Homeowners often ask us if they should worry about algae on a concrete tile roof: the dark or green growth that shows up over time. The short answer: it doesn’t look great, but it’s normal, and it won’t hurt the roof’s integrity.
Why algae grows on a concrete tile roof
According to tile makers, algae and mildew don’t grow on the tile itself. Dust and bits of organic matter settle on the tile. When there’s moisture and sun, spores start to grow in that layer. Shade, morning dew, nearby trees and water all make it more likely.
How to clean it
There are spray-on cleaners that kill the growth so it washes off over time. Follow the label and the tile maker’s instructions. Walking on tile is risky. Tiles can break underfoot, and wet tile is slippery. If you’d rather not get on the roof, have a licensed roofing contractor do it.
What to watch on a tile roof instead
Algae is mostly cosmetic. The things that cause leaks on a tile roof are different. On a tile roof, the underlayment under the tile usually wears out before the tile. Water gets in mostly at gaps along the hips and ridges, plus valleys, clogged drainage channels, broken tiles, and around walls, chimneys, skylights and pipes.
The same debris that feeds algae can clog the drainage channels. Most tile roofs need their first repairs around 15 to 20 years, especially when those channels aren’t cleaned. Learn more about tile roof repair.
A roof tune-up
A tune-up seals and patches the valleys, roof-to-wall areas, drainage channels, chimneys, skylights, pipes, ridges and hips. It works on flat, medium-profile and S-tile roofs. It usually costs about 30% of a new roof on the same house, with a 2 to 10 year warranty on the areas fixed. When the underlayment is worn out across the roof, see tile roof underlayment replacement.
Related: Roof inspection · Roof stain colors and what they mean · Roof restoration vs. replacement
Want a look at your tile roof? We’ll inspect it for free, take photos, and give you a written quote the same day. Call (916) 678-9786 or request a free inspection.
