On our current job in Mansfield, Fiona has requested seven niches be put into the strawbale walls. These look great if they’re done pretty neatly, but can look pretty rugged if you don’t pay close attention.
Fiona has two totally different looks in mind – one is the classic look for a niche in a strawbale wall, about 350mm – 400mm high, arched top, flat back and a little sill on the front, projecting about 50mm or so from the surface of the wall, while the others are square, again with a flat back, and no projecting sill – a much more modern look.
The first photograph here shows the first of the arched niches after it’s been cut out of the wall and first coated. I’ve always cut them out of the straw wall, after compression, with a 100mm angle grinder, but it can also be done with a chainsaw.
ALWAYS TAKE EXTREME CARE – it doesn’t matter how long it takes to perform this part of the job as long as you’re in one piece when it’s finished. It’s dangerously easy to hit a piece of baling twine inside the wall, causing the grinder or saw to get very out of control very quickly. If possible, cut through the twine, grab it with a pair of pliers and pull the whole length out of the wall – it won’t make a bit of difference to the wall, as it’s all compressed by the wire and gripples. Generally, the baling twine is positioned 100-130 mm from the surface of the bale, so cut your way into the bale for 100mm or so, and then poke around with your fingers or a knife until you find it. It’ll make a quite distinctive ‘pop’ when you cut it, and then it can be pulled out from around the bale. Don’t forget that each string will have a corresponding one on the bale above or below it. Depending on the position of the niches in the wall, you’ll also have to be aware of where the trench-mesh reinforcing is, as hitting the mesh with a chainsaw will ruin the chain in seconds. If the mesh is in the wall where the niche needs to be, make sure the wall surrounding the niche has a good heavy first coat of render on it, then cut through the mesh with a small angle-grinder. If the straw inside the niche does happen to catch fire, just pat it out with a rag and keep going, the render on the wall surrounding it will prevent the flames spreading up the wall. Contrary to popular belief, it’s almost impossible to burn a strawbale wall once it’s been rendered – even if it’s only first coated.
After cutting out the basic shape of the niche, it’s then coated with render in the usual way, taking care to ‘evolve’ the shape of the niche required as you go. The final shaping and finishing are done with a plasterer’s small tool and a damp sponge.
Our second photograph shows a finished niche in an east-facing wall, which looks somewhat gritty due to the flatness of the light; however, it will finish up smooth with a good coat of lime wash or lime paint.
Until next week,
Hooroo,
Mark
