Strawbaling is a very simple building technique. It has been a ‘peasant’ form of building for hundreds of years, is quite forgiving and relatively simple.
There are two major types of strawbale wall – load bearing or non-load bearing. In load bearing, a plate or plank is placed onto the top of the walls, onto which the roof is supported.
Our house is non-load bearing or ‘infill’ strawbale. The timber frame which will support the roof is built first, next the roof is fully constructed, resulting in a gazebo appearance. The strawbales are then put in, with the roof providing shelter.
We chose this technique because it takes the pressure off the strawbale walls, resulting in less cracking, and was more practical given the size and complexity of our build. The roof being in place first gave us protection in case it rained during wall construction.
- Waterproof base. Our walls are built onto the concrete pad of our house. It is important to raise them up off the concrete to stop the damp seeping into the straw. We achieved this by running two single-course lines of bricks and filling the gap between with a mix of blue metal and builders rubble.
- Stack on the straw! Start laying the strawbales just like bricks or building a Lego house. Make sure that each course is off-set from the one above and below for strength.
- To give strength and ‘hold it together’ we inserted mild steel rods through the walls at regular intervals. These were pushed in from the top effectively ‘skewering’ the bales. Bamboo stakes are also commonly used.
- Chicken wiring. In some places, such as along very long walls or with window joins, chicken wire was wrapped around the outside of the bales, and tied on with baling twine threaded through the wall. The threading is done with a gigantic ‘sewing needle’ tool – we borrowed ours from a local farmer who had made it himself.
- There will be gaps. There will also be a lot of loose straw all over the floor. Pick it up and shove it in all the holes until they’re full!
- Now is the time to shape the walls to suit your wants. We chose rounded corners (some prefer square) and were also quite keen on the walls having natural undulations in them. A garden trimmer / whipper-snipper was used to trim the walls just how we wanted them.
- We used a lime cement render, mixing a ratio of lime:sand at approximately 1:3. We used builders lime, purchased in 25kg bags from the local hardware store, and sand sourced from a local supplier. It was an enormous job and we brought in professional plasterers to help. The application technique was crude – wet the walls very lightly and then manually smoosh the plaster on with plenty of force! Three layers of plaster were added, allowing drying time between each layer, resulting in a final thickness of around 50mm. If you’re not using pigments or dyes in your plaster, make sure you use the same sand for the whole project otherwise there will be variations in colour!
- In the Roof. It’s important that the straw is completely encased in the plaster – and that includes the top of each wall. David spent many days crawling in the narrow space at the edge of the roof cavity sealing the top of each wall with plaster.
Of course, that all sounds easy, but there are a few fiddly bits!
Sometimes you need a bale that is smaller than regular, for example at a corner. Splitting bales is fairly easy as long as you have a splitting tool – basically you thread this giant 4-pronged sewing needle with new baling twine, press it through the bale at the right spot, tie the new strings in place, then cut the old. The bale will fall apart into two smaller bales. It can be tough on the wrists if you’re doing a lot though!
Above windows and doors
As bales won’t magically balance in thin air, David built timber frames for above windows and doors. These were a simple shelf that the bales could be stacked on.
Next to windows and doors
Where strawbales met openings such as windows and doors, chicken wire was used to ‘tie’ and strengthen the straw to the window / door timber framing.
It is itchy, scratchy, dusty work. Make sure you cover up, drill cotton is the best, wear PPE and be prepared to have little itchy bits of straw everywhere – in your hair, underpants, up your sleeves. Hayfever sufferers may need to take additional precautions.
Bales are heavy and awkward, and you are lifting them high to get to the tops of walls. Ensure you have a safe working platform, employ correct lifting techniques and don’t strain to lift more than you are capable of.