How to paint a Tiled Roof
What are roof tiles?
Roof tiles are usually made from cement or clay (less common). Cement tiles are prone to carbonation due to the effects of carbon dioxide and water in the atmosphere, which forms a very weak acid called carbonic acid. This extracts the cement from the surface of the tiles and produces a weak, friable surface layer. The effect becomes more severe as the tiles age on a roof. Clay tiles do not have this problem, but tend to be highly porous. This can lead to poor paint film curing.
This is the critical part of any painting project. Poor preparation is the principal cause of coating failure. Both types of tile can be prepared in the same way. The object of surface preparation is to provide a strong surface bond before applying any paint. The necessary steps are as follows:
- Wash the surface thoroughly using water and a strong brush. This should remove all loosely bound sand particles and any poorly adhering paint coatings. A high-pressure water jet is recommended.
- Rinse the roof with clean water and then leave it to dry out. The moisture content should be below 15%. This can be measured using a moisture meter.
- Check the adhesion of any existing paint coatings by pressing adhesive tape (e.g. masking tape) onto the dry surface. Pull the tape off the surface and inspect the underside of the tape.
No coating removed; no dirt or chalky material on the tape: Surface is suitable for painting*
Powdery layer removed Surface is chalky: apply Fired Earth Bonding Liquid.
Sandy particles removed Surface is friable: rewash the surface**
Paint coating removed Surface under the coating is weak: strip
The paint film and repeat the cleaning process.
* Check the porosity of the surface before painting by applying a droplet of water. If it is readily absorbed into the tile then it is recommended that Fired Earth Bonding Liquid be applied to seal any residual particles.
** It may not be possible to remove all sand particles. It is recommended that Fired Bonding Liquid be applied to seal any residual particles.
4. If Fired Earth Bonding Liquid has been applied to the surface, leave it to harden for at least 2-4 hours before continuing.
Apply Fired Earth Extreme Roof to the prepared surface using a roller (wool or synthetic type); brush or by airless spraying. Two coats are recommended for optimum durability and quality of finish. Allow the first coat to cure for at least 2-4 hours before applying the final coat.
Calculating the amount of paint required
- Estimate the plan area of the roof by measuring the length and breadth of the walls
- Multiply this area by 1,5
- Estimate the paint quantity needed by dividing the above area by 7, multiplied by 2 for two coats. This should produce a slight excess of paint, which is useful for touch-up work as required.
Other important information
- NEVER apply paint if rain is forecast, or expected, during the day of application.
- Apply paint after 8h00 (summer) or 10h00 (winter) to ensure the roof is not too cold or damp.
- It is recommended that the paint is applied before 12h00 to avoid excessive roof temperatures and to allow the paint to harden sufficiently before any afternoon rain may occur.
- Always use the SAME batch number for touch-up work. This reduces colour variations, which otherwise may be visible on the painted roof.
Fired Earth paints description of products described above
- Fired Earth Bonding Liquid Water Based Nano-Tech is an alkali-resistant penetrating bonding sealer for a wide range of friable surfaces such as gypsum and cement plasters. Increases substrate strength for optimum durability of all finishing coats.
- Fired Earth Extreme Roof acrylic is a high quality acrylic, medium sheen finish paint with outstanding weathering and alkali resistance properties. It can be applied onto suitably prepared fibre cement tiles, roof sheet, clay or cement roof tiles and pre-primed galvanised iron roofs. Available in the following colours: Black, Grey, Charcoal, Burgundy, Red, Brown, Terracotta & Green.
Other important information
- NEVER apply paint if rain is forecast, or expected, during the day of application
- Apply paint after 8h00 (summer) or 10h00 (winter) to ensure the surface is not too cold or damp.
- It is recommended that the paint is applied before 12h00 to avoid excessive temperatures and to allow the paint to harden sufficiently before any afternoon rain may occur.
- Always use the SAME batch number for touch-up work. This reduces colour/sheen variations, which otherwise may be visible on the surface being painted.