Fix for Uhaul floor?

[Lorelei L]

We have a saggy/bouncy Uhaul floor, mainly in the doorway and a little beyond. The flooring is removed and the plywood floor seems ok, just bouncy. The Uhaul is a heavy duty egg, with plywood floor bolted on metal "spools" and the bottom of the spools bolted onto the fiberglass bottom. We were thinking of using the spray foam instant dry insulation in holes drilled in the plywood to stablize the floor before we put down new flooring or carpet. Does this sound stupid? Go ahead, be brutal and set me straight!

[Francesca Knowles]

Originally Posted by Lorelei L

Does this sound stupid? Go ahead, be brutal and set me straight!

Yes.

How's that?

I'm just not feelin' the love for using insulating foam for this presumably structural purpose...

Is there any way to reinforce the problem areas from below? If not, and you want to add rigidity to the wood floor, why not overlay with another layer? The addition of even a 1/8" thick sheet securely/frequently fastened to the existing plywood would add quite a bit of rigidity.

[Donna D.]

Lorelei, there are no stupid questions.

However, spray foam is not the solution.

Is there something wrong with the frame area under the doorway? Sounds like something isn't fastened down, or the metal is fatigued or even broken in that area. If none of those things exist, then maybe a metal support needs to be added.

Your floor shouldn't be soft/spongy/saggy or baggy.

[mary and bob]

Can you get a picture of what you're talking about "spools"? I just looked under our Uhaul by the door, and I've been under ours many times previously, and can't imagine what you're describing as spools. The floor sets on the trailer frame with large flat soft washers between. There is a lot of support in the door area, with two frame brackets for the body bolts in the door area, and one just ahead. It is very common that the body bolts, those large flat head bolts known as elevator bolts, that go through the floor and held by a nut underneath, to rust away in the floor. Some can rust so much that they fall off underneath, others will rust down to almost nothing where they pass through the floor and will break off if you try to turn the nut with a wrench. First thing you should do is check for rot in the floor wood. It seems common for water to leak in around the door, plus in many other areas of these trailers where it can't be seen. Since the floor covering is out this is the perfect time to replace all the body mount bolts. Some are also located in the storage areas and under the counter area. If you do have rot in the floor you may have to replace a section. I had a very small area at the floor edge in the doorway. I repaired it with fiberglass resin and cloth. It was only on the edge. I think you'll find other areas of leakage if you do a thorough investigation in a heavy rain storm. Typical areas are around the windows, especially the side windows, marker lights, tail lights, door seal, door hinges, and possibly the roof seam. A blowing rain can be driven in the stove vent. These trailers have a good frame, but I have seen pictures of rust through in them. Check it out.

[ruscal]

Lorelei,
You should first determine the cause of the springy floor. New plywood will span 16" between supports without much movement when walked on. If the plywood has been exposed to moisture the glue between the plies could fail which would let the plies slip and cause the panel to "trampoline". If you see moisture stains on the ply surface it would be a clue. If the plywood subfloor is OK then see if the support members are in position and undamaged.
Russ

[mmeyer]

Uhaul used a plywood with fiberglass on the top and bottom so it is likely extremely difficult to view whether the plywood has delaminated. The edges are visible in some locations as least on the VT, mainly around the wheel wells. I caulked mine and under coated all the seams just because I felt like it. I have one soft bouncy area in the back under the bed and plan to inject the thin epoxy wood repair to stabilize it. From time to time uhaul sells fiberglass plywood panels on their online store but it is a pain to scroll through all the items looking for just trailer related items.

[Lorelei L]

Thanks to all for a lot of info and food for thought. It's hard to tell if the floor has had water damage because the previous owner had it stripped down to the plywood and was using it that way, so the plywood is discolored from foot traffic. It does seem solid, tho. When I said "spools" I think I'm talking about the bolts, set at about 10" intervals going between the plywood and the bottom of the shell. They sort of look like metal spools to me. They seem solid.

[mary and bob]

The floor bolts rust away where they go through the plywood. You can't see this until you remove the bolt. You'll need a 1/4" punch to drive the bolts up through the floor, and a 7/16 deep socket to fit the nut. The ones that didn't break off right away, or the bolt turned, I put vise grips on the nut or bolt threads, wiggled it side ways and broke the bolt. Almost all my bolts were partially rusted through.