Why does my bathroom ceiling paint keep flaking?

A bathroom ceiling is the coldest surface in the wettest room, so it gets more condensation than anywhere else in the house. Paint that is not designed for that, on a surface that was not prepared for it, fails predictably.

What you'll need

• A scraper and abrasive paper
• A stain-blocking or mould-resistant primer
• Bathroom-grade emulsion
• Fungicidal wash
• An extractor fan, or a working one
• A dust mask and goggles

Step by step

1. Fix the ventilation first.This is the actual cause. An extractor that runs for at least fifteen minutes after a shower, vents to outside rather than into the loft, and is powerful enough for the room. Nothing else you do will last without it.
2. Check where the fan discharges.A shockingly common fault is a fan ducted into the loft space rather than through a tile vent or the wall. That soaks the loft and the ceiling from above.
3. Check for a leak from above.A bathroom on the top floor with a flaking ceiling may have a roof or flashing problem rather than a condensation one. Look in the loft on a wet day.
4. Strip back to sound material.Everything loose comes off, and the edges of the sound paint are feathered by sanding. Painting up to a flaking edge just gives the next failure a starting point.
5. Wash off any mould.A fungicidal wash, left on for the time stated, then rinsed. Painting over mould with anything, including mould-resistant paint, does not kill it.
6. Let the surface dry completely.Days rather than hours in a bathroom that has been damp. Run the extractor and leave the window open.
7. Look at what is underneath.If the failure is down to bare plaster, the original problem may have been no mist coat. If it is coming off a shiny layer, there may be an old vinyl silk or a PVA seal under it.
8. Prime appropriately.A stain block if there are marks, a plaster sealer or mist coat on bare plaster, or a bonding primer over a glossy old surface. The primer choice depends on what you have exposed.
9. Use bathroom-grade paint.Moisture-resistant emulsions have more binder and often a fungicide. They cope with condensation and wiping in a way that standard matt emulsion does not.
10. Avoid vinyl silk on a bathroom ceiling.It holds moisture behind a relatively impermeable film. If the substrate is ever damp, silk peels in sheets. A bathroom matt or a specialist kitchen and bathroom paint is better.
11. Apply two thin coats.Rather than one heavy one. Thin coats bond better and dry more completely, which matters in a room that will be humid again by tomorrow.
12. Give it time before the first shower.A full cure, not just touch dry. A day or two if you possibly can, with the room ventilated.

Tips

• Run the extractor with the door closed and a small gap under it. A fan with no air path pulling in from elsewhere achieves very little.
• A humidistat or timer fan that runs on after the light goes off is the single best upgrade for a problem bathroom, and it is not expensive.
• Wiping the ceiling and the tiles down after a shower sounds tedious and makes a genuine difference in a room with poor ventilation.

Common mistakes

• Repainting without improving the ventilation — Condensation is what pushes the paint off from behind. A new coat of any paint on a surface that will be soaked in condensate every morning fails on exactly the same schedule as the last one.
• Using vinyl silk in a bathroom — Its relatively impermeable film traps any moisture that gets behind it, so instead of drying out through the surface, the water lifts the paint. It also shows every imperfection in the ceiling under bathroom lighting.

If it doesn't work

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