Civil Engineering Reference
In-Depth Information
Construction-grade bales
above conditions apply equally to all bales,
whether they are being used for loadbearing
or infill.
As more and more buildings are being
constructed out of straw, this has given us
the opportunity to really find out which are
the best bales for building. 'Construction
grade' bales can be ordered from particular
wholesalers who are familiar with the above
requirements. These are becoming more
readily available, and suppliers can be
found listed under Agricultural Merchants
in directories. These bales are often made
using a modern baling machine which
creates very dense, uniform bales that are
delivered to site in packaged bundles with 21
on a pallet. Their dimensions are 42” x 14” x
18” (1,050mm x 355mm x 450mm).
Bale size
It is important to know the size of bales you
will be using before finalising the dimensions
of foundations, wallplate, roofplate, etc.
Bales can vary a lot in length, from supplier
to supplier and within each load, since
whether or not the straw is picked up unifor-
mly as it is baled depends on the skill of the
tractor driver and the evenness of the field.
In practice, relying on the farmer to tell you
the length of bales is not a good option, as
you are unlikely to get an accurate picture.
Besides which, you will need to satisfy
yourself that the straw is baled dry, and
kept dry while in transit and storage. It is
far better to look at the bales once they're
harvested and determine the average length
of bale at the same time. The best way of
doing this is to lay ten trimmed bales (see
page 75) tightly end to end. Measure the
whole and divide by ten to find the average.
(It is almost impossible to measure the
length of one bale accurately). However, if
you find that your delivered bales are not
the same length as you expected, this is not
an insurmountable problem. It may mean
a little more work in shaping the bales to
fit, but this is straightforward and not too
time-consuming.
Knowing what your bale dimensions and
properties are makes a big difference when
you are designing and building. If using
pre-compression methods, these bales
are so dense that they will each compress
by no more than 10mm (
3⁄8
”), so you can
also predict with greater accuracy what the
settlement of the walls will be and factor
that into the building process. Although
it is still possible to use other types of
bales, you must remember that there may
be greater settlement on the walls, and
allow for up to 25mm (1”) per bale if using
pre-compression methods or a reasonably
heavy roof.
It is possible to harvest and store straw
in bales of uniform length and moisture
content, ready for the building market each
season, and we would expect wholesalers
to start doing this as demand increases.
As long as the bales are kept dry and well
ventilated, they can be stored for a long
time before using. As demand increases, so
will the reliability and availability of supply.
