Civil Engineering Reference
In-Depth Information
for casements, and vertical and
horizontal pivots, can still be seen
surviving in common use.
It has been estimated that UK
joinery manufacturers annually
produce around 1.5 million wood
windows
(155)
. Increasingly,
hardwoods such as European oak are
being specified rather than
softwoods, though European
redwood, which is comparatively
easy to treat with preservatives, is
still popular. The current standard for
wood windows is BS 644-1
(156)
.
Steel frames
Early cast iron windows were
sometimes used in domestic work,
but mostly in other building types.
However, one occasionally comes
across early rolled section windows.
Window frames in rolled steel
have been manufactured in very large
numbers since the interwar period,
and were popular in speculatively
built housing of this period, having
cockspurs and stays in bronze.
(Figure 4.4). They were standardised
in BS 990
(157)
. Projecting hinges were
introduced in the 1930s, the so-called
easy-clean hinges, making the
windows more useful in multi-storey
developments.
So far as replacement windows are
concerned, hot-rolled galvanised
steel sections do not lend themselves
well to the production of made-to-
measure windows. Also, they have
not been suitable (in domestic sizes)
for double glazing units, although
steel windows which can take wider
airspace double glazing units are now
available. Polyester powder factory-
applied coatings which overcome the
problems of site painting of
galvanised steel, and the regular
repainting that was needed, are now
the normal finish
(158)
.
Steel windows can be the
appropriate choice for replacement of
old steel frames in pre and postwar
houses and flats where the distinctive
slim frame appearance of the
windows must be kept. They are
available in matching sizes and
patterns to the old ones. Thermal
break frames are not widely
available. The current standard for
steel windows is BS 6510
(159)
.
Figure 4.3
Victorian double hung sash window frames
with a stone central mullion carrying a
decorative lintel in the same material
astragals, either broad (2 inches or
more) or narrow (down to half an
inch), depending on date and fashion,
or by wrought iron standards and stay
bars or transoms to which lead cames
were wired to take the small pieces of
glass (confusingly also known as
quarries). In later times, when glass
became more easily available in
larger sizes, fewer glazing bars were
needed.
The double hung sash window
began to replace the side hung
casement in popularity in late Stuart
times; from Georgian times to
Edwardian, and even later, it took
over as the preferred design of the
domestic window. Most were
counterbalanced with cords and
weights accommodated in the sash
boxes on the jambs; many continue to
give satisfactory service, though
cords need renewing from time to
time. Some, however, in the poorest
dwellings, have no such mechanisms,
and need to be opened by brute force
and held by wedge or pin.
After the 1939-45 war, the
manufacturers took the lead in
producing standard designs. The
English Joinery Manufacturers'
Association (EJMA) sections used
Figure 4.4
Galvanised steel window set directly into
the masonry with the widow-to-wall joint
having little protection from driving rain
Expanding foam
DPC
Thermal break
Sealant, preferably with a convex shape
Figure 4.5
A thermal break window
