Thread: OT Moss and other junk growing on roof

About 10 ft of the roof at one end of my house is shaded by oak and hickory trees. Roof is just architectural shingles... nothing fancy. I've got some moss growing on it in a few places, and a fairly widespread growth of some sort of gray-ish colored flat growing something-or-other that grows in sorta medallion shapes an inch or two in diameter.

Anyone have experience with any products or magic potions that are good for killing these sorts of growths?

Thanks in advance.

the other thing that is growing is lichens.
A simple way to prevent is by putting a strip or copper or zinc flashing under the shingles near the ridge. The runoff from rain will have an anti microbial effect on everything below it. I think they recommend a strip every 20' of roof run.
When you go up to install the flashing, I would start by cleaning off what is there first,and wash with a bleach/water solution to kill it off. Then the copper or zinc should keep it away.

Amen to the above !

Originally Posted by APD

the other thing that is growing is lichens.
A simple way to prevent is by putting a strip or copper or zinc flashing under the shingles near the ridge. The runoff from rain will have an anti microbial effect on everything below it. I think they recommend a strip every 20' of roof run.
When you go up to install the flashing, I would start by cleaning off what is there first,and wash with a bleach/water solution to kill it off. Then the copper or zinc should keep it away.

Use one or the other, not both, and neither with aluminium. My attached garage room has the same problem, and bigtime, but ..
partly because it has too flat a pitch and is shielded from wind as well as sunlight.

Airborne 'food' deposits for the lichens and moss just doesn't wash-off, and fibreglass/asphalt shingles are not at their best on shallow pitch anyway - they are meant to divert water to run-off, not actually resist immersion in it.

I may have to switch to overlap-ridged sheet fibreglass as well as replacing the aluminium flashing with copper, as it is trapping enough water to nurture ant colonies and destroy the underlying felt and plywood.

Watch where you step if atop it. I put a foot clear through one spot on mine.

Bill

Lichen are a peculiar symbiotic creature. Cross between animals and plants sort of. Fungus and a bacterium.

Mine sort of died out when my neighbor cut down the tree shading my garage roof. Poor fellas didn't like
the sunlight.

Thanks for the great information. I had no idea something that simple could prevent its return once its cleaned off. One further question on the flashing material though. Can it be slid all the way under a row of shingles? Or should it be placed such that half of it, or whatever, is exposed? I'd assume it needs some exposure, but obviously I'm no expert

Originally Posted by metlmunchr

Thanks for the great information. I had no idea something that simple could prevent its return once its cleaned off. One further question on the flashing material though. Can it be slid all the way under a row of shingles? Or should it be placed such that half of it, or whatever, is exposed? I'd assume it needs some exposure, but obviously I'm no expert

The toxic salts will form so long as air and moisture can reach the metal. A bit more water is needed to actually carry the zinc or copper salts TO the intended victims, so yes, a fair amount of exposure.

Bill

I've had the same problem on my roof, I bought a product called spray and forget.
You can either mix it 9 parts water to 1 part cleaner or 5 to 1 for a darker stained roof.
I used the 5 to 1 ratio and used a pump sprayer to spray the shingles, you do not rinse it off the rain does.
It comes in a gallon jug and costs $40.00.
This stuff really works, after 2 good rains my roof looks alot better.
The bottle reads that you can respray trouble spots in about 3 months.

This is probably an urban legend, but the tale goes that after a guy priced out all the options for a fix like this, he grabbed fifty cents worth of pennies, tossed 'em on the roof, and called it good.

Your mileage may vary. (He probably used old pennies, by the way...)

Chip

To follow up on this, I used a mix consisting of 4 gal water, 1 gal bleach, and 1 cup TSP to clean the roof. Sprayed it on an area, let it sit for about 30 minutes, and washed with a garden hose. Did a real good job of cleaning, but I did find the lichens in particular washed off much easier if I let the stuff sit a while rather than starting to wash it down immediately after spraying.

Ended up adding pre-formed zinc strips made for the purpose along the lower edge of the first course of shingles below the ridge. Was planning to shear some strips from copper roll flashing, but when I went to a roofing supply wholesaler to get the copper, one of the guys there told me about the zinc strips. They're in 3 ft lengths, about 3" wide, pre-punched and have a jog formed in them to allow easy installation with even exposure.

I'm not particularly enamored with the appearance of the zinc strips since the shingles are a medium brown, but I'd rather live with that than an ongoing battle with moss and lichens. Wifey hasn't griped about the appearance, and that's all that really matters That said, it would be good if they offered the same thing in copper as well as zinc.

One other thing worth mentioning here. Some of the rest of my roof had some areas that looked dirty but didn't have any moss or lichens. From another website, I was able to determine those stains were most likely algae. The same cleaning mix makes short work of the algae, but a caution is in order for anyone who attempts to clean anything like this off their own roof. I was wearing canvas shoes with a deck shoe type sole, and had good footing anywhere on the roof, wet or dry. But, the instant I sprayed the algae with cleaning solution, it became slick as greased ice. Once it was rinsed, it was back to normal, but if a person happened to be near the eave and step on some of this stuff it could put them off the roof before they had any time to react. The only safe way to work it, IMO, is to start at the ridge and work down, taking care to keep your feet on previously cleaned areas.