Sealing Utility Bay to Block Rodents and Underbelly Odors

[Oregon Coast]

2016 Montana 3721 RL (39ft, rear living room, 4 slide outs, one bedroom slide out was an extra that this model doesn't usually have)

Bought this RV in 2024. It is installed semi-permanently in an RV park, on the Oregon Coast, bordering a forest, and a Salt Water Bay, thus lots of rodents and insects. The first summer, while attempting to rodent-proof it, I found easy Rodent access to the Living Area, Basement(Basement storage and Utility Bay), Underbelly, and even Attic. A squirrel, cat, rat, could easily enter unrestricted through existing openings.

The Route: Crawl up through the 4” space adjacent to the center Leveling Jack, walk 7 feet along the Cosmetic Chase to the Utility Bay, from there they can easily go to the Underbelly, or the Basement Storage. An animal large like a squirrel couldn't go any further due to there size. A mouse/insect, from the Utility Bay, because they are small, can easily travel to the Attic, or into the Living space. I have already sealed the gap next to the Center Jacks, and Underbelly Coroplast.

The Utility Bay, where the Hot Water Heater, Furnace, and lots of wiring/plumbing is located, acts as a Return Air Plenum for the Furnace. Air from the Underbelly, Outside, Basement Storage area, and the Living Space all supply return air, to the furnace when it is running. When the furnace is running, it will pull air from the path of least resistance, which is the Underbelly(Where the Black Water tank is located, and outside (air leaks in the coroplast, the route the squirrel and rat could get in)

I hate the idea of pulling air from around the Black Water Tank, and delivering it into the living space. So far, our Black Water Tank hasno leaks, so no sewer smells. If you run your Bathroom and Kitchen Fantastic fans, without opening a window, you are also pulling this Underbelly air into your living space, along with odors (any dead mice/rats laying down there)

Question: Has anyone sealed the Utility Bay from the Underbelly? If so, what did you use, and any suggestions? That would make the underbelly more prone to freezing, but I don't live where freezing is a problem. It would also make the furnace more efficient. And reduce drafts that are common with these rigs. And obviously help with rodents.

I did find a post,Furnace return vent,which covers Heating and Air Conditioning air flows, but did not include any discussion on rodent access.

I have talked to folks over the years about how do mice get into the attic, everyone had a guess, including me. But discovering an easy route, I wanted to share this information. Along with odors, and drafts.

 

[Spartacus]

Yep, don't you just hate this, in storage I put rat trap at all of the leveling jacks which is only the front and I put them around my tires because they can crawl up on the tires. I have found that is the most appropriate place I always get them before they enter into my rv, I will also admit, I don't always get mice but I find some birds that get into the traps.

 

[Carl n Susan]

I recall some members, unafraid of freezing temps, used Styrofoam panels and Duct Tape to seal the off from the dropped frame area, with its many access points, from the Pass Through compartment and the rest of the RV.

Others (ChuckS??) have sealed the coroplast and frame openings to prevent rodents.

 

[Mikendebbie]

I think forum member Daryles has several good posts about his rodent-stop’em plan. I think he removed coroplast bottom, cleaned up the wire and hydraulic hose routing, and closed off every hole he could find…even posted pics…but I don’t think the info is in a “single thread” - so it would take a few searches.

 

[Mikebikeman]

I have a 2016 High Country 353RL. I was have problems with the small red squirrels making holes in the coroplast to turn the Montana into their nut storage house! I bought a 6 foot wide roll of 1/2”x1/2” hardware cloth and covered the entire bottom with it. Used the coroplast attachments to hold it in place. Added a few more just to be safe. Also covered the plastic close out panels at each end of the slide reliefs in the underbelly. It’s been two years now and no more squirrels. No mice either except for where the slide and the wall meet on the inside. I put a chunk of steel wool there. That’s seems to stop the mice.
Fingers crossed….

 

[DutchmenSport]

In the second year of owing our current camper when it was brand new, I took the time to seal the underbelly Coloplast to block out air drafts being drawn up from the underbelly, and into the camper. I first applied dozens (yes, "dozens") of tubes of calking and liquid nails at the edges of the Coloplast that had gaps and holes, and then used dozens of screws and screwed those gap areas down tight.

I then used dozens (yes, dozens), of foamy "Stuff" expanding spray insulation on all the gaps that were too big for calking.

The end result, the drafts were stopped, the air conditioner and the heater functioned better because neither was sucking outside air into the underbelly where the furnace return is located.

I thought I'd done an adequate job of "mouse proofing", but time eventually unearthed, mice are horrible creatures and can get "in" at locations I don't even know about. But, sealing everything up with calking, Liquid Nails, and screws, all the drafts disappeared. That was my objective.

There are still way too many holes between the underbelly and the living space of the camper. Under cabinets and behind panels, wherever electric lines come up from the underbelly, and wherever pipes come into the living space are all entry points for critters and drafts. Pump those areas full of Foamy Stuff spray insulation.