If you've ever clipped a tree limb pulling into a site or kissed a gas station pole on the way out, welcome to the club. Impact damage on the exterior wall is one of the most common calls I get, and the right repair depends entirely on one question: how deep did it go?
Most RV sidewalls are a sandwich: a thin Filon fiberglass skin laminated to a luan plywood backer, glued over wood or aluminum framing with insulation in the cavities. A few older rigs wear corrugated aluminum siding instead. The repair is different for each, so figure out which one you own before you buy a single thing.
Triage it in three tiers
Tier 1 — Cosmetic. Scuffed gel coat, a shallow spider crack, no daylight through the skin. This is a weekend touch-up, not a surgery.
Tier 2 — Skin cracked through. Water can now get in. It will, given one good rain. This needs a real repair before the next storm, not "sometime this summer."
Tier 3 — Structural. The wall is caved in, the skin is delaminated across a wide area, or the impact hit near a window or door frame and moved the opening. You're rebuilding a section of wall, not patching a hole.
Stop the bleeding first
Whatever tier you're in, seal it today. Drill a small hole at each end of any crack — that stops it from running further, the same way drilling the ends of a windshield crack works. Then lay a strip of EternaBond RoofSeal tape over the damage. It's ugly, but it's a waterproof bandage that buys you time to do the real job once instead of panicking twice. Nothing — not even more sealant — sticks to cured silicone, so skip the silicone tube from the junk drawer.
The honest quick patch
For Tier 2 damage where the wall behind it is still solid, the field patch is an aluminum plate. Cut a piece of 16-gauge aluminum a few inches larger than the damage in every direction. Butter the back with Dicor self-leveling lap sealant, screw it through into solid skin — not into the cracked mess, into good material — then run a clean bead of Dicor around all four edges and paint it to match once it skins over.
Does it look like a patch? Yes. Does it keep water out for years? Also yes. I'll take honest and watertight over pretty and leaking every single time.
The real fix: rebuild the panel
When the impact punched through the backer or caved the wall, here's the actual process:
Cut it out. Trim the damaged Filon back to clean, straight edges — square cuts between framing members, windows, or moldings. Ragged edges make weak joints. Peel back the skin to expose whatever it broke behind it.
Fix the bones. Pull out any cracked or water-damaged wood behind the break and replace it. It does not get better on its own, and covering it up just builds you a future rot job. Dry-fit everything before you glue anything.
Laminate the new panel. Cut your new luan backer and Filon skin slightly oversized, bond them together with a panel adhesive, then glue the assembly back to the framing and lock it down with staples around the perimeter — the moldings, windows, and hatch frames cover the staples, so the finished repair looks factory.
Seam it right. Leave about an eighth of an inch between new panels and cover the seams with bead molding, don't try to butt them tight — walls flex down the road and tight joints crack. Then paint to blend, and reseal every molding and trim piece you disturbed.
Aluminum siding version
Got the corrugated aluminum instead of fiberglass? Straighten the sharp edges as best you can, rivet a patch of matching aluminum over the damaged area, seal the edges, and run EternaBond over the whole repair if it needs belt-and-suspenders. It's less pretty to blend, but the patch is straightforward and permanent.
Mistakes I see on every other job
- Sealing the outside while the broken structure behind it still flexes and cracks the seal.
- Painting over a crack and calling it repaired — the crack is still a hole, it's just a painted one.
- Using silicone, then discovering nothing (not even more sealant) will stick to it later.
- Skipping the water test. Hose the repair down hard and check inside before you declare victory.
Impact damage looks scary, but the triage is simple: stop the water today, decide whether it's a patch or a panel, and do whichever one you picked all the way. Halfway is how you get to do it twice.
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