Reading the failure pattern
| What the paint is doing | Likely cause |
|---|---|
| Blistering into bubbles that hold water | Active moisture behind the film |
| Flaking in sheets, taking plaster with it | Salt contamination in the plaster |
| Peeling low on the wall in a level band | Rising damp |
| Peeling in a patch on the weather elevation | Penetrating damp |
| Fine cracking then lifting at the edges | Painted over a dusty or chalky surface |
| Black spotting under the film, no lifting | Condensation and surface mould |
| Whole coating detaching cleanly, exterior | Non-breathable coating on a damp wall |
The mistake almost everyone makes
Scraping it back, filling, and repainting. If moisture is still arriving from behind, a new coat is a new membrane for it to lift, and it will — usually faster than the last one, because the substrate is now more damaged.
Worse is the common escalation: because the paint keeps failing, someone specifies a tougher, less permeable coating. That traps the moisture more completely, and the next failure takes the plaster with it instead of just the paint.
On a parapet, peeling along the top of the inside face almost always means water is entering at the coping or the upstand — see parapet wall leaks.
On an older solid-wall property, a breathable coating is not a preference, it is a requirement. Those walls are designed to take up moisture and release it outward. Seal one and you have removed the only exit.
What to do in what order
- Find the moisture source and deal with it. Everything else is decoration over a live fault — start with the four types of damp.
- Let the wall dry. Roughly a month per 25mm of thickness.
- If salts are present, hack off the contaminated plaster and re-render with a salt-inhibiting mix. Painting over salts never holds.
- Prepare properly — remove everything loose, back to a sound edge, and stabilise chalky surfaces with the right primer.
- Use a breathable system on older solid walls and anywhere that has had a damp history.
Paint on an external elevation almost never fails on its own — it fails because water is getting behind it through the plaster, which is wall crack repair and façade sealing.
Related reading
Start with The Four Types of Damp for the overview, or:
- What a Damp Survey Should Actually Cover
- Water Ingress Explained
- Efflorescence and Wall Salts
- Moisture in Walls
Common questions
Can I just repaint over peeling paint?
Only if the cause was poor preparation rather than moisture. If the wall is damp, a new coat lifts as well — often within one wet season, and taking more of the substrate with it.
Why is my exterior paint coming off in sheets?
Usually a non-breathable coating on a wall that holds moisture. Water vapour trying to leave cannot pass the film, so pressure builds behind it and the coating detaches as a sheet rather than flaking.
Does anti-damp paint work?
It has legitimate uses as one component of a specified system on a wall that is already dry. As a treatment for a wall actively drawing water from the ground it does not work — it seals the surface while the moisture keeps arriving, and it fails.