Fixing marks coming through paint

BlazingSaddler

Hi all, this Wall is an extension, approx 6 years old, over the last couple of years these marks have started to show through. I know need to repaint. How can I prepare it so the marks don’t come through again? Also, what causes the marks in the first place?

J_A_F_A

BlazingSaddler wrote: »

Hi all, this Wall is an extension, approx 6 years old, over the last couple of years these marks have started to show through. I know need to repaint. How can I prepare it so the marks don’t come through again? Also, what causes the marks in the first place?

You've got damp behind the wall. The screws/nails are rusting. You need to cover the stains with a sealer. Something like this. https://www.mcmahons.ie/zinsser-b-i-n-primer-sealer-1l

5T3PH3N

They’re the mushroom fixings, thermal caps weren’t used on the fixings by your builder.
The cold air in the cavity is traveling along each fixing to the inside of the wall.
I don’t know an easy fix for this tbh, other than chipping all the skim off each fixing and putting a cap on and skimming the wall again. I’ll be interested in hearing of an easier way to fix this issue.

BlazingSaddler

A work colleague suggested covering the marks with oil based paint and then the couple of coats of emulsion, would this work?

wait4me

If it was me, I'd cover the marks with white oil based undercoat; and when dry cover it with a couple of coats of emulsion. If it was me.....

dok_golf

Shellac based primer, zinnser B.I.N. or Fleetwood Terminator. Spot prime the marks, overlapping the stain by 50%, then 2 coats of paint on top.