Wednesday, 17 August 2011

Fenestration


When someone approaches my building, the first thing - and the dominant thing - they're likely to see is the fenestration. That's because pretty much everything else is buried in the hillside; the only face of the structure that's exposed is the south face, which is primarily glass. My intention has always been to use commercial patio door units, because they're mass produced they're far cheaper than any custom unit I can make myself, while having well engineered latches and reasonable insulation.

In the 'sousterrain' design, the shape of the fenestration was to some extent masked by the eyebrow lintels and flying butresses. All the swoopy curves of the exposed concrete structure relieve the industrial regularity of the windows. In my first 'singlespace' drawings, I set the window units back behind the pillars, and thus behind the ring-beam and its braces, and this too masks the shape a bit.

But in reconsidering the front joinery I've considered first that the elements of the frontage are extremely visible, and second that they're exposed to weather. While making the rest of the structure in softwood seems acceptable to me, using oak for the front pillars and lintels will both reduce maintenance and add elegance. Given that it's only five pillars and four lintels, the increased cost is not going to be high. And it you're going to do that, the relatively lightweight 200x50 mm lintels of the front ring beam as originally planned are going to look wrong (and in any case require a lot of additional joinery to make a weatherproof space). Better, I thought, to make them true lintels, with a section of 200x200 mm or possibly even more. Yes, more expensive and not required from an engineering point of view, but the fenestration can now be fitted directly into the aperture between pillars, sill and lintels, completely solving the weatherproofing problem.

The trouble with that is, if the pillars are still roundwood, the only place the windows can now go is between the centres of the pillars, or else you're back to bodging the weatherproofing. Which means you can't easily get well engineered braces in front of them. Mind you, there's no longer an engineering justification for braces - all they're doing is relieving the shape of the aperture. If the windows are to be set futher back into the aperture, the pillars must be sawn wood - but they can be sawn to the angles I want, so that can be a feature. And I can have braces.

And the windows themselves?

OK, let's start with the ideal. If I were a plutocrat James Bond villain, the windows would drop vertically into wells in the floor to open them, and would be closed by hydraulic lifts or something similar. In summer, when the weather is warm and pleasant, I'd like them just not to be there at all. If not a plutocrat but merely very rich, I would have a custom made fold-and-slide door, where there was one continuous track and all the leaves of the left-hand two apertures folded and slid left while all those on the right-hand two folded and slid right. That would achieve almost the same end result - in summer, a clear space open to the outside - although the folded leaves would now intrude into the living space on either side of the single opening.

The whole point of this design, however, is that I'm neither a plutocrat nor rich. I'm poor. As I said to the woman from the planning department, the whole purpose of this proposal is cheap hooses for puir fowk. A single two metre by two metre fold and slide unit in oak veneer - not even real oak - costs of the order of £1,200 ex VAT, so the four of them cost £4,800 ex VAT. Solid oak costs more. That's in a structure which, even with my oak front joinery, has a materials cost for everything else except the front windows of under £7,000.

So, here's the rub. I can halve that cost by using uPVC units. uPVC units come in at £600 per unit, or £2400 for the whole set. But can I really live with uPVC?

Let's go back to the matter of doing things on the cheap. Makers of sealed glazing units often sell units that have been made but which weren't used in the project for which they were made, cheap. This is because once made they can't be refashioned, and if they aren't a standard size then they're pretty much scrap. So you can get cheap units but you're unlikely to get the size you want. Poor self builders often start by buying these cheap units and then making their window apertures to fit the units they've got. I could, and probably should, do this; if I can get units which are almost the right size it might even be worth respacing the pillars a bit to fit them.

However, that means spending out on the fenestration right at the start of the project. I don't want to do that because if I'm going to run out of cash at any stage I want to run out of cash with a weatherproof structure. Window apertures can be made good cheaply with weatherboard (at the cost of no daylight). A bloody great hole in the roof can't be made good cheaply.

But also, I don't, in the end, know how much I've got to spend. The financing of the farm is complicated and not relevant here, but it's possible that in due course I'll get some money back - possibly as much as £20,000, which makes a difference. If I don't get any of it back, then I'm going to have to see what cheap fenestration I can get. If I get a little, then four uPVC units are not a lot of money. If I get more, then I can have oak. But if I get a lot of it back, a custom fold and slide isn't utterly impossible... and it would make a significant difference to the space.

One question that I haven't answered in all this, and which will have to be answered, is... where will the cat-flap go? Penny and Ivan are going to be seriously unamused if there isn't a cat-flap, and I'm going to be seriously unamused if I have to keep getting up and going to open the door for them.
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