How to Seal an RV Roof in Canada: The Complete Dicor & Eternabond Guide
Step-by-step guide to sealing an RV roof using Dicor self-leveling lap sealant and Eternabond tape. Covers EPDM, TPO, and fibreglass substrates. Canadian climate considerations included.
If you own an RV and have never resealed the roof, you should. The average RV roof develops sealant failures within three to five years of the original manufacture date, and by year seven or eight, every lap joint and vent flange is a potential water entry point. In a wet Canadian climate, that means damage that starts as a stain and ends as delaminated wall panels and rotted subfloor.
The good news: sealing an RV roof is a half-day job that doesn't require professional training. The materials exist, they're accessible in Canada, and the process is straightforward once you know which product does what.
This guide covers the full sequence: inspection, Dicor lap sealant application, and Eternabond tape for open seams.
What You Need Before You Start
Materials:
- Dicor 501LSW Self-Leveling Lap Sealant (1 tube per vent flange, plus extras for screw heads)
- Eternabond RoofSeal Tape 4" × 50' (for any open seams or tears)
- Isopropyl alcohol (IPA) wipes for surface prep
- A caulk gun for the Dicor tubes
- Gloves
Tools:
- Soft-bristle brush for cleaning
- Putty knife for removing old failed sealant
- A seam roller or stiff credit card for Eternabond edge-pressing
Allow a full day for a typical Class C or travel trailer. Do not start if rain is forecast within 24 hours — though Dicor can be applied to damp surfaces in an emergency, dry conditions give the best bond.
Step 1: Inspection
Get on the roof safely. Walk the entire surface and look for:
Cracked or lifting sealant. Old Dicor turns chalky and eventually pulls away from the substrate. Any sealant that isn't bonded flush to both the flange and the roof membrane needs to come off before you apply new material.
Open seam lines. The longitudinal seams running the length of the roof are common failure points. Run your finger along them. Any gap wider than a hairline needs Eternabond, not just Dicor.
Soft or spongy spots. Press the roof firmly with both hands in a grid pattern. If any area gives slightly, there may be water trapped in the insulation below. This is beyond DIY scope and should be assessed by a dealer before you coat over it.
Bubbles or lifting membrane. On EPDM roofs, small bubbles are usually cosmetic — trapped air from installation. Larger areas of lifting membrane indicate adhesive failure and need professional attention.
Mark any problem areas with painter's tape before you come back down.
Step 2: Surface Preparation
For areas receiving Dicor: clean away any old sealant with a putty knife. Don't gouge the membrane — just lift the cracked material and remove it. Wipe the area with an IPA-dampened cloth and let dry completely.
For seams receiving Eternabond: this step matters more. Eternabond bonds permanently and cannot be repositioned, so the surface must be clean, dry, and free of oil. Clean with IPA, let dry fully, and confirm the surface is bone-dry before peeling the Eternabond backing. Even a trace of moisture under the tape will reduce the bond quality.
Step 3: Apply Dicor to Vent Flanges and Screw Heads
Dicor 501LSW is a self-leveling sealant, which means it flows and levels itself after application. You don't tool it with a finger the way you would a window caulk — just apply a continuous bead and let it flatten.
Around vent flanges: Apply a generous bead where the plastic vent flange meets the roof membrane. Start at one corner and work around the complete perimeter, including where the flange crosses any seam lines. The bead should be wide enough that, once leveled, it bridges the gap completely and extends onto both the flange and the membrane.
Over screw heads: Every screw penetrating the roof is a potential leak point. Apply a small bead directly over each screw head, centering the tip on the screw and letting the sealant flow outward. A properly applied screw bead looks like a small white dome when cured.
AC unit bases: The air conditioner base is the highest-traffic area and often the first to fail. Apply Dicor along the entire perimeter where the base flange meets the roof, including all four corners, which are the most vulnerable points.
Allow Dicor to cure tack-free before moving on to Eternabond. This takes 2–4 hours in warm weather.
Step 4: Apply Eternabond to Open Seams
Eternabond's microsealant adhesive is the permanent fix for any seam that Dicor alone can't address. If you've found open seam lines, rips, or areas where the membrane has pulled away from an edge, Eternabond is the correct product.
Measure before you cut. Cut the tape to length before peeling the backing. Eternabond becomes fully adhesive the moment the backing is removed — you don't want to be trying to reposition a sticky strip while on a ladder.
Centre the tape on the seam. Position the tape so the seam runs down the middle, with at least 1.5 inches of tape on each side. Peel the backing slowly while pressing the tape down, working from one end to the other.
Press firmly. Run your thumb along both edges of the tape with firm, sustained pressure. Pay special attention to the corners and edges — these are where the tape will lift first if not fully bonded. Use a seam roller if you have one; pressing with the flat of your hand works too.
The tape is immediately water-resistant. Full bond develops over 24 hours.
Canadian Climate Notes
Temperature: Both Dicor and Eternabond bond best above +10°C. In BC's shoulder seasons (March–April, October–November), try to pick a day forecast above that threshold. Cold surfaces slow the Dicor cure and can reduce Eternabond's initial tack.
Rain delay: After Dicor application, avoid rain for 24 hours. Eternabond is rain-safe immediately. If you're racing a weather system, prioritize Eternabond on any open seams first, then do Dicor on a dry day.
Annual inspection: Canadian freeze-thaw cycles are hard on sealants. Plan an inspection every spring after the last freeze, and again in early fall before the wet season. Catching a failed bead before it lets water in is a 30-minute Dicor job. Catching it after is a delamination project.
The Full Maintenance Kit
If you're doing this job properly, the Better Kit from Buy Roof Vent Repair contains everything in this guide: a roll of Eternabond, a gallon of Liquid Rubber for field coverage, and three tubes of Dicor — sized for a typical RV roof in a single maintenance session.
The Dicor and Eternabond application sequences above are what the kit is designed around.