Water stains on plaster can be quite unsightly. They often appear on ceilings due to roof leaks or on walls from plumbing problems. You may also end up with water stains low on the walls due to rising damp issues in the past. Although the first priority is to dry out the plaster and fix the initial cause of the water stain, eventually the ugly discolouration must be attended to. Special techniques must be used or the stain will bleed through any new paint that is applied.

Cleaning

A thorough cleaning is in order even if the wallboard only has minimal damage. Dampness can lead to mould spores, which may eventually begin to grow if further moisture is introduced. Any residue, such as salt from rising damp, must also be removed so it doesn't seep through the newly applied paint.

Cleaning is typically completed with a product that contains bleach. The bleach destroys any mould and helps lighten the water stain. The stain shouldn't be soaked with the bleach solution, as this can cause further damage to the plaster. Instead, carefully wipe it on with a soft sponge and then use a dry cloth to soak up any remaining moisture before it can be absorbed by the plaster.

Preparation

The damaged wall does need some preparation prior to painting. If the area consists of plasterboard or drywall, then it must be checked for damage such as warping or softness. Damaged spots must be cut out and a replacement piece of plasterboard is then fitted into place. For true plaster walls, a fresh coat or two of plaster may need to be applied to repair any damage that occurred when the wall was wet.

Once repairs are made, the painters will gently sand the wall to prepare it for painting. Any uneven areas are smoothed out and divots will be patched with a wall compound to create an even surface.

Painting

Paint will go on in two parts. The first will be a primer formulated to cover stubborn water stains. The primer evens out the colour so that the final coats of paint go on evenly. This is especially important if you are using a light-coloured paint.

Once the primer dries, the paint colour of choice will be applied. For most walls, at least two coats are used but there may be up to three coats.

Contact a painting contractor in your area if you need to address water stains on the walls or ceiling.