Restoring Your RV Roof with RussOnTheRoad’s Three Minute Easy-Peasy RV Rooftop Bleaching Glop. No Scrubbing Required – Free Recipe

Reading time 8~12 minutes

Click or tap to enlarge. This is an unretouched photo showing sections of my RV’s mildewed roof before and after I used my bleaching glop. The bleached area isn’t perfectly white but it’s a lot better than it was and I’m hoping the sun will bleach out any staining that remains. Time will tell.

Recently I went up to the roof of the RV. I don’t remember why it was that I did, but when I got up top I was horrified to find that the roof was covered by black looking mold or mildew in places. As if I didn’t already have enough problems to deal with!

And so I panicked, thinking that my roof may have been destroyed and also knowing it costs thousands of dollars to have a new one put on a 5th wheel such as mine. Well, the good news is, if you can call it “good”, that I found out from Dicor, the company that makes the EPDM roof membrane that is probably used on most RVs, that their EPDM rubber RV roofs do not support the growth of mold and mildew in terms of providing nutrients for them to feed upon. What this means is that mold and mildew, if growing on the roof, are not so much attacking the roof as they are just living on top of it. So, this means that mold or mildew growth aren’t a major concern when it comes to the overall health of an EPDM roof. Phew!

Still, and even though such growth on an RV roof may not represent a major concern in terms of the integrity of the roof, it can’t lead to anything good, it is very unsightly, can prove difficult to remove, and can result in staining. I wanted it gone. The question was how to accomplish its removal. I am uncertain there is a one-size-fits-all solution but certain things would seem to apply across the board.

Mold, mildew on RV Roof
Mold and mildew can turn a pristine white RV roof into an ugly, frightening mess like this…my RV’s roof.

It may help to begin with what Dicor has to say. The company has published a series of articles for RVers in The Rudy RV Improvement Report Library. In Part One of their Roof Cleaning series of articles, Get The Stains Out, Dicor says that bleach can be used to remove stains from EPDM but they also caution that “overuse of such cleaners can damage the rubber”. Sodium hypochlorite, the chemical in household bleach, is dangerous stuff and I recall reading somewhere, I think on a bleach manufacturer’s web site, it should never be used full strength. One product Dicor recommends for mold and mildew removal is Tilex, and the active ingredient in Tilex is guess what, sodium hypochlorite, or good old household bleach. Tilex, at least some versions of it, also contain sodium hydroxide, otherwise known as lye, which is caustic.

One of the problems with using a bleaching agent on RV roofing, however, is the risk of bleaching things you do not want bleached, such as the sidewalls and paint or decals on them should the bleach run off the roof and down the sides of the RV. So, how do you prevent that from happening? This is the problem to which I struggled to find a solution and I believe I have. I call it RussOnTheRoad’s Three Minute Easy-Peasy RV Rooftop Bleaching Glop. No, I’m not selling it, but I will give you the recipe of this easy-to-make glop in exchange for your undying gratitude, or for using my Amazon Affiliate links when you shop at Amazon, or both 🙂

The idea behind my rooftop glop–kinda has a ring to it, doesn’t it?– was to make a thick bleaching agent that wouldn’t run, something gloppy that could be easily laid down, would stay in place while working for a few minutes, then be easily removed without the stuff running places where it wasn’t wanted, and, or course, something that would actually work well. I have concocted such a glop and tested it on my own RV EPDM roof. It works! Yay, me! LOL.

The magic ingredient in my roof glop is nothing other than, drumroll….cornstarch. Yep, cornstarch that you can buy at the grocery store for less than $2 a pound. Apart from that all you will need to make RussOnTheRoad’s Rooftop Glop is water and household bleach. I’ll provide a recipe that makes about a cup and you can adjust it to make more or less as need be. You can also adjust the strength of the glop by adjusting the amount of bleach and/or water you add to the glop’s cornstarch base once it’s made. I don’t know how long it will keep so I use what I make right away.

Recipe: RussOnTheRoad’s Three Minute Easly-Peasy RV Rooftop Bleaching Glop. Note: Bleach is Hazardous – Use at Your Own Risk – No Warranty is Expressed or Implied
1 cup cool water
4 Tbsp. cornstarch
2 Tbsp. water
3 Tbsp. of household bleach

Step 1: The first step of making RussOnTheRoad’s RV Rooftop Bleaching Glop is to prepare the base cornstarch glop. To do so pour one cup of cool water into a saucepan and gradually add 4 Tbsp. of cornstarch while stirring until you have a smooth milky mixture. Next, place the saucepan with mixture on medium heat on the stove and heat while stirring until it starts to thicken. You’ll see it starting to coagulate into clumps and then all a sudden the whole thing will turn into a glop and the mixture will begin showing some translucence as if it is starting to become clear. Once that happens–it happens quickly–remove the saucepan from the heat and let it cool. When cooled you should have a thick, pasty glop.

Step 2: Spoon out the cornstarch glop into a bleach safe container with room for stirring. I used a plastic food storage container with a snap on lid to make spillage less likely when transporting the glop to the roof.

Step 3: Stir two tablespoons of water into the glop until blended in.

Step 3: Carefully–because bleach is dangerous–stir three tablespoons of bleach into the mixture until thoroughly mixed in.

The idea is to make a bleaching glop that has enough bleaching power to remove the mold or mildew from the roof while remaining thick enough that it won’t run and wind up in places where it is unwanted. Depending upon how thick your cornstarch glop comes out you may need to adjust the amount of water you add to it to achieve the ideal consistency for your application. It may require that you make several test batches until you have the recipe just the way you like it. The recipe I have provided should be a good starting point. I prefer a recipe with slightly more bleach.

Glopping Your Roof
I used a plastic putty knife to apply the glop to my roof. I wasn’t able to apply it with perfect uniformity, but that shouldn’t be necessary. How thick it should be applied may be a matter of trial and error, but I don’t think it’s critical except to make the application thick enough. I’d say 1/8″ to 1/4″ thick should be sufficient. If applied to thinly it may not bleach as well as it might otherwise. If applied too thickly I think the only consequence may be using more than you need. Experiment.

Note: all the photos with this article can be enlarged by clicking on them, sometimes twice.

Bleach glop on the roof
This photo shows my third batch of test glop that has been applied to all three test areas. Note the yellowish color on left of in Area 3 which is being bleached for the first time.

After applying the glop I let it sit for about 3 minutes, watching it to make sure it didn’t run. It didn’t. Not in any of the tests I performed. I had previously tried using baking soda as a base instead of cornstarch but it didn’t work well. Liquid tended to seep out and run to places it wasn’t wanted.

After 3 minutes or so–I expect you can let it sit a little longer or for less time if you like–I used the putty knife to scoop up as much of the glop as I could, rinsing the putty knife in a bucket of water briefly with each scoop. For larger areas I think I might use a plastic dust pan to gather up the glop. You might find more suitable tools, but don’t use anything sharp on your roof that could damage the EPDM, or anything that can be damaged by bleach or combined with it to create something noxious.

Once I had gotten as much of the glop off the roof as I could easily do with the putty knife I wiped the area with a water moistend sponge to gather up the rest. Then, to neutralize any bleach that might have been left behind I wiped the area with another sponge that I had moistened with white vinegar. The pH of bleach is very base, and vinegar is acidic so they tend to neutralize each other. Then I gave the area a final wipe with plain water. DO NOT mix bleach with vinegar as it will form chlorine gas which is toxic. If you’re outdoors and merely wiping a surface that has been bleached and then wiped clean or rinsed, applying vinegar isn’t going to create any appreciable amount of chlorine gas so it should be safe to do.

Below are some photos showing my tests and results on my own RV roof. I tried three different concoctions. I started with one but it didn’t bleach as well as I wanted so I added more bleach. That worked better and it’s the recipe I provide on this page. Then I tried a third mixture that had yet more bleach, a little more water and more cornstarch. The recipe is adjustable, but I’d say start with the one I offer and adjust as you see fit.

Firs bleaching test
This photo shows a section of my roof that had been bleached for 3 minutes or so with my first test batch of bleaching glop. I wasn’t satisfied with the amount of stain removal so I added more bleach to the glop.
Area 2 has been bleached one time with my second batch of test bleach glop. Area 1 has been bleached twice: once with my first batch of test bleach glop, then again with the second batch of test bleach glop.
Here, Area 3 has been bleached once with my third test batch of bleaching glop; Area 2 was bleached twice, one each with my second and third batches of glop; Area 1 was bleached three times, once with each batch of glop.

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