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Repairing Your RV Underbelly? Here’s What You Need to Know

Repairing Your RV Underbelly? Here’s What You Need to Know

When RVers head out for a weekend camping trip, they usually do a walk-around to inspect their rig. They look for loose bolts, check the lug nuts and the tire pressure, and perform other tasks before taking off. But one area you may not think to look at is underneath your RV. Inspect your RV underbelly regularly. Some RV’s have a plastic cover that protects your RV, and you don’t want road debris or rain getting inside as you travel. Let’s look at what you need to know if you need to repair your underbelly.

RV Underbelly With Repair Tape

What Is Your RV Underbelly?

The RV underbelly is just the term for the underside of an RV. Many times the term is used to refer to the actual covering that protects and insulates the underside. It also prevents small critters from crawling up into the RV, where they can do serious damage. But this doesn’t mean it never gets damaged. Just like any other part of your RV, maintaining and repairing your RV underbelly is important to the overall condition of the rig.

Not Covered Underbelly of RV
Not all RV underbellies are covered. This is an example of an underbelly with exposed tanks (Although they are protected)

Are All RV Underbellies the Same?

RV underbellies vary. Some have coverings and others do not. If an RV is 4-season rated or a higher-end build this usually means it has an underbelly covering that includes added insulation to keep tanks and pipes from freezing. Different manufacturers use different materials for these covers. Higher-end fifth wheels won’t have the same underbelly as an entry-level travel trailer. Some underbellies use a flexible tarp-like material, while others have Coroplast sheets. Many motorhomes

Dielse Motorhome Underbelly
Diesel Motorhome Underbellies are usually metal or wood with a frame holding them together.

Still, other RV underbellies have one solid piece of corrugated plastic. This can make repairing them a bit more difficult since you have to deal with one huge sheet. Older RVs and many diesel motorhomes may have underbellies made from metal or wood and fiberglass RV’s usually use a fiberglass sheet.

One Solid Piece of Plastic Underbelly
This is an example of a single-piece RV underbelly covering. Usually, repairs of anything under the RV floor with this type require cutting into the material and then taping it back together.

What Causes RV Underbelly Damage?

It may seem like road damage would be the most likley cause of RV underbelly damage, but usually the damage comes from within. Water damage is the most common and can come from a cracked water tank, a broken hose, a broken valve seal on the water filter, or something else. This could make for extensive repairs that must be taken care of immediately. Water and moisture are RV enemies.

Additionally, you may encounter a torn piece of tarp or a broken sheet of plastic. This could happen from the wear and age of the RV. You might have hit something in the road that bounced up and struck the RV underbelly. Or an animal may have clawed at it.  But no matter what the reason for the damage, it’s sometimes not a difficult task to fix yourself.

Pro Tip: We took a closer look at The Biggest Downfall to RVs and how the damage could impact your trip.

Underbelly seperation from RV
Underbelly damage is not uncommon on RVs. This underbelly material has started separating from the RV and the edge material that held it on.

How to Fix a Torn Underbelly

If you have a simple tear in the tarp or plastic, most of the time, you’ll just need to tape it back together. Luckily there is specific underbelly tape for this purpose. You won’t need to remove it or have any special tools nearby. RV underbelly tape uses an adhesive polyethylene material. You can easily use this sturdy, durable, and waterproof product. Clean the area around the tear before applying the tape. Ensure all edges and corners bond tightly to the underbelly, and you’re all set!

RV underbelly Material RV Underbelly Tape Mobile...
  • What you will receive: the package includes 1 piece of RV...
  • Good adhesiveness: the home wrap tape has good adhesiveness,...
  • How to use: the mobile home tape is convenient to operate,...

If you don’t have underbelly tape on hand, Eternabond makes a great alternative. While not as stiff, it usually works well for smaller areas or areas that wrap around the frame. We always recommend RVers have a roll of Eternabond on hand.

EternaBond RoofSeal White 4" x50' MicroSealant UV...
  • MULTI-USE: Perfect for use on metal buildings, trailer/RV roofs...
  • NO ADDITIONAL SEALING REQUIRED: Aluminum backing, combined with a...
  • DURABLE SURFACE: Industry leading one step repair system that...
eternabond holding underbelly together
Eternabond is more flexible and tends to sag, but it can be used in a pinch

How to Fix a Broken Sheet

Your first step in fixing a broken sheet is to find out how the RV underbelly is attached. Manufacturers use nails, screws, and other types of fasteners. You’ll need to raise your rig on jacks to do this. Secure it before crawling underneath your RV.

RV underbelly attaching

After you’ve discovered how the underbelly is attached, you can proceed to remove the nails, screws, or fasteners, which might require a hammer, screwdriver, or crowbar. Do so carefully, so the pieces of underbelly don’t fall on top of you as you remove them.

In this instance, you’ll replace a broken sheet with a new sheet. Properly secure the nails or fasteners again, and you’re done. Fixing a broken sheet will take more time than simply tearing off a piece of tape. But it’s still not a difficult or lengthy process.

underbelly fasteners
Usually, the fasteners are pretty easy to see, but sometimes they are stapled and can be very hard to find.

How to Fix a Leaking Underbelly

Fixing a leaking RV underbelly is the most time-consuming repairs. Water and moisture cause extensive damage to RVs. You don’t want to let water sit and develop mold and mildew. That becomes an even more expensive repair.

First you need to locate the leak. Usually you will need to take a knife and cut into the underbelly in a few places and peak up under the RV. Hopefully you will be able to locate the leak without removing the whole cover. If you cant remove just a section of the cover you might need to get the underbelly taken off so you can find and deal with fixing the problem.

Once you remove the underbelly, you’ll need to remove all the wet insulation. You don’t have to pull out all of the insulation unless the entire bottom of your rig is wet. But get all affected areas. Insulation tucked underneath the RV will dry slowly, creating mold. Use a Shop-Vac or fans to dry the underbelly once you remove the insulation.

Once the area dries, you can replace the old insulation and underbelly with new products and seal it up. If you have extensive leaking, let professionals handle the repairs. But you can tackle this repair yourself if it’s just a small area.

leaking underbelly
Water always finds a way, in this fiberglass RV it made it out the edges

Pro Tip: You may not be able to repair your RV underbelly with duct tape, but these are 15 Ways Duct Tape Will Save Your Camping Trip.

Why It’s Best to Have Help When Repairing Your RV Underbelly

Always have a second person helping with RV underbelly repairs. If you’re dealing with a long piece of foam board, you don’t want it to come crashing down on you. Plus, it’s difficult to hold the board or tarp with one hand while trying to hammer or screw it in with the other hand. Grab a friend or spouse who can help you for an hour or so.

Can You Upgrade Your RV Underbelly?

You can change the type of RV underbelly you have pretty easily. If you don’t like having a one-piece underbelly, you can remove it and install sheets. If you don’t want the tarp-like material and would rather have something stronger and more tear-proof, you can replace it. This is one part of your RV that you can easily upgrade.

DIY RV Underbelly Repair | Coroplast Repair | rv repairs and upgrades

Don’t Delay Your RV Underbelly Repair

If you want to keep out critters, keep your RV underbelly in good condition. Ensure it has no tears or broken sheets to keep out moisture from driving in the rain. Properly maintaining your RV underbelly is important. It protects the frame and insulation and keeps road debris from getting into your rig.

So the next time you head out on a weekend camping trip, take a good look underneath the RV. If you see any problems, don’t delay repairs. Get them done quickly, and then enjoy making memories around the campfire.

Have you looked underneath your RV recently? Tell us in the comments!

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Michael Farley

Tuesday 24th of October 2023

Does the underbelly need to cover the rear cap on a 5th wheel? Mine is being repaired and this was not done


Wednesday 13th of September 2023

Our 1940LTD popup doesn't have any covering but since moisture can be the problem with covered under bellies, I think leaving it that way is fine with me. I do intend on putting the wires that are just hanging loose in wire looms and using zip-ties where needed to help prevent anything getting snagged or rodents from snacking on the insulation.