Anybody have an idea what these spots are on my roof?

For the past few years I have noticed little black dots the size of the head of a pencil eraser. They will not wash off and I am persistent keeping the roof treated and washed with dicor cleaners made for the rubber roof .

The top layer of the roof is white but it's black underneath. Is it possible you're scrubbing too hard and rubbing the top layer off? I wash our roof every year or two, maybe. Only washed our last RV roof once that I can remember, never treated any of them. Last one was 10 years old when I sold it and it was in good shape. It sat outside year around...Just sayin..Don

I use the softest brush they had at CW and I only do it twice a year (beginning and end of the season). I started noticing them when I washed it the first time so I don't think so. Its parked under trees so I thought it may be sap but it will not wash off so I'm stumped.

Park under evergreens? I get the same where evergreen pitch drops onto my roof.

Brian

They don't come off. It's common to have the black spots show up around the 3rd year you have it, from what I understand they are spots where water or sap sat long enough to 'push' dirt into the membrane. Unless you wash it every week or never have rain and trees, its always going to look like that unless you decide to replace it. Scrubbing with anything but soap and water isn't a good idea though I did get some of ours to lighten using vinegar and baking soda.

I called Dicor regarding the same black spots.They are mold and recommended using household Tilex mold remover and that's what I have been using for the last 4 years on the Landmark.Just spray it on the roof and it will turn white again.I then thouroughly wash the roof with Dawn and then do the sides and ends of the RV .It looks like new again.I remove the mold annually but wash the roof twice a year.

Birchwood said:

I called Dicor regarding the same black spots.They are mold and recommended using household Tilex mold remover and that's what I have been using for the last 4 years on the Landmark.Just spray it on the roof and it will turn white again.I then thouroughly wash the roof with Dawn and then do the sides and ends of the RV .It looks like new again.I remove the mold annually but wash the roof twice a year.

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It is mold but I didn't want to say it, most folks freak at that thought. The reason I don't use chemicals is because it also thins the membrane, soap water wash, spot clean home made method. Eventually they will come up with a membrane that doesn't absorb mold and discolor.

ParkIt said:

It is mold but I didn't want to say it, most folks freak at that thought. The reason I don't use chemicals is because it also thins the membrane, soap water wash, spot clean home made method. Eventually they will come up with a membrane that doesn't absorb mold and discolor.

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Chemicals may not thin the rubber membrane as much as manual scrubbing with home made methods.

Birchwood said:

Chemicals may not thin the rubber membrane as much as manual scrubbing with home made methods.

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I avoid manual scrubbing at all costs. At my age its starting to fade out of my realm of reality.
It's why a bowl of vinegar and box of baking soda are easier...sprinkle on baking soda, sprinkle on vinegar, watch the bubbles, hose off

I will try the tilex. I figured it was sap or mold and now I know. I really appreciate all the replies.

ParkIt said:

It is mold but I didn't want to say it, most folks freak at that thought. The reason I don't use chemicals is because it also thins the membrane, soap water wash, spot clean home made method. Eventually they will come up with a membrane that doesn't absorb mold and discolor.

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And what proof do you have that it thins the membrane. You seem to have a lot of replys to threads that hold little, to no water.

The black spots on mine are usually around the vents and other protrusions in the roof. The vent caps are nearly black from it. I don't care what it is, it gets washed twice a year so I figure it is as clean as it is going to get. I am with those who don't care for too harsh of chemicals as long as it isn't in a living area it won't hurt you.

greatwhitenorth said:

And what proof do you have that it thins the membrane. You seem to have a lot of replys to threads that hold little, to no water.

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That's the goal, no water leaking.

Ok, seriously, the thickness and composition of EPDM is not designed to withstand UV-C rays, molds, pitch/sap, natures own so to speak. It's a porous surface so it can and will break down if you start using harsh chemicals on it over and above what nature does to it as well.
When working for the largest RV dealership out here we saw it all and got to mess with it all. Owner brings in a new unit with a tear so we had to replace it, out of sheer curiosity we took a 6x4' section, put it on the roof of a wrecked TT and did 'spot' tests of all types of cleaners. After letting it sit for a month checking it weekly we'd find the places where bleach, simple green, drain cleaner, 409 and 'roof cleaner' were thinner than the spots we used dish soap and water, baking soda and vinegar, and a citrus cleaner.

Somethings do not change in the industry, dicor and EPDM are two of those and we are due for a new material after using it for 30+ years.