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Exterior Paint Flaking Off
Masonry paint, render coating or paint on window frames and fascias is flaking away outside.
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What's happening?
Outside, paint has to move with the wall and let it breathe. Failure almost always comes down to one of two things. Water gets behind the film — through a hairline crack, a failed sill, a leaking gutter, an open joint at a frame — freezes or simply saturates, and pushes the coating off. Or the wall is trying to lose moisture outwards and a film-forming coating will not let it, so the pressure builds behind the paint until it lets go. This is why flaking so often follows a specific line: below a windowsill, under a gutter joint, along the splash zone at the bottom of a wall. The pattern of the failure usually tells you which defect caused it.
What usually causes it?
- Water entering behind the coating through cracked render, open pointing or a failed sill drip
- An overflowing gutter, a leaking downpipe joint or a blocked hopper soaking the same strip of wall
- A non-breathable masonry coating on a solid or lime-rendered wall that has to lose moisture through its face
- Painting outside in the cold, damp or wet, below the minimum conditions on the data sheet
- Painting over a chalky, powdery or unsound existing coating rather than stabilising it first
- Rust bleeding out from steel lintels, brackets or fixings and lifting the film locally
- Timber windows and fascias with moisture content too high when they were painted
Is it dangerous?
The paint is not, but the ladder is. Falls from height account for a large share of serious home DIY injuries, and gable ends, fascias and upper windows are the places homeowners most often overreach. The paint underneath may also contain lead if it dates from before the 1990s, so avoid dry sanding and burning off.
Can I fix it myself?
Ground-floor patches on sound render are reasonable. Scrape back to a firm edge, brush off, treat any organic growth, allow the wall to dry properly, apply a stabilising solution where the surface is chalky and recoat. Fix the water source before you paint anything: clear the gutter, seal the frame joint, repoint the open bed. Anything above ground-floor reach, and anything needing a ladder against a wall you cannot secure, is not a DIY job.
When should you call a painter and decorator?
Call a painter and decorator for any exterior work above ground-floor level, for a wall where the coating is failing repeatedly, or where the render or the pointing is opening up and the coating cannot be blamed. A decorator will work out whether the wall needs a breathable coating, and will get access safely — which is the real cost and the real risk on external work.
What will the painter and decorator actually do?
- Survey the elevation for the water path — gutters, sills, pointing, render cracks and frame joints
- Scrape and wire-brush back to sound material, treating moss, algae and organic growth
- Stabilise chalky or powdery surfaces and make good cracks and open joints before coating
- Specify a breathable masonry coating where the wall needs to lose moisture through its face
- Work from safe access, applying coats within the temperature and weather window on the data sheet
Frequently asked questions
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