Why is my gloss paint peeling off?

Peeling is the one paint fault where the evidence survives. The flake that comes off carries the answer on its underside, and reading it takes a few seconds and saves stripping a whole door for no reason. This guide is about diagnosis first, because the repair is completely different in each case.

Step by step

1. Lift a loose flake and turn it over.Use a filling knife at the edge of the peeling area and take off a piece large enough to see. What is on the back of it is the diagnosis, and everything below follows from it.
2. Shiny and clean on the back means adhesion failure.The gloss was applied over an existing sound but glossy surface that was not abraded, or over one that still had polish, wax, grease or hand oils on it. Nothing was wrong with the paint. It simply had nothing to grip.
3. Old paint stuck to the back means the failure is below you.Your coat is holding on perfectly to a layer that has itself let go. Repainting the patch achieves nothing, because the weak layer is still there. This is common on woodwork with many decades of coats on it.
4. Bare or grey timber on the back means moisture.Water reached the wood from behind or through an unsealed edge and pushed the film off. Sills, the bottom rail of an external door and the back edges of window frames are where this happens. Painting over it without finding the water simply repeats the fault.
5. Powder on the back means a chalky substrate.The gloss stuck to a layer of loose material rather than to the surface underneath it. Common on old exterior work.
6. Take the loose material back to a firm edge.Scrape until the paint you are pulling at stops coming away. If the edge lifts as you scrape, keep going. There is no repair that survives being built on a loose edge.
7. Feather the sound edge so the repair does not telegraph.Abrade the boundary between bare and painted so it becomes a shallow ramp rather than a step. A step will show through the new gloss as a visible line however many coats go on it.
8. Prime the bare area for what it actually is.Bare timber, previously painted wood and bare metal each want a different primer. GuideHQ has a guide on choosing that by substrate; the mistake to avoid is assuming one tin covers all three.
9. Abrade the whole surface before recoating, not just the repair.The reason the paint failed the first time is very often that this step was skipped. A dull, uniformly keyed surface is what gloss needs; a shiny one gives it nothing.

Common mistakes

• Painting over a peeling area without removing the loose paint. — The new coat is only as attached as the layer beneath it. It will lift in the same place, usually taking a bigger piece.
• Sanding a surface smooth rather than keying it. — Smooth and keyed are not the same thing. The aim is a uniform dull scratch pattern, not a polish.
• Treating peeling on an external sill as a paint problem. — It is nearly always a water problem. Repainting seals the moisture in and the film lifts again within a season.

If it doesn't work

Questions people ask