Asbestos cement is found in varying forms in buildings – mainly as wall partitions, ceilings, plain and corrugated roofing sheets, tiles, gutters, and downpipes.
Asbestos cement should be dry before painting.
It is highly absorbent, often highly alkaline and may contain a relatively high concentration of salts.
“Oil” paints must not be used on new exterior asbestos cement surfaces. Blistering and peeling can be caused by moisture entering from the back of the structure. This may, for example, occur when gutters or downpipes are not internally painted and the continued flow of rainwater maintains damp conditions within the asbestos cement.
Gutters, windowsills and fascia boards should therefore be painted on both sides to prevent moisture penetration. Bituminous solution should be used on the inside of gutters.
For external asbestos cement surfaces, 100% Acrylic type Emulsion paints or Dekrolite Masonry Paint are preferred due to their high alkali resistance.
Fungus tends to grow easily on unpainted asbestos cement because it is alkaline and porous – a perfect breeding ground for spores. Therefore it is highly recommended that you waterproof unpainted surfaces with Dekro Water Repellent.
New asbestos cement surface
Ensure surfaces are clean and dust free.
Previously lime washed or distempered surface
Remove all traces to bare surface.
Previously oiled, alkyd, PVA or acrylic painted surface
If the existing paint is in poor condition:
- remove it by scraping or burning
- wash the surface with a concentrated detergent solution,
- allow to dry
If the existing paint is in good condition:
- wash with soap and water, concentrated detergent or solvent to remove dirt, grease, wax polish or other contaminants.
- Glossy surfaces need to be abraded to form a key for subsequent coats.
- Rinse clean and allow to dry.
Previously painted or unpainted and covered with fungus
- Remove the visible fungi and dirt with a suitable asbestos cleaner.
- Sterilize surface by applying an HTH solution or use one coat of Dekro Fungicide Solution.
- Leave to dry overnight.
- Brush down with a stiff bristle brush