How to Remove Green Stuff From a Roof

Green stuff on your roof is likely algae or green mold.

Unless your shingles have been chemically treated to repel these little monsters, then algae and mold not only can grow on your roof if you live in humid areas, but they can even eat away at your shingles. Fortunately, you can easily rid your roof of this green stuff with a good day's worth of work. Just be sure that day is dry and overcast for the best results.

Sweep off your roof. Use the broom to clear the roof of debris. You will likely dislodge some of the green stuff in the process.

Put on your safety gear. You should already be wearing slip-resistant shoes; put on gloves and goggles, too.

Mix your cleaning solution. In the pump sprayer, combine a gallon of water, a quart of bleach and 1/4 cup of TSP powder.

Wet the roof with the solution. Cover the roof with the cleaning solution using the pump sprayer. Work from top to bottom and left to right. Allow the solution to sit for no more than 15 minutes on the roof. If it sits longer, it can damage many types of shingles.

Rinse off the roof with the hose. Use the highest pressure that your garden hose can supply. If you notice any stubborn green stuff still hanging on, scrub it with the push broom until it disappears.

Things You Will Need

  • Slip resistant shoes
  • Safety goggles
  • Rubber gloves
  • Push broom
  • Pump sprayer
  • Bleach
  • Trisodium Phosphate (TSP)
  • Ladder
  • Hose

Tips

  • Prevent recurrence of mold, mildew and algae by running a thin, copper strip under the top layer of shingles.
  • Protect your landscaping from the diluted bleach runoff by spraying the plants down with water and covering them with plastic before you start working.

Warnings

  • Do not work on the roof without letting someone know where you are and what you are doing.
  • If you have an asphalt roof, do not leave the bleach on one second longer than 15 minutes.