Stephen Cornish PhD MA BSc FRICS FFPWS Managing Director of Woodward Chartered Surveyors investigates whether painting roof tiles is a good idea.
Some commercial companies claim that the painting of your roof tiles/slates will prolong the lifespan of the roof covering, waterproof the tiles, and/or reduce heat loss from your property. To the best of our knowledge there is no independent research to support such claims. Rather than benefiting your property, there is a risk that the application of paint can cause damage.
Roof tiles are laid in a staggered pattern with small gaps around each tile. These
gaps are important as they allow air movement in the space between the underside of the tile and any underlay material. This reduces the presence of moisture laden air and so helps to prevent condensation occurring on the underside of the roof tiles.
When a roof is painted these gaps are sealed and the moisture laden air rising from within your property cannot escape and condenses on the underside of the tiles. This can cause decay in the timber battens and flaking of the tiles.
Roof tiles will absorb a small amount of water during rainfall but not to the extent that water will pass through the thickness of the tile. Any moisture absorbed by the tiles will naturally evaporate away in drier weather. When a tiled roof is painted the coating will only stay impermeable for a short period of time.
The effects of sunlight will cause fine cracks to open up in the paint which will then permit water to enter. The paint will then prevent that water from evaporating trapping it against the face of the tiles and causing deterioration of the roof covering. A thin coating of paint makes no discernible difference to reducing heat loss.
If you are concerned that your roof covering as a home owner or homebuyer, contact Woodward Chartered Surveyors and arrange an inspection.