Home>Discussions>EXTERIORS>Algae Sealant for Shingle Roof ??
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Algae Sealant for Shingle Roof ??

Is there such as an acceptable product called sealant for shingle roofs to keep off algae, black stains, etc.

Here's my story:

My current house (moved in 2.5 years ago) has "black stains" (3 ft strips) running along the sides of 2nd floor dormers. We assume they are roof parcels shadowed by the dormers (blocking the sun) which permitts wetness, and therefore, spores to form. The home inspector said it is cosmetic, but worthwhile to clean off at some point. Fast forward 2.5 years to present, and my wife, who is ruled by design & looks, bumped into a contractor who was roof cleaning a neighborhood house, and guess what, asks him to clean our roof. The contractor says he uses biodegradeable cleaner & spore killer which won't harm our close-in plantings. My wife is pleased with the result -- basically, the roof is uniformed color again, and not too painful to the wallet ($400), and getting rid of organic matter from the roof (we think, basic quality installed 9 years ago to sell the house) is a good thing.

Yesterday, my wife calls at my workplace in the afternoon and says the contractor descfribed to her a process of adding a clear "sealant" to the roof shingles that would keep algae, moss, black stains (whatever) from attaching for a period of years for $X,YYY. I said, what ?? Let me think about it. Wife said, too late, work was done . . . . check written out. She's no dummy, but wants what she wants, and sometimes in an instant, and previously heard about roof sealant from others so her scam alarms didn't ring.

So I Google roof sealant and that's not much out . . . there're products claiming to seal gaps & minor water leaks, but almost nothing about keeping out spores (but learned about copper strips, interesting). I'm not concern of getting overcharged, but does this stuff work ?

The receipt for the work has no description of the applied sealant.

Re: Algae Sealant for Shingle Roof ??

Good luck with that, let us know how it goes.

Aside from being unsightly, the alge / moss isn't a huge deal for the roof. To get it to not grow you'd need to decrease the water supply. That's best achieved by swapping out the composition shingles to a metal roof.

Re: Algae Sealant for Shingle Roof ??

You were taken by this subcontractor...twice. First time he tested you, second time he took you for a ride.

1. Algae can be killed off the roof with a few gallons of bleach (99 cents per gallon) and a garden sprayer (7.99 at Lowes). Spray the bleach on, algae's gone in 20 minutes.

2. Any outdoor sealant, for tiles, fences, stones - any surface - is bound to break down very quickly, without giving you the anticipated protection. Tell me, how can a sealant on a surface like the roof, which is under constant attack from the sun, rain, wind, snow and ice, ever survive?

Next time, do some research before committing.

Re: Algae Sealant for Shingle Roof ??

I can't tell the wife that . . .

Re: Algae Sealant for Shingle Roof ??

May want to look at using some Zinc strips an in stall like deveters

Re: Algae Sealant for Shingle Roof ??

Lead or copper may work too, but will leave their own stains.

When in doubt I always say, "Gee, your hair looks terrific today"

Re: Algae Sealant for Shingle Roof ??

Maybe clear all out the bank accounts for cash then get a single one-way plane ticket to a country which doesn't have an extradition agreement with the US. I'm afraid that's the only long-term solution which is going to work here.


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