Health check
Expert Roger Hunt advises on maintaining windows
Sash and casement windows are among the most important architectural features of a house, and also play a vital role in letting in light and air. Sash windows are particularly efficient at providing ventilation as they work on convection, although, for this to happen, both top and bottom sashes should be open at the same time.
For any window to work effectively, regular maintenance is essential.
Maintenance checklist
● Note any peeling, bubbling or cracked paintwork and exposed timber
● Check for failing putty
● Investigate the cause of sticking, binding and rattling
● Look for rot, decay and loose joints
● Replace broken sash cords
● Ensure all latches and hinges are working correctly
● Consider draughtproofing windows
Questions and answers
Alison de Roeck, managing director of Retford-based Kierson Sash Window and Timber Restoration, answers some common questions about wooden windows and the best methods of repair and renovation.
Q What are the main considerations when working with wooden windows?
Retain as much of the existing windows as possible, including ironmongery, and think carefully about whether any work, such as complete paint stripping, is necessary. Remember that consent may be required if the house is listed or in a Conservation Area. Stop and think whether you have the skills required or if professional assistance is needed.
Q The window sill is rotten, so what should be done?
New sections can be spliced in to match. Use a quality resin to act as an expansion gap between existing timber and a new splice – however good a splice is, the two pieces of timber will always expand and contract at different rates. This can cause the coatings to weaken, crack and fail, leading to moisture penetration.
Q What is the best way to cure a window that is sticking?
The window will probably have expanded due to moisture ingress, which means that, when it dries out, it is likely to shrink and become rattly and draughty. A build-up of dirt can cause binding, so thoroughly clean the rebates and apply wax or silicone spray to lubricate. If that doesn’t work, lightly sand down areas of paint where sticking occurs. Never plane a window when it has been wet and is swollen. When painting, always coat all exposed wood. With sashes, don’t topcoat the sides that face into the box as this will clog the movement of the sash; a primer is all that is required.
Q One of the sash pulleys is jamming; how can it be made to run properly?
Grasp the cord above the sash and pull it down to check the cord and weights are free. Remove any build-up of paint with a chisel, wire brush or carefully placed paint remover. Grease the wheel with a 3-in-1 oil, or something such as WD40, and spin it back and forth until it eases.
Q How can glazing putty that is cracked and breaking away be fixed?
Traditional linseed oil putty is notoriously difficult to repair; it will not bind to itself so new putty won’t fill in the gaps. It is always a good idea to leave as much of the original as possible as it is very difficult to remove sound putty without damaging the glass. Also, in many cases, old putty contains asbestos. Using a modern glazing alternative, such as an elastic glazing compound, is a good solution. It will go over existing putty and create a watertight, slightly rubberised bond. Modern glazing ‘putties’ have the advantage that they can usually be painted over in 24 hours; linseed oil putty requires a minimum of six weeks before painting.
Q Are sash cords easily replaced?
Everything on a sash window is designed to come apart so, with patience, anyone can re-cord a sash window. Guides are readily available on the internet. However, it is quite a mucky job as a lot of old paint will probably have to be scraped off before refitting sections. It is more than likely that the wooden trims, the staff bead and parting bead will be damaged in the process, so these will need to be sourced and cut to the appropriate size. It is worth considering installing draughtproofing at the same time.
Q What can be done about a sash that won’t stay open?
This is a weight issue. The window will need to be taken apart, weights removed and lead added as required to ‘balance’ the sash. It must then be re-corded and everything refitted.
Q Can a rattling sash be cured?
Yes. The simple method is to check the staff bead is tightly fitted. This will push the two sashes together.
Alternatively, get the windows draught-proofed to fill the gaps.
Q How can loose joints be fixed?
Remove the window, take the loose sections apart, clean away any paint and old glues, and use a ‘fast grab’ timber adhesive. Then, protecting the wood, use a clamp or strap around the window or something heavy to push against the joint while the glue takes.
Q Should old paint be stripped off?
The build-up of paint is part of the history of the window and older paint has the advantage of containing more protective ingredients than modern paint. Stripping can cause damage to the timber, joints and glass, while removing lead paint has safety issues. If stripping is carried out, avoid using a heat gun as this may crack the glass. Where paint must be removed, a chemical peel may be the solution.