Sash Windows
We have included the article below - written by David Wrightson MCD BArch
RIBA IHBC DipCons (IoAAS) - which is a clear and highly informative, dealing
in a practical way with the various problems encountered by sash windows.
"The sliding sash window has been ij existence for over three centuries
and the operating principle has remained almost unchanged throughout that
time. Some of the components, such as the staff bead and the parting bead
can still be bought off-the-shelf.
Sash windows are made in such a way that they can be easily dismantled for repair, or for replacing broken sash cords. Many people fail to realise this when they encounter problems, and think that the only sensible option is replacement - in some cases, with plastic ones - which is simply not the case. Some timber windows have lasted for centuries, because they have been properly maintained and painted regularly. Plastic windows (PVCu) by comparison, cannot be dismantled and repaired so easily, and the components cannot be made by any competent joiner. They have not been tested by time, and there are already signs of failure. Plastic windows which usually come with double glazed scaled units, are generally only guaranteed for ten years, and are expensive to replace if they fail. What is more, they are constructed in such a way that they cannot reproduce the mouldings and details characteristic of traditional timber windows. They are - almost without a single exception - completely unsuitable for use in any historic context.
The problems most likely to be encountered with traditional timber sashes are:
- sticking
- failure of joints
- failure of putty
- wet rot
- rattling, and
- draughts.
The first four of these are the result of poor maintenance and the lack of a good protective coat of paint.
MAINTENANCE
You should aim to inspect your windows every year (and, ideally, get a qualified professional to inspect the whole house every four or five years). Typical sash window problems likely to be encountered include:
* Cracked and flaking paintwork: the outside of the windows should be
repainted at intervals of five to eight years, normally.
* Sticking windows: usually the result of either careless replacement of
staff bead, following repair or re-cording, which is easily remedied, or
a build up of paint which needs to be removed.
* Failed putty and broken glass panes: these are relatively easy to replace.
* Broken cords: in former times people re-corded their own windows - the
cords and sash weights were available at any ironmongers (and still are
at some).
* Timber decay, particularly to the bottom rail: fillers are invaluable
for minor decay and surface imperfections where the strength of the timber
is unaffected; loose corner joints can be strengthened by means of corner
brackets which can then be painted over; and more significant repairs can
be carried out by any competent joiner.
PAINTING
Preparation
Carry out any repairs, such as rot treatment, re-glazing or re-cording. Then remove all sash furniture (window fasteners and sash lifts or handles), and wash down the previous paintwork with sugar soap, soda or detergent, and rinse off. Rub down with pumice stone, pumice block or sandpaper and brush away all dirt and grit. If your windows were painted with a lead based paint, you must use a wet or damp process to prevent the release of toxic dust into the air. Use a hot air paint stripper only if necessary (if a build up of paint is causing sticking or completely obscuring mouldings). Protect the glass by using a suitable shield, and use a shaped shavehook to strip mouldings. It is recommended that a respirator should be worn when burning off old lead paint, due nto the toxic fumes. Never use a blowlamp or propane torch - they have been responsible for too many fires in the past. Next, spot prime any areas of exposed bare wood. If you have taken out the sashes for repair or re-cording you will notice the edges of the stiles are unpainted, leave them this way; that's how they're meant to be.
Paints and equipment
Provide yourself with a safe ladder, protective dustsheets, appropriately
sized brushes, a paint kettle, and the correct type of paint. In most cases
you will find it easiest to use a one-inch brush for the glazing bars, and
a larger brush for the other areas. Professionals tend to use the largest
brush they can in any given circumstances, but this requires experience."
The above article is reproduced from The Building Conservation Directory,
2001
Author
DAVID WRIGHTSON MCD BArch RIBA IHBC DipCons (IoAAS) is a partner in Acanthus
LW Architects, Chiswick, London