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Old 07-22-2015, 04:00 PM   #1
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Roof Algae/ mildew/ mold ??

The weather has finally gotten nice ( read.. stopped raining ) here in southern Ohio. Today I decided to go up and do my annual on the fiberglass roof of the RV.
Normally car wash soap, and a long handled brush does the job and gets it 95 % clean. However today the roof was covered with small dark round spots, I scratched at one with a fingernail, and it looked green, so I am assuming algae. I tried a stronger cleanser, I tried a stiffer brush, nothing would touch the !$@#% spots. So as a last resort I got powdered Comet and a wire brush. Darn that's hard work. After 3-4 hrs I had to quit half done because I was afraid if I stayed up there any longer i wouldn't have the arm strength to get back down. Can anyone hazard an opinion on what these spots are ? Does anyone know of an easier way to remove them? I have a pressure washer which I use to clean my wood deck. I haven't used it on the RV roof in the past because the hose is relatively short, however, if it would get out these damn spots, I would be tempted to buy a longer hose.

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Old 07-22-2015, 04:11 PM   #2
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I would be reluctant to use the pressure washer on the roof.

I wonder (NO I am not prepared to suggest this as I said I wonder)
Would adding a bit of bleach help? Any one know enough to answer?

I do not?

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Old 07-22-2015, 04:26 PM   #3
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This year it rained every day before yesterday and today. I cleaned my roof back in the first of June and it was just dirty so I scrubbed it with a brush and Simple Green which makes the job easy. Put the unit back into the garage and it looks good.

But I offered to clean up my friend's trailer that sits out all the time. It had mold and moss growing all over it from all the rain and no sunshine for 1.5 months. The roof had mold growing under the TV antenna and under the AC shrouds and the sides were covered with black streaks. The only method I found to clean it was to spray Kroil oil on it and rub it in with a cloth and then spray with L.A. Awesome cleaner and scrub it off. Did only a spot about 2 sq. feet at a time but it got clean. Took 2.5 days to get it all clean and looking new.
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Old 07-22-2015, 07:27 PM   #4
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I live in Fl- I sprayed mine with a hydrogen peroxide solution-2 or 3 times

It works & I used it on the awning (applied solution with a wash mitt on a stick)
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Old 07-22-2015, 07:43 PM   #5
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Every 5G bucket of soapy water (car soap) gets 2-3 oz bleach too. I use an old long handled RV wash brush to scrub the roof. I've never had a problem with remaining mold or mildew after washing and rinsing. All the sides, awnings and covers are washed with the same solution.
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Old 07-22-2015, 08:48 PM   #6
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Bleach, that's what I use on the boat.
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Old 07-23-2015, 04:25 AM   #7
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I have used a combination of "car wash soap" in a bucket of water with a generous spray of Super Clean directly on the surface that I am scrubbing.
I use a 'soft' scrubbing brush on an extendable handle and scrub about 4 ft by 1/2 roof width at a time. (No longer kneel down and scrub...not necessary after the first time.
This has worked for me for years.
I scrub my fiberglass roof once/yr and hand wax after the cleaning.

So far, the roof is a clean bright white and only requires yearly maintenance.

I also use appx 30% bleach wash on the sides to keep the dreaded black spots away. Plenty or rinsing and the sides look like new and feel smooth. Next job is to wax .......
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Old 07-23-2015, 06:17 AM   #8
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Thanks Ray and others.. Now I know instead of wonder.. Sadly I'm not the O/P.

I had a trailer once that was parked for over a year under a pine tree. It was no longer anything approaching the factory shipped WHITE

I used bleach full strength. It was nice and white after that

Had a bit of moisture inside caused mold and mildew.. Took that out too Eliminated 100% but that puppy was not EDPM ruber, Bright Tech or anything other than fiberglass. So I had no qualms about bleadching it.
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Old 07-23-2015, 06:47 AM   #9
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Try a Mr. Clean Magic Eraser mop. My 15yr. old roof looks brand new.
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Old 07-23-2015, 07:24 AM   #10
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I used Mold Armor on the exterior sides of mine to remove the layers of dark mold. Stuff works fantastic. Home Depot carries it. I also used the HD brand (cheaper) and it worked well also.
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Old 07-23-2015, 07:30 AM   #11
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I mix up a mixture of water, car washing soap, and bleach in a two gallon yard sprayer. I use about two cups of bleach. Spray it on my RUBBER roof and simply let it sit for a while. I then spray it off using an aggressive spray nozzle and rinse everything away with lots and lots of water. If there are stubborn spots, I will apply a second coat and use a SOFT brush. If after all that there is still spots, I leave them alone.

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