To paint window frames, wash them down, sand back any flaking paint, fill and prime bare timber, then apply two thin coats of exterior-grade paint. Work in dry weather above 10°C and out of direct sun. uPVC needs an adhesion primer or a paint made for plastic.
You can, with the right primer and paint, but it is worth asking why you want to. uPVC frames need no painting and no oiling, and that is the point of the material. Painting one puts a coating on a surface designed to weather without one.
The practical problem is adhesion. uPVC is smooth and non-porous, and ordinary exterior paint has nothing to key into, so it flakes at the edges within a season or two. Paints made for plastic, or an adhesion primer underneath a normal topcoat, are what make the difference.
There is a second issue people meet later. Painting a uPVC frame can affect the manufacturer's warranty, and it makes the frame harder to recycle at end of life. Check the terms that came with your windows before you open a tin, and ask the manufacturer if you are not sure.
A dark colour on a south-facing uPVC frame is the case to think hardest about. Dark paint absorbs more heat than the white surface underneath was specified for, and heat is what moves a plastic frame. Lighter shades are the safer choice.
Match the paint to the material and to the position. Exterior faces need a coating that handles UV and rain. Interior faces can take an ordinary trim paint.
Water-based exterior paints have caught up with oil-based ones for durability and they stay flexible for longer, which matters on timber that moves with the seasons. Oil-based gloss still gives the hardest finish and the traditional look on a period window.
Preparation is most of the job. Wash the frames with sugar soap to get the grime and any residue off, rinse them, and let them dry properly. Paint applied over a greasy frame fails at the edges no matter what it cost.
Then deal with what the washing reveals. Scrape back any flaking or blistered paint to a firm edge, sand the edges so the transition is not a visible ridge, and probe any soft timber with a bradawl. Rot gets cut out and filled before anything gets painted over it.
Fill cracks and open joints with an exterior wood filler, and sand the repairs flush once they have cured. Prime every patch of bare timber, including the fillers, because bare wood drinks the topcoat and leaves a dull patch.
Mask the glass last, and leave a two millimetre margin of glass showing along the putty line. That margin is deliberate. The paint has to lap onto the glass to seal the top edge of the putty, and masking tight to the frame leaves that edge open to water.
Work in the same order on every window: the opening sash first, then the frame, then the cill. Start with the parts you would otherwise lean against, and you will not find a handprint in wet paint on the piece you did first.
Two thin coats beat one thick coat on a vertical surface. Thick paint sags, takes days to cure properly through, and hides the brush marks it is about to develop. Thin it slightly if it is dragging rather than loading more onto the brush.
Pull the masking tape while the second coat is still soft. Tape removed after the paint has skinned takes a ragged edge with it, and on a glass line that shows from both sides of the window.
Repainting is the same job with one extra decision at the start: keep the existing finish or strip it. Sound paint that is firmly attached can stay. Sand it back to a key, spot-prime any bare patches, and go over the top.
Strip it when the build-up is thick enough to stop the sash closing cleanly, when the paint is flaking over most of the surface, or when you are changing from oil-based to water-based. A heat gun and a scraper handle the bulk, and a chemical stripper gets into the mouldings.
If the window was painted before 1992 in the UK, treat the old coating as possible lead paint. Do not sand it dry and do not burn it off. Wet-sand it or use a stripper, and keep the dust down.
Count the coats before you commit. Three or four thin coats on a well-prepared frame will outlast a strip and rebuild on a frame you did not prepare properly, and a full strip on a multi-pane window is a weekend rather than an afternoon.
Weather decides everything outdoors. Aim for a dry spell above 10°C with no rain forecast for 24 hours, and avoid direct sun on the face you are painting. Sun skins the surface before the coat underneath has flowed out, which is what leaves brush marks.
UK painting season runs roughly April to September. Later than that and overnight temperatures drop below what most exterior paints cure at, even when the afternoon feels warm. Morning dew on a frame you painted at four o'clock will spoil the finish.
Follow the sun around the house rather than working one elevation to completion. Paint the east face in the afternoon and the west face in the morning, and you keep every coat out of direct heat.
Check the sealant joint around the frame while you have the ladder up. If it has cracked or lifted, it needs redoing before the paint goes on, and resealing windows covers that job.
Paint protects sound timber. It does nothing for timber that has stopped being sound, and a fresh coat over a rotten frame hides the problem for one more year. Four cases where the money goes somewhere else:
If you are at that point on most of the windows, compare what repeat painting costs in weekends against a replacement. Our timber windows are made in slow-growing Scandinavian pine, and when to replace your windows covers the signs that settle it.
Good luck with the job. Whatever you paint, do the preparation properly, because that is the part that decides whether you are back up the ladder in three years or in ten.
No. The aluminium face on an alu-clad window is a factory finish that needs no painting, and the maintenance routine is washing the frame and sash a couple of times a year with pH neutral soap and lukewarm water. That is the whole job.
Painting over it means stripping or keying a coating that is performing, then maintaining a new one that will not last as long. If the colour is wrong, the honest answer is that the frame is the wrong colour rather than that it needs painting.
Our alu-clad windows pair that exterior with timber inside, so the inside face takes paint or stain in the normal way. It is only the outside that should be left alone.
