Straw Bale House
Don visited Jo and Kerry Armstrong in Beenleigh, Queensland, and chatted to them about the straw bale cottages they built as an extension of their permaculture philosophy.
They say straw is often considered a waste product and many tonnes are burnt every year, polluting the atmosphere. Using straw bales for housing reduces this impact, and also helps to preserve forest resources. Straw bale houses might not appeal to everyone, particularly people living on average suburban blocks. However, if you dream of escaping from the rigid formality of urban life and want a house that sits comfortably in a natural bushland setting, maybe a straw bale house is for you.
How they are built
There are two building styles for straw bale houses: load-bearing, and non-load-bearing. The non-load-bearing method uses a range of traditional building techniques such as post and beam, portal or frame construction, with straw bales as infill. Because the structure is built using common building practices, this method is easier to construct and easier to get approved by local councils. In load-bearing construction, bales are usually stacked one on another and secured with reinforcement rods. Then the bales are either left to settle under the roof load or mechanically compressed before being trimmed with a whipper snipper and covered inside and out with small gauge chicken wire. In both methods the stacked bales are then given three coats of render (3 parts sand: 1 part cement) or plaster.
The pros and the cons
Strength: it is claimed straw bale houses can be designed to withstand hurricanes, so it’s no wonder there are straw bale houses in Europe and America that have been standing for more than 200 years. The key to durability is keeping the straw dry.
Damp: bales used in construction have low moisture levels, and strict precautions are carried out during transportation and building to ensure the straw remains dry.
Insulation: computer simulations by Energy Efficiency Victoria show that straw bale houses can be up to 20% more temperature efficient than traditional homes.
Fire risk: straw bales are so tightly packed they don’t hold enough air to permit combustion. Rendering makes them even more fire resistant.
Pests and vermin: bales provide fewer spaces for pests than do conventional wood-framed houses, and straw is not attractive as a food source. However, straw bale houses should be treated for termites in the same way as conventional houses are, to protect timber framing members, timber fittings or furniture. Control methods include – chemical barriers (Chlorpyrifos, Bifenthron or Premise, as approved by your local council) physical barriers (Termimesh or Granite Guard, as approved by your local council) annual inspections
Further information
Huff ‘n’ Puff Constructions run three-day workshops for groups of 15-30 people, costing $330. They can also help you answer any questions your council might ask. Phone: (02) 6927 6027, or visit their website at http://strawbale.archinet.com.au
Straw Bale Australia run on-site workshops for up to seven days, and people can join on any day. The cost is $25 per day. Phone: (03) 5476 2027 for further details. The cost of a straw bale house ranges from $100 per square metre for owner builders, up to $1000+ per square metre for architect designed houses. For more information on straw bale houses, see the June issue of Burke’s Backyard Magazine, on sale now for $4.20.