Week Two

Welcome to Professional Strawbale’s blog for the second week of February. A small correction from last week’s page – the rye straw was grown for seed harvesting, not feed harvesting – any straw used for building purposes must have minimal feed value.

The project at Barwite, about 10km north of Mansfield is progressing well, and the owner, (who is also the builder), can see the light at the end of the tunnel, so the pressure is on!! The internal walls have been plastered, and the electrical and plumbing fit-off starts next week. This means that any sections of strawbale wall that have plumbing or electrical work in them will need to have  the top coat of render complete by Wednesday or Thursday. However - I would like to back-track to the stacking stage of this particular house to illustrate a very important point.

If you look closely to the photograph we’ve posted, you’ll notice there is a post in the wall corresponding to every one of the oregon beams that support the roof. These posts are 90mm X 90mm, and are spaced at 900 mm centres – meaning that there’s almost exactly 855mm in between each post. The upshot of this is that virtually every bale in the wall shown had to have a 90mm X 90mm notch cut in the side of it, so the outside face of the straw and the outside of the posts were ‘flush’.

The owner was keen to have the entire wall surface covered in chicken wire reinforcing, so the posts gave us plenty of places to staple to, but I think that’s where the advantages end!!

 Not only does notching the bales around the posts consume a fair bit of time and energy, but it makes the cut bale want to bow around the cut to form a banana shape. Bales like this not only have to be handled pretty carefully to avoid their tendency to ‘pop’ and fall apart, but take a considerable amount of bashing into shape once the walls are compressed.

 If all of the 300 x  50 mm oregon was sitting on a perimeter beam of some sort, say 250 or 300 by 50 mm hardwood, the posts could have been spaced as much as 3 metres apart, radically reducing the amount of chainsaw work, and meaning each bale stayed as a whole, integrated unit.

I reckon that’s about it for the stacking on this one; so next week we’ll discuss the rendering process. Hoo-roo,

                                Mark

The current project

Welcome to Professional Strawbale’s very first blog page. For the past few weeks, and a couple to come, we are in Barwite, a locality about ten kms north of Mansfield in Victoria’s North East. At this point, the building has been stacked, with 320 bales of rye straw, and the first coat of render is on and dry.

Firstly, I would like to mention the straw. Sourced from a farm a kilometre or two up the road towards Mansfield, the straw has come from a paddock grown for feed harvesting, and though technically not a cereal crop, it fulfilled all the requirements of a building bale in that it consisted of long, tough ’straws’, thus trapping the air required for great insulative value. It was however, extremely dirty, and hard to work with because of the dust trapped in the bales. The process of cutting the bales with a chainsaw and whipper snippering after they had been stacked was very dusty, and required a dust mask – not pleasant in hot and humid conditions. Strictly speaking, a mask should be used when cutting straw, as the cell walls of grasses have a high level of crystalline silicates (giving them their inherent rigidity) which we now know can do serious damage to your lungs. So, if you are sourcing and stacking the bales for your house, try to make sure they are as clean as possible, but wear a mask anyway. Safety first!

All this leads me to say that the whipper snipper work on this building was more rigorous than usual as the owner builder had only allowed 35mm for the render, meaning that tolerances were tighter than average, and in order to avoid thin spots in the render, a fairly heavy cut-back of the straw on the outside was necessary. At a guess, I would say it took two full working days to whipper snipper the surface of the walls to prepare for rendering.

If you are an owner builder, or an owner who wants to stack their own straw prior to getting a professional to do your rendering, don’t skimp on the amount of work with the whipper snipper – a bit of extra effort at this stage can save a lot of drama further down the track. Many’s the time I’ve had to stop rendering, cut my way through the reinforcing mesh and trim the bales back to allow a reasonable thickness of render, always important, but critical on external surfaces to guarantee a waterproof finish. There’s probably not a lot more to say on the stacking of this job before I move on to the rendering when I return home next weekend, so you’ll hear from me then.

Hooroo, Mark