LouB wrote:

Pete C. wrote:
Aaron Fude wrote:
Hi,

On the north side of my house I have moss on the slate roof. I'm
concerned that it's pushing the slates apart. My roof is 90 years old.

How do I combat this problem?

Thanks,

Aaron

Wash the roof regularly (quarterly is probably good) with a bleach
solution.

He said Moss not Mold. Will bleach kill moss?
And how does one wash a roof with bleach?

Bleach kills moss just fine.

I've used a pressure washer with the chemical feed from a bucket of
bleach solution on a stone patio in an area that grows moss and algae.
I've also used this on an asphalt shingle roof in the same area with
good results. Pressure washing with bleach solution kept the moss and
algae away a lot longer then pressure washing with plain water. I
suspect that walking on a slate roof with a pressure washer gun might be
a bit dangerous, so you may need to do this strictly from a ladder.