Hiring help to clean moss on Roof, Questions!

janjan212August 28, 2005


This is my first post to this forum, We have owned our 1993 built home for a few years now but have never had to hire anyone to do any maint. or repairs yet.

We have a fairly good amount of moss built up on the North side of our 2 story home and we don't feel at all comfortable attempting to get up there and do the cleaning job ourselves, and really wouldn't know what we were doing if we did. It's my understanding that basically they use a power washer to remove the moss and then treat with zinc to inhibit further growth.

We plan on getting several estimates but I would like to know what people have paid (or what people that do this type of work charge)...we have called one guy so far, he will do a drive-by and call us with an estimate but based on what we told him (2100 sq ft house, 2 story) that it will run us about 250.00. He was basing this on about 1000 sq ft (one side of the house) however when my hubby told me this I questioned the Sq footage as our house is 2 story so the roof is actually covering 1000 sq ft....and we only need the north side done, so I am thinking it's really only estimated at 500 sq feet??

Also, I saw some postings on Craigslist of others that do this type of work, if I inquiry about an estimate from here, what kinds of questions should I ask....for example, should I expect they be bonded, licenced, insured? I mean, if they aren't Am I liable if they fall off the roof?

I'm sorry if my questions sound so naive, like I said, I've never hired anyone to do anything in or at the house so I am not quite sure where to find people that do this type of work and what to expect. (We got this one guy's number off an flyer)

Any experiences or knowledge you can share would be appreciated!



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Is it a tile roof ?

I would call a regular roofer if I were you.

    Bookmark   August 29, 2005 at 6:45PM
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Sorry, I should have clarified. It's a shingle roof and I live in the Pacific NW so it's a typical moss buildup common in our area.

    Bookmark   August 29, 2005 at 8:35PM
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I have lived in the PNW for 30+ years and have always had cedar shakes...and the inevitable moss. I used to do it myself using a hose with a high pressure nozzle. I switched to a pressure washer about 5 years ago. The work goes faster, but I concluded during that time that it was also harder on the roof. I just had a professional do it for the first time and his approach was to use a powerful air blower to clean off the crap on the roof, and then spread a plant-safe, moss killing chemical that took about 6 weeks to completely zap the moss. He said this approach made the roof last longer and was as effective as a pressure washer if done regularly. I think he charged about $250 for over 2000 square feet of roof. If you live in the Seattle area, send me an email and I'll give you the contact info.

    Bookmark   August 29, 2005 at 8:59PM
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I would not want a pressure washer to be used to remove moss off an asphalt-based shingle roof. The granules would be removed which provides a lot of the shingle protection.

I would think there would be a chemical to spray on & rinse off w/ a regular water hose.

    Bookmark   September 6, 2005 at 12:26PM
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I'm in the northwest also, in deep forest. Four years after installing our asphalt shingles were mossy. I'd heard not to use pressure and wash off the granules, so I had someone come out and spray it with Safer moss killer. I don't remember how long it took - a month? The moss was gone without any damage to anything. It wasn't nearly as expensive as the estimates for pressure cleaning.

    Bookmark   September 16, 2005 at 12:08PM
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Someone told me once that spraying Roundup weed killer on a roof will kill the moss.

    Bookmark   October 13, 2005 at 5:16PM
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Hi Jan,

I would imagine that you may have decided upon a course of action by now but being that I am a pressure washer and before that I was a roofer for several years I just couldn't help throwing in my two cents.

First of all as far as cost goes I would say that the rough estimate you received was a pretty a competitive price, it's hard to be certain without seeing the job though. As far as questions to ask I would definitely ask about the insurance, license and bond; fortunately most people never have to use it but it does say something about the contractors approach to his work (operating legally is a good thing). If you choose to clean the moss off your roof by hiring a pressure washer you want to make sure that you hire an experienced professional and ask them what precautions they take against damaging your roof. People never ask me for references but I sure will if I ever hire a pressure washer when I'm too old to do my own roof.

It is very true that pressure washing can do serious damage to roofs but when used correctly it can be a safe means of cleaning. As far as the absolute safest way to clean moss off of a roof though I would have to say that the advice previously posted is good; to put moss killer on it and kill the moss first. You'll still usually have to clean the dead moss off but it comes off easier when it's dead. The best thing is to put moss killer on it every year whether or not you have moss and just prevent it from ever growing.

Hope this is helpful,


    Bookmark   October 29, 2005 at 3:30PM
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I live in New York and had moss build up on my Garage-I used a clorox mix specially designed for this . I purchased it at Home Depot. I used a garden hose and a sprayer to apply it and rinse it off.

    Bookmark   December 7, 2006 at 12:27AM
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