Milky roof

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.


Jan 13, 2005
When we washed the roof of the coach prior to this trip, we saw for the first time milky white streaks down the sides of the coach. I asked the service tech to look at the roof and he reported that it was "oxidation" he'd seen on the roof of many coaches. If you rub the roof when it's dry, it leaves a white power-like residue on your hand.

Today I washed the roof with just plain water and a soft brush and from the photo you can see the milky pools of water under the coach. Also attached is a photo of a milky streak on the side of the coach.

The roof is white and very shiny. Although it's fiberglass, it doesn't appear to be gelcoat. What is typically used on the roof of a modern coach? If it was gelcoat, the only way I know to prevent oxidation is to apply a good coat of carnuba wax, but it wouldn't be safe to walk up there.

Any ideas?



  • milky.jpg
    43.5 KB · Views: 87
  • milky2.jpg
    14.1 KB · Views: 77
That white dust is called "Chalking" (THink of good old blackbord chalk) and it is absolutely normal on most materials.

It is how the roof cleans itself, as the sun beats down and damages the topmost surface of the roof, or the outer most molicules of paint on your house or anything else that is "Finished" the finish flakes away as dust, exposing fresh finish.  This is completly normal

On your house when it rains it washes the chalk off and you don't see it, (Usually) but your RV roof is flat enough that you do.

Brush up against your house, be it painted or aluminum sided, and you get a white streak on your arm.. Same stuff

So, what do you do about it:

Regular inspection and cleaning
Understand chalking John, but this is not normal. I'd call it excessive. I never had this on our prior coach and this coach has only just started to do it. No sign of it for the prior 2 years.

If the roof is fibreglass, wax it if it is rubber as in Brite tek, there are several cleaner/protectants that can be used.  I betting it is FG and it needs waxing.

Why I don't have a fibreglass roof.  that and cost.  OH, there is another alternative, Paint it and coat it with clear coat.  :-((

James Godward said:
If the roof is fibreglass, wax it

Jim, as I said, waxing it would make it unsafe to walk on.

I have the same problem with mine but not to a great extent. there always seems to be some white streaking. I had it on the Intrigue which also had a fiberglass roof. Clear coat would help but they just don't do that. It is a normal process.

Hi Jim. Understand that oxidation is normal on fiberglass - we work hard to prevent it on the boat, but this just seems so excessive on the roof of the coach. That's why I made the comment to John that this isn't normal. What's really strange is that the roof still has a very shiny appearance, which is not what I've seen on boats that have oxidized or, for that matter, our old coach. It made me wonder if the roof has been painted or had something applied and that coating is what we're seeing come off.

Do you apply anything to your fiberglass roof to prevent this?

It is strange that the roof is still shiny. Perhaps it's only areas of the roof that are oxidizing.

No, I don't do anything to prevent it though I have often thought about having clear coat added to the cap on the front and reapplied to the sides as it is peeling off. One thing I did, at Rons suggestion, is added a drip cap to the awning side rails made from a welting used in upholstery. It is white and matches the sides so it's not noticable and does prevent some of the streaking. Unfortunately when they repainted the coach they removed it and I didn't realize it hadn't been replaced until I started seeing the streaks. I really need to buy some more.

Thanks Jim. I'll take a look to see if gutters would help.
Fiberglass shouldn't chalk unless it oxidizes and it ain't gonna be shiny if it oxidized.  My guess is that you've are getting some kind of industrial fallout on your roof, which then washes down.  How long does it take for this stuff to accumulate enough to be noticeable?

Experiment: place some other material on top of the roof - maybe a 2x2 piece of tarp or even plywood. Let it sit for several days and see it if too gets a milky coating.
RV Roamer said:
Fiberglass shouldn't chalk unless it oxidizes and it ain't gonna be shiny if it oxidized.

That's my point. Good idea to put a catcher on the roof. This has happened at several geographic locations as much as  hundreds of miles apart, so I doubt it's the same fallout.

I wash the roof on our coach about every three or four months and there is always white chalking on the slide awning and on the ground, also down the sides but the roof has remained shiny and our coach is a '97.  I don't wax it for the same reason that I never waxed the non-skid on our boat because of it becoming slippery and unsafe.  Supposedly there is a wax or coating that you can apply that doesn't make it slippery and preserves the finish but am afraid to try it.  Can't remember what it is called either.  One of the service people several years ago said that it is very important to keep the roof clean and was glad to hear that I was washing it often.
Thanks Lorna. When the coach is in storage, it's a few months between washes. But we wash it much more often when we're on the road. The milky streaks appear down the side of the coach even when the a/c drips come down the side.

I'm with you on not waxing the roof. I don't do heights so, like you, Chris normally does the roof of the coach. But I've done the roof myself a few times, including yesterday.

Now I come to think about it, Chris also does the hard top on the boat (I shove her up through the hatch from the bridge). Admittedly the hard top gets carnuba wax, but not as often as the rest of the old tub gets waxed, and I've never seen this milky stuff come off there.
Gary Brinck said back in February:

Fiberglass roofs work fine and are probably the premier roof but they add quite a bit of weight and are generally not used unless the rig's chassis has plenty of weight capacity to spare.? ?There are also roofs that some people (including RV salesmen) erroneously refer to as fiberglass but in fact are a shiny, hard-finish EDPM rubber called by various brand names such as Britek. These are also excellent.? Next in quality are the soft EDPM rubber roofs.? It's only drawback is that it chalks a lot and sometimes gets dirt embedded into the pores of the material. Thus it typically requires a lot of cleaning of both the roof and the sides of the RV.

I don't think my chassis has plenty of weight capacity to spare, but I've been told that my roof is fiberglass.? Of course, I have no proof of that.  My roof is an off shade of white but isn't really shiny, except for the cap areas, but it doesn't feel soft either.? ? How do I know if my roof is fiberglass, hard-finish EDPM rubber, or soft EDPM rubber?? Is there any way to tell one from the other?

Latest posts

Forum statistics

Latest member
Top Bottom