Is is easy to understand why straw bale building has captured the imagination of people wishing to construct in an ecologically sound manner.
Small straw bales are cheap to buy, easy to handle and quickly stack up just like giant lego blocks in a most satisfying manner. The first two buildings by ABC were straw bale, and many valuable lessons were learnt.
Building One was made with load bearing walls, where the straw bales carry the weight of the roof. For a variety of reasons this system is not ideal. Straw is a compressible material and the lime render used to finsih the bales becomes structurally importnat. The system dictated the use of narrow windows which makes the building a bit dark inside on overcast days. Changing the windows or re-locating the door are tricky with weight bearing walls.
Building Two employed a timber frame and was slightly quicker to build. However there were still some issues that needed to be addressed.
The glossy books from America painted a tempting picture of a simple, cheap and fast building method. However, the reality is a bit more involved. There can be as much carpentry and timber in a load bearing straw building as in a timber frame wall, The roof needs to be firmly attached to the walls, the walls to the foundations and the doors and windows need to be secured. Skirting boards, curtain poles, electrical sockets and the like all require some form of anchor point which generally involved timber, so some form of timber frame is advisable.
A quality of straw bales is their size - they can make wall construction quick because they are so large - and yet this can also be a drawback. The need to create and cut bales to define doors and windows is time consuming and fiddly, equally constructing gable ends for a traditional pitched roof is also a major undertaking.
The bale walls themselves need to be compressed downwards when they are finished to increase stability - which involves specific detail on the sole and wall plates to permit this.
After tensioning, the walls need to be trimmed ready to be rendered, a filthy and onerous task. The gaps between bales need to be filled to prevent draughts.
The building of complicated shapes such as curves is not simple to achieve with bales and the size and stability of the bales also raises issues.
These concerns led to a re-assessment of straw bales as a building material and a search for a better straw building method.