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When you start working on RV projects, it’s tempting to treat every sticky product as interchangeable. In reality, “sealants” and “adhesives” fall into a few different categories, and using the wrong one in the wrong place is how you end up with leaks, damage, or a nightmare removal job later.

Bedding adhesives (like butyl tape)

Bedding adhesives are used between a fixture and the RV roof or wall to create a waterproof layer under the hardware. Think of roof vents, windows, antenna bases, or cable entry glands—anything that bolts or screws down to the exterior.

• Butyl tape is the classic bedding adhesive for these jobs.
• It stays flexible, helps fill small gaps, and provides a long-term watertight layer under the flange.
• You still use mechanical fasteners (screws/bolts); the butyl isn’t there to hold the part on by itself, it’s there to seal the joint.

Once the part is bedded in butyl and fastened down, you usually finish the job with a separate sealant around the edges.

Combination adhesive–sealants (like 3m 5200 or 4200)

Some products are both adhesive and sealant. You can bed a part with them and also rely on them for some structural holding power.

• These vary a lot in how strong they bond, how flexible they stay, and how painful they are to remove later.
• Strong marine or construction adhesive–sealants can make future service very difficult if you ever need to replace the part.
• Many still need mechanical fasteners; you don’t want to rely solely on glue to hold critical exterior hardware on an RV.

I treat these as “glue that also seals,” but I still think about future maintenance before using the really permanent ones.

Straight adhesives (like VHB tape)

Some products are primarily adhesives, even if they’re weather-resistant.

• VHB (Very High Bond) tape is a good example: it creates a very strong bond and can be weatherproof, but it doesn’t replace a proper bedding layer or a separate sealant in most roof or wall penetrations.
• It’s great for mounting certain brackets, trim, or accessories where you don’t want to drill holes, but it’s not a cure-all for every waterproofing situation.

In other words, “sticks well” is not the same as “properly sealed.”

Sealants (like Lexel)

Sealants are mainly there to waterproof edges and joints, not to hold things together structurally.

• A product like Lexel is good at sealing seams, cracks, and the edges of attached fixtures or panels.
• It does not provide the same kind of long-term structural adhesion you get from a true adhesive or adhesive–sealant.
• You use it to keep water out at the edges of an assembly that’s already properly fastened and bedded.

Think of it as the weatherproof “bead around the outside,” not the thing that keeps the part from falling off.

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If you tell me whether you prefer this to be more technical, more casual, or to name specific brand/product examples you use, I can tune the tone and add a short closing paragraph.