60 Making traditional and modern windows
(un- jointed) abutment of outer- lining head to the
outer lining. Such joints are skew- nailed on their top
edges with 38mm oval nails and reinforced with glue
blocks across the joint on the inside of the box. The
alternative at (d) shows a 45° mitred edge – which
extends the head by 24mm to allow for the removal
of the pulley- stile groove in the outer lining above the
mitre, thereby creating a more solid edge to receive
the skew- nail fixing. Again, as indicated by broken
lines, glue blocks are used to reinforce these butt
joints.VENTILATION/WEATHER BEADS
Figure 4.8: As listed in the beginning of this chapter,
under component parts No.7, so- called ventila-
tion/weather beads can be found fitted to sills as an
alternative bottom staff- bead on existing boxframe
windows – and therefore might need to be repro-
duced upon replacement work. As seen in Figure
4.8, these extra deep beads are tongued into the sill
and, because of their depth and relative instability,
they are sometimes tongued at their ends into the
edges of the inner linings also. Their main function
for replacing the common staff bead on the sill –
apart from keeping out draughts – is to keep out
wind- driven rain (which I have seen brimming over
a common staff bead fixed to the sill of a boxframe
window in a coastal property). These deep beads are
also known to have a secondary function, whereby
a degree of ventilation at the meeting rails can be
achieved without causing a draught; this is done
by raising the lower sash and by keeping the deep
bottom- rail just below the top of the ventilation/
weather bead.OUTER- LINING ABUTMENTS
Figures 4.7(a)(b)(c)(d): Where the outer linings are
joined to the sill and to the outer- lining head, a few
variations can be found and these are highlighted
here. Figure 4.7(a) shows the most common recessed
abutment of an outer lining to a sill, when the 16mm
projection from the pulley stile is notched out to fit
over the sill. The alternative at (b) shows the notch
scalloped out slightly above the sill, to allow the
release of trapped rainwater. At the top end of the
boxframe, (c) shows the most common shoulder- line
Figure 4.6 Common joggle shapes drawn to scale at 60mm from the meeting rail; the broken lines indicate the 16mm
projection of the outer linings and are used as a guide to position the shape. Note that the 16mm guide also ensures
that joggles projecting above the meeting rails of bottom sashes have enough unshaped area to accommodate the sash-
cord grooves. The named shapes above are (f) ogee, (g) ovolo, (h) cavetto or scotia (i) quarter- round or quadrant (j)
bevel or splay.
(f) (g) (h) (i) (j)(a) (b)(c) (d)Figure 4.7 Part front elevational views of variations in
outer- lining abutments to the sill and outer- lining head:
(a) Commonly, the recessed outer- lining is notched over
the sill and fitted to the weathered slope; (b) The notched
projection can be scalloped out to within 3 or 4mm of the
pulley- stile cross- housing (as indicated) to inhibit rainwater
retention; (c) Commonly, at the top of the boxframe, the
outer- lining head is butt- jointed and skew- nailed to the
outer lining and reinforced (as indicated) with glue blocks;
(d) Alternatively, the join is partly mitred and glue- blocked.