“Advanced biological colonization” is a new one for me—makes it sound like your roof’s about to sprout legs and walk away. I get why inspectors do it, but yeah, it’s a bit dramatic. As for moss, I’ve seen it both ways. Sometimes it’s just ugly, but I’ve also torn off shingles where moss held moisture so long the decking underneath was soft as a sponge. It’s not always sales talk, but it does take a while to get that bad. If you catch it early, it’s usually just a cleanup job. Let it go for years, though, and you might be looking at more than just a green roof.
Let it go for years, though, and you might be looking at more than just a green roof.
Had to laugh at “advanced biological colonization” too—my last report called it “vegetative incursion.” I let moss go a couple years on my north side and it really did a number on the plywood. Didn’t look like much until I stepped through it. Lesson learned.
Funny, I’ve actually let moss go on my shed roof for a while and it didn’t seem to cause much trouble—maybe it’s just luck or the type of shingles? Did you try any of those zinc strips or sprays before it got bad? I always wonder if they actually help or just slow things down a bit.
- Gotta say, letting moss hang out too long can be risky, even if it seems harmless at first.
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“I’ve actually let moss go on my shed roof for a while and it didn’t seem to cause much trouble”
- In my experience, it really depends on the roof pitch and sun exposure.
- Zinc strips do help, but only where rainwater actually washes over them. Spots under trees or in shade still get mossy for me.
- Had a client’s shed roof rot out underneath the moss—looked fine from the outside till we checked under the shingles.
- Sometimes it’s just luck, but I wouldn’t count on it long term.
Had a similar situation on my old garage roof—figured the moss was just cosmetic, since it didn’t look bad from the ground. Ended up pulling a few shingles for a minor leak and found the plywood underneath was soft as a sponge. I’m in the PNW, so shade and rain are just part of life, but still… lesson learned. Tried zinc strips too, but like you said, spots under the overhangs stayed green. Now I’m more proactive with a broom and occasional moss killer. Not fun, but cheaper than new decking.