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Why not use West System Epoxy to adhere components to RV roof?

Dear Dave, 
I’ve seen videos of folks using different adhesives to glue down various components on the RV’s roof and other places. Is there any reason why epoxies like West System are not used? I’ve used it extensively on any boats I’ve owned for repairs and construction as well as an adhesive. Works great. So why not on RVs? Thanks. —Mike, 2022 Thor Freedom Elite 24HE

Dear Mike,
I was not familiar with the West System Epoxy so I did some research. It looks like it is a resin/epoxy that is designed for fiberglass repair, which makes sense for boats. There are only a handful of RV manufacturers that use a fiberglass skin, such as Winnebago, Newmar, and some of the highline REV products. Typically the fiberglass skin of those RV roofs does not need to be repaired or reglued, rather, the seams are protected with a flexible component. Anywhere there is a hole cut in the roof and a component installed, like a roof vent, skylight, or water system vent, the space or gap between the component and the roof material needs to be sealed.

West System Epoxy would crack

The West System Epoxy cures hard. With temperature changes and road vibration, it would crack, causing a leak. Flexible sealants such as the Dicor Self-Leveling Lap Sealant or Heng’s NuFlex 311 are used as they adhere to fiberglass and the plastic of the component but have enough elasticity to expand and contract with temperature changes.

You probably saw several videos on sealing not only these components but also the front cap to roof material, roof to sidewall, and roof to backwall. Most front caps are a hard molded fiberglass that meets up with the roof, which could be either fiberglass or a rubber-type membrane. This is secured with a “J” channel, as these materials expand and contract at different rates during temperature changes, so the material and sealant need to expand with it.

Use recommended sealant

It is important to use the recommended sealant for the material that needs to be protected. Inexpensive units would have EPDM, that was first introduced to the RV market back in the mid- to late-1980s. Newer technologies have TPO, Alpha Systems, and some marketing as a PVC material trying to get away from the negative press of “rubber roofs”. However, all of these are a soft, flexible material. The West System Epoxy would harden and the flexing would crack it, even if it was just used to make a repair on a cut or adhere a component to the roof. It makes sense on a boat, as the shell of the boat is a hard molded fiberglass that is either a blown-on “chop gun” manufacturing process, or mat rolled, with both having a resin applied to “wet” it and dry as a hard shell.


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What should I use to clean and protect RV’s fiberglass roof?

Dear Dave,
What do you recommend to clean and protect my RV’s fiberglass roof? I have used Dawn dishwashing liquid and warm water with a soft brush to clean the tent material, but the top seems like it needs something stronger and maybe a stiff brush. Any suggestions would be appreciated. Thanks. —John Bilbrey, 2021 Forest River Flagstaff 206STSE pop-up camper

Read Dave’s answer.


Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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Dave Solberg
Dave Solberghttp://www.rv-seminars.com/
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.

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Cancelproof
2 months ago

Dave is 100% correct on this one. Using an epoxy for a roofing repair on anything but fiberglass is not the best choice. TPO , PVC, Hypolon, EPDM and other membranes will not flex the same with epoxies. None of the the membrane manufacturers would support or recommend the use of an epoxy.

I dont always agree with Dave but he has this one right. However, I don’t think silicone is a good product for these materials either. Use a single component Urethane caulking for durability and longevity.

Cal20Sailor
2 months ago

I doubt RVs experience anywhere near the pounding and temperature swings that a boat can see on a typical blue-water day sail or cruise, so the use of any good marine epoxy should work perfectly well on “land yachts”. Epoxy can be reinforced with fiberglass tape or chopped fiberglass filaments for areas that receive extra stress, and for “through hulls” or any other penetrations of the skin of the coach other marine sealants, such as the 3M products, would be perfectly adaptable, as well. Care should be taken to de-wax all surfaces to which the epoxy will be applied, and second coats should be preceded by a careful cleaning of the amine blush that forms on the skin of curing epoxy.

Cal20Sailor
2 months ago
Reply to  Cal20Sailor

Cancelproof is right, too. My comment should have been prefaced as being applicable only to fiberglass exterior skins.

Thomas D
2 months ago

Has Dave ever been on a smaller boat? The hammering of waves against the bow would be enough to open small cracks. A friend restores old wood boats and uses west system and never had any leaks later. Epoxy and rubber roofs probably won’t go together though.

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