While the jury is still out on its effectiveness compared to commercially available roof cleaning solutions, the following remedy is often cited as effective:
- One quarter bleach
- Three quarters water
- ...and a dash of trisodium phosphate
A representative of House Washing Brisbane suggests spraying the roof with a large hand pump spraying device, then letting it sit for 15-20 minutes. If it doesn't fall away under a brush, repeat the entire process until it does.
If you're concerned about nearby trees or plants, spray them generously with pure, clean water first. This will drastically reduce the risk of damage from bleach spray.
When you're done, very thoroughly rinse away the solution with a hose to prevent the bleach from damaging the roof shingles.