How to paint wooden window frames.

A wooden window has several parts that need different treatment: the frame, glass, glazing material, seals, hinges and opening edges. Paint can protect sound timber, but it will not put rotten wood or loose glazing right. Check the condition first so the work is more than a fresh coat over an existing problem.

Inspect before scraping

• Probe suspicious soft areas gently; do not paint over rot.
• Look for open joints, cracked putty, failed sealant and water staining.
• Check that opening sections move and close correctly.
• Identify drainage slots and keep them clear.
• Older paint may contain lead. Get competent advice before scraping or sanding if it is suspected.

Soft timber, open joints and loose glazing need proper assessment. A joiner or glazier may need to repair the window before it is painted. Filling over rot or painting loose putty does not make the frame sound or restore the weather seal.

Choose the weather window

Check the product’s permitted surface condition, temperature and humidity before starting. Most decorating systems need dry timber and enough suitable weather for the coats to dry. Think about rain or dew after you finish, not just while the brush is in your hand. Strong direct sun can also make paint dry too quickly. If conditions fall outside the instructions, postpone the work rather than painting to a deadline.

Preparation

1. 1
   Clean.

   Remove grime, algae and chalking with methods suitable for the existing coating.

2. 2
   Remove failed paint.

   Scrape loose edges without damaging sound wood or glass. Feather boundaries rather than leaving sharp ridges.

3. 3
   Repair the timber and glazing.

   Have failed timber or glazing repaired with suitable materials. Different putties and sealants have different painting intervals; some need to be painted after a skin has formed, while others have a stated curing period. Check compatibility and the permitted painting window before coating the repair.

4. 4
   Sand and remove dust.

   Where the coating system requires it, prepare sound gloss and smooth repairs. Do not sand suspected lead paint without appropriate assessment and controls.

5. 5
   Prime bare wood.

   Pay attention to end grain and repaired areas. Follow the window and paint system requirements.

6. 6
   Undercoat and finish.

   Use an exterior-rated system, keeping coats thin at joints and moving edges.

How neat should the glass line be?

Traditional putty glazing may require paint to overlap onto the glass to protect the putty-to-glass edge. The amount and timing depend on the glazing product and coating system. Modern beads, sealed units and sealants have different details, and some sealants cannot be painted. Follow the glazing and paint instructions rather than taking paint onto every pane by the same amount.

Avoid painting the window shut

Plan how the window will open and dry before starting. Keep paint out of hinges, catches, seals and drainage openings. Avoid heavy build-up where painted surfaces meet, and do not close them tightly until the coating is dry enough under the manufacturer’s instructions. Touch-dry paint can still stick to another surface. For work at height, use suitable access equipment; do not lean out of a window or reach sideways from an unstable ladder.

Interior window frames

Condensation can damage paint on the inside too. Clean the frame, repair failed coating and investigate persistent moisture rather than sealing over it. Use a finish compatible with the frame material, existing coating and any paintable sealants. The guide to painting over gloss explains preparation for sound glossy coatings. Leave rubber seals and operating hardware free of paint.

Maintenance beats wholesale stripping

Check exterior woodwork regularly and after noticing leaks or coating damage, paying attention to lower rails, sill ends and areas that stay damp. Follow any inspection interval given by the window or coating manufacturer. Dealing with a small split while the timber is sound can prevent a larger repair. Clean gently, let the wood meet the coating’s moisture requirements and keep a record of the products and colour used for future maintenance.

Window-painting FAQs