In a coincidental but fitting end to 2011, we’ve been finishing up several jobs that were almost but not quite complete. Both upper rooms in the larger building now have new floors and finally we have finished the roof!
Since completing the external stairways at the end of September, the southwest corner of the roof has been sitting waiting for suitable schist slabs to complete its covering. The last load of stone (from the community stone mine about 1.5km away further up the mountain, dug out and brought down by man-of-many-machines Senhor Angelo from the village directly above) contained some huge slabs of good-quality roofing stone that were ideal.
The schist is enormously variable. Even across the space of a few metres, it can vary dramatically in colour and density. The stone of the small building the other side of the quinta is quite different to the larger building, even though the mines for each – directly behind and above each building – are less than 150m apart. So it’s easy to tell the new stone from the original roof stone by its colour. In time though, lichens and mosses will grow on it and even it out somewhat.
The curve of the building and its eccentric proportions – accommodated to the shape and curve of the slope it’s built on rather than vice versa – is clear from these images and illustrates nicely why random schist slabs work so well as a roof covering for these dry-stone schist buildings. Imagine trying to cover this roof with uniformly-sized roof tiles!
In this last image, you can also see the foundations for the toilet that have been put in behind the building. The walls for this will be constructed in cob and there’ll be a turf roof extending from the back of the building to the slope behind it. This is a crucial part of keeping the building dry: at the moment, rainwater runoff soaks through the thin soil and comes straight down the rock face and into the back of the building. A substantial gully cut into the rock itself and lined with a stiff mix of concrete to prevent water soaking down through and along the bedding planes (which run mainly vertically and perpendicular to the line of the back wall) should be enough to divert runoff away from the back of the house and, with the roof, keep the building dry without resorting to the use of artificial synthetic waterproof barriers.
Yes, it’s using Portland cement, but as I’ve written elsewhere, there are times when its strength and impermeability make it an ideal material for the job. Yes it would have been possible to construct without it if we were enormously skillful, but when the skills required are in short supply and beyond budget, both financially and temporally, compromises become unavoidable. This is a compromise I’ve been prepared to make; mostly, though not exclusively, in structurally critical instances. The cement we use is dug and fired 40km away (around 60km by road) using energy more than 50% of which is generated from renewable sources. As the main contributor of embodied energy to the project, it could be a lot worse.
Many times I’ve gone over what we’ve done, especially following discussions with those of a more rigorously natural perspective, thinking could I have done it differently, and come to the conclusion that for this project in this context, it’s appropriate. A new natural build on a level site has different challenges to renovating an existing natural building perched on a narrow terrace half way up a mountain. Damp and water ingress is a feature of much of the Portuguese rural housing stock and something people appear to simply live with, traditionally providing ways for water to pass through buildings rather than trying to keep it out (though latterly trying to keep it out with large amounts of cement render which has produced a whole raft of problems). Here we are changing the use of the building and having water running through the ground floor rooms is not really compatible with the use we want to put them to.
There goes another principle … but I can live with it.