Saturday, April 25, 2009

Econospace Framing - step by step

Some very good workshops happened near Castlemaine this summer and I was lucky enough to catch one of them. For a long while I'd been wishing for the skills to build my own shed, houseboat or composting toilet, but the mystery of how to make walls and roofs stay up on their own eluded me. This changed after I attended Peter Cowman's Econospace framing. In one weekend, the construction of a small building had become something within my range of experience. What follows are my notes on how to build an Econospace - in our case, a 10 square metre structure.

We began with some theory: the principles of foundation and triangulation, the benefit of a good work bench and appropriate tools.

We quickly saw these principles in action. The foundations: basalt crushed rock under a brick foundation covered with ant guard. The floor is raised to keep it accessible to check for termite damage, which should be held at bay by the rock and ant guard.

The floor was constructed before our arrival. The framing was laid and levelled and beams placed across and attached to frame from below. The cross pieces tie it all together. The lip here where the frame joins the beams allows for the placing of insulation.

Notice how the triangulating pieces run opposite ways at each end.

The basis of frame of the Econospace is the Peter post. The peter post is designed for exterior and interior cladding, with space for insulation in the middle.

We made up the peter posts on a jig and nailed them together with 75mm flathead nails.

One problem you can encounter with conventional timber framing is thermal bridging, where the timber provides a bridge - points at which wood can transfer heat inside to outside. The peter post avoids this problem, as no part of the wood travels all the way through from inside to out.

With our peter posts ready, we built the frame. Firstly, we made a temporary floor and laid out 4 peter posts, lining them up with the foundation and measuring the distances carefully. 4 sheeting rails were nailed across, with one laid diagonally along the top for the sloping roof.

A diagonal cross-brace was added, running in the opposite direction to the diagonal roof rail. Two bottom rails were added.

Bracing beams were fixed at a single point, to allow them to pivot. Then we raised the wall and braced it in position.

The front wall was constructed in a similar way, except that the wall sat on the floor joists when raised. It is essential to accurately measure the width of the peter posts relative to the floor joist to ensure it fits.

With all four walls raised, we secured them and removed the bracing.