RV roof · SEMCO Liquid Membrane
Projects › RV Roofs
By the time you can see an RV leak, you're not fixing a roof.
You're fixing the walls. RV roofs leak at the seams for months without a single drop showing inside — and the lightweight panels underneath soak it up until something goes soft. Seal the whole roof once.
A weekend, not a re-roof
Four steps. Every seam at once.
RV roofs leak at the penetrations, not in the middle of the membrane. Coat the whole roof and you stop chasing which one it was.
Clean it properly
Wash off dirt, chalk and road film, then use the cleaner pair matched to your roof. Rinse well and let it dry completely.
Reinforce every penetration
Fabric Reinforcement around each vent, fan, AC flange, skylight, antenna, ladder mount and both cap joints. This is where RV roofs leak.
Roll two coats
½" nap roller, thin and even, second coat perpendicular to the first. Coat the whole roof, not just the area you suspect.
Give it a dry window
Dry to touch in about an hour, initial cure at least 7 days — longer with thick coats or high humidity. Apply between 50–90°F — out of direct afternoon sun — and check the forecast before you start.
You won’t see an RV leak until it has already done damageThe first symptom is usually a musty smell, not a drip. RV walls and floors are lightweight laminated panels that hold moisture rather than shedding it — which is why the damage is structural before it’s visible. One customer paid a dealer to reseal preventatively and was smelling a leak within months.
Your rig
What does your roof need?
You know your rig’s length. We’ll work the roof area from it, then pick the right prep for what the roof is made of.
How long is your RV?
We work the roof area from your length at a typical 8 ft width.
What is the roof made of?
Not sure? Wipe it with a damp white rag — if the rag comes back chalky white, it’s EPDM.
Has it been coated before?
Dealers, previous owners and past DIY all leave something behind. “I don’t know” is the honest answer for most rigs.
Enter your length and roof type — we’ll work out exactly what the job needs.
Untick anything you already have. Quantities are editable.
Will it stick to mine?
Four roof types. No primer on any of them.
Most coatings in this category need a separate primer before they’ll bond to EPDM or TPO. This one doesn’t — it needs the right cleaning, which the calculator works out for you.
The most common RV roof, and the one that chalks. If a damp rag comes back white, that’s EPDM.
Prep B: Power Cleaner + Stone SoapCommon on newer rigs. Smoother than EPDM and doesn’t chalk, but the seams and penetrations fail the same way.
Prep B: Power Cleaner + Stone SoapRigid one-piece roofs, including moulded caps. Sand any gloss back for the best key.
Prep B: Power Cleaner + Stone SoapOlder trailers and vintage rigs. Seals fastener heads and lap joints — the two places metal roofs let go.
Prep D: Nu-Lift + Stone SoapVery common. Treat it as unknown and use the heavy-duty pair — then test a patch if there’s any chance of silicone.
Prep C: Power Cleaner + Nu-LiftSoft or rotten decking, delaminated panels, or structural damage. A coating seals a surface — it can’t rebuild what’s underneath. Fix that first.
Real rigs
Owners who got off the cycle.
Every RV review on file rates it five stars. These are unedited except for length.
“We started smelling evidence of a leak.”
Months after taking our camper to the dealer and paying for the roof to be resealed as a preventative measure, we started smelling evidence of a leak. After inspecting the rather poor job the dealer had done I decided to try resealing all the seams myself and bought this product. Painted this stuff on and it did the trick — smell went away and no evidence of leaks.
“Been holding up great last few years.”
Did my entire outside of my RV. Been holding up great last few years. Just recently bought myself some more of it to do parts of my house.
“Might need two or three coats.”
Easy to use, forms a great rubber barrier. Make sure to prep and clean first. Bonds really well. Might need two or three coats depending on how bad your RV roof is.
“Been holding up pretty great so far.”
I used the Liquid Membrane for my trailer to protect the wood. Been holding up pretty great so far! Will use it for some other projects around the house too.
“MUCH easier than replacing the membrane.”
Overall, I am impressed with the results I obtained in using your liquid membrane on my roof trailer. It was MUCH easier than replacing the membrane with new, and seems to have repaired my leaking roof, extending the life of my RV.
“Follow the application instructions correctly.”
I used this semco liquid membrane on my camper roof. First I prepped the surface using the cleaners. Then I used a 1/2" nap roller and applied 2 coats. I must say I’m super impressed, it goes on well — you have to follow the application instructions correctly to get the best results.
The honest part
You’re not choosing a sealant. You’re stuck in a cycle.
Every RV roof is punctured. Vents, fans, air conditioner, skylight, antenna, solar mounts, ladder brackets, plumbing stacks — and the cap joints where two panels meet. Each one is a hole through the membrane with a bead of lap sealant over it, sitting in UV all summer and flexed by every mile you drive.
So the sealant dries, shrinks and pulls away at the edges, and you go back up with a caulk gun. Everything in that aisle is maintenance rather than a fix. Coating the whole roof once is the exit.
The full version
Detailed application instructions.
01 Clean the roof
- EPDM, TPO, fiberglass — Prep B: Power Cleaner then Stone Soap.
- Aluminum or metal — Prep D: Nu-Lift then Stone Soap. Nu-Lift chemically etches the surface.
- Previously coated or unknown — Prep C: Power Cleaner then Nu-Lift.
- Sweep off debris and wash away road film.
- Apply the first cleaner, work it in with a soft brush, rinse thoroughly.
- Follow with the second, rinse again.
- Let it dry completely before you coat.
02 Reinforce every penetration
You’ll need: Fabric Reinforcement · Liquid Membrane
- Coat around the penetration generously.
- Lay Fabric Reinforcement into the wet coating and press it flat.
- Wait 10–15 minutes, then coat over it to encapsulate.
03 Roll two coats
- Check the reinforced areas are fully dry.
- Stir the product well — pigments settle and unstirred product gives uneven color.
- ½" nap roller, thin and even. Second coat perpendicular to the first, same day.
- Inspect for pinholes and thin spots — it dries lighter, which makes them easy to see.
04 Cure — and watch the forecast
Dry to touch in about an hour. Initial cure is at least 7 days — longer with thick coats or high humidity. Apply between 50–90°F, avoiding direct afternoon sun and anything over 85°F.
| Coverage | ~200 sq ft per gallon at 2 coats |
| Roof area | Length × 8 ft (typical RV width) |
| Initial cure | 7 days minimum · longer if thick or humid |
| Temperature | 50–90°F · not in direct afternoon sun or over 85°F |
| Warranty | 5 years, covers mobile applications |
| Primer | None — prep only |
RV questions
The ones worth asking.
Does the warranty actually cover a vehicle?
Yes. The 5-year warranty covers mobile applications, so it holds on a roof that travels at highway speed. Most coatings sold for RVs quote one to three years of expected life and don’t warrant vehicle use at all.
Do I need a primer for EPDM or TPO?
No. No primer for any of the four roof types. What you do need is the correct cleaning — the calculator picks the right pair from your roof type and whether it’s been coated before.
How do I know what my roof is made of?
Wipe it with a damp white rag. Chalky white residue means EPDM. Clean rag and a smoother surface is likely TPO. A hard, rigid one-piece surface is fiberglass. Metal is obvious. If you’re unsure, answer “yes or I don’t know” to the coating question — that routes you to the heavy-duty prep, which is the safe answer.
How often will I need to redo it?
Only when it needs it. There’s no annual reapplication built in, which is the main difference from lap sealant — that needs inspecting and topping up every year or two by design.
How much do I need?
Enter your rig’s length and we’ll work the roof area at a typical 8 ft width, then size it at 200 sq ft per gallon over two coats. A gallon covers a small trailer roof. A badly weathered roof may take a third coat, so size up if you’re between.
Can I walk on the roof afterwards?
Once fully cured, yes, for maintenance access. Dry to touch in about an hour, initial cure at least 7 days.
My ceiling already has a soft spot. Will this fix it?
No — and this is the honest answer. A soft spot means water has reached the structure, and a coating seals surfaces rather than rebuilding them. Get the damage repaired, then coat the roof to stop it happening again.
Not sure it’s right for your rig? Call 1-833-211-2297 — the team will tell you honestly if you need a shop instead.
Before you start
Additional information.
The manufacturer notes that decide whether this goes well. Most of the problems people report trace back to one of these.
Stop resealing it every spring. Seal the whole roof.
If you’ve been up there with a caulk gun more than once, the problem isn’t your sealant. It’s that you’re sealing one join at a time.
Size my roof