Using permaculture ethics & design principles to transform an old energy guzzling bungalow into a showcase of sustainable design. It's about energy cycling, building community, self-reliance,creatively using & reusing materials... all without spending heaps of money.

Monday, August 24, 2009

Getting framed

Principle 5: Use and value renewable resources & services

Timber seems the obvious choice for framing the house in this location. A renewable resource with low embodied energy. While I intended to reuse the hardwood framing timber from the old house, there were a few things that we considered.

Problems of using seasoned hardwood for framing include:
- the need to pre-drill holes before fixing (to avoiding splitting), which is very time consuming
- it will often have twists and bends in it, which make it difficult to fix cladding onto later, and to get square

But there are benefits too:
- low embodied energy, bringing new life to an existing resource
- it shouldn't bend or twist any more, that's already happened
- more resistant to termite and borer attack than soft woods like pine
- more fire resistant than soft woods

Since I was intending on building a deck anyway, reusing the old framing timber for that purpose makes a lot of sense.

So what timber should I use? Treated plantation pine is the mainstream choice. The big things to consider are: what is it treated with? and where does it come from? Be careful not to buy timber treated with Chromated copper arsenate (CCA) - also branded as 'Tanalith'. It can be very harmful to the environment, especially after it is burnt. "A ticking time bomb". There are other wood preservatives available, I'm pretty sure that the pine I ended up getting was treated with 'Light organic solvent preservatives' (LOSP), which is not as bad - but not great either.

When I asked where the timber I was thinking of getting came from, I got a nasty surprise. Aparently it came from Russia, shipped down to Melbourne, then up to Queensland for treatment, back down to Melbourne and then to Seymour. Not very sustainable. After asking if I could get something more local, my supplier found a company in Tumbarumba NSW (360km N.E. of Seymour) that could supply us. Much better, but again not ideal. While using plantation pine is much better than the indiscriminate logging of native forests, it does come with its draw backs. Monocultures are devoid of diversity (See Principle 10: Use and value diversity), sustainably managed native forestry are a much better solution for our timber needs than big scale monocultures.

Ideally, it would be best to use a suitable local green hardwood timber that is milled locally - unfortunately the Red Gum that was milled on site wasn't suitable for framing. When you build with green timber, letting it season after it's been used in framing, it helps to make the building even stronger as it shrinks together. Ensuring that the joints are rebated will reduce the amount of twisting that will happen. This is the way most houses were built in Australia, until relatively recently - when pine took over. Hardwoods are more naturally resistant to termite damage than softwoods, but physical barriers and regular maintenance will always be your first line of defence - regardless of what timber you use.

Quentin checking out our first day's work on the framing

Quentin framing up on the slab, which makes a great work bench. The studs are rebated into the base and top plates to reduce twisting.

We decided on using curved box beams for the roof structure. Partly because I love curves, partly because Peter has built with them many times before and partly because they have less wind resistance - reducing fire risk. One of the things that I love about this building method is that both pine and corrugated iron can be sprung to around the same curvature before they give in.

Peter and Andrew working on the first curved box beam. Clamps are used to bend the pine into the correct shape.

Plywood is cut to shape and fixed onto the curved timber using both wood glue (PVA), and 50mm nails spaced at 75mm. A nail gun is very handy for this, as a 4.5 metre spanned beam would have about 300 nails in it.

The beams are fairly light and easy for two people to handle

The framing and box beams well underway

Wednesday, August 12, 2009

Getting out of the ground

Principle 9: Use small and slow solutions

I've tried to source materials from as close as possible. Supporting small, local businesses, like Chris's Timber in Seymour. Chris makes his own concrete stumps on site, with a machine made by a fella just around the corner. Chris could make about 8 x 800mm stumps for me at a time, each batch taking about a week to fully cure. I used about 40 of them.

Concrete stumps getting made locally at Chris's Timber. Machine built locally too, in Abdallah Road.

Finished stumps delivered

I didn't salvage much in the way of material that I could use for bearers (100mm x 75mm) from the house, so I bought them second-hand from McIvor Hwy Recycled Building Materials in Heathcote (60km west), where all sorts of building materials are recovered from demolition jobs in the local area.

By drilling a hole in the bearer, fitting the stump rods through the hole and bending them over, we could hang the stumps in the holes - resting them on bricks. We could then level the bearers, with the help of a laser level, by adding small pieces of concrete sheet under the bricks.

I managed to complete about half of the joists with materials salvaged from the original house and garage

I purchased the rest of what I needed second-hand from Heathcote, which were denailed on site

Each joist was rebated with a hand saw and chisel, so that they sat on the bearers at the same height. A 45 degree cut joins the joists together. I needed to pre-drill the holes before nailing, because the timber was so hard. A time consuming, but enjoyable, job.

Joists nearly finished, preparing for the next stage... the framing.

Sunday, August 9, 2009

The cellar story continues...

Principle 4: Apply self-regulation and accept feedback

In order to ensure that the cellar performs the tasks that it is designed to do we need to build it to last. A crucial feature of the design is the roof. The roof needs to be able to hold a substantial weight - that of the water tank that will sit on top of it and the weight of the roof itself. About 8 tonnes (8000kg).

A combination of design elements, including: the four brick piers used in the construction, heavy duty reinforcing steel, a relatively high cement component (25 MPa), 200mm thickness and a slow drying process - all help to ensure that the roof will do what it is designed for.

The combination of the thermal mass in the roof and the water tank that will sit on top of it, will help to regulate the temperature in the cellar, help keeping it cool.

Quent lays the final course of bricks for the cellar

Quent fits reinforcing steel in place in preparation for concrete pour for the cellar roof

Timber supports for the ceiling of the cellar hold up the corrugated iron form for the concrete pour

Quent removing formwork from cellar slab roof

Cellar with plastic over slab roof to slow down drying, which helps maximse the strength of the concrete

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