Sign of damp
Rust stains
Orange-brown streaks or spots on a ceiling, beam, column or wall, sometimes along a straight line. In worse cases the plaster or concrete cover bulges or cracks along that line, or a piece has fallen off and exposed corroded steel.
What it might mean in a flat
Brown or orange streaks on plaster and concrete.
Rust stains mean water has been reaching steel for a long time. Along a straight line on a slab or beam, they can mean the reinforcement is corroding, which is a matter for a structural engineer rather than a damp inspection. A rust stain around a pipe route more often points to an old GI line.
Common causes
- Water reaching the steel reinforcement in a slab, beam or column, so it corrodes and stains the surface
- Rusting GI supply pipes concealed in walls or floors, common in older flats
- Iron fixings, grilles or window frames rusting where they are set into the plaster
- Long-term leaks under a terrace, bathroom or sunshade
What an inspection checks
How we confirm it.
- Meter readings on and around the stain to see whether the area is still wet, against the dry reference
- Thermal scan to trace any wet area back towards a terrace, bathroom, sunshade or pipe route, confirmed with the meter
- Visual check for cracking, bulging or spalled concrete along the stain line, recorded with photos
- Whether the flat still has GI supply lines and where they run
When to worry
Signals that it's active.
- Cracking, bulging or fallen pieces of concrete along the stain line: Megahedge does not assess structure, and the report will recommend a structural engineer
- The area is still wet, which means the corrosion is likely to continue
- Stains are on a top-floor slab or under a bathroom and spreading
Where it usually comes from
Questions buyers ask
Is a rust stain a structural problem?
It can be. Megahedge reports the moisture and records the cracking or spalling it can see, but does not certify structure. If steel corrosion is suspected, the report recommends a structural engineer.
Can you tell if my pipes are GI or CPVC?
Often from exposed sections, fittings and the age of the plumbing. Concealed lines are not opened, so the report says what is seen and what is assumed.
Will painting over rust stains help?
Only cosmetically, and rust usually bleeds through. The water reaching the steel needs to be stopped.
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