Resealing an RV roof means renewing the sealant around everything that passes through it or meets its edges: vents, the air conditioner, skylights, antenna and pipe boots, screw heads and the edge trim. The method barely changes between roof types. What changes is which sealant you use and which cleaner is safe on the membrane. This guide follows Dicor's own instructions, from its product pages, FAQ and roof care handbook.
Step 1: find out what your roof is
Dicor's handbook gives a simple test. Look at a cut edge of the membrane, for example where it wraps over the roof edge under the trim or at a vent opening:
- Colored on top, black underneath: EPDM (rubber).
- Solid color all the way through: TPO.
- Fleece backing on the underside: TPO (fleece-backed).
Dicor doesn't give a visual test for PVC, so if you think you have a PVC roof, confirm it with your RV maker. Fiberglass and metal roofs are hard and obvious. Our Dicor roof reseal and coating kits page groups the parts by roof type once you know.
Step 2: choose the sealant for your roof
| Roof | Dicor sealant | Source of the rule |
|---|---|---|
| EPDM rubber | Self-leveling lap sealant on flat areas, non-sag lap sealant on edges and vertical faces | Handbook: "If your roofing is EPDM you can confidently use Dicor Lap Sealant" |
| TPO with fleece backing | Lap sealant | Handbook: lap sealant "will probably be the right choice" |
| TPO without fleece backing | Dicor's current FAQ says 501/551 lap sealant is compatible with TPO; the handbook recommends the Ultra Sealant System | FAQ; handbook (see note below) |
| PVC | Lap sealant (compatible per Dicor); Ultra Sealant is listed as an alternative | Lap sealant page; 2025 catalog |
| Roof coated with Dicor Signature silicone | Self-leveling or non-leveling Ultra Sealant | Signature coating page |
| Fiberglass or metal | Lap sealant (Dicor's fiberglass and metal coating directions use 501 lap sealant on fasteners and protrusions); Ultra Sealant is an alternative | Coating pages; 2025 catalog |
The TPO note. Dicor's handbook, printed in 2012, explains that some TPO membranes RV makers started using in 2011 reacted with the lap sealants then on the market and bloated. Dicor described this as cosmetic, not a loss of performance. Its current FAQ says 501 and 551 are compatible with EPDM, TPO and PVC. If you have a 2011-or-later RV with non-fleece TPO and want to follow the more cautious advice, use Ultra Sealant. Dicor requires its Ultra Sealant Primer on polypropylene roof accessories and some membranes before Ultra Sealant, and says the primer must never touch polycarbonate skylights. We carry that primer only inside the EPDM Plus roof installation kit, so ask us first.
For more on the two lap sealants, see Dicor self-leveling vs non-sag lap sealant.
Step 3: inspect before you seal
Dicor's handbook starts inside the RV, not on the roof. Leaks are hard to spot from above, so open cabinets and closets and look for mildew, mold, wet patches, water streaks or pooled water after rain. Then, on the roof:
- Press on the roof, including old patches. Soft spots can mean loose membrane or damaged decking underneath, which sealant won't fix.
- Look for low spots and ripples where water can pool. On EPDM, swollen or uneven areas can be a sign that cleaners with petroleum distillates were used.
- Check every bead of sealant around the edges, skylight, vents and accessories. Cracked, brittle, loose or curled-up sealant is a prime leak source.
- "Follow the dirt." If dirt streaks run underneath a seal, pull back the loose sealant. If the dirt continues underneath, water is probably getting in too.
Step 4: clean
Sealant only bonds to a clean, dry surface. Dicor's directions are to remove all dirt, loose paint, rust, oil and grease and let the surface dry. Dicor Rubber Roof Cleaner is formulated for EPDM, TPO, vinyl and fiberglass: spray it on, scrub in a circle with a sponge or medium-bristle brush, rinse and let it dry completely. On a rubber roof, Dicor warns against cleaners with petroleum distillates, harsh abrasives or citrus-based ingredients, because EPDM swells and can come loose from the deck. More in our guide to cleaning an RV rubber roof.
Step 5: remove what has failed
Dicor's handbook says minor cracks may only need cleaning and a fresh bead on top. Sealant that is too far gone needs the old material taken off first. Work carefully with a plastic scraper or putty knife so you don't cut the membrane. If you find a tear or puncture while you're there, repair it before resealing; see patch, tape or sealant.
Step 6: apply the new sealant
- In cold weather, warm the tubes to room temperature (Dicor's direction).
- Run self-leveling sealant over flange edges, screw heads and joints on the flat roof, and let it flow out.
- Use non-sag sealant on the edge trim, termination rails and any vertical face.
- If you are replacing an accessory, set it on butyl first. Dicor's Seal-Tite rooftop accessory install kit is made for that: Dicor says it's for any rooftop accessory, regardless of manufacturer or roof membrane.
- Keep the job dry. Dicor's lap sealant is waterproof in about 4 hours at 50 to 70°F, 80% cured at 48 hours and fully cured at 30 days. Ultra Sealant skins in about 30 minutes and is dry in about 2 hours at 77°F and 50% humidity, but Dicor says it may take several days to fully cure.
Expect some rippling as 501 cures, and a slight lift of the membrane next to the bead. Dicor says both are normal and settle within about two weeks.
Step 7: if you plan to coat the roof
Reseal first and wait. Dicor's FAQ says to do sealants about two weeks before coating; its handbook and fiberglass coating directions say one to two weeks. See Dicor roof coating: how much you need and how to apply it.
Stay safe up there
Dicor's own advice is that most inspection, cleaning and small repairs can be done from ladders or scaffolding at the side of the RV, and that a dealer is the safer option if roofs make you nervous. If you go up: never on a wet or slippery roof, check your shoe soles for stones, start on hands and knees, step on the roof's cross members where you can find them, and spread your weight with 2 x 8 or 2 x 10 planks. The deck under the membrane can be anything from 1/4 in lauan to 3/4 in plywood. Watch where you are when working backward.
FAQ
How do I tell EPDM from TPO?
Look at a cut edge. Dicor's rule: colored top and black bottom is EPDM; the same color all the way through, or a fleece backing, is TPO.
Does the roof warranty cover the sealant?
Dicor's FAQ describes its roofing warranty as covering the membrane against premature weathering, not the glue, lap sealant or butyl tape used to install it. Keeping the sealant in good shape is the owner's job.
Can I seal and coat on the same day?
No. Dicor says to let sealants cure for about two weeks before coating.
What do I need for a full reseal?
Cleaner, lap sealant in both versions in your roof color, a caulking gun, a plastic scraper, and butyl for any accessory you lift. Browse the Dicor collection, and send us the link if you see it for less elsewhere. Found it cheaper? We'll beat it.