Capri half-ton campers
Northstar Campers in 2017
Question Of The Week

The First Verdict on Waterproof Campers

This week we asked our readers about different ways we could improve the roof, side, and underbody seals on our truck campers using spray-on coatings and tapes.  We wanted to know if we could collectively find a way to waterproof campers.  The responses are fascinating.

Evidently, we’re not the only ones who have thought about this topic.  Finding sealant on your jeans – again – will do that.  So will finding a break in a seal you repaired a few months prior.  As I have said before, there has to be a better way.

This is going to be a long term project.  As truck camper owners ourselves, we are excited to try a number of possible solutions, and write about our experiences.  That said, we need to do more research, and it’s going to take time.  Since we love our truck camper, and want it to last, we are ready for the challenge.

“Hi Guys!  I have no research whatsoever to enlighten you with, but you did get me thinking about this subject.  In my opinion, the sealants that we have available to us are of good quality.  I believe flex and vibration are what actually causes the sealants to fail.

The flex and vibration in truck campers is caused by at least two things.  The lightweight construction demanded of RVs allows them to flex, almost by design.  How can a roof hatch physically seal to a panel that is almost constantly flexing?  It’s also moving due to temperature changes, road vibration, and the entire truck camper box being distorted by road bumps and the twisting of the truck bed.

Current truck camper tie downs have several mounting points; truck frame mounts, or bed mounts, and sometimes a combination of both.  Truck frames flex a lot!  Truck beds are even worse as they are mounted to the flexing frame by flexing rubber mounts.

Our truck campers are being pushed and pulled in all directions during normal driving conditions, and its wood or aluminum-alloy framing cannot keep the exterior panels from flexing.  I think rubber gaskets or O-rings are the closest thing we’ll find for an engineering solution (think roof mounted air conditioners) to this kind of flex issue.

We have a lot of custom sheet metal details in our house.  These elements need caulking where they seal, and where fasteners go through them.  It’s not so different than RVs, but admittedly the materials are sheet metal and wood, or sheet metal and steel with screws/nails.

That said, I have thirty years of experience sealing this beast and by far the best stuff is Vulkem 116 Polyurethane Sealant made by Tremco.  It’s available in a variety of colors.  Now, I’ve never tried it on our truck camper, because Truck Camper Magazine told me to buy Sikaflex 715 and 521 sealants!

If you’re going to try any experimentation, you might try the Vulkem caulk.  It’s a lot more viscous than the 715 and much different texture than other caulks, so really special stuff.  Just my two cents.  Keep up the good work!” – Bruce and Kathy Allison, 2000 Ford F350, 2012 Adventurer 910 FBS

“Having spent a large amount of my life outside in everything from deserts, to rain forests, to full monsoons in steaming jungles, staying dry is always a challenge.  One of the things I learned many years ago is that waterproof is not going to happen.  Designing to prevent water intrusion one must never forget the cardinal rule; that which can be kept out, also keeps in.

I have lost more to water retention than I have from water intrusion.  If you want to keep it dry, then you must be able to dry it out when – not if – it gets wet.  Without passing judgment on the application of Line-X on the Palomino, caution is advised or it becomes a container for water.

The key is to plan for mitigation when water is ingested.  For truck campers this begins at the design and material phase.  Use no fiberglass or other wool-like insulation.  Go with closed cell foam.  Choose an aluminum superstructure rather than wood.  In general use materials that do not absorb liquids.

If wood must be used, then it should be marine grade or waterproofed wood.  By design, you should avoid forward facing windows.  Rain at sixty-five miles per hour will find its way in.

Another major issue on truck campers are the seams on the front nose.  I can find no reason why the nose piece could not be a solid piece or bonded seams.  I have driven fiberglass cars since the 60s and never saw the ugly seams used like in the truck camper business.  I have never had a Corvette leak water through its body.

In addition, the aerodynamics of a truck camper are on par with a barn at best.  Water is often invited in due to poor aerodynamics.  This is 2015, not 1965.  Its time the truck camper industry looks at proven materials and designs to bring truck campers into the 21st century!” – Don Pryor, 2015 Ford F350, 2008 Arctic Fox 1150

“While my response does not specifically address your questions, I would like to weigh in on the topic.  Simply renewing the caulking on an older camper is really only a stop gap fix.  When I find that a line of caulk has failed on my older camper, I frequently scape it off and remove the molding and its sealing.

The butyl tape under the caulked molding ages, dries out, and becomes brittle.  As this is the last line of defense in the fight against water intrusion in my camper, I feel it is important to keep the molding sealant in good condition as well.

I generally remove the molding, remove all the butyl tape remnants from the molding and the camper, and then reapply a suitable putty to the molding.  The molding is reinstalled.  After a week or so, when excess putty has oozed out from beneath the molding, I apply the caulk.  While this is quite time intensive, it also works extremely well.

Butyl tape tends to come in three-quarter inch widths, too small to cover many moldings with one strip.  Since it is so expensive, I no longer use it under the moldings.  I use Gardner-Bender duct putty instead.  It is a fraction of the cost of butyl tape, seems to stay flexible over a larger temperature range, and is available at many hardware and building supply stores.” – Arn Chamberlain, 200 Ford F250, 2004 Palomino Maverick 8801

“I think the Kemper System liquid-applied waterproofing membrane for roofing and surfaces would be lighter and better than Line-X.” – Kevin Pinassi

“Well, unfortunately the Bronco truck camper is gone.  I needed more room and it was replaced by a toy hauler.  But I’m a huge fan of your magazine so I’ll still be following along. If I can find a good Lance 815, I’m going to buy it for beach travel.

I was involved in boat building for a few years.  Sealing a boat is even more important than sealing a truck camper!

I used 3M sealant and adhesives exclusively.  3M 5200 marine adhesive sealant is amazing stuff.  It should be at nearly $25 a tube!  Not only does it seal with a very flexible joint, but it has great adhesive qualities, so it stays attached to whatever you are sealing.  If the surface was prepared and cleaned properly, it isn’t coming off!  I’ve used it to secure fixtures where I simply didn’t want to drill a hole.  I’ve never had anything come lose.

The 5200 takes seven days to cure, but it is now available in a fast cure formula.  I’d suggest calling 3M and have a discussion about this and the other tapes and caulks they offer.” – Roy Bertalotto, 2006 Dodge 2500, 1998 Palomino Bronco 1200

“My 2015 Northstar 12STC camper came from factory nicely sealed everywhere with Eternabond.  Given that we carry a canoe, encounter low branches at put-ins, and rocks and sand from shoes when walking on the roof, I just had the polyurea coating applied.  It’s a step up from Line-X in thickness, flexibility, and adhesion to RV roof materials.

On the underside of the camper overhang, I’ve applied a couple of coats of Rust-Oleum LeakSeal to cover the factory paint and seal moisture out of wiring connections, screws and other penetrations.

On three previous trucks I’ve had Line-X bed liner applied before delivery.  On this truck I’ve just got the Ford rubber mat.  I don’t plan to carry lots of gravel as I did in the past.  When the bed eventually gets scratched up, I’ll go for Line-X again.” – Duncan Crawford, 2016 Ford F350, 2015 Northstar 12STC

“I have had the pleasure of working as a RV tech for quite a number of years, when I was a bit younger.  In my climate, the Canadian prairies, most of the water damage on campers happens while it’s been stored.  Up here RVs spend most of their lives idle, sitting, usually not under cover in the winter.  The freezing and thawing cycle can really beat up roof coatings.

Keeping an eye on sealants every season, and doing touch-ups and repairs is a must.  An experienced RV owner does not assume that all of the sealants around vents and windows are good for years without regular investigation.  Most of the expensive repairs that we do at the RV dealership could easily be avoided if the owner had paid more attention or brought it in for winterizing and a total exterior inspection.

After that, the best advice I constantly give our northern RV owners, is that proper storage is everything.  If possible store your camper under a roof.  The next level would be to build some mini trusses that sit up on your camper so you can use a tarp to keep the weather off.  This will allow a little slope and keep the tarp from touching the camper directly, and promoting some air movement.  Finally, at the very least, after a caulking and sealant inspection, store your camper on its stands on a little slope so that the moisture doesn’t just sit.  And remember, the most common failure point is the intersection of the front corners between the nose cone, the rubber roof, and the upper side molding.  When the self-leveling compound is applied here a little depression is created, which is unavoidable.  That’s where water can sit.” – Wes Hargreaves, 2016 Ford F450, 2006 Snowbird 108DS

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