Window putty repairs: how to do it and what replacing putty costs

Window putty seals the joint between the glass and sash in a traditionally glazed window. The outer putty is shaped to direct water away from the joint. A traditional timber window also has bedding putty beneath the glass and glazing pins that hold the pane in place.

Putty repair therefore involves more than filling a visible crack. Check whether the damage is limited to the outer putty or whether the glass fixing and timber also need attention. Windows with glazing beads and other sealing systems should be assessed according to their construction.

For a local repair, remove loose putty, clean the area, pretreat exposed timber and apply new putty. The steps below apply to a traditionally puttied timber window with secure glass and a sound sash.

1. Check the damage. Look for cracked glass, loose fitting and damaged timber. Stop the simple repair if the glass needs removing or the sash needs repairing.
2. Remove loose putty. Work carefully along the edge of the glass. Leave firmly bonded, compatible putty in place where it can form part of the repair.
3. Clean and pretreat. Brush away dust and prepare exposed timber according to your chosen putty and paint system.
4. Apply and shape the putty. Fill the joint without leaving gaps and smooth it with a putty knife. Check the contact with the glass and the corners.
5. Plan the painting. Follow the product instructions for when and how the putty can be painted. No fixed number of waiting days applies to every product.

Anza's guide to applying window putty shows preparation and application. A larger restoration also requires checking the bedding and fixing of the glass; local repair steps do not replace that work.

Can you repair window putty in place without removing the sash?

A small repair may be possible in place if you can safely reach all the damage and the glass is secure. If the pane needs removing, the underside of the sash needs repairing or several sides need work, the sash may need taking down. Assess access before choosing a method.

Linseed oil putty is used in traditional timber windows, but the choice needs to suit the glazing, timber treatment and paint. The window's age alone does not determine which putty is suitable.

Check the following before choosing a product:

Byggfabriken's window guide distinguishes between putty repair and a larger restoration of the sash, fittings and glass. Match the work to the damage instead of replacing everything out of habit.

How long should window putty dry before painting?

The overpainting time depends on the putty, paint and working conditions. Check the instructions for that combination; some systems allow early painting while others need a longer wait. Putty that is dry to the touch is not automatically ready for any paint.

NLL quotes for replacing putty and full window restoration after assessing the scope. A general per-window price for painting with repairs is not a price for putty work alone or complete restoration.

State how many windows and sashes are involved, where the putty has come loose and whether the glass or timber is damaged. Ask for labour and materials to be separated, and for the quote to specify whether painting, transport or other tasks are included.

Read about window restoration by NLL for that service. The cost calculator shows indicative prices for the work available to select there; it does not replace an assessment of putty replacement or full restoration.

Get help when the glass is loose, the sash has rot, access is unsafe or the window has a construction you are unfamiliar with. Send close-up photos so the damage can be assessed before the scope is decided.

A small, accessible area of damaged outer putty is a different task from reglazing an entire sash. If painting is also needed, read about painting and repairing windows and doors. For a more extensive assessment of the window, restoration is the appropriate service to discuss.