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t h e b u i l d i n g c o n s e r v a t i o n d i r e c t o r y 2 0 1 2
3.3
has failed will spread beneath the paint
by electrochemical reaction as the areas
underneath the paint have less access to
oxygen and are therefore differently charged.
The repair of inter-war steel windows may
involve some or all of the following works:
In situ repairs
Degreasing and removal of debris and
dust
This should be carried out as part of the
regular maintenance of steel windows and
in preparation for any repairs. Degreasing
can be carried out using the same methods
as for wrought iron windows (see above). The
removal of debris and dust can be assisted by
careful brushing and vacuum cleaning.
Preparation
All hardware (except
hinges) may have to be removed
and glazing masked or temporarily
removed, depending on condition.
Surface preparation
In situ stripping
back of paint and rust to healthy metal may
be carried out using a variety of tools such
as needle guns, disc sanders, hand scrapers,
wire brushes and sandpaper. Grit blasting
is a more rigorous alternative but extra care
should be taken as the blasting medium can
collect in crevices where it holds moisture and
can cause rust or distortion through build
up. Health and safety considerations relevant
to the removal of lead-based paint should be
observed carefully. Paint samples should be
taken to assist with the identification of the
original colour scheme. The extent of stripping
will depend on the condition of the window,
sometimes it is enough to rub down, prime
exposed metal and repaint.
Priming
Stripped metal should be primed
with a rust inhibitor immediately to avoid the
re-formation of rust on exposed surfaces.
Realignment
Once stripped of paint
and/or cleaned of rust, window frames
and casements can be realigned, adjusted
and eased so that all operable windows are
returned to good working order. Loss of
alignment may be the result of rust behind
the frames causing metal expansion and/or
paint and debris build-up, both of which can
cause distortion. Poor maintenance and user-
pressure on uncooperative windows may be
contributory factors.
Assessment
Condition and the extent of
necessary repairs are assessed at this stage
and a decision made on whether to carry
out in situ repairs or to remove the window
for repairs at a workshop or to replace it.
A detailed schedule of window repairs may
include all three possibilities as the condition
of individual windows in a building may vary.
Metal repair
Even when metal frames
appear to be in very poor condition, often
very little metal needs to be replaced. In situ
repairs may involve the use of metal fillers.
Piecing in of new metal is usually best carried
out using brazing (rather than welding)
because of its versatility and reduced fire risk.
Replacing even small amounts of metal would
require material from suitable reclaimed
windows, or adjusting currently available steel
window profiles.
Hardware repair
Operators, hinges
and locks should be cleaned using a fine
wire wheel. Operators may have small
lubrication holes and these are sometimes
painted over. Mechanisms may have seized
and can be repaired by flushing out the gears,
then freeing the works by oiling. Missing
or broken hardware and hinges should be
replaced, perhaps using matching parts from
salvaged windows. Alternatively, readily
available parts can be adapted although this
may necessitate filling existing screw holes
with steel epoxy or plug welds and tapping
in new screw holes. If the hardware is a
highly significant element of the historic
window, reproductions can be made.
Re-glazing and weatherproofing
Depending on the degree of distortion,
de-glazing and re-glazing may be necessary.
Cracked or broken glass and failing putty
should be replaced. Re-placement putty should
be appropriate to the use and be allowed
to harden for approximately two weeks or
longer before it is painted to match the colour
of the fenestration. Silicone sealant is not
aesthetically appropriate for conservation
work. Weather-stripping using silicone beads
can also be undertaken.
Painting
Similar considerations to
painting wrought iron apply (see above).
Inter-war steel windows were used to imitate Tudor glazing
at The Fox public house, Bix, Oxfordshire, 1936
1930s terrace, Muswell Hill, London