Wall problems

Mould and damp on walls

Black spots on the bathroom ceiling, corners that darken again every winter. Painting over it isn't enough: treat it first, then paint.

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How to recognise it

  • Black, green or grey spots and patches, mostly in corners, on ceilings and behind furniture.
  • A musty smell and walls that feel cold.
  • Blistered or yellowed paint around the patches.
  • It comes back in the same place, even after cleaning.

Where it comes from

  • Condensation: steam from showers and cooking settles on the coldest walls, especially with little ventilation and windows shut all winter.
  • Cold spots: corners, beams and shutter boxes get colder than the rest of the wall.
  • Leaks: water coming in through the roof, terrace, window frames or façade.
  • Leaking pipes inside the wall or in the flat above.

What the painter does

  1. Find the cause

    Check whether it is condensation or water getting in, ideally on a visit.

  2. Clean and kill the mould

    Brush it off, apply a fungicide, leave it to work and dry.

  3. Scrape off what is loose

    Blistered paint comes off. If the plaster is crumbling, it is repaired.

  4. Primer

    On the treated areas, so the new paint grips and the stains don't bleed through.

  5. Anti-mould paint

    Two coats of paint with fungicide, made for bathrooms and kitchens.

What it adds to the job

  • More time: the treatment has to dry before painting. Often one more day, or longer if plaster needs repairing.
  • Specific materials: fungicide, primer and anti-mould paint, which cost more than ordinary paint.
  • On the quote, "Anti-mould treatment" and "Primer or sealer" should be their own lines, with the rooms or m² they cover.
  • If water is getting in, fixing that is usually not included: ask.

Photos that help the painter

One close up, to tell mould from a water stain, and one from further back, to show the size and where it is: corner, ceiling, by the window.

Frequently asked questions

Does bleach fix it?

It removes the visible stain, but it usually comes back: on porous walls it doesn't reach all the mould. A proper fungicide and anti-mould paint last longer.

Is anti-mould paint enough on its own?

It delays the patches coming back, but if the cause stays (steam with nowhere to go, or water getting in), the mould returns. Cause first, then paint.

Does the painter need to visit before quoting?

It helps a lot: the cause is easier to see in person. On pintores.pt the painter offers visit times and you pick one.

Get quotes with this problem already noted

The request opens with "Damp / mould" chosen as the wall condition and a note for the painters. You can change anything.

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