000 Circular Saw
I already owned this circular saw, so that was one less thing to come out of the house budget.
The model is an Erbauer ECS2000 from Screwfix (2000W, 235mm blade) and it cost £120.
It was used for cutting all the floor joists and ripping down the odd piece of timber as required.
I consider this to be an ideal size. It’s not too large so as to be unmanageable or place too great a strain on the generator. It does though have a good cutting depth (85mm) and plenty of power.
Supplied with a tough canvas toolbag, cutting fence and good cord length, it’s an excellent, good value piece of kit.
*UPDATE* Alas, it seems that the ECS2000 is no longer available. Alternative saws with the same blade size and cutting depth are available from Makita and Bosch for about £230. Quite a jump in price although I also own a smaller Makita circular saw and it is an excellent machine.
SDS Drill
This is another Erbauer item that I already owned, the ERH750 SDS Plus drill from Screwfix.
Erbauer ERH750 SDS+ Drill
These type of drills are really good for drilling into concrete, stone and brick as the hammer action has more ‘hitting power’ than a normal drill, even at low rotational speeds. When building the tiny house I didn’t have to drill into concrete but I did have to drill lots of holes in the wall studs for the electrical conduit to pass through. The Erbauer drill had plenty of torque to drill the large holes using a spade type drill bit fitted to a chuck adapter. You could just about use a cordless but I didn’t want to risk damaging it. A corded drill like this was much better suited to the task.
As for price and quality, I have no complaints. At £80, it’s pretty good value and it’s performed exactly as it should. If you’d rather have a ‘big name’ brand, I noticed that the equivalent Makita drill costs £120.
Angle Grinder
MacAllister750w Angle Grinder
Like a jigsaw, you probably won’t use an angle grinder every day but it is handy for some jobs. In my case I knew I would need one for cutting up the steel reinforcing bars for the foundations and possibly some roof tiles.
So for a whopping £25 I bought the MacAlister MSAG750, again from Screwfix (I have a branch close to my house!).
The guard was a bit fiddly but otherwise the grinder did the job with no problems. I didn’t need to cut any roof tiles with it but it was great for cutting the 10mm steel bar and for trimming the tops of my concrete pier foundation blocks.
Laser Level
While not being absolutely necessary, my laser level was very useful for building the foundations of the tiny house. I used it to mark where to cut the tops off the concrete piers, leaving them all exactly the same height. The level I used was the Stanley Fat Max cross line laser kit. I originally bought this for a tiling job but have also used it to install plasterboard ceiling rail hangers and to help level floor joists.
Stanley cross line laser kit
At £110 the kit isn’t cheap although it is easy to use, accurate and reliable. One thing to note is that the line isn’t visible outside in bright, sunny conditions (it’s fine indoors though). So when I used it for the foundations, I waited until dusk, marked the levels and cut them the next day.
Hand Tools
These are the hand tools that I used to build the tiny house, in no particular order.
Hammer
Tape Measure
Spirit levels, small and large
Aluminium straight edge
Carpenter’s pencils
Tri square
Set of chisels
Mastic gun
Foam gun
String line
Plumb bob and line
Hand saw
Bucket trowel
General purpose trowel
Plasterer’s hawk
Plasterer’s finishing trowel
Rigid plastic plasterer’s float
Set of screwdrivers
Wire strippers
Tin snips
Wheelbarrow
Spade and shovel
Pick
Rake
Adjustable spanners
Stanley knife and spare blades
The bulky items like the wheelbarrow and spade I bought locally. Most of the smaller items I brought with me from Scotland to France. I find that, in the UK, Screwfix and Toolstation are convenient places to buy handtools, screws, nails and consumables. Prices and stock levels are good and there are branches in larger towns and cities.
Before starting work on the tiny house, I made sure I had most of the above ‘ready to go’. Otherwise a lot of build time would have been wasted making repeated trips back and forth to DIY shops.
Access equipment
I was lucky in being able to borrow or make all of the access equipment needed to build the tiny house.
Bandstands
Builders trestles
Also known as builders trestles, I was able to borrow four of these from Rob (the carpenter who helped me with the build). Used in conjunction with some stout timber planks they were enough for most access up until we started insulating the roof.
If you were to buy them in the UK, they are about £20 each for the larger size.
Stepladder
6 tread aluminium stepladder
Again (thanks to Rob loaning me one) I didn’t have to buy a stepladder. They are an essential item on any building site but you don’t need anything special.
For years I got by with a basic aluminium stepladder but have also used a professional quality item made from glassfibre. Either is fine and Screwfix have a good range. The 6 tread model pictured is suitable for trade use and costs under £50.
Normal ladder
I was on good terms with the old couple who sold me the land and they very kindly loaned me an aluminium ladder that I used to access the roof and the high points on the gable end when installing the weatherboarding.
Another option would be to buy a ‘two-in-one’ ladder that can also be used as a step ladder.
Homemade ‘hop ups’
I made two ‘hop ups’, of different heights, from left over timber and pieces of OSB. The smaller hop up can be used to step up onto the larger one. They are also handy as somewhere to place trowels and buckets of plaster.
Large hop up
The photos give an idea of what they are like. I was careful to brace them at the corners so that they were nice and rigid. Apart from costing nothing, they are quite light and you can make them to exactly the height you need (to be able to reach the ceiling, for instance). I didn’t have to worry about keeping them clean as they are basically just scrap timber.
The very first step was to build the concrete pad and pier foundations, which I describe in this post.
On the right is a photo of one of the six piers just after it had been filled with concrete.
It was important that this concrete was still soft as I would be driving some steel into the wet concrete to ‘pin’ the wooden frame to the foundations.
Floor beams
These are the large beams which sit on top of the concrete piers and support the floor joists. Like all the structural timber of the tiny house, the beams were made from Douglas Fir. Their sections were 70 x 200mm and the lengths were 4.8m (sides) and 3.6m (ends). The 4.8m lengths were supported in the middle by a concrete pier.
As for calculations, I think the floor beam size was simply suggested by Rob, the project’s ace carpenter, who knew from experience it would be sufficient.
Before putting the beams in place, I attached the joist hangers. It was easier to nail them on at this stage. I must say that the hangers were very easy to use. Just position them at the right depth, nail them on, then bend over the excess ‘tabs’ at the top. Remember to use the special twist nails that are made for them. Neither the hangers nor the nails are particularly expensive. I got mine from Screwfix in the UK and brought them with me for the build. These are the sort of items that you don’t want to be running around trying to find locally at the last minute.
Joist hangers attached to floor beams
Fixing the floor beam to the foundations
After nailing on the hangers, the floor beams were put on top of the concrete piers and joined using heavy duty, galvanized corner brackets.
A piece of steel rebar was driven into the wet concrete through a second angle bracket in order to ‘pin’ the floor beams to the concrete piers.
I was assured by Rob that this was good enough. The weight of the house means there is no need to bolt the floor beam down. We just need to prevent to beam from moving laterally relative to the concrete piers.
I didn’t use any damp proof membrane between the beam and the piers as I reckoned that the weatherboarding would prevent rainwater from getting to this area.
The photo below shows the installed floor beams ready to accept the joists.
Concrete piers with floor beams in place
Floor Joists and insulation
The floor joist section was 45 x 200mm and they were spaced at 60cm. You can find online calculators such as this one to help choose joist sizes and spacings according of the span and load of your project.
Installing the joists was simple, I just slotted them into the hangers and secured them with some screws.
Next I nailed some battens along the sides of the joists. I then loose fitted some wooden boards between the joists. These simply rested upon the battens and were necessary to retain the hempcrete insulation.
My Metabo mitre saw and stand combination.
This looks like a lot of work but it was actually done in an afternoon. Using the chop saw with the end stop meant that the boards could be cut to the exact length very quickly.
One mistake I made was to fit the boards together quite tightly.
I should have left an expansion gap of a few mm between the boards. After all, the boards were only acting as a kind of permanent shuttering.
What I later found was that mositure from the hempcrete caused the boards to expand and some of them buckled in a sort of concertina fashion. This wasn’t a major problem as the hempcrete remained in place, but it was a bit annoying all the same.
Anyway, the photo below shows the floor ready to receive the hempcrete.
Tiny house floor ready for hempcrete insulation
The hempcrete was simply wheelbarrowed up a ramp, tipped into the spaces between the joists and raked out. It was compacted slightly so as to leave an air gap between the top of the hempcrete and the chestnut flooring that would be laid on the joists.
I used a ‘lightweight’ hempcrete mix of 10 litres of lime, 50 litres of hemp and roughly 10 litres of water. In terms of buckets, this represents a ratio of 1:5:1 respectively.
This mix, which is relatively weak in lime, could be used as the hempcrete didn’t need to have any mechanical strength. All the floor loads were taken by the joists and beams. The lime did add a little bit of thermal mass though.
The photo below shows the hempcrete infill almost complete.
Wooden floor with hempcrete infiill.
OSB platform
I used tongue and grooved OSB sheets to cover the floor and provide a working platform for the rest of the build. From memory, the OSB was 22mm thick. I butted the sheets quite tightly together and screwed them in place. The photo below shows the floor at this stage.
Tiny house floor, ready for framing
Fitting the OSB was simple enough but I did have a problem later in that it expanded and caused a slight bump in the floor surface. This was rectified by cutting out the raised area and fitting a patch of new OSB in its place.
With hindsight I should also have glued the boards to the joists and ran some glue into the tongue and grooved joints. I would also have fitted them together less tightly. This might have stopped the buckling issue. Ideally though, I would have been able to wait until the hempcrete insulation had fully dried before fitting the OSB. Time constraints meant that I couldn’t.
Chestnut floorcovering
It was a full year later before the OSB floor ‘platform’ was covered by the final chestnut floor. By this time the tiny house had been built and the interior walls had been plastered and limewashed.
I chose the least expensive grade of solid chestnut from a local sawmill. This had a few more knots than the dearer stuff but still looked nice and went together just as easily. The boards were just over 20mm thick, came in bundles of various lengths and were tongue and grooved.
Fixing the chestnut floor board through its tongue.
Upon Rob’s advice the boards were screwed through the tongue into the joists in order to get a firm fixing that would minimise squeaks.
After a few tests, I found some woodscrews that were the right diameter and length to do the job. This system meant drilling a pilot hole and countersinking each screw, which was obviously slower than simply nailing the boards down. However, with 2 cordless drills, work progressed quickly enough.
Overall, laying the floor was quite straightforward. I left an expansion gap at the edges and used a scrap piece of board and a hammer to tap each board home before fixing. The boards that were cut at the end of one row were used to start the next row. Being accurately machined and super smooth, the boards didn’t need any sanding.
Laying the chestnut floor boards
In order to protect the floor I chose an eco friendly oil that was sold by the board manufacturer. This gave a clear finish and went on very nicely but I later found that it didn’t seem to offer a great deal of protection. This was disappointing as I had previously used similar oils with good results. Furthermore, the oil was quite expensive.
The floor oil and application brush
A few weeks later, I re-coated the floor but this time I used linseed oil. This is a natural product too but is much cheaper and is easily available in DIY shops and even some supermarkets in France. I highly recommend it. It’s important to add some drying agent to the oil, otherwise it could be sticky for a long time. I coated the floor with linseed oil in the morning and then went out for the day. Although the weather was very warm, the oil was still very slightly tacky when I got back at night. I just about got away with it! Ideally, I would have left it for 24 hours (if I had somewhere else to stay that night).
Although I had given the floor a good wash and let it dry before oiling, it was still somewhat stained from dirt being brought in from outside. That, plus the linseed oil, had the effect of darkening the floor slightly.
I was still happy with the final result, pictured below, and it’s completely in keeping with the rustic theme of the build.
The tiny house floor after treatment with linseed oil
