Civil Engineering Reference
In-Depth Information
quite a square look if so desired. Timber,
known as a dropper, is to be fitted from the
underside of the top bale boxing basically
down to the top of the window buck.
Measure the distance from the underside of
the top bale boxing to the top of the window
buck and deduct 10 mm for clearance.
Depending on the desired shape of the
render over the window it may be necessary
to cut an angle onto the bottom front corner
of the dropper. Nail the dropper to the
underside of the top bale boxing, ensuring
that the droppers are fitted vertical both
ways. If the top bale boxing is slightly
twisted, which is often the case, it will result
in the dropper being tight to one side of the
boxing and slightly open on the other. The
droppers are to be fitted at 450 mm centres. Nail a nogging onto the underside of the top
boxing between each of the droppers. Skew nail through the side of the dropper into the
nogging (see Figure 5.9).
Figure 5.9
Droppers and nogging for dropped rolled
head secured to the underside of top boxing
Fitting wire netting to emulate the
finished wall shape required
Fix wire netting on the inside of the top
boxing and feed it through the 10 mm gap
between the droppers and the top of the
window a buck. The render will eventually be
added to the outside of this wire so it is
essential that this wire replicate the final shape
required over the window. Once this shape is
attained, with the wire fed over the top of the
window buck to the outside of the building,
secure the netting in the correct position by
stapling it to the droppers at the inside only
(see Figure 5.10).
Dropper
Window
buck
Window
stabilising
rail
Fixing the window stabilising rail
Once the wire is fixed to the droppers, a
window stabilising rail will be fixed to the
outside of the droppers and secured to the top
of the window buck. This rail will tie all the
droppers together, increasing their strength, and will reduce, if not remove, the possibility
of the window moving independently from the wall in the case of impact or strong
winds. Lay the window stabilising rail on top of the wire netting, thereby resting on the
Figure 5.10
Dropped rolled head for infill
construction
