Civil Engineering Reference
In-Depth Information
The process is very simple. First, as you are no doubt aware, earthen render, while
being tough and aesthetically appealing, is no match for the constant banging of little feet
swinging aimlessly in the breeze while sitting on a window seat. I suggest that window
seats be covered in timber to overcome this problem. You will need a frame onto which
the seat will be fixed, and to enable the compression of the bales below the window. Build
bale boxing as per the construction of the bottom bale boxing but without the flat
noggings. Fit the structural ply to the face of the bale boxing and then position this on
top of the bales below the window with the ply against the straw bales. Wrap the polyester
compression strapping around the bottom bale boxing and the window sill boxing,
thereby encasing the bales, then compress the bales over three days as per normal. Once
compression is complete, fit 70 × 35 timber vertically between the sill bale boxing and the
bottom bale boxing. Fit these vertical timbers at 450 mm centres on both the inside and
outside of the building. It will be necessary to trim the bales where the vertical timbers
are to be fitted to allow the timber to be fitted flush with the face of the sill bale boxing
and the bottom bale boxing.
Preparation of the timber-lined window seat
The window sill boxing is unlikely to be flat and level so you will need to fit packers to it
to provide correct framing for support of the timber lining. To reduce movement at the
junction of the seat timber and the window sill, it will be necessary to fit noggings along
the length of the window. The noggings are to support both the inner edge of the window
sill and the timber of the window seat (see
Figure 5.12).
Trim the straw between the vertical
timbers back approximately 20 mm below
the line of the timber to allow sufficient
depth for render to be applied to the
straw and the timber lining to cover over
the render. Ideally apply two coats of
render to the straw prior to fitting the
lining timber, as this will prevent airflow
through the bales as well as create a
barrier against vermin penetration. Note:
the second coat of render should be no
more than 10 mm thick, thereby reducing
the likelihood of cracking.
Figure 5.12
Timber framing for a timber-lined window seat
Cracking between render and timber
Without treatment the junction of render to timber will crack. This can be reduced, if not
negated, by applying a mixture of glue and coarse sand to the timber surfaces. I have found
that Bondcrete® and PVA wood glue both work well when mixed with the sand. If you are
trying to avoid the use of commercial adhesives you could make up a cooked flour and
water adhesive, however if this gets too wet during construction it is likely to come away
from the timber. Apply the sand-glue mix to the surface of timber that is going to be
covered with render, including the sides of the vertical timbers beneath the window seat.
