Civil Engineering Reference
In-Depth Information
Chapter 8
ROOF AND FITTINGS
Wallplate or roofplate
affords compression of the straw walls at
an even rate around the whole building.
This is a continuous, rigid, perimeter plate
that sits on top of the strawbale walls at
each floor level and under the roof. It is usu-
ally made beforehand in sections for ease
of installation, and fixed securely together
once in position. The size of timbers used
will depend on the loading it will carry
from above, the span of the building, etc.
They would never be less than 100mm x
50mm (4” x 2”) in cross section, and can
be as much as 225mm x 50mm (9” x 2”)
or even be made out of TJI, FJI or Trus joist.
To give this plate structural strength and
make it into a box beam it will need to have
a strip of board, preferably 18mm SmartPly
(because it doesn't use formaldehyde) glued
and screwed to the bottom and top. The
top plate is added only once the wallplate/
roofplate is in position and hazel pins have
been fixed down into the bales.
• It provides a fixing point for strapping
or anchors to the foundation in order
to hold the roof structure down against
wind uplift, and the fixing point for the
rafters themselves.
The foundations or baseplate can provide
a good template for the wallplate, and it's
sensible to construct one on top of the other
and place the wallplate to one side for use
later. Don't worry if your straw walls don't
seem to be quite level once you've finished
building - the wallplate will sit on the high
points first, compress those, and then
compress the rest of the walls evenly.
Make the wallplate sections as large as
physically manageable; a well-coordinated
team of volunteers can move surprisingly
large and heavy objects with ease. The
fewer joints you have in this perimeter
plate the better, as it will be stronger. Once
the wallplate is in position, any distortion
in shape that the walls have suffered as a
result of their flexibility, or bale frenzy (over-
excitement when working with straw!),
can be adjusted. The weight of the plate
immediately gives the walls greater stability.
The wallplate or roofplate performs various
functions:
• It evenly distributes the load of the roof
or floor across the width of the wall, and
around the perimeter of the building.
• It provides a rigid perimeter plate that
