The one thing with a back-to-front build like this, building the walls last, is that it’s a long time before the building starts to feel like a real building. It’s been worth the wait though. A month ago, we finally started to build the cob walls.
The end of October in Portugal is usually quite mild and we started work in T-shirts and bare feet. By the end, a month later, it was welly boots and several layers of clothing including multiple pairs of gloves. At least building at this time of year means the cob will dry slowly with the minimum of cracking, and hopefully should be dry enough by January’s frosts to avoid damage.
A note on the clay … In most cob construction, the clay subsoil from the site is used. We do have clay subsoil here. Clay is a breakdown product of schist so the soil contains a lot of it. In fact, the subsoil in one part of the quinta contains clay in perfect proportion to build with, needing only the addition of organic material for tensile strength. So why not use the clay from the quinta in the interests of reducing external inputs and embodied energy? The answer to that is that we’re on a mountainside. Bedrock is never far from the surface and a lot of it is the surface. Subsoil depth varies, but is rarely much more than ½ to 1 metre. If we were to excavate enough subsoil to build in cob with, we would need to remove all the subsoil from an area several times the footprint of each building. I didn’t feel this was acceptable. So I bought in a truckload of pure clay from a local brickworks 20km/12 miles away and the sharp sand to mix with it from the local builders’ merchants.
Here is a succession of snapshots from the cob construction. It’s mostly self-explanatory or covered in previous posts.
Cord on the cob!
This was a piece of chestnut hollowed out by a woodpecker and given to a friend for a drum. But it split slightly as it dried so was no use for a drum and he gave it to me. I cut it in two and sandwiched a double-glazed unit (free from the scrapyard) between to make this window.
Previous posts in this build …
- Foundations, post and beam framework and green roof
- Installing the bath, toilet and basin
- Plumbing and electrics