I have a rubber roof on my 2000 Allegro Bus and I was wondering the same thing. We also have some "powdering" on our roof but I have read that this is normal and that a rubber roof, properly cleaned with proper cleaning agents, will last a long time...this is what I found...hope it helps....
A Guide to Camper Care
One of the most neglected areas on your RV is the roof, out of site out of mind. The problem is if you donít keep the roof clean and inspect the roof seams on a regular basis you could end up with, expensive to repair, water damage. Most RVs built today use a rubber roofing material. If you want to get a long life out of your RV roof here are some things you can do.
Safety first! Be extremely careful whenever you are working on your RV roof. You can be seriously injured from a fall. You have to get on the roof of your RV to properly clean and inspect it for any damage or potential water leaks. The first step is the ladder you use to get up on the roof. If your RV does not have a ladder on the back to access the roof it is probably not designed to be walked on. In this situation, it may be necessary to use a couple pieces of plywood or particleboard to help distribute your weight. Many RV manufacturers have an option called roof rack and ladder ready. If the RV dealer orders this option the roof is built with a heavier roof decking. Even so, you need to walk lightly when youíre on the roof and be careful.
Rubber roofing on an RV is a great product, but like everything else without routine preventive maintenance it will not last as long as it could. First of all there are different types of rubber roofs. Different manufacturers provide different instructions with their product. What we want to concentrate on today is what applies to all rubber roofs used on RVs.
Caution: There are other types of RV roofing material used like fiberglass, aluminum and vinyl. READ your roof manufacturers instructions for proper cleaning and sealing techniques to prevent damage to your roof and possibly void your warranty.
Rubber roofs should be cleaned three to four times a year and depending on where you park or store your RV it may need to be cleaned more often. Regardless of the type of rubber roof you have, NEVER use any cleaners or conditioners that contain petroleum solvents, harsh abrasives, or citrus ingredients. These types of cleaners can cause permanent damage to any rubber or vinyl surface. Most manufacturers of rubber roofs recommend you use a medium bristle brush and a non-abrasive cleaner. For light cleaning you can use warm water and a mild detergent like Dawn dish washing liquid. To clean, condition and protect the roof I use B.E.S.T Rubber Roof cleaner and protectant. Hard to clean areas like stubborn stains caused by leaves, sap, mold or mildew may require a second treatment. Use caution to prevent the cleaners from getting on the sides of the RV. ALWAYS rinse the sides, front and back of your RV before rinsing the roof to prevent streaking or damage to the finish on your RV.
Cleaning the roof is only part of maintaining it. Every time you clean the roof you need to inspect the sealants around all of the openings and the seams on the roof. Water will take the path of least resistance and if there is the smallest opening it will find it. You need to thoroughly inspect the roof sealants for potential leaks and reseal any areas of the roof seams and around openings where you suspect a leak. Caution: Check with your RV dealer for sealants that are compatible with your roofing material.
I recently discovered a product called Eternabond, EternaBond
that you only need to use one time and the area youíre sealing is sealed for good. You can use it to permanently seal all the seams on your roof and itís great for repairing any damaged area like a rip or tears in the roof. Eternabond works on any type of RV roofing material and itís as easy to apply as a piece of tape.
Cleaning, inspecting and sealing your RV roof can add years to the life of the roof and help prevent costly repairs caused by water damage.