Cleaning your roof will extend its life. Roofs collect leaves, pine needles, and dirt, and grow moss, algae, and lichen. All of these lead to problems. Sometimes moss can look charming, but it isn’t good for your roof. All of these form mini water dams extending the time that water “sits” on your roof. The living plant life can secret acids that breakdown roof shingles, although admittedly very slowly. Most growth is far too uneven to look good even if you like it. How do you you clean a roof?

On this subject the many experts argue, most claiming only their way is right, and using alarmist warnings about daring to try a different method. Here is what we have found:

Pressure washing:

• Pressure washing, if done right, will not harm asphalt composition shingles and can be very effective in removing contaminants.  Some will disagree, but if done right, the evidence indicates pressure washing is a valid option. Proceed with caution on very old wood shingles and shakes. Tile roofs are not at all damaged by pressure washing, but if the wand is angled facing the bottom of the tile, water is easily driven into your attic, wetting ceiling insulation.
• Pressure washing produces a slick working surface. First because of the water and secondly because of the material being removed. Safety harnesses are recommended.

Chlorine based solutions and Tri Sodium Phosphate (TSP) solutions:

• These products do work and they seem to be as effective as their alternatives. The competition claims they only take care of surface problems, merely buying you time before moss, algae, and lichen grow back. Most find that  growth comes back with all the products, so we are really involved in ongoing roof maintenance.
• After plant life is killed it will wash off with the rains or you can use a garden hose.
• Chlorine based solutions (containing Sodium Hypochlorite) and TSP solutions in some concentrations can harm some plants. Depending on where run off is going you may affect your plants or local watershed. The big problem of phosphates was in the huge quantities used in detergents which causes algae blooms in lakes and oceans which deprived waters of oxygen. Though mostly a problem of the past you may want to use something more eco-friendly. Some “eco-friendly” products may not be as claimed.
• These solutions can be considerable skin irritants. Always use rubber gloves and avoid contact with eyes, face, and overall skin.
• Chlorine bleach, TSP, and water solutions are sprayed with a garden sprayer, allowed to sit for 15 or 20 minutes, and then rinsed.

Prevention strategies:

• Some roof shingles contain small amounts of copper that inhibit growth. Similarly you can spray your roof with a copper sulfate solution.
• Placing zinc strips under the bottom of the top row of shingles can have a preventative effect on the whole roof.
• These are only effective after existing problems have been remedied.
• When reroofing never use inferior 3-tab shingles, which may have come with your house. The slots that give the roof its pattern are holding spots for moss. The additional cost of upgrading to the starting level of architectural shingles (which have no slot), may be as little as 15% more if you are hiring a contractor (cost of shingles themselves are about 40% above 3-tab).

Most people find roof maintenance an excellent thing to have done for them by expert professional roof cleaners. Find out exactly what they are going to do and the prices for each. If you use someone annually, there will be times when you only need a removal of debris with a blower and a cleaning out of gutters. Other years you might opt for preventative solution sprayed on and sometimes you’ll need a thorough cleaning. Clean roofs are happy roofs.