To wash or not to wash you RV roof? That is a good question. A lot of dealers and people in the RV industry will tell you to wash your roof yearly. Many will tell you to wash and apply a coating to it yearly. If your RV roof is EPDM rubber membrane this advise is incorrect. I don't think they intentionally give you the incorrect information, I just think many are not aware of the actual manufacturer recommendations. I can assure you that this practice did not come from the manufacturer.
EPDM rubber roofing was developed for commercial applications. The black EPDM dominates the commercial roofing market today, but it is not used in the RV market due to heat related issues. It was intended to install and simply leave it alone. The EPDM rubber roofing is created to withstand UV sunlight and the exposure to outside elements. It was designed to be a low maintenance product.
The White EPDM rubber roofing is what I want to talk about today. It is what is used in the RV market. The White EPDM has a tendency to chalk. What I mean by this is that you will notice after a few years streaks running down the side of your camper. This occurs because the sunlight and UV rays shine on the membrane which causes the chalking. This will happen to almost any white rubber product when exposed directly to sunlight. Don't be alarmed when you see this happen, it is common. The manufacturers of the white EPDM membrane have never recommended cleaning it yearly. When you clean this membrane regularly, you are washing off the material that has chalked. This exposes a new layer to direct sunlight and it will also chalk. In a round about way you are washing away some of your roof. The dealer are recommending washing it and then coating it. Once you start coating a roof it can turn into an ongoing project which can prove costly as the years add up. A yearly inspection to check for holes or problems is a great idea, but not washing.