How to paint exterior window frames

Video by Charlie DIYte. This walk-through is based on the video "Can You Repaint Windows Without Priming?" from Charlie DIYte, who tests whether you really need to prime before repainting and what happens when you skip that step. Worth watching before you buy your materials — the section on preparation and what paint products actually work without a separate primer coat is particularly useful.

1. Check what you are actually dealing with

Before you buy a single tin of paint, have a proper look at the frames. Softwood timber frames are the most common in older East Kent houses — Victorian terraces, 1930s semis, post-war builds. Run a fingernail along the surface. If the paint is firm and just looks dull or crazed, you can work over it. If it is lifting, soft, or peeling away in sheets, those sections need stripping back to bare wood.

Check for rot too, especially at the bottom corners and along any horizontal sills where water sits. Press with a screwdriver or bradawl — if it goes in easily, the timber is soft and needs treating or replacing before you paint. Painting over rot just seals the problem in and you will be back out there within a year.

2. Strip back, sand, and clean the surface

Loose or flaking paint has to come off. A heat gun on a low setting works well for softwood — keep it moving so you do not scorch the timber. A shave hook or flat scraper gets the softened paint off neatly. For areas where the paint is sound but rough, a thorough sand with 80-grit followed by 120-grit is enough to key the surface and feather back any edges.

Once stripped and sanded, wipe everything down with a damp cloth and let it dry fully. Any dust, grease, or cobwebs left on the surface will show under the paint. That said, do not be tempted to skip this step on a dry warm day — the surface needs to be genuinely clean, not just dry-looking.

3. Treat any bare wood and fill gaps

Any area you have sanded back to bare timber needs a wood primer or a dual-purpose primer-undercoat before the topcoat goes on. This is the step that determines how long the job lasts. Bare softwood is thirsty — it will soak up the topcoat unevenly and leave a patchy, porous finish if you try to skip straight to the colour.

Fill any cracks, splits, or nail holes with an exterior-grade flexible filler or linseed oil putty. Standard interior filler is not flexible enough for outside use and will crack when the timber moves with temperature changes. Once dry, sand the filler flush and give bare patches a second coat of primer if needed before moving on.

4. Mask up the glass and ironmongery

Take the time to mask the glass properly with low-tack tape. Aim to leave about 2 mm of paint onto the glass around the perimeter — this creates a seal that stops moisture creeping under the frame at the edge. Remove any handles, stays, or hinges you can easily unscrew; what you cannot remove, mask off. Paint on ironmongery looks scruffy and is a pain to remove later.

It is also worth checking the rebates — the inner edges where the sash or casement sits when closed. These get missed all the time and the bare wood there is where water tends to get in first. A quick coat of primer in the rebates goes a long way.

5. Apply undercoat, then topcoat

If you have bare wood areas that are now primed, apply an undercoat over the whole frame before the topcoat. This builds body, covers any variation in the primer, and gives the final coat something consistent to go onto. On frames that are already sound and just being refreshed over existing paint, a light sand and a clean may be enough to go straight to topcoat — but read the tin guidance on your chosen product first.

For the topcoat, use a proper exterior gloss or satin finish rated for exterior timber. Apply with a good quality 38 mm or 50 mm brush in long, even strokes following the grain. Work from the top of the frame down, and do not overload the brush — thin coats dry harder and last longer than one thick coat. Two topcoats are always better than one, with a light 180-grit sand between them once the first is fully dry.

6. Remove tape and leave to cure

Pull the masking tape off before the paint is fully hard — usually after a few hours while it is still slightly flexible. If you leave tape on until the paint has gone completely solid it can lift the edges cleanly along the tape line and you will need to touch up. Run a blade along the tape edge first if you are unsure.

Leave the windows open or propped while the paint cures — at least 24 hours before closing them, longer in cool or damp weather. Fresh exterior gloss takes longer to harden fully than it does to dry to touch. Closing a window too soon can leave a mark in the paint where the frame meets the opening, and on a freshly painted sash you risk the two surfaces bonding together. Mind you, in October in Kent that is a real possibility even if you wait a day.

When to call a handyman

Call Richard if the frames have significant rot that needs cutting out and splicing, if the windows are large sash windows that need careful work to stay operational, or if the job needs scaffolding or a tall ladder on an upper floor. A full repaint of all the windows on a house is also the kind of job that is much quicker with someone who has done a few hundred of them — the prep alone on a terrace house can take a full day.