How to paint exterior water stains

How to paint water stained walls
What you will need:

This guide explains how to block exterior water stains and permanently prevent mould and mildew from seeping through newly painted surfaces.

Surface Preparation

All surfaces must be clean, dry and free from anything that will interfere with the adhesion of the materials to be applied. Remove loose and failing material by scraping or brushing with a stiff bristle brush to a sound edge. Feather sound edges with a fine grade abrasive paper. Prior to painting, the moisture content should not exceed 18%. Remove all dust. Remove all visible signs of organic growth and treat the areas with Zinsser Mould Killer in accordance with the manufacturer’s instructions. Allow to dry.


Wash with hot water and liquid detergent solution to remove any contaminants, frequently changing the water. Rinse thoroughly with clean water to remove all residues. Allow to dry. Fill any cracks and small surface defects with a suitable filler in accordance with the manufacturer’s instructions. Allow to dry. Rub down with a fine grade abrasive paper. Remove all dust. Patch prime all bare and filled areas with one coat of Cover Stain® Primer Sealer in accordance with the manufacturer’s instructions. Allow a minimum drying time of 2 hours in normal drying conditions. Bring forward patch primed areas with one coat of Cover Stain® Primer Sealer. Allow to dry.

Water Stains

Prime all water stained areas with one full coat of Cover Stain® Primer Sealer. Allow a minimum drying time of 2 hours in normal drying conditions.


Decorate with two full coats of AllCoat® Exterior Satin or Gloss in accordance with the manufacturer’s instructions. Allow a minimum drying time of one hour between coats.