Professional Roof Cleaners Association


Tile Roof Cleaning Before  After

Tile Roof Cleaning

Mildew, Algae and Moss

Many climates across the country are conducive to mildew, algae and moss growth on everything from glass, stucco, siding, and driveways, to roofing products including concrete tiles. While this growth can result in a dirty surface appearance, it can be treated to restore the original look.

Mildew, algae and moss do not grow directly on the tile, but grow on the accumulation of dust and other organic materials that settle on the tile. When enough cycles of heat, moisture and light are present, these spores start to grow. Many environmental variables affect the potential for this organic growth. The location of the house, the direction the house is facing to the sun, and the quantity of trees, canals and lakes in the area can contribute to mildew growth.

While research continues, currently there is no known manufacturing procedure or job site coating that would have any long-term preventative effect on this condition. Fortunately, mildew, algae and moss can be removed or treated. If the growth returns, the treatment can be repeated, as necessary. We recommend that a professional cleaning company be used, so you avoid the dangers associated with walking on a wet tile roof. We at P.R.C.A adhere to the manufacturers recommendations and use a Non-Pressure or Soft Wash cleaning method as described  below.

Non- Pressure / Soft Wash Roof cleaning

The use of a chemical treatment allows for the tiles to absorb the cleaning agent and get into the pores of the tiles, This provides the most effective and long-lasting  cleaning process, in general, cleaning is seldom needed again for 3-5 years or more. Most, if not all, manufacturers endorse this method and is publicized  in technical bulletins provided  from them.

Surface Cleaner or Pressure Washing

Can be used without the use of chemicals, but can present bigger problems by having foot traffic on 90% of the tiles. Concrete tile or clay tiles are more fragile than many think, most manufacturers of tile, who warranty your roof recommend methods that keep traffic to a bare minimum. They understand that the fragility of the tiles and the expenses that can occur to replace them are not pocketbook friendly.

More importantly, if the tiles are cracked or broken, how will you, the homeowner, know?  Unless your comfortable getting on your roof, there is virtually no way to inspect for any damage.  Will your contractor admit he broke the tiles and offer to pay for replacement?  Will this void your warranty with your original installer if he performs the repairs?   For these reasons, it is best to hire a roof cleaning contractor, who can clean your roof with minimal foot traffic. Some roofs can be cleaned from a ladder and not walked on at all. Some larger homes  will require the use of a lift to prevent excessive foot traffic and also for safety of the roof cleaner. This can not be done with a pressure washing method.

Depending on the pressure set on the pressure washer running the surface cleaning machine, usually 3000 to 4000 psi, [psi is the amount of pressure-pounds per square inch]  will erode the surface and edges, causing  small pieces of tile to break away. The motion used to lower and pull the cleaner up and down causes it to drag on the edges of the tiles. It also does not have the capability to give it a through cleaning, leaving thousands of tiny misses and living algae to continue growing immediately. In some instances the pressure from a surface cleaner will be intense enough to cause the tiles to bleed, the dye pigment used to color them will be literally washed away. You will see the run-off coming out as a colored water. When the roof is dry it will often have a lighter appearance and may look faded or chalky. The degree of pressure coming from the tips causes water to be jetted into areas that normal rain fall may not. This can cause a leak from the jetted water and may affect the interior painted drywall.