5 Reasons NOT to Use Flex Seal For Your RV Roof

As RVers, we’re all aware of the threats to the RV roof that can result in water leaking into various crevices of the rig, further threatening its structure and integrity, while potentially introducing (potentially dangerous) mold into the RV environment. While we’ve used a few different products over the years to keep the roof of our 2005 Newmar Mountain Aire well sealed, we’ve heard about, but never used, Flex Seal for our RV roof.

There are a number of reasons for this, and in today’s post, we’re going to share them with you in hopes of bringing a bit of awareness to what this product may be good for – and what it isn’t good for, including your RV’s roof.

What Is Flex Seal?

Flex Seal is a product that’s described by its manufacturer as a “liquid rubber sealant coating”, but in fact, Flex Seal is a name that represents a family of products including a paste, a caulk, a spray, a glue, and a tape.

These are deemed as amazingly adhesive and waterproof. Flex Seal is actually a silicone-based family of products.

Is Flex Seal the Best Product to Use on an RV Roof?

While it may be used in many applications, and some RVers have used the products with success, most RV technicians will tell you vehemently never to use Flex Seal on your RV for a number of reasons… and we agree.

In our opinion, Flex Seal is NOT the best product to use on an RV roof, and we’re here to tell you why we feel this way.

5 Reasons Not to Use Flex Seal on an RV Roof

There are a variety of products on the market for use on an RV roof. These products are intended to effectively seal areas of your rig’s roof to prevent leaks that can eventually seriously impact the structural integrity of your RV. So, products like these are no minor consideration.

When it comes to preventing leaks, you want the best product for the job. And generally speaking, your RV’s manufacturer has some opinions and recommendations about this very important maintenance matter as well.

Here are several reasons why the RVgeeks and many (if not most) RV techs and RV manufacturers are unlikely to recommend Flex Seal as a first-choice option for RV roof maintenance and repair.

Flex Seal is Not UV Stabilized

Flex Seal is not UV-stabilized, which means that its protection is highly unlikely to last in the harshly sunny environments that most RVs experience.

UV protection is a very important part of any product used to seal any part of your RV’s roof. Without UV protection, the product will dry out and crack, and the protection you think you’ve established will be gone, leaving your rig susceptible to leaks that you may not even be aware of until significant damage has occurred.

There are hundreds of complaints online about Flex Seal cracking and failing, and its lack of reliable UV stabilization is likely partly to blame.

Remember that RV manufacturers are well aware of the importance of UV protection and are unlikely to recommend the use of any product that doesn’t offer it, particularly for an RV roof.

It’s Made from Silicone

The members of the Flex Seal family of products are silicone-based. Silicone is not what you want to use on your RV’s roof because it leaves a residue that NOTHING else can stick to (including more silicone!), which bodes very poorly for any future repairs.

The Flexibility and Expansion/Contraction Characteristics Don’t Match That of an RV Roof

Your RV’s roof is a complex environment. The flexibility and/or expansion and contraction characteristics of Flex Seal products may not match those of the other materials on your RV’s roof, making these products more prone to cracking and separating, leaving your rig vulnerable to its greatest threat – leaks.

There are very good reasons why RV manufacturers use the products that they do. They’re matched as closely as possible to the other products they’ve used, ensuring the longest life and most durable protection.

The Movement of an RV Challenges the Holding Power of Flex Seal

An RV is a tough environment. Not only is the roof constantly subjected to UV rays and other threats, but the constant movement of a home-on-wheels poses special challenges to products used to seal all areas of an RV.

Is the holding power of silicone-based Flex Seal up to those challenges? We wouldn’t risk finding out the answer to that question the hard way.

There are Better Products on the Market for Your RV’s Roof

Perhaps the clearest reason we see not to use Flex Seal on your RV is the fact that there are plenty of better, more appropriate, tried-and-true products on the market to entrust with the critical responsibility of protecting your RV.

These products are regularly recommended by RV manufacturers and RV technicians alike, and have been proven to effectively protect RVs over many miles and decades. (Our 2005 Newmar is living proof!)

What Products Are Superior to Flex Seal for Use On an RV Roof?

The following products are superior to Flex Seal for use on an RV roof. These products are well proven to offer the protection an RV requires, and are recommended by professionals and consumers (RVers!) based on long-term experience.

Dicor Self-Leveling Lap Sealant

Way back in 2012 we published a post and a YouTube video about preventing roof leaks with proper Dicor maintenance. Ten years later (nearly 20 since we’ve been using the product), this system has never failed us – and we’ve put some serious miles, and constant full-time use, on and our.

You may also have seen us using Dicor on DIY tasks like our solar upgrade and our plumbing vent upgrade. You do NOT want your roof leaking, and tiny leaks from improperly sealed roof penetrations can be insidious and destructive. Using the proper product is absolutely crucial in our book.

Dicor is REGULARLY recommended by RV manufacturers and technicians, and this is with good reason. Actually, with many good reasons.

Dicor effectively seals everything from roof vent fans, to vent pipes, to screw heads, to the edges of your RV roof. It’s a lap sealant that was developed with the particular challenges of RVs in mind, and is compatible with EPDM and TPO roofs. Moreover, Dicor firmly and reliably adheres to fiberglass, metal, vinyl, aluminum, and a host of other surfaces not associated with RVs.

Stick with what works. You won’t want to encounter the consequences that can befall you otherwise.

Note that this Dicor product is a self-leveling lap sealant appropriate for HORIZONTAL (flat) applications.

If you need to use Dicor in a spot that ISN’T flat/horizontal, they offer a non-leveling version that is thicker and won’t run:

EternaBond Tape

You may have seen our post asking the question “Is EternaBond Tape Really Eternal?” EternaBond tape is made from synthetic polymers with a built-in primer and it’s not only supremely sticky but it’s UV resistant as well.

The bond created between your RV’s roof and EternaBond tape is a lasting bond that can only be interrupted with tremendous, purposeful effort. What you seal with EternaBond tape will remain sealed.

EternaBond tape has a specialized, UV-stable backing which, in combination with its layer of advanced MicroSealant, provides a waterproof, air-tight protection that is said to be flexible to -70 degrees Fahrenheit (-57°C).

Due to the extraordinary durability of EternaBond tape, once applied it doesn’t require regular maintenance.

This is a product that should be in everyone’s emergency kit onboard the RV.

ProFlex

If you happened to catch our post and video on how to replace an RV window, then you saw us using this product.

ProFlex is the sealant that Newmar, the manufacturer of our Class A RV, uses around the tops of all of the windows of the RVs they manufacture. They do this because it offers a reliable watertight seal, and that’s what all RVers want – reliable protection from potential insidious, tiny leaks that can ultimately cause mold and very serious damage to the structural integrity of the walls of an RV.

Since ProFlex isn’t silicone-based, it won’t leave behind a silicone residue. That means future seals/repairs will be sure to stick in place.

Newmar’s long-standing reputation for absolute top quality is enough for us. We’ll continue to go with their recommendation, which hasn’t failed us in our 17 years of ownership of this 2005 Newmar Mountain Aire.

If you intend to use ProFlex to seal your RV windows, be sure to watch the important tip at the end of our window replacement video.

Surebond SB-140 

And finally, if you’re resealing or replacing a skylight, Surebond SB-140 is the recommended product to use. Other sealants may react with, and damage, the plastics used to make skylights, meaning you’ll just have to replace your skylight again a lot sooner than you should have to (but be sure to check with the manufacturer of your replacement skylight and use the sealant they recommend).

Surebond SB-140 is made of butyl rubber and is rated to 200°F. The roof of an RV gets HOT (and especially the darker parts like a smoked plastic skylight), and exposure to the elements aren’t just a possibility – they’re guaranteed. Never risk using anything but the best and most highly recommended sealants on your roof.

Believe us when we tell you, you don’t want to risk a skylight leak. They can be hard to identify, and they can cause a lot of damage before you even know there’s a problem. Risking your RV to underrated or questionable sealant products is never a good idea.

Pro tip: If you do replace your skylight, we recommend having two tubes of Surebond on hand for this job. One tube just barely did the job for us, and we’ve heard from others that they couldn’t complete the job with a single tube.

For step-by-step instructions on skylight replacement, see our post and accompanying video here.

Have Some RVers Experienced Failures Using Flex Seal On an RV Roof?

Oh, yes. There are many complaints about the failure of Flex Seal online. With due respect to Flex Seal, there are also people who swear by the Flex Seal family of products or some member thereof. We just happen to believe in going with the RV manufacturer’s recommendations and not risking leaks – ever.

With that said, we offer these few online complaints from people who used Flex Seal on the RVs, in an effort to give you an idea of what to look for in terms of potential issues:

“I have used FlexSeal and it worked okay but only for a short while. Maybe it is better when used in a home. In an RV that is moving and shaking, FlexSeal will not stay attached to the repaired surface and will detach after a few drives. At least that was my experience.”

“I have used it. The product doesn’t hold up well to UV rays, and starts to peel after a while. The commercials are overblown. Once you put that crap on, it would be hard to get rid of it. If it is a leak on a roof, get eternabond tape and dicor caulking. It’s the proper product to use. It could save you thousands.”

There are numerous other comments online from experienced users of Flex Seal on an RV. We’ll let you search those out for yourself. We’re not trying to disparage the products here, after all. We’re simply pointing out that RVs may not be the best application for them.

When Would It Be Appropriate to Use Flex Seal On An RV Roof?

We recommend using Flex Seal on an RV roof only in an emergency – if you don’t have the appropriate products on hand and Flex Seal is what you have for your time-sensitive repair.

We choose to keep Dicor and EternaBond on hand, but if Flex Seal is your choice, then we certainly wish you the best with it. We don’t feel it’s the best product for an RV roof.

Just remember – RVs are twisting and turning and bouncing and vibrating all the time. If you have an issue in your static home, you may have success with any one of the Flex Seal products. But for your home-on-wheels, we believe there are better choices.

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