A LEG TO STAND ON
It's green, it's clean, its bigger than Ben Hur, better than
sliced bread, and the saviour of western civilisation as we know it today. It's strawbale building!
Well, maybe not quite. Yet the funny thing is, once the rose tinted glasses are taken off, it still stands up as a valid building
technique. However, as with any building style, it is only as good as the legs on which it stands, literally!
The advantages of straw as a building material are quite well known by now. Its insulation value is
better than anything else, it is cheap to buy, it is a waste product with a new use, it is easy to handle and
work with, and creates an aesthetically pleasing ambience.
The first decision to make is whether to
go load bearing or infill. My feeling is that if one is to go to all the effort of a building framework, then there
are cheaper ways of infilling the walls. Not only is there the extra expense of the frame, but more labour is
involved, more materials are consumed, and the job in total takes longer. Pole frame construction with a
wattle and daub infill, or part timbered with a solid plaster would be cheaper, less work, and you would not
lose the beauty of the poles. Strawbales work very effectively as a load bearing structure, so to complicate it
is to waste time, effort, money and materials.
Regardless of the building material used, the most
expensive parts of construction are the roof, the footings, and fitting out. Walls are in fact, the cheapest part
of the house. What it all boils down to is skilled labour costs. The faster something is to be put up, the cheaper
it is. There are certain areas where material costs have an impact, but more of that later. This is where
strawbales come in, but like all things that seem too good to be true, there is a catch. To be effective,
strawbale must have owner involvement.
Strawbale is a labour intensive system. There is the
laying of the bales, pinning, stitching, connection of the top plate and tensioning. Next, a scratch coat of
render is applied, then one or two coats of render on top of that. Very labour intensive, very time consuming,
and if you are paying current rates of labour for it all, very expensive. The saving grace, and to my mind the
greatest advantage of over any other building material, is that any seven fingered, three handed, all thumbs
person can not only do it, but do it well and thoroughly enjoy themselves. It is a building technique that
compels people to do what comes naturally - build their own home. We all did it as children, so what stops us
now? It is a way of building that allows people to reclaim their birthright, to exercise their right to shelter,
and do it with the communal assistance of family and friends. It is done in such a way that it has come into its
own as a fast, simple, and efficient form of building. From children to the elderly, everyone is able to
contribute. A truly democratic form of construction.
Now, back to the the issue of the legs. The traditional way of
mounting the strawbale house is either on a concrete strip footing or on a raft slab. It is a pretty standard
procedure, particularly here in Western Australia, mainly because of the prevalence of brick and other
monolithic construction. Yet it does present problems for strawbale building. This is where material costs, as
mentioned earlier, come to the fore. Strip footings for strawbale have to be big. Not because of the weight,
but because the bales themselves are wide and need to be above ground level. This gives a footing that by
volume is almost twice that required for brick, yet carries less weight. If you then run that with an in situ
slab you have to take into account excavation, sand fill, compaction, a water proof membrane, reinforcement,
metal supports and chairs and so on. On top of this, concrete really needs to be laid in all one hit. It needs
skilled people onsite, and then takes much time and care in curing it properly. All this becomes intimidating
and expensive, and the money is paid up as one rather large lump sum, which is not really a very owner
builder friendly way of doing things. To add to the woes, concrete can heave around in heavy clay soils,
termite detection becomes very difficult and if the estimation that one in three house slabs in Perth is cracked
is accurate, that gives more cause for concern.
The leaves the option of a suspended floor on
stumps. The advantages of this system are many. Stumps can be timber, pre-cast concrete or concrete cast
in situ. It can be done in stages as money and time allows and does not call for great skills other than
getting things level and plumb. There is minimal site disturbance, especially if it slopes somewhat, and all
work can be done by hand. Because the floor is suspended, termite observation is good, access for services is
easy and flexible and under floor ventilation can now be taken advantage of. The choice of flooring material is
wide and varied and the bales are attached in a manner surprisingly similar to that involving strip footings.
The stump system works particularly well in clay, but it is just as at home in sand. If there is any settling of
stumps, solutions are easy to apply. The system is flexible, figuratively and literally.
Of course this works well if you are in an area where timber is reasonably cheap and available. Otherwise you
may find that the cost differential dwindles to the point where masonry footings gain a cost and practical
benefit. However it is worth keeping this approach in mind. Strawbale is open to many types of footing
systems, and if you are in a position where a stumped arrangement suits your budget or your house site
better, consider the benefits. You just might even improve the view!