How to maintain timber windows

As the eyes of a house and a key architectural feature, it’s important to maintain and repair original timber windows with care

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Windows contribute more to the look of an old house than any other single feature, and their varying historic styles are very closely aligned to the development of glass. Originally, only small panes could be made so early windows were divided by multiple, and quite wide, glazing bars.

As the 18th century progressed, the bars became thinner and more delicate and, in Victorian times, fewer in number as the manufacture of larger sheets of glass became possible. Despite their importance and beauty, old timber windows are often sadly neglected and can easily fall into disrepair.

In reality, many are precious and should be cared for in much the same way as antique furniture. Careful repair of your existing windows, as well as upgrading them to improve thermal efficiency, is generally more cost effective than opting for replacements and, at the same time, allows the character, history and value of the house to be maintained.

Brick building with grey sash windows

Material facts

  • The simplest type of window is the side-hinged casement. Offering better ventilation, as air can be allowed in at the top and bottom, the vertical sliding sash window is suspended on cords and counterbalanced by weights contained within boxes either side of the frame.
  • Timber The timber used to make Georgian, Victorian and Edwardian windows was slow grown and straight grained, so considerably more durable than that available today, and is one of the reasons so many old windows have survived.
  • Glass Whereas modern glass tends to appear flat and lifeless, old glass has ‘imperfections’. Rather than detracting from its appearance, these bubbles and ripples bring the glass to life, distorting reflections and causing it to sparkle in sunlight.

Tall timber window in period home

Warning signs

If left unchecked, window problems only get worse. Where possible, open the sash or casement and inspect it both inside and out to check for any problem areas, but take care when opening windows that are stuck or in particularly bad condition. Damp weather, overpainting and structural movement in the building can often cause windows to jam.

What to look for

  • Damaged or loose hinges
  • Broken sash cords
  • Rotten timber
  • Missing, loose or damaged putty
  • Cracked or peeling paintwork
  • Loose joints
  • Draughts and rattles
  • Difficulty opening
  • Cracked or broken glass

General repairs

Try to retain original timber and glass wherever possible. If necessary, new timber should be jointed with the old and the work done using matching materials and construction techniques on a like-for-like basis.


  • Re-glue joints using exterior-grade adhesive.
  • Use brass or stainless-steel screws.
  • If necessary, strengthen corners with metal brackets.
  • For complicated repairs employ a good joiner or a company that specialises in overhauling windows.
  • Apply beeswax or tallow to the edges of sashes to help them run.
  • Oil squeaking or stuck pulleys.
  • Check hinges, locks and catches.

White sash windows with red brick arches


Regular painting of windows is vital as poorly maintained and unprotected timber will rot and swell, resulting in joints failing, windows rattling or sticking and draughts.


  • Cut out rotten wood and make repairs.
  • Thoroughly sand down, clean and prepare all surfaces.
  • When stripping paint, use hot air guns with care as the heat easily cracks glass.
  • Re-putty glazing where necessary with linseed oil putty.
  • Use a good-quality paint system.
  • It’s important to properly prime all surfaces, including unseen edges, to prevent the timber swelling in damp weather.
  • Avoid painting over draught strips as this prevents them working effectively.

Sash cords

Although sash windows can initially seem complicated, replacing broken or frayed sash cords is a relatively easy task and the work can be done from inside the house, although it’s usually advisable to have a helper.


  • Purchase sash cord from a DIY store, checking the pulley size first.
  • See for a step-by-step guide to replacing a broken sash cord.
  • Always repair both cords.

Stone cottages with timber windows and doors


Draught seals, which are inconspicuous and installed around window edges, help cut draughts and prevent heat loss from within the home, while also reducing the entry of dirt and noise.


  • Choose the type and colour of draught seal carefully to ensure the best finish.
  • Avoid stick-on draught strips that may peel off.
  • Fit ‘brush’ strips to the edge, meeting rails and parting beads of sashes.
  • Employ a company that specialises in overhauling and draughtproofing windows.
  • Don’t draughtproof windows if secondary glazing is to be installed; the space between the unit and window must be ventilated to prevent condensation.

Secondary glazing

Although highly effective, draughtproofing doesn’t deal with the heat loss through the glass and its cold internal surface. Modern secondary glazing addresses both of these issues as well as helping to cut draughts, while being discreet and avoiding significant interference with the original window.


  • Consider a lift-out magnetic panel system, which may be removed in summer.
  • Choose between plastic or glass systems.
  • Where windows need to be opened, consider sliding secondary glazing.
  • Take careful measurements or templates when ordering as old windows are often not square.

Keeping warm

In addition to well-maintained windows, traditional internal wooden shutters can offer big energy-saving benefits in a period home, so they are worth overhauling and using if they are already in place. Thermally insulated or reflective roller blinds, fitted close to the glass within the window reveal, are almost equally as good, especially when used with heavy curtains. When fitting curtains, try to minimise any gaps between the wall and the fabric. The greatest benefits come if shutters, blinds and curtains are closed just before dusk so the warmth of the day is trapped in the room.