The Sound of Building
Vrooommm! Slish… slash… slosh… Ahhh, the sound of a well-mixed lime stabilised earth plaster. What else would you want on a sunny Monday morning on our revered building site? It is the ‘slosh’ that makes it, you know, the sound of the right amount of clay mixed with (sharp!) sand, lime, chopped straw and water, whizzing around in the mixing machine. Anyway, that’s what the experts on this building site say… It remains quite difficult for a humble novice like me to determine if the mix is sloshing or slashing… But we get there, we do.
Earth Plaster Mix ratios
As mentioned before on this blog, this mix was made out of a 5:1 sand to clay ratio, with an added lime volume of about 20% of the clay, 2 volumes of chopped straw and water added to taste. We determined this ratio based on extensive testing of different ratios. The more clay, the smoother and the stronger, but the more likely cracking will occur. The more sand, the less strong, the more dusty, but the less cracking. For the outside plastering, which is the final coat to seal the strawbales before the cladding goes on, a 5:1 ratio seemed ideal. For other applications, such as the earth floor or inside plastering, we might have to use other ratios. Cracking in earth floors for example is really difficult to patch up, so – to be sure – we will probably use a mix with a higher sand to clay content for the floor.
Nail Gun time!
In between the slosh sounds, on occasional BANG! could also be heard. This time, it was not the sound that comes with people being extremely frustrated over a piece of wood that just does not want to be level. No, it was the nail gun in full operation, slamming nails into the soffit boards. These beautiful, freshly cut larch boards form the underside of the eaves and cover up the outside parts of the rafters. As experience can tell, this nail gun is a treacherous, yet very nice piece of kit. Like chainsaws, it needs to be respectfully dealt with, with an occasional, caressing brush over its fragile head.
Cladding goes on the strawbale house
And so the days of this twelfth (!) week on the build progress. Looking back, days quickly fade into weeks, and weeks even into months. Having finished the outside plastering on Monday, the battens which would support the cladding could be quickly put up. And then the cladding could go on, and that would be the outside of the building finished by the end of this week! Or, that is what we thought… Because, as we learn over and over again, reality is more difficult to deal with than we think it is (life lesson?). At least it is sometimes. And so it happened with the cladding. Because strawbale walls with outside posts and braces covered in wood fibre are not straight, but the cladding has to be straight and plumb and level and everything. So how do you go from wonky wobbly to plumb and straight? Indeed, no idea, just fiddling around with packers until it is… Luckily, after a few days, the battens were up, nicely level and plumb, ready to receive the cladding, which we started putting up on Friday. Again, the cladding was freshly cut larch. Hmm, so nice to work with, the colour, the smell,…. Since it was freshly cut, we needed to take into account how it would shrink and warp over time. When wood dries out, the grain wants to become straight, and so fresh boards which are straight now, will become warped when dry. We can take advantage of this by putting up the cladding so that it warps ‘into’ the building, which will eventually make a stronger structure.
Hindsight, ‘wobbly wonky to straight and plumb’ describes pretty well the rest of the tasks of this week. More soffit boards being installed, more dubbing out of internal strawbale walls and gables, and a continued effort of putting up plasterboards on a straight-ish ceiling.
After the plasterboards had been put up, we filled in the gaps in between the plasterboards with a light straw-clay mix, and painted the boards with a (very) wet clay slip. This was to ensure a good adhesion of the clayplaster that would come next onto the ceiling. Clay likes clay, and sticks more easily to itself (the slip) than to a very dry plasterboard.
The Friday Challenge
Among other things, the challenge of Friday was to plaster the whole ceiling of the small workshop. The mix used for this plaster was slightly different to the one we used on the outside building. This time we used a 4:1 ratio sand to clay and finely chopped straw, because this gives a smoother finish.
And indeed, plastering this whole ceiling in one day proved a challenge. Breaks were skipped, finishing the workday at 5pm became a vague memory of better times. But we succeeded, after a loooong day. Rumours go that our fellow companion Mike is still plastering, stuck in a perpetual motion of pushing plaster onto the ceiling, biting through the pain in his shoulder. But we do not know for sure. It is out of our hands, and we hope he will be taken care of appropriately…