RV’s kitchen floor has soft spots but was told there are no water leaks?

Dear Dave,
I thought my fifth wheel might have a water leak causing soft places in the RV’s kitchen floor. I took it to Lazydays RV and they said it has no water leaks, that it’s the Styrofoam breaking down. I bought new flooring; I just need someone to fix the soft spots. —Milton, 2015 Forest River 5th wheel

Dear Milton,
Unless they ripped back the vinyl flooring to check, there is no certainty it was not caused by a moisture leak. Your RV’s floor is a sandwich design of wood, block foam insulation, and framework. The challenge is, most RV manufacturers don’t tell you what thickness or type of wood decking that is used, or the density of the block foam insulation other than using the description “dense.” (Insert your own joke here!)

Forest River construction

The other challenge is that your unit is about 10 years old and there was little documentation available on the construction from back then. Some Forest River products did use aluminum framing in the floor and block foam insulation. However, the framework was not 16” on center, or even 24” like residential construction. Others used wood framework and loose fill insulation, relying on the wood substructure or decking to support the weight of traffic.

This is what we found under the soft floor of the Forest River Salem we worked on. Wood joists but loose fill insulation and major water damage.

Looking at your photo, I see a heater vent in the middle of the floor, which tells me there is a heat plenum running underneath. This is a good feature; however, it doesn’t provide much structural integrity if the plenum goes further down the floor where the wrinkles are.

Look inside the heater vent

I would start by removing the vent and take a look inside. Maybe use an endoscope camera with your phone to see if the plenum is collapsing. [From Merriam-Webster: plenum: an air-filled space in a structure, especially one that receives air from a blower for distribution (as in a ventilation system).]

Otherwise, you will need to peel back the vinyl flooring and inspect the wood decking to find out what is causing the wrinkle in the flooring, as there is more than just a soft spot happening here. You might need to cut out the decking to visually inspect the foam insulation, as well.

Foam insulation issues

Foam insulation will compress due to moisture, heat, and traffic. Show units are the worst, as thousands of people trample in and out of these units at every show and can cause premature fatigue. In the case of deteriorated foam, I have cut out the decking and the foam in RVs and oftentimes replaced the soft area with 2×4 braces to reinforce the soft area and then added loose fill for insulation.

Motorhomes also have an issue with foam deteriorating down the middle, where the exhaust system can create tremendous heat and literally melt the foam. It happens more often to units that idle for a long time, as the heat is not dissipated by driving down the road.

I would suggest finding a local flooring installer to help investigate what is happening and install the new flooring. The construction is not uncommon to some of the residential floor joists and design, and I have had many flooring specialists work on RV floors.

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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