November 13, 2026 · 4 min read
Why a small roof leak ends as delamination
Most RV sidewalls are built like a sandwich. An outer fibreglass skin is glued to a thin backer board, which is bonded to the framing and insulation, with the interior panel on the inside. The wall gets its strength from that bond. When water reaches the backer, it swells, the adhesive lets go, and the skin stops being attached. You see it as a bubble, a wave, or a soft ripple in the side of the unit.
Water also travels. A leak that enters at a roof seam can run down inside the wall cavity and appear well away from where it got in, under a window, above a slide room, or along the floor edge. By the time a stain shows up inside, water has usually been working on that wall for a while.
That is why a useful inspection focuses on seals rather than stains. Checking sealant means checking the only places water can get in at all. Once the laminate separates, the job moves from a tube of sealant to structural repair.
Where seals actually fail first
An RV roof is really a collection of holes that have been sealed. Roof vents, a powered fan, a skylight, the air conditioner, the antenna, the plumbing vent, the fridge vent, solar brackets and ladder mounts all pass through the membrane. So does the long seam where the roof meets each sidewall, plus the joints at the front and rear caps.
Sealant fails in a predictable order. It shrinks, pulls back from the edge of a flange, develops fine cracks, then lifts at the corners. Cap seams usually go first because they take the most flex on the highway and the most sun. Around the air conditioner the rubber gasket compresses over the years instead, so watch the ceiling panel near the shroud for staining.
Do not stop at the roof. Window frames, corner trim, the awning rail, exterior lights, storage door frames and slide seals all fail the same way, and a leak there ends up in the same laminated wall. If you find a bubble low on a sidewall, the awning rail and the window above it are worth a close look.
A twice a year check you can do yourself
Start with safety. Not every RV roof is built to be walked on, and the weakest decking is often right where the leak is. If yours is not rated for your weight, work from a ladder at each corner or use a phone camera on a pole. Pick a dry day and wash the roof first with a cleaner safe for your membrane, so you are looking at sealant and not dirt.
Then work across the roof one section at a time. Look for cracks, gaps between the sealant and the membrane or flange, chalky brittle sealant you can lift with a fingernail, sealant pulled back from a screw head, any spot that feels soft underfoot, and low areas where water sits after rain. Follow both roof to wall seams end to end.
Finish inside. Check ceiling corners, the trim around vents and the skylight, the tops of overhead cabinets and the inside of storage lockers. Press anywhere suspicious. Spongy panelling, a dark line along a ceiling seam, or a musty smell all mean moisture. Outside, crouch at a corner and sight down the sidewall in low angled light, which makes waves and bubbles obvious.
Alberta weather, and when to bring it to Horton
Alberta is hard on sealant. Strong UV at our elevation, wide day to night temperature swings, chinooks that push an RV through freeze and thaw cycles all winter, hail and steady prairie wind all work on the same beads of caulking. Water that seeps in on a mild afternoon can freeze overnight and widen the path it came through, so sealant that looked fine in September is often cracked by spring.
Some of this is owner maintenance. Cleaning a seam and recoating a short crack is reasonable, as long as the product is right: a self-levelling sealant on horizontal roof surfaces, a non-levelling one on vertical seams, and a formula compatible with your roof material. The wrong product will not bond properly, and it can trap water underneath while looking tidy from the ground.
Bring it to Horton RV Services in Calgary when you find a soft spot in the decking, staining inside, a bubble or wave in a sidewall, water that appears in the rain from a source you cannot locate, or sealant that has been patched over several times. We can lift a vent or a section of trim and see what the water has actually reached, which is the only way to know how far it has gone. Caught early it is a seal job. Caught late it is a wall.
Common questions
How often should I inspect my RV roof and seals?
Twice a year is a good baseline: once in spring before you start using it, and once in fall before it goes into storage. In Alberta, add a check after any hailstorm, any windy highway trip through the mountains, and any time you notice a new smell or stain inside.
Can I just put fresh sealant over the old cracked sealant?
A thin refresh over sound, well bonded sealant is sometimes fine. Layering new product over sealant that is cracked, chalky or lifting is not, because it bridges the gap at the surface while water keeps running underneath. Failed sealant should be removed and the surface cleaned and prepped before new material goes on.
My sidewall has a small bubble. Is it too late?
Not necessarily, but it will not reverse on its own and it tends to spread. The first priority is finding and stopping the water. After that, the repair depends on how far the skin has separated and whether the backer and framing are still wet, so it is worth having it looked at before the next season of heat and freeze cycles.
Coverage and payout are determined by your insurer. Horton RV Services documents damage and writes repair estimates; we do not adjust claims or decide what a policy covers.