Timbering up for Austrian weather
Architect Bruce Nichol's house in Austria is an elegant and fundamentally simple structure which was economical to build and will be thermally efficient to run.His use of softwood in a harsh climate is an inspiring example which deserves to be copied in the UK Austria may conjure up picture postcard images in people's minds, but it does not exactly have a gentle climate. Summers are hot, winters are cold and snowy, autumn can be very foggy. So the fact that a British architect has built a house entirely in softwood, relying on his detailing to ensure durability, is hugely encouraging.
The only item that Bruce Nicol anticipates having to replace after 10 years is the handrail on the balcony. If it can be done there, then surely it can be done here.
That is what Nicol believes, and he is keen to develop his dramatic, but fundamentally simple, house into a kit system.
At the moment, however, there is only one such house - the house he and his family are occupying, on a sloping meadow in the village of Dietach, just outside the pretty town of Steyr.Woods above and to one side shelter the house, protecting it from the worst of the winds but also making ventilation tricky. What Nicol has designed is a fundamentally simple rectangular, timber, single-storey box, with glass and timber cladding. It sits on a level concrete platform, beneath which are a car-parking space, a garden, and a technical room containing the building's service inlets and outlets.
Although timber construction is common in Austria, this stands out from its neighbours as being more simple, more open and more, yes, modern than they are.
Nicol has adopted several of the principles of self-builder Walter Segal, although only the really ambitious would treat his house as self-build. Chief among these is that the building has no basement, and has as few foundations as possible. His house is supported on concrete columns sitting on 1m-cube concrete pad foundations. These are 1m deep, beneath the freeze-thaw zone.
The systematic approach continues with the superstructure. 'Segal has a very basic sound, simple idea of creating houses for people, ' says Nicol. 'It is based on a grid.'
Nicol's grid is based on a 4 x 4m bay, although the house, in fact, consists of two rows of these with a 2m-wide service zone at the back. The end bays, however, are only 3m long, 'so they don't look as if they are falling off the edge of the building', he says.
Just in front of the service zone (which contains bathrooms and a utility room) is a top-lit corridor that runs the length of the house, from the front door at one end to a full-height window at the other. This window butts right up against the woodland, giving an exotic green view in the summer - although Nicol admits 'it looks rather like The Blair Witch Project in winter'. Forward of the corridor are the main spaces - from living space to kitchen to bedrooms, from public to private - as one moves away from the front door.All the rooms have full-height glazing that opens onto a decked balcony.
The structure is glulam (glued laminated timber). Nicol was determined to use locallysourced material, and the columns and beams are in fir glulam - with the exception of the front, external columns. These are larch, which will have greater resistance to sunlight and temperature variations. The cladding at the sides and back, and the decking are also larch. Nicol is confident that the timber will weather naturally and that it will not rot. 'It is high enough above the ground to avoid splashback or rising damp, ' he says. The overhang of the roof is sufficient to ensure that no rain strikes the structure directly.
The primary beams span from the front to the back of the building. These beams and the columns sit on top of a specially designed steel fixing, consisting of a plate with four bolts, cast into the columns. The tolerance for the position of these fixings was very strict - only 5mm. Roof beams span 11m from the front to the back of the building, and the roof has a 7degrees slope.
Both the roof and the floor are highly insulated. Made in 8 x 4m plates, the floor comprises Stirling board as the lower outer face, with approximately 250mm of Rockwool insulation above it. Above the joists is 20mm-thick ply, and above that a weatherproof vapour barrier. This allowed the floor to be constructed before the roof was complete. On top of the vapour barrier is a 30mm-deep service zone with all the heating and gas services inside it; above that is 19mm chipboard with a 20mm oak floor on top.
The house has an aluminium standingseam roof, with 160mm-deep high-density insulation board beneath it. The timber board ceiling sits directly on top of the joists.
There is some additional stiffening in the roof, in the form of 2mm stainless steel strips, arranged in a cross pattern across the end bays. The rear part of the roof is glazed to bring light into the corridor space and service zone, which has just a few small windows.
Light is not a problem at the front of the building, with full-height frameless glazing from Nicol's employer Eckelt. These panels, 3.2m high and up to 2m wide, are tripleglazed with low-iron Diamant glass. Both the inner and the outer leaves are toughened.
There are two solar-protective coatings and a thermal coating, and both cavities are filled with argon, improving the insulation properties. The glazing has a stainless steel fixing from Eckelt which is fixed only to the outer layer of glass. This avoids cold bridging through the bolt, and means that soft coatings on the other leaves of glass are not exposed to oxidation. With a roof overhang of 2m, there is no direct sunlight on the south-east facing elevation after mid morning in summer. In winter, however, there is sunlight penetration through most of the day, providing valuable preheating.
Although Nicol has accepted that the balustrade will have a finite life, he expects durability from the exterior decking. It receives some shelter from the overhanging roof but will get wet. However, it is 50mm thick and well ventilated, with decent gaps between the boards.
Nicol admits that there is a degree of experiment involved in the house: 'With a lot of the things here, I am waiting to see how things work. There is a lot of theory here.'He has had some problems with solar gain from the roof glazing, and the through-flow of ventilation has not been as successful as he hoped. Occasionally there is an inelegant compromise, for example, where the decision to cantilever the roof over the entrance stair meant that the size of the roof beams in the end bay had to be increased. But the overall effect is of a simple, elegant and open structure which, with its abundant use of timber, is both contemporary and warm.
Energy performance is looking good, although the house has not yet completed a whole year's heating cycle. And at £220,000 for an internal area of 280m 2(360m 2including the terrace), it is not expensive. 'I would like to do another one, ' says Nicol, who envisages a very different house to fit different circumstances. Form and cladding elements could change, but by maintaining the bays, structural elements could be standardised. This would be a kit house in the way that Meccano is a kit - producing different results every time - and one, believes Nicol, that would be as appropriate to the UK as to Austria. Indeed, since an article in the Sunday Times in the summer, he has received about 40 enquiries, the bulk of them from the UK.Nicol's kit of parts would be an exciting alternative to much of the housing currently on offer.