Wall problems

Cracks in walls

A hairline above a door is not the same as a crack that keeps growing. Most are filled before painting; some need someone to look at the structure first.

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How to recognise it

  • Hairline cracks, in a web or a line, in the plaster.
  • Diagonal lines running from the corners of doors and windows.
  • Gaps where wall meets ceiling, or between plasterboard sheets.
  • Wide cracks you could slide a coin into, or that show on both sides of the wall.

Where it comes from

  • Plaster shrinking as it dries (fine, web-like cracks).
  • Expansion with heat and cold, especially on sunny façades.
  • Plasterboard joints without tape or badly finished.
  • Small building settlement, vibration, building work next door.
  • Structural movement: wide cracks that grow, doors that stop closing.

What the painter does

  1. Open the crack

    It is widened slightly into a V so the filler gets in and grips.

  2. Remove the dust

    Without dust, the repair doesn't come loose.

  3. Fill

    Repair filler. For cracks that move (façades, joints), flexible filler or sealant, with mesh or tape where they keep reopening.

  4. Sand and level

    So the repair doesn't show once painted.

  5. Primer and paint

    Primer on the repairs and two coats. On a façade, elastic paint helps keep hairline cracks from coming back.

What it adds to the job

  • More time: filler has to dry before sanding and painting. Many cracks, or big repairs, can add a day or more.
  • Materials: filler, mesh or tape, primer; on façades, elastic paint.
  • On the quote, "Repairing cracks and holes" should say where and how much: which walls, or how many metres.
  • A crack that moves can show again: ask what the guarantee covers.

Photos that help the painter

Put a coin or a tape measure next to the crack and take a close-up; take another of the whole wall.

Frequently asked questions

Do cracks come back after painting?

Fine ones, properly repaired, usually don't. Those caused by movement (plasterboard joints, façades, a settling building) can show again; that is why flexible filler and mesh are used. Ask for the method to be written on the quote.

When do I need an engineer?

When the crack is wide, growing, goes through the wall, appears on several floors or comes with doors sticking. That is structure, not painting.

Get quotes with this problem already noted

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

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