Review: Oehler, M: The Underground House Book

Mike Oehler is an autodidact, and a man - he admits it, nay, proclaims it - of strong and idiosyncratic opinions. He has a recipe for building small dwellings cheaply in Pacific Northwest USA - which is to say it's as wet as western Scotland, warmer in summer and considerably colder in winter. He designs houses that I could afford to build using materials which are - with the exception of the polyethylene membranes which are key to his system - considerably more ecologically sound than most modern building materials. He makes substantial use of roundwood poles - which I have in abundance for the cost of cutting and seasoning them.

All these are reasons I should take him seriously. And yet, I'm wary. He's built - or claims to have built - remarkably few dwellings (two, as far as I can see, although people using his method have built many more). He doesn't seem to use any moisture barriers in his floors - in fact, he extols the virtues of earth floors. I simply don't see that working in Scottish conditions (In fact in the 'Update' section at the end of the book, Oehler now has a membrane under the floor of his house - which is now carpeted).

The other thing is that I strongly suspect that if you showed one of his houses to any self respecting British Building Control Officer you'd get something between a hearty guffaw and a shriek of horror. Indeed, Oehler's own response to building standards is clearly expressed on page 100 of his book: 'will a home built with the PSP system pass the code? The answer is, sadly, no... you may move to an area which has no codes...'

Well, you may. But I want to build my home on my land in my home valley, so I can't. I could adopt Oehler's alternative suggestion, of evasion... but the less said about that the better.

Finally, a note of caution about the title. Oehler's quoted prices relate to the 1970s; and even then I think a certain amount of creative (or merely forgetful) accounting was involved.

Nevertheless Oehler's book is both thoughtful and thought provoking. I'm glad I read it, and will continue to mull over it.

To cast or not to cast

To cast concrete or not to cast concrete, that is the question. 'Tis undoubtedly nobler not to. Cast concrete requires a huge amount of energy, and so inevitably has a high carbon cost. On the other hand, provided it's done right, it will stand and be useful for hundreds of years, so that energy cost is ammortised - potentially - over a very long time. But here's the rub. I don't need a dwelling that will stand for a very long time. I need a dwelling which will be reliably warm and weathertight for thirty years. After that, it's someone else's problem, and someone else may not choose to live underground.

The wood/epoxy alternative is probably but not certainly good for thirty years. If it starts to fail in twenty years, when I'm in my mid seventies and probably pretty broke, that's going to be bad news. I don't think it would, but it might. Also, the cast concrete structure is remarkably cheaper, and remarkably easier to insulate, than the wooden one. Given how tight I am for money, that's a very significant consideration.

Casting on-site is definitely out. I can't get a readimix truck to site, and I can't quality-control the concrete I can mix for myself on site. Also, the shuttering cost of casting on site is high because it would be necessary to cast a whole dome in one go. I had ruled out my original idea of casting off-site because I had thought that I could not afford the heavy equipment to move stuff on site. But Boy Alex's Unimog can do exactly that. Casting off-site is once again an option.

If anyone thinks that, like Hamlet, I'm labouring this decision, well, I am. This is almost certainly the biggest decision of the rest of my life.

Structure Review

OK, I'm getting very close to the point where I have to commit to a structure for my new home. I have to apply for planning consent, and I have to do it soon. If - improbably - I get consent quickly, then I can build this summer. And that would solve a lot of problems.

Of course, I can't actually afford, now, to build the full structure I want for the long term, so it has to be modular: I have to be able to build some 'now' and some 'later'. So let's again review the arguments and the options.

Conception

The original conception was for an underground structure sunk into a south-facing slope, comprising four hexagonal domes each 4.8 meters in diameter: one for services, one for kitchen, one for day, one for night - where the 'service' dome held bathroom, store and spare bedroom. The roofs were domed mainly because, in concrete, that's a good self supporting shape, and form followed function. They were 4.8 metres in diameter mainly because they would be cast over fundamentally plywood forms, and plywood comes in 2.4 metre sheets.

Underground is important both for insulation, for landscape considerations, and, most importantly on the very windy site, gets down out of the wind. The alternative of, for example, a timber framed straw-bale building would be both very intrusive in the landscape and very exposed to wind.

The south slope is important because it allows a fundamentally underground dwelling to have passive solar gain through south facing windows. In any case I've deliberately bought a south-facing slope for exactly this reason. An underground dwelling on a fundamentally flattish site in Galloway would have more significant problems with drainage and with daylight. I could get a more conventional house out of the wind by sheltering it behind my wood, but then it would lose the south aspect and consequently the passive solar gain.

The case for a hexagonal grid is a bit less compelling. Mass produced furniture is designed for rectangular spaces. Deliberately choosing a non-rectangular space means that much more of the interior furniture must be custom designed, which pushes the cost, either in money or time, up. However the human eye is very good at finding linear features in a landscape. Straight lines are very obvious, very noticable; and a structure with a rectangular grid exposes longer and more obviously related straight lines. It becomes more noticable in the landscape. However, my choice of a hexagonal grid is primarily aesthetic rather than rational.

Realisation

However, I've now doubtful about cast concrete. I don't think I can guarantee the engineering qualities of concrete I can make on site. I could as I originally intended cast concrete units in the void and hire Alex's Unimog to move them to site, so that is still a real possibility, but these are heavy units.

Against it, concrete has very high embodied energy, and I really would have to hire an engineer to check my structures.

For it, concrete is extremely durable - there aren't any doubts that it would stay up for my lifetime.

I've considered a wood epoxy composite structure. The problem with that is that if the epoxy encapsulation is breached it will rot, and lose structural integrity; and it's hard to imagine that it can support the overburden required for good soil insulation, so insulation would need to built into the structure. Which could be done. For the roof sections, the 'well it might rot' problem is to some extent mitigated by the fact it can't be buried deep - if a module rots, it can be unburied and repaired or replaced.

However, one of the important considerations is that this is a dwelling to grow old in. As I get older, my ability to do repairs myself reduces, and my ability to pay others to do repairs also reduces. If the structure has ongoing maintenance problems it will become unsustainable.

If I'm dealing with a structure which cannot sustain a heavy overburden, paradoxically larger modules become easier to achieve. Instead of four 4.8 metre domes, I could have fewer, bigger ones. But actually the small domes have two significant advantages. Firstly, I can build them one at a time, as I can afford them. A single 4.8 metre dome would be a small but tolerable living space for next winter. Two 4.8 metre domes - the service and the kitchen dome - would make a perfectly acceptable space. And realistically that is almost certainly as much as I can afford for just now.

Equally, if I'm not designing in a heavy material with a significant overburden, the dome is no longer form following function: it serves no functional purpose at all. It becomes, in fact, a sculptural conceit - and one which does not come for free. It makes the whole structure taller - and thus harder to bury - than flat ceilings. Like the hexagonal grid it becomes simply an aesthetic conceit. Yet it remains one that appeals to me. I believe it will make a graceful space. Furthermore, actually, a wooden dome lined with birch plywood becomes an even more graceful space than a concrete one.

So the compromise solution - concrete walls and wood/epoxy roof - seems the most attractive at present. I think. I'm almost decided.

The Fool on the Hill

I've sold my house and am buying, in effect, a field. And a bit of wood and a share in a common, but basically a field. This is foolish. There is no planning permission on the field, and I'm unlikely to get any. Also, it's still possible that the deal to buy the field will fall through, but my house is sold. This is even more foolish. The field is five hundred feet above sea level, at the top of a very windy ridge. This is getting idiotic. Because I thought I would have more money than I've ended up with, I'm buying more land than I strictly need; and the consequence of that is that even if I get planning permission, I don't have much money left to build with. This is mad. Oh, and speaking of madness, I'm recovering from a bout of mental illness. At least, I think I'm recovering. So, this really is insane... Oh, and I don't have any income. At all. I could claim benefit - my doctor would certify I'm not fit to work (and he's more or less right) - but I've chosen not to. This is crazy.

But. But not that insane, I'd like to argue. Not wholly irrational. There are reasons. I'm not certain that they're good reasons, but...

I will have enough land to be self sufficient, which if I'd been more prudent I wouldn't have. The land, despite its altitude, is actually good; it's well drained, faces south west, and grew a barley crop last year. It's even soil-association certified as organic. I could live on what it can produce. I probably have enough wood to be sustainably self-sufficient in firewood.

Also, my breakdown over the last two years - which got quite bad - was at least partly because of the stresses of a failed relationship, and of working eighty-five miles from home. I couldn't sustain either of those things. I certainly couldn't sustain both together. I've no income because I lost my job, and I lost it because I could no longer do it. I'd planned to keep working until I could afford to buy my ex-partner out of my house, but I clearly can't do that. So I've sold my house in order to separate from my ex-partner. I couldn't have bought any house in my home valley on the money I thought I would realise from doing that, let alone for the money I actually did realise.

So the field is not necessarily a bad thing. Obviously, if I can't get planning permission I can't legally build a house on it. But there are workarounds. A couple of weeks ago - on two of the wildest nights of the winter - I slept in a yurt. It was a good, comfortable, pleasant, warm space. I could live in one (although I'd have to give away a lot of stuff). As it's a tent, it doesn't need planning permission. Of course, you're not supposed to live in a tent, but, on my own land and hidden by my own wood, who is actually going to stop me? And, importantly, I can actually afford a yurt - even a good one.

Of course that isn't the plan. The plan is to get planning permission to build something comfortable and interesting. But it is a fallback if that should prove impossible. And, in the meantime, I have to be living in my field in ten weeks from now - because I've borrowed a bothy for ten weeks, which keeps me warm through the rag-end of winter. But in ten weeks time it has other tennants, and I must be gone.

So this essay introduces a series of other essays which I'll post from time to time as the project develops, using as title my new persona:

The Fool on the Hill.

On Yurts

The last two nights I have mostly been sleeping in a yurt. No, scratch that. The last two nights I have entirely been sleeping in a yurt - it is much too cold to leave a foot stuck out for the sake of a meme.

Outside, that is. Inside the yurt it is quite startlingly warm - certainly much warmer than I would be at home. A small centrally located woodstove heats the space exceedingly effectively. My second night in the yurt was, coincidentally but rather fortunately, the windiest night for a year - and one of the wettest. In the depths of this cold, wet, violently windy night in early February, the yurt was cool. But not colder than I should have been at home, not draughty, and (apart from a slight anxiety about a tree actually falling on it) not insecure.

This yurt is from Yurts Direct, and is, I believe. authentically imported from Mongolia. It's about 6 metres in diameter - frankly spacious and generously propeortioned; it is in itself a work of art. The curtain which lines the wall has a damask weave with a crysanthemum pattern, in fabric somewhere between ivory and gold. The poles of the roof - some eighty-one of them - together with the roof crown and the two posts which support it, are of a burnt orange colour apparently individually hand painted, and yet with a regular repeating pattern, as are the doors. The doors comprise two inner doors and a single outer door, all housed in a substantial and rigid wooden frame, with windows in the inner doors and on either side of the door opening.

A curious thing is that while there is a cord to tie the outer door open, there appears to be no mechanism for latching them shut, short of leaning something heavy against them. And this matters, since it's been extremely windy both nights. Which raises another issue - there's remarkably little sound insulation. While only occasional gusts rattle the crown cover, the noise of the wind in nearby trees is loud.

At the eaves the roof is certainly less than 1500mm from the floor; at the crown ring, about 2300, and at the top of the crown perhaps 2500. What this means in practice is that I can't stand upright within one metre of the wall, but in practice this doesn't matter since the space against the wall is naturally used for seating and storage, leaving the main area of the floor free.

Although the only fenstration is the (small) glass panels in the door and the transparent sections of the crown cover, they let in a surprising amount of light in daylight - and from my bed at night I could see stars.

The floor of this yurt is made of (apparently) chipboard flooring panels, which are supported off the ground on sturdy wooden joists laid on pillars of concrete breeze blocks. The floor is not part of the package you get from Yurts Direct, but is something you have to construct for yourself.

This yurt cost £4,000, and similar yurts are available now for £4,495 (Yurts Direct describe it as a 'size 5'). Quality yurts made in Britain by (e.g.) Woodland Yurts cost about the same or slightly more. That isn't an unreasonable price - there's quite a lot of work, and a fair bit of material, in one of these.

As low cost housing for rural Scotland, how does it stack? This yurt is, I think, generous and elegant living space for one, and adequate but a bit tight for two. Indeed, a single person would get away with a smaller one. It doesn't, of course, have anything like a bathroom, which would horrify the planners. It is adequately warm with the burner lit, and clearly adequately wateerproof - this yurt, which has been up all winter, shows no signs of water staining anywhere, despite the relatively low pitch of the roof.

Most of the materials could be sourced locally in rural Scotland. The frame is wooden. The insulation is wool felt - and let's face it, we're not short of wool. The outer covering is canvas, which could be flax (in this case it isn't, but it could be). In terms of durability, the frame, with reasonable maintenance, is likely to be good indefinitely - certainly for a lifetime. Also, individual components of the frame can be individually replaced with little impact on the surrounding structure.

The canvas covering is likely to have to be periodically replaced, perhaps every ten years. The layers of felt will also need periodic replacement. Apparently it is a good thing to dismantle and overhaul a yurt at least annually, and I can clearly see the sense in this.

The major problem with a yurt in Scotland is of course damp. If the stove is not regularly lit, moulds and mildew attack the canvas and felt. This shouldn't be a problem in a yurt that's permanently inhabited, provided there is a reasonable supply of firewood. There's obviously a risk of fire; a yurt which I have seen which caught fire burned to little more than a ring of ashes. In a yurt made predominently of natural materials there should not be a great problem with toxic fumes, and, being all one space, there isn't a complicated route to find to the exit. So whether the risk to life of fire in a yurt is greater or less than the risk in a conventional structure I couldn't say. However, it's certain that in the event of a fire very little of what is in the yurt could be saved.

I don't know what happens to wool felt in the long term. People I've spoken to talk about infestations of mites or insects - probably something like the chitin-eating silverfish - and this sounds somewhat unpleasant. But inorganic felts - fibreglass, for example - also present problems, not least long term environmental problems in disposal.

The stove in the yurt I stayed in is a locally made one, not of very high quality, but it stayed in both nights even with my inept management. Good stoves suitable to use in a yurt are, obviously, available.

In summary, I was sleeping in the yurt to test-drive it - to get a feel for whether it would be a temporary dwelling I could survive in until I get planning permission for my permanent dwelling. And the answer, simply, is that it is. But - and it's a big but - it's not cheap. The combined cost of the yurt and the platform it sits on and a suitable stove add up to a fair proportion of my available building budget. On the other hand if you turn the equation on its head and say the yurt is the permanent structure - and it is comfortable enough that one could do that - then suddenly it does not look expensive at all, but on the contrary very cheap.