Flex Seal, Dicor, or EternaBond: What Belongs on an RV Roof

Flex Seal, Dicor, and EternaBond come up whenever owners ask what to put on a roof, and they aren’t interchangeable. One is a sealant for flat joints, one is a tape for seams, and one is a spray that belongs on a gutter, not an RV roof. Here’s how we sort them on a real job.

What is Dicor lap sealant for?

Self-levelling lap sealant is what most owners mean when they say Dicor, the way people say Kleenex. It goes on as a thick bead and flows out into a smooth, low dome that sheds water. That flow is the point, and it’s also the limit: self-levelling sealant only works on flat surfaces. Use it on vent flanges, skylight frames, the A/C surround, solar mounts, ladder feet, and antenna bases. On a vertical joint it runs off.

Non-sag lap sealant holds its shape. It’s for the front cap seam, sidewall transitions, window tops, and anything else that stands up. Self-levelling sealant on a front cap is a common owner mistake. It slumps into a thin smear with a crack along the top edge.

The catch with lap sealant is compatibility. Standard formulas are made for EPDM rubber and are fine on fiberglass (fibreglass) and aluminum, but some lap sealants aren’t rated for TPO. TPO roofs need a sealant the membrane maker approves, which is why we identify the roof type before opening a tube. The roof manufacturer, not the sealant brand, has the final say.

When should you use EternaBond tape?

EternaBond-style tape is a wide strip of butyl-type adhesive with a tough facing. It bonds by pressure, not by curing, so it’s much less sensitive to temperature than a wet sealant. Once it’s rolled down hard on a clean, dry surface, it holds well through a winter. That makes it the right product for seams, small tears, and the long transition where the roof meets the front cap. It’s also the right stopgap for any repair that has to last until spring.

Two rules. The surface has to be clean and completely dry, because the tape bonds to whatever it touches, including chalk and dew. And the edges get a thin bead of lap sealant afterwards, so water can’t work under the leading edge as the roof flexes. Tape without that edge seal is a common failure point on DIY repairs.

Can you use Flex Seal or silicone on an RV roof?

No. Spray-can and brush-on rubberized sealers are marketed hard, and they look convincing on television, but they aren’t made for RV roof membranes. They don’t bond reliably to EPDM or TPO, and they can’t flex with a seam the way lap sealant does. What they do well is contaminate the surface. Every proper repair that follows has to start by scraping and solvent-cleaning the overspray, and the membrane underneath is often damaged in the process.

Household silicone is the same story with a different label. It won’t bond to most membranes or to aluminum, and once it’s on a surface, nothing else will bond there either. Sealant applied over silicone residue lifts within a season. Both products turn a small sealing job into a removal job first. That is not a technician being fussy. It is the bill.

What does a professional RV roof reseal use?

• Failed sealant removed, not covered, so the new bead bonds to membrane rather than to cracks
• Membrane washed and de-chalked, then primed where the product calls for it
• Repair tape on seams and transitions, edges sealed
• Self-levelling lap sealant on every horizontal penetration, non-sag on every vertical joint
• Products matched to the roof type, especially on TPO
• Two coats of liquid rubber only where the whole roof qualifies for a coating

So what belongs on an RV roof?

Lap sealant for flat joints, non-sag for standing joints, tape for seams, nothing from a spray can, and always matched to the membrane. If the roof is EPDM and the sealant says EPDM, you’re fine. If the roof is TPO, read the label twice. And if you’re not sure what the roof is, that’s what an inspection is for.