Basement sag appears to be getting worse

[Ron Davis]

Anyone looked into replacing the floor in the basement of their rig?  Someone before me appears to have attempted to prevent sagging from driverside near the water..  I noticed the city inlet appears to have had a leak over the years and as such much of the drivers side of the coach's basement floor sags below the angle....I think it might be time to empty the basement and pull up this entire floor and rebuild it.  Has anyone out here had this problem or considered this type of prospect.  She is old and her belly sags. Lol..  just trying to decide if supports of steel will be enough or just rip it out and replace with some fresh wood or plastic sheet floor material.  Thoughts?

[Ron Johnson]

I have somewhat the same issue only worse from your description of your problem so would be interested in ideas as well.

[Fred Brooks]

   Ron,
  I have replaced the bottom flooring such as you are describing. The biggest challenge is removing all the obstacles in the way. You will have to replace it in sections to get in in thru openings. Purchase the fabric vinyl from your local RV dealer or online and secure with 3M-08090 contact cement. Use urethane windshield sealer on all exposed joints when you assemble and install the floor. Secure with self-tapping screws and trim off excess. Fun project if you approach it with an attitude of gratitude! Blessings, Fred

[Ron Davis]

I have decided to put some aluminum square tube bracing under the bays in the center of the sagging area.  It is held by selftapper angle on the 2 inch alum rail on each side or the rig……and am looking for a place to run a self taper up from the bottom into something more than wood and foam.  Any idea where there is existing steel or aluminum framing that crosses the center of the rig either front to back or side to side. 

[Fred Brooks]

  A stud finder or heavy duty magnet will do for steel. Fred

[Jeffrey Antonelli]

How about replacing the bottom outside plastic sheet that runs the length? Where to buy?

When I was young I worked in restaurants that had something similar on the walls, I guess for the chronic splashes and cleaning.

I just restored the water bay panel and noticed the chronic leak did a number on the bottom layer under the wet bay near the drain and where the combined black and grey drain pokes out. I sprayed a foam filler into this layer (Locktite brand) and say water bubbling out. Eventually I’d like to tackle this but will need the long sheets of the outside hard plastic and know how to secure it once ripped out.

[Fred Brooks]

   It is the same material that 5th wheel manufacturers use as a belly liner. Laminate it to the bottom of the new plywood using 3M-08090 spray adhesive from home depot. Seal all joints and seams with Sikaflex urethane sealer. Fred

[Fred Brooks]

   Here are some suppliers.
https://www.amazon.com/rv-underbelly-material/s?k=rv+underbelly+material