The question of caring for an EDPM roof is one which frequently comes up on the internet and via email which I receive. I will try to help with this issue, although I am not the final authority.
When we first purchased our RV, in 1998 I contacted Dicor Company via their company service line to ask about care of the roof. At that time I was told that the best thing to clean the roof with was a mild dish detergent like Ivory or Dawn. That is what I have used to clean ours with ever since. They also told me that to clean the roof too often was worse in terms of roof life than to not clean it at all. Dicor has made EDPM materials for use on flat industrial roofing for more than thirty years and some of the first installed are still in use today. If not subjected to abuse, they will last for a very long time with very little care. He suggested that we only wash our roof one or two times per year, just enough to keep it white. They also stated that the chalking is normal and if too much is removed it will speed the eventual failure. At that time they did not recommend any of the after care products, nor did they sell any.
Today they do sell both a treatment and a detergent. We continue to use dish detergent for washing but the treatments do seem to extend the life of the roofing now and so are probably worth the cost and work. What they do more than to extend the life is to slow the chalking effect and to thus keep the sides of the RV looking better. For that reason, I do suggest that you wash the roof about every six months and then apply one of the treatment products to it. I continue to use the products made by Dicor, just to be on the safe side, but I also know that there are other good products available. If you buy a product that is not from Dicor, do be sure to read the lable carefully to make sure that it does not contain any petroleum products as that will harm the roof.
In addition to an occasional washing, your roof has seams that are the largest potential problem for long life of the RV. Roof leaks are the enemy #1, in my opinion. They can be difficult to find and will cause hidden damage to an RV, sometimes before we know that they exist. For that reason I suggest that you examine the roof at least two times per year and also any time that you may have a limb or something rub along the surface of it.You want to make sure that the sealants around all roof penetrations are in good condition and replace if they show any signs of cracking or of coming loose. If the problem areas are small it is acceptable to just add some new caulk to that area but I like to replace all of ours on about a three year cycle. You can remove most of the old product with a plastic scraper/putty knife before you reseal. You do not need to get every single bit of old material off, only enough to prevent a major build-up over time which will begin to look ugly. I also always wash the roof well prior to starting this project. I use a soft brush on the seams and caulking as that will aid in getting it clean and it is much easier to see the condition if the roof and seams are as clean as possible.
When replacing the caulk, I always remove the material from one area at a time and then apply the new, just to be sure that any removed material has been replaced before I stop for the day. It is also wise to time this to a good weather forecast because you want the new caulk to have 24 hours to cure before you get significant rain on it. I only use caulk from Dicor, but there are others that are approved and can be used. When you buy the material, make sure that you get the right color as there are two or three of them. The Dicor self leveling, butyl caulk is what I always use, evn though it can be very messy. I am always amazed by the neat way that many of the professional RV techs can lay down a bead, when compared to what I do! Keep in mind that this is not a case of "more is better." With caulk you do want to be somewhat generous, but do not be wasteful as there is an effect on the EDPM by the curing of the caulk, even when from Dicor, so do not over use it.
While you are doing this, check the roof for any signs of tears or for loose spots in previous patches. There are some very good kits for repair of EDPM that are readily available at RV supply stores and which come with excellent instructions. This is a good time to take care of any roof repairs, if needed. Previous repairs will normally have caulk along the edges and if in question, carefully remove and replace that at this time. When you scrape the old material off, always scrape from the center of the patch toward the edge and away from it to avoid loosening the patch material. If you must make a patch, follow the insturctions very carefully, and do not omit any steps.
When doing the project, be sure that you look very closely at the areas along both sides of the cover over the end caps of the RV and also around the refrigerator vent, the skylights, bathroom and kitchen vents, all plumbing vents, any antennas or solar connections and any other place that there may be something which makes a hole in the roof material. Do not overlook the places where the ladder attaches to the roof. Side seams where the roof goes over the edge are not normally of much concern if you have a cove roof with rounded edges because in that design the roofing extends down over the top of the material of your side walls. If you have a flat roof those areas are of special concern because the water will stand in those areas.
I also examine the seal material along the edges of the front and rear caps where they are vertical and meet the sides of the RV as well when I do the roof. Vertical seams do not usually cause a problem but can when traveling in rain because moisture could be forced into any cracks. This is not a difficult job to do, but it does take quite a little time and effort. Use great care when you work on the roof for safety reasons and pay particular attention when it is wet. In addition, wear shoes that have a good grip and which do not carry any gravel or other foreign materials in the treads.
The last step in this process is to check the area well to be sure that no tool or materials are left on the roof, before carefully departing the roof with the knowledge that you have just saved yourself several hundred dollars! Clean your tools as soon as you stop since the caulk will be more difficult once cured. The final step is to get yourself your favorite cold beverage and chair, then sit and tell yourself just what a talented RV owner you are! If you happen to have an interested spouce or neighbor, it might well be a good time to share the information about your talents with them.