RV Roof Sealants — What to Use, When, and Why It Matters

The Question Everyone Asks

"Should I use Dicor or Alpha?" gets posted in RV groups every week. The answers are all over the place. Some people swear by one, some swear by the other, and a few will tell you both are fine. The confusion isn't because people are wrong — it's because they're skipping a step.

The real question isn't Dicor or Alpha. The real question is: what roof do you have, and what are you sealing?

Once you know that, the answer gets a lot clearer. Not always clean-cut — this is an RV, after all — but a lot clearer.

Know Your Roof Before You Buy Anything

Before you grab a tube of anything, you need to know what material you're working with. The roof type dictates the sealant — not the other way around.

If you're not sure what you have, look for a label or stamp on the roof membrane itself — sometimes near the edge or around the ladder area. Your owner's manual may also list it. If all else fails, the manufacturer can tell you based on year and model.

Self-Leveling vs Non-Sag — They're Not Interchangeable

This is where a lot of people go wrong. They grab whatever tube is on the shelf without thinking about where it's going. These are two different products for two different jobs.

Type	Where It Goes	How It Works
Self-Leveling	Horizontal surfaces — roof seams, around vents, AC units, antennas, anything flat on top of the roof	Flows out and levels itself into seams and gaps. Settles into a smooth, even bead. Needs a flat surface to work properly.
Non-Sag	Vertical and angled surfaces — side edges of the roof, trim, corners, end caps, around windows and doors	Stays where you put it. Won't run or drip. Holds its shape on vertical surfaces.

If you use self-leveling on a vertical surface, it runs. You end up with a mess and no seal. If you use non-sag on a horizontal roof seam, it works — but it won't flow into the seam the way self-leveling does, and you're more likely to leave gaps.

Match the product to the surface. It's one of those things that seems obvious once you know it, but nobody tells you until after you've made the mistake.

Dicor vs Alpha — What's Actually Going On

Here's the part that causes all the confusion: both Dicor and Alpha say their products are suitable for TPO roofs, but both also recommend using only their own brand. That sounds contradictory. It's not — once you understand why they say it.

Each company tests and warranties their sealant with their own roofing material. They can only guarantee performance under those conditions. When they say "use only our product," they're protecting themselves from liability — not necessarily telling you the other product will fail.

Dicor

Dicor is the universal aftermarket sealant. It's designed to work across multiple roof types — TPO, EPDM, PVC. It's been the go-to for RV owners and techs for years. If you don't know your roof brand, Dicor is the safer bet because it's formulated for broad compatibility.

Alpha Systems

Alpha is a system-specific sealant designed to match Alpha-brand roofing materials. A lot of RV manufacturers install Alpha roofs at the factory. If your rig came with an Alpha roof, their sealant is formulated to bond best with that specific material.

So Which One Do You Use?

In most cases, both products will adhere to TPO, remain flexible, and hold up under typical RV roof conditions. The difference isn't that one works and the other doesn't — it's about intended use and which system it was designed to match.

Don't Mix Sealants on the Same Seam

This one is straightforward: if you're resealing a seam, remove the old sealant before applying new. Don't layer one brand on top of another. Don't put self-leveling over non-sag. Don't put Dicor over Alpha or vice versa on the same joint.

Different formulations can have different adhesion chemistry, flexibility rates, and curing behavior. Layering them can cause the new sealant to not bond properly, peel, or crack along the boundary between old and new material.

Take the time to clean it down to the roof surface. If you're going to do the job, do it right. A reseal done over old product is a temporary fix that usually comes back as a leak.

Prep Matters More Than the Tube

This is the part most people skip, and it's the reason most reseals fail. The sealant is only as good as the surface it goes on.

If you lay new sealant over dirt, old residue, or oxidized material, it's not bonding to the roof — it's bonding to the junk on top of the roof. It might look fine for a few months. Then it lifts, cracks, or peels, and you're chasing the same leak again.

How to Prep Properly

Remove old sealant. Use a plastic scraper — not a metal blade — so you don't gouge or scratch the roof membrane. You want to get down to clean material without damaging the surface underneath.

Clean the surface. Use a solvent designed for the job. Acrysol body solvent works well — it cleans without attacking the membrane. Wipe it down, let it dry completely. If the surface isn't clean and dry, the sealant won't stick the way it needs to.

Inspect before you seal. Once the old sealant is off, look at what's underneath. Is the roof material in good shape? Is there any discoloration, soft spots, or signs of moisture intrusion? If the substrate is compromised, sealing over it won't fix the problem — it'll hide it until it gets worse.

Tools for the Job

Here's what we'd grab for a roof reseal — not a sales pitch, a tool list from a tech who does this regularly. You don't need everything on this list for every job, but these are the products that work and hold up.

Disclosure: Some of the links below are affiliate links. If you purchase through them, we may earn a small commission at no extra cost to you. We only recommend products we actually use and trust.

Prep Tools

Roof Seams & Penetrations (Self-Leveling)

Roof Edges & Vertical Surfaces (Non-Sag)

Body & Exterior Sealing

Hardware

When to Reseal vs When to Call It

A reseal fixes the problem when the sealant has aged, cracked, or pulled away from a seam — and the material underneath is still solid. That's a maintenance task. It's normal. Sealant doesn't last forever, and resealing your roof every few years is part of RV ownership.

But a reseal doesn't fix everything.

If the decking underneath is soft, spongy, discolored, or delaminated, moisture has already gotten past the sealant and started breaking down the structure. At that point, sealing over it is hiding the problem, not fixing it. The water that's already in there will continue to do damage — and now you've sealed it in.

Signs You've Moved Past a Reseal

Soft spots on the roof — if the surface gives when you step on it, the substrate is compromised.

Discoloration or staining around seams — water has been getting in for a while.

Interior ceiling stains or bubbling — the leak has already traveled through the structure.

Delamination on the sidewall below the roofline — water has migrated down and is separating the wall layers.