What about mice and rats?
There is no greater risk of encouraging mice and rats into a straw bale building than there is for any other type of building. Straw is the empty stem of a baled grain crop and, unlike hay, it doesn’t contain food to attract furry creatures. Any home where food is left out in the open is a potential lure for vermin. Once your straw bale building is plastered, the walls seem no different from other plastered walls to a mouse. Mice and rats like to live in spaces between things, as they are very sociable animals. In barns, they live in the gaps between bales and in buildings they live in cavities and under floors. If you build straw walls and then clad them in timber, with an air gap between, this might attract mice: but it’s the gap they like, not particularly the straw. If you build straw walls, plaster them with clay or lime and maintain them; then there are no gaps to invite mice or rats in, and no cavities in which they can live.
How long will it last?
No one can completely answer this question, because the first straw bale building was built only about 140 years ago. In the USA there are about a dozen houses of 100 years old that are still inhabited and showing no problems. They have an increasing stock of houses built since 1980 that are also enduring with no problems. In the UK we started building in 1994, and in France there is a house built in 1921. As with any other technique of house building, if your straw bale house is constructed with a good design, with quality work and is properly maintained throughout its life, there is no reason why it should not last at least 200 years.
Isn’t it a fire risk?
No. It may seem strange, but when you stack bales up in a wall and plaster them either side, the density of the bales is such that there isn’t enough air inside the bales for them to burn. It’s like trying to burn a telephone directory – loose pages burn easily, but the whole book won’t catch fire. Straw bale walls have passed all the fire tests they have been subjected to in Europe, USA and Canada. And, regardless of whether the bales themselves are a risk, if you plaster any wall with a half inch of plaster it gives sufficient fire protection to satisfy Building Regulations. In fact, plastered straw bale walls are so much not a risk that they are being used as fire walls between semi-detached houses.
Is it really cheap to build?
It depends entirely on your approach to building. If you can put lots of time into collecting recycled materials, or do the drawings yourself and keep the design simple, or organise training workshops to build the walls and plaster them, or get your friends and family to help, then yes, it can be cheap to build. For most people, it is more sensible to think of doing the simple bits yourself (initial design, foundation, straw and plaster), and employing others to do the rest (carpentry, roofing, plumbing and electrics). A small office in the garden might cost £35,000 (although substantially less with recycled materials and volunteer labour), and a self-built two-bedroomed house could be £50,000. Council houses were built for £130,000. And a saleroom near Stansted airport cost £950/m2. Savings are greater on bigger buildings.
Can I do it myself?
Yes, parts of a straw bale building are quite easy to build. Other parts, such as roofing and carpentry, are more difficult. It depends on how much time, determination and dedication you have. It is advisable to go on some courses and to get practical experience before attempting to build your own house, and then to have someone on site who has a lot of experience to give supervision and make sure quality standards are high. But the straw building technique is simple, straightforward and accessible to almost anyone. Most self-builders take a couple of years to build their own house, working most of the time on it: it’s a slower process than having a contractor doing it for you.
What about temporary buildings?
The design of straw bale buildings is very versatile, and can be adapted for a more or less durable function. If a building is required for only a few years, then there may be no need to build elaborate foundations, or plaster it inside or even outside. Or you can buy an off-the-peg building and sell it on when you’ve finished with it. The meaning of temporary is subjective when it comes to planning, and not all planning officers will agree. You can build a moveable small building on a low-loader wheeled base. You can also build a high quality strawbale building that can be classed as temporary, because it could be taken down again easily if required, but the same building could also last for 200 years.
What else can be built with straw?
Straw has been put to many uses. Apart from houses, studios, offices and public spaces, straw is also used for schools, warehouses, retail units, holiday homes, salerooms, hotels and restaurants, barns and stables, sound studios, meditation centres, acoustic barriers for airports and motorways, food storage and farm buildings.
What if some of my bales do get wet?
It depends on where, and how badly. Generally, if a bale gets wet through the top or bottom into the centre, then it will not dry out before it starts rotting, unless you make holes in it to provide ventilation. So any bales that are rained on, or stand in water while in storage, should be discarded. This also applies to any bales already in the walls that are not covered against the rain. But if you have covered the tops of the bales, and the sides get wet from the rain, this usually presents no problem, as they will quickly dry out once the rain stops. The only time this may not be the case is if the walls are exposed to severe wind and rain at the same time for prolonged periods, as the wind may drive the rain into the bale, where it cannot dry out easily. Most moisture related problems in strawbale houses are due to accidents during construction eg not covering the tops of walls adequately. Once a house is built, it takes catastrophic failure to cause a problem eg flooding, trees falling on the house. In general, if there is a water ingress problem in a plastered strawbale wall, the best policy is to let it dry out. The lime or clay plaster will draw moisture out from the bale. In severe cases this might mean making holes through the wall to allow ventilation to access the interior of the wall, but often it only means keeping the walls well-ventilated and using a de-humidifier at night.
Is it possible to repair straw walls?
It is not only possible, it’s very easy! The hardest part is making a hole through the straw. This can be done with the claw on a hammer or crowbar, and by just pulling at the straw. It can be quite difficult to make the first hole, due to the density of the bale. However, once this is done, wedges of the bales can be pulled out quite easily. Hazel pins can be cut through if necessary, and fresh straw wedges can be packed tightly back to fill the gap. Experience has shown that if a section of wall does get wet, damp remains remarkably localised. It tends not to spread further through the straw, and so wedges or flakes of the bale can be removed and replaced.
What if I want an extra window?
Again, it’s fairly easy to cut through the walls to create a window-sized hole. Usually there is no need to support the rest of the wall as the wall plate carries most of the load of the floor above, and the straw bales act together as an integral material because of the way they are pinned. Either follow the method described above for repairing straw walls, or you can use a hay knife, even a chainsaw, although power tools like this tend to clog up very quickly. Once you’ve cut the hole, a structural box frame can be fixed into the gap, with the window inside this.
Can I use straw to add an extension to my building?
Yes, both load-bearing and framed systems work well here. You may need to think carefully about settlement, and not make the final attachments from the straw to the house wall until after the walls are compressed. Better still, use a slip joint by attaching a timber post to the existing wall and notching the bales around it. You can also easily add an extension to your straw bale house by cutting a doorway through, in the same way as described above for making a window. Families have sometimes encouraged their children to build their own add-on spaces once they’ve reached a suitable age!
Can I insulate my existing building with straw?
It’s perfectly possible to wrap your existing building with straw to give it better thermal efficiency. You will need to extend the roof over the top, and add a small foundation for the straw, plus think carefully about details around windows and doors, but you could transform your non-descript concrete bungalow into one that looks like a beautiful old Devon cottage – at least from the outside! And reduces your heating costs whilst increasing your comfort.
What if I don't want to build it myself?
There are several companies or individuals who can do this for you, or you could work together with a local building contractor. Or you can buy a small straw bale building ’off the peg’ and have it delivered!