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Question DetailsAsked on 11/19/2013

Need roof cleaned of moss

Looking for company to remove moss from my roof in Lake or Cuyahoga counties

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1 Answer


Some Handymen do roof cleaning, if you trust a handyman with your roof.

On the more professional side, a lot of gutter cleaners also do roof cleaning, and of course probably the least likely to cause damage would be a roofing company. Commercial cost - about $200-300 typically for cleaning with just washing and brooming followed by moss killer application. I have seen people have to pay $1000+ for detailed cleaning of every shingle slot on a heavily mossed roof.

Of course, if your roof is really heavily mossed (a mat of growth rather than just a light fuzz layer and little tufts at the tops of the slots) then you should initially clean a small area or two and look at the shingle condition - it might be better to put your money into a reroof job if the moss has heavily invaded the shingles, as the roots penetrate and break up the shingles, and also grow up under the shingles and cause water backup under the shingles, causing rot in the tar paper/wrap and sheathing under the shingles. I have seen several 20-30 year old roofs in my area recently that were total tearoffs and some even had truss/rafter damage due to heavy (1/2-6 inch thick) moss accumulation for many years - ond roofer even fell through into the attic while doing an estimate becausethe sheathing was so rotten it had turned to punk.

If you are up to getting on the roof yourself, you can use a jet nozzle like this one I use from Gilmore on your garden hose (assuming you have moderatley good water pressure - say about 40 psi plus -

to initially wash away the worst of the moss buildup and dirt from the roof. You do NOT want to use a pressure washer unless you are VERY good with it and keep it on fan setting, as it will remove the protective granules and can actually cut right through non-metallic shingles. A garden hose with a jet nozzle will not significantly damage a roof in decent condition as long as you do not push it right down tight to the shingle - just spray from standing position. Of course, if your roof is on its last legs, then you will get a lot of granule washoff. For thicker accumulation you may need a stiff pushbroom (a so-called "contractors" broom) to get the worst of it broken up after wetting.

Then after washing and brooming away the worst of it, sprinkle MossOut or similar zinc or copper based moss killer on the roof - for this type initial moss buildup application I recommend double the dosage shown on the can. Leave sit a week to two - it will kill the moss and mold and most lichens. Once they have all turned brown or gray, then wash off again thoroughly, using a scrub brush or stiff broom as necessary on tough spots, then retreat with MossOut as a preventative going forward.

I do NOT recommend the spray on type killer - because it is water based, it seems to just wash off in the first rain - use the granular powder type.

On a roof where moss has really taken hold for several years, for the initial cleaning you may have to get down and dirty and use a wire brush like this -

get ones like shown with a good upward handle arch to protect your knuckles, and wear a pair of REALLY heavy canvas or leather welding gloves or your hands WILL take a beating on the shingle granules. It takes sitting down on the roof and wire brushing out every shingle slot, scooting across the roof as you do. Be sure to either wear a pair of gym shorts under your pants or coveralls over pants, or you will end up feeling like you skidded down the street on your bottom afterwards - a single layer of jeans does not protect against several hours of sitting on granule-covered shingles. Yourhands will get tired, so if you do not do manual work commonly you may need several sessions of an hour or two each spread out over several days to brush the entire roof. One of these type steel bristle wire brushes will do about 500-1000SF of roof with moss in every shingle slot before it wears out, so it may take 2 to 4 of them to do an entire roof if mossed on all faces. Only costs about $1 or so per brush at places like Harbor Freight, Amazon, etc, so get extras. Generally, unless you roof it totally covered in moss, the narrower ones like I showed work better than the 1-2 inch wide ones, because you are largely going to be scraping only the slots in the shingles and along the bottom edges of the shingles, not the entire roof surface. BTW - for wood shingles/shakes, I would recommend brass rather than steel bristle brushes, so you don't gouge the wood so badly.

Do NOT try to remove the thin lichen or mold - you will just wear away the granules and not get all the lichen. It will wash away on its own after being killed. Also, scrape enough to get the moss off, but do not cut a groove in the shingles, removing all the granules. Typically, with the bulk of the moss already broomed or washed away, it takes about 2-3 swipes per slot to get it clean enough that the MossOut will take care of the remaining bit and roots.

Of course, keeping organic material and dust off the roof and allowing as much direct sunlight as possible is the key to stopping moss growth, which means cutting back overhanging and shading growth if possible, and washing the accumulated dust and seeds and debris off the roof at least yearly (usually after fall leaf fall just before snow cover) - twice in some areas of the country (especially if you get both fall leaf accumulation and heavy spring seed/seed pod buildup), maybe only every other or every third year or so in areas without adjacent trees to remove accumulated dust that can support lichen and moss growth. And of course reapplying moss killer after each thorough washing, or at least every 1-3 years depending on your rate of debris accumulation.

A zinc strip like ZincArmor or ZStop moss killing strip applied just below your ridge (or ridge vent) can also help matters, but will not handle it by itself in heavy debris accumulation or shade. On my roof, for instance, the zinc strip does fine for about 80% of the roof, but the shadier northwest corner still needs annual moss killer powdering to keep moss from growing.

Note that copper or zinc based moss killer washing or leaching off the roof will stress grass and can kill flowers and ornamental shrubs, so be sure your downspouts are at least 2 feet or more away from shrubs and gardens, and I would say 3-4 feet from food plantings. Normal lawn will yellow for a month or so where the roof runoff comes down after an application, but generally will not be killed. Sensitive lawn types like pure Kentucky Bluegrass and Zoysia have been know to be killed where the downspout dumps out, expecially in areas with infrequent rainfall so it does not get diluted fast.

Metal roofs are normally not as susceptible to moss buyildup, but if you need to use it check first with roof manufacturer - moss killer can damage raised seam metal roof paint and cause a whitish buildup on it, and can seriously discolor and bleach out copper roofing.

I fully realize some contributors will say wire brushing your roof and washing it every year will remove granules and shorten its life, which is true to a limited extent - but not as badly as letting things grow on it will.

Answered 6 years ago by LCD

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