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.

Extending the roof area right round the house in this way will, aside from providing covered walkways, give all round protection to the walls from most direct weather action: a major consideration with dry-stone walls, especially ones that are going to be clay-pointed.

The stairs to the right of the building were already enclosed by the log store, so all that remained was to construct the wooden supporting framework, bridging the gap between the log store and the building. Again, we’ve used round-pole sweet chestnut for the framework and maritime pine planking.

I’m not overly impressed with the ‘ecological’ wood preservative we’ve been using so far. I’ve still not been able to discover the active ingredients, and although it produces a nice-looking finish when dry, the PVA it contains makes it unsuitable for external use as it becomes milky and opaque if rained on. It also appears largely ineffective against wood-boring wasps since we’ve noticed fresh activity in treated timbers. Consequently, I’ll be preserving these external timbers with 2 applications of borax, then linseed oil, and using a more concentrated borax gel or paste to deal with the active infestation in the treated timbers. When your roof weighs 8-9 tonnes, it doesn’t do to have the supporting timbers eaten away …

The left hand stair well is now in the process of being created. The stairs have been repaired and a schist wall constructed (with cement, since it has to support the weight of the chestnut framework).

We didn’t have enough large lengths of chestnut for this stair-well, and our local source of recycled timber has none of the required length, so rather than looking to buy some, we found a long straight chestnut tree in a crowded area of the quinta and felled it for the purpose, leaving enough of a stump for the tree to regenerate. It feels perfect that the renovations should include timber from the quinta, as well as stone and clay.

Cork insulation and breathable membrane go on

The view from the inside

With the membrane fixed in place, the roof was ready to start re-laying the original schist slabs.

Laying the schist. Chris looking over the first few courses

Handing up the large schist slabs

Wayne drilling slabs for nailing in place

We are fixing the bottom, middle and top courses of schist slabs in place to prevent any slippage. We’re also creating slightly more overlap between courses than was used in the original roof, both for better coverage and waterproofing and to hold the stone in place. This roof should never move!

Lunchtime today: two thirds of the way up the first half

The end of today: almost half complete

How it used to look before we started renovations

Wayne laying planks, Chris behind him

Michael in the sky with … a plank

Ema, queen of the linseed oil

Building from the south side

Building from the north side

The cleaned, preserved and oiled chestnut rafters, beams and wall plates are now all leveled and in place and work has begun on fixing the wooden planking to them. These photos are from this morning. By the end of the day, the planking had been completed up as far as the middle beam.

Michael, Wayne and Chris lay the first planks

Rafters in place, both full length and in halves

The challenges of working with round pole timber: creating a level surface for the planking

The other side of the building

Additional timbers on the cross beam required to level the rafters

Michael and Wayne fix the first planks in place

The planking we’re using is rough planking. Dry maritime pine, unplaned. About 22mm thick, compared to half of that for tongue-and-groove, so double the insulation for half the price, stronger, and easier to lay on a very asymmetrical building. It’s been treated, as has the chestnut, with an ecological wood preservative (apparently – still haven’t had a response from the manufacturers to tell me what the ingredients are) followed by a boiled linseed oil and turpentine mixture (roughly 1 part turpentine to 7 parts linseed oil). Boiled rather than raw for its more rapid drying time, and the turpentine (genuine turpentine, not the mineral ‘white spirit’ turps substitute) performs a similar function as well as being slightly repellent to insects in its own right.

So exciting to see construction at last! Although we’ve been making good progress dismantling the old roof and cleaning and preserving the timbers, it’s been a process of deconstruction rather than construction and has made the building look less finished rather than more. Now the roof is finally going on, it’s much easier to visualise it in its finished state.

The chestnut timbers have a satisfyingly rich colour after being cleaned with a draw knife, treated with an ecological preservative and coated with linseed oil

Ema and Chris treating the new timber. Behind Em is the cork insulation we’ll be using

Michael and Tom puzzling out where the beams should go; Chris and Em painting

A welcome to visitors-cum-wwoofers Tom and Nelle from Belgium who are helping out when they’re not out looking for their own place.

And what is it with the menfolk on this quinta and teeth? Michael, Tom and Chris have all paid visits to the dentist in the last month for repairs and extractions. And different dentists for each, so we’re now acquainted with practices in Coja, Arganil and Oliveira do Hospital!

Removing the large slabs of schist

The existing roof covering comprised large irregularly-sized slabs of schist (the local slate-like stone from which everything in these hills is built), probably weighing in the region of 8 tonnes, supported on beams, rafters and purlins of sweet chestnut. Most of the schist and most of the chestnut is still sound, so we’ll be re-using it. The rotten and broken pieces will be replaced from local sources, re-using old chestnut beams taken from collapsed buildings, and schist from old mineworkings.

Work is now underway on cleaning the chestnut – stripping off the outer layers which have weathered or been eaten by insects to reveal the sound timber beneath.

We’re using an ‘ecological’ wood preservative made by a Portuguese company. So far I’ve been unable to find out exactly what’s in it – the website, like a lot of Portuguese websites, has no information at all, and the data sheet for the preservative (Xilotrata ‘VNZ 8000′) gives nothing away on that subject. It appears to contain PVA as well as whatever-it-is that’s to prevent insect attack. We’ll be following treatment with this by a coat of linseed oil on the roof timbers.

Schist removed and woodwork exposed