Lap sealant is the soft, rubbery material applied at every seam, joint, and penetration on your RV roof. It’s your roof’s first — and usually only — line of defense at the most vulnerable points. Understanding lap sealant: what it is, what it does, how to apply it correctly, and critically, when it’s no longer the right tool for the job, can save you thousands of dollars.

What Is Lap Sealant?

Standard RV lap sealant is a flexible, water-based or solvent-based polymer compound designed to remain flexible across a wide temperature range. The most common types are self-leveling (used on horizontal surfaces, flows into gaps) and non-sag (used on vertical surfaces and edges, holds in place). The most popular brand is Dicor, and it’s available in matching colors for most common roof colors.

Lifespan Realities

Here’s the honest answer the RV industry doesn’t emphasize enough: standard lap sealant has a functional life of 1–3 years under normal conditions. In harsh UV environments (the Southwest, high altitude), that drops to 1–2 years. In cold climates with significant freeze-thaw cycling, 2–3 years. This isn’t a product defect — it’s the inherent limitation of the material. Lap sealant is not a permanent solution. It’s maintenance. And it requires consistent re-application forever.

Proper Application

If you’re going to maintain your sealant, do it right. Surface prep is everything: clean the surface thoroughly, remove all old cracked sealant down to clean material, let it dry completely, prime if required by your sealant manufacturer. Apply in temperatures between 40°F and 90°F. Apply in a smooth bead, then smooth with a wet gloved finger. Don’t apply over old cracked sealant — you’re just hiding a problem.

The Decision Point: Stop Patching, Start Coating

There are three signs that lap sealant maintenance has stopped being effective and a permanent solution is needed: you’ve resealed the same areas two or more times and they’re failing again, you have evidence of water infiltration despite recent sealing, or your roof membrane itself is showing oxidation and aging. This is the point where polyurea coating makes economic sense — one investment that eliminates the maintenance cycle permanently. Our certified applicators can assess your specific situation and give you an honest recommendation.

For more hands-on guidance, visit our maintenance tips page or ask in our community forum where experienced members share their sealing routines.