It’s easy to forget about the condition of your roof since you don’t really see much of it. But over time moss, algae, bird droppings and other contaminants can build up on a slate roof. Moss can tear through slate shingles with its roots and can promote excess dampness that rots the wood beneath your slate shingles. Clean slate roofs in hot weather so they dry fast – or at least on a clear day with plenty of sunlight.
Prepare a cleaning solution in a large bucket once you’re securely on the roof. Thisoldhouse.com recommends a 1 to 1 mixture of bleach and water. Askthebuilder.com advises using oxygen bleach powder, which is non-toxic. Mix the powder with water according to the manufacturer’s instructions.
Set up a ladder so you can access the roof.
Grab the hose and walk toward one edge of the roof. Spray a 3 foot wide strip of slate. Don’t spray more than one small area at a time, this will avoid a slippery hazard. Dip your brush in the cleaning solution.
Run a hose fitted with a spray nozzle up to the roof. You may need to attach an additional hose to your garden hose to enable it to stretch that far. Turn on the water. Climb the ladder with your bucket and scrub brush in hand.
Carefully climb down the ladder with your cleaning supplies and turn off the water.