Coastal humidity and the blistering wall
Walk any older street within a kilometre of the sea — Deira, Sharjah's Al Majaz, Ajman corniche, RAK's old town — and you will see paint blistering: bubbles, flaking sheets, and the tide-mark staining of salt migrating through render. The mechanism is simple. Moisture gets into the wall, from humid air, a plumbing leak, a dripping AC line or rising damp, and when the sun heats the surface, that moisture turns to vapour and pushes the paint film off from behind. No paint, however premium, survives being applied over a wet substrate.
The fix is diagnosis before decoration. A competent painter arriving at a blistered wall should ask where the moisture is coming from before quoting, and on a bad case use a moisture meter rather than guesswork. If the source is a leak, that is a plumber's job first and a painter's second. If it is ambient coastal humidity in a bathroom or kitchen, the answer is surface prep down to sound material, an alkali-resistant or damp-tolerant primer, and a paint specified for wet areas — not another coat of standard matt over the bubbles.