Civil Engineering Reference
In-Depth Information
having to increase the strength of the top bale boxing. When using roof trusses, there is
little that can be done to vary the load over the windows. However if the roof and ceiling
are to be assembled piece by piece, known as stick framing, much can be done to reduce
the load over these openings, thereby increasing the width capacity of the top bale
boxing. It is not that the total weight of the roof and ceiling are necessarily reduced, but
that the weight distribution is changed.
Window and door bucks
Windows and doors are generally fitted inside a timber frame that is fixed within the
straw bale wall. These frames are known as bucks. Window and door bucks can be built
by a variety of different methods, ranging from the construction of a frame that is then
covered in plywood, to solid timber. It would generally appear that in Australia most
people have chosen to use solid timber. It has been suggested that there are cost savings
associated with the use of plywood, however my experience would not support this claim.
Apart from the magic dollar, I have other reservations regarding the use of plywood.
Plywood is manufactured with the use of a lot of adhesive, and while I am not paranoid
about the release of fumes, neither do I invite it into my homes unnecessarily.
Much of the plywood is imported from Asia and is likely to contain timber from
native forests rather than plantation-grown material. I personally will avoid the use of
timber from old growth forests and rainforest. When designing the construction system
and its components for any house, we go to a lot of trouble to avoid the use of steel, and
timber from old growth or rainforests. I can see no valid reason to introduce a product
that is likely to draw material from these sources, to say nothing of the energy used to
produce and transport the plywood. The use of plantation pine, being a renewable
resource, is ecologically responsible. Sadly, many owner-builders are more concerned
with the saving a dollar rather than saving the environment. This is one time that
everyone wins, for not only is plantation pine ecologically responsible, but it's cheaper
than most other alternatives.
External doors
External doors can be hung on the posts between the floor and roof supports. They can
be hinged to uprights that are fixed to the floor and to the top boxing or pitching beam.
They will be fixed at the floor by nailing them to the bottom bale boxing. Alternatively,
doors can be hung inside a simple door buck. It is also possible for the door to be hung
inside a separate door jamb which is fitted into the door buck or between door posts that
are secured to the floor and top boxing. If the door is to be hinged directly into the door
buck or onto door posts the timber will need to be a stronger than 90 × 45 pine to
provide a stable fixing point for the door. When the door is hinged directly to the door
buck, the door buck effectively becomes a door jamb. I have used 90 × 75, 140 × 45,
190 × 45 as door bucks and door posts and found them all to be successful.
When deciding what size timber to use on your house you will have to give
consideration to the height of the door posts, the position of the door, the weight that
might be carried by the door posts and the final appearance that you are after. In some
