What causes this?

[ctgo4it]

This moss-like substance was covering most of the deck and parts of the roof. There happened to have been a light rain falling all day, so I don't know if the air is wet there usually (there was a pool in the backyard, don't know if it means anything)

Any help would be appreciated.

Thanks

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[homnspector]

Its algae on the deck and lichen on the roof. The deck looks pretty much shot and not too long for the roof. I would call both "symtoms of advanced age".

[kurt]

The deck looks shot. The roof doesn't look all that bad.

I find lichen on roofing all the time. Heck, I've got lichen on my current roof; it's been there for about 10 years. I brush it off from time to time.

I'm not saying lichen is good, but it's mere presence doesn't necessarily indicate a roof that's about to die.

[homnspector]

I was looking more at the curling shingle tabs in pic #3. I agree, lichen probably doesn't hurt much. I guess technically it is breaking down the mineral, but very slowly.

[Terence McCann]

Isn't lichen due to moisture and not enough sun to dry things up? Like what you might find on the North side of a tree?

[John Dirks Jr]

Originally posted by Terence McCann

Isn't lichen due to moisture and not enough sun to dry things up? Like what you might find on the North side of a tree?

Yup, mainly a result of a moist shady enviroment.

[StevenT]

I've seen stuff like that growing on trees. I'm not a hornyculturist, but I remember being told that it is some type of disease that will spread to all the nearby trees. The only way to kill it is to remove the tree.

Is there anything that looks like this on the surrounding trees?

[ghentjr]

Sprinkle powdered tide detergent on the lichen (lightly) before a rain. After a few treatments it may be gone. But then again, it may not.

[ctgo4it]

Honestly, I thought the roof was in decent condition. There was a pool in the backyard, but I don't think that creates the moisture to cause this (probably on the deck it did). This part of the roof was under trees though

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[StevenT]

Is any of the "lichen" on the trees?

[homnspector]

The roof does look pretty good.

[ctgo4it]

Originally posted by StevenT

Is any of the "lichen" on the trees?

I didn't notice any. What does it come from and what can I recommend to my client?

[hausdok]

It's just a fungus. Get some moss kill, apply it to the roof on an overcast day, let it work and then rinse it off with a garden hose. If it's stubborn, use a soft-bristled brush along with the hose to work it loose.

It usually grows on organic material around here - even in bright sunlight. I almost never see it on a roof unless there's a lot of bird crap for it to eat. I don't see any bird crap there, so I don't know why it would be growing there.

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

It's not a disease that spreads and it's not a parasite. Lichen is a mutually dependent marriage of fungus & algae. It reproduces by spores that become airborne and attach to surfaces with the right texture for it to grab hold.

It doesn't feed on organic material or even roof coverings. It gets its food from natural airborne dust, rain and primarily, photosynthesis. It grows very, very slowly -- that's why I see it covering much more surface area on very old slate roofs. It only causes very minor damage to materials from its waste, that is slightly acidic, and it retains moisture. It doesn't really want to destroy its host.

To get rid of it, bring in some reindeer or caribou, that survive on it in extreme arctic climates. Any treatment that kills algae, fungus or other plants would probably do it in, but physically removing it would probably do more damage to an asphalt roof than leaving it.

[ctgo4it]

So I ended up sending the client the report without mentioning the Lichen. Was that a bad idea? Should I write an addendum?

Thank You

[homnspector]

Might be good to mention it so some roofer doesn't convince him it is a major problem. I think I would just send a quick e-mail explaining lichen. It is so common you don't usually mention it but later realized he may not be familiar with it, and may be concerned when he sees it on the roof.

[ctgo4it]

send him an email, gave him some links. Thanks for the idea

[Jim Baird]

Around here there's a game similar to "snipe hunting" called "lichen lookin'".