Foam Core Floor Repair. Epoxy?

Gdetrailer wrote:

valhalla360 wrote:

Gdetrailer wrote:
Doubt it would work for long, resins without some reinforcements like fiberglass tend to be brittle and will just crack and shatter under the flooring.

The fix would be in compression, so it shouldn't crack or shatter (or if it did it won't matter).

The issue with coming up from the bottom is stopping it from draining back out before it sets. You can't thicken it because you want it to flow into the voids which are likely quite narrow. Also, you need somewhere for the air to escape.

By going from above, gravity tends to keep it in place and allows it to find the voids. The other holes allow the air to escape.

All "depends" on the thickness of the void you are dealing with.

Pretty much any modern RV uses the same foam core sandwich floor with a thin plywood or strandboard bottom and top layer, random reinforcement cross studs and foam insulation laminated in between.

The problem however, manufacturers to save weight and money have shifted to using thinner layers of bottom and top plywood or strand board that flexes much more. This additional flex over time breaks down the wood and the foam..

Adding something that turns solid as it cures in the middle while it can help short term, in the long run eventually is going to fail as the other foam beside the resin degrades. That failure will be the weakest component in the system.

Drilling holes also compromises strength in a laminated system and drilling on the underside will weaken wood that is not in compression..

I know folks tend to gravitate to the "easiest" way which is to drill bunches of holes then fill with a liquid fix but it only fixes a symptom of an inherent problem.

New floor coverings are not all that expensive so one could easily lay a new subfloor over all the floor areas you walk over and floor areas where movable furniture may be. Done correctly you will never notice a 3/8"- 1/2" floor height change. Even in the largest RV you would be talking less than 200 square feet.. Will not add all that much weight, will not cost all that much and in the end a long term fix.

The foam that got compressed is already compressed, so it's less likely to compress a lot more.

While it's possible areas around the original compression will fail, the limited space in RVs tends to create very distinct walking paths. If an area hasn't degraded yet, it's unlikely to do so in the future as it rarely get's walked on.

The skins in the sandwich construction rarely fail in compression or tension, so the holes won't be a big concern. If you go in from the top, they will be filled flush anyway and work in compression. Epoxy does fine in compression.

Tearing out the floor entirely, is a drastically larger project and generally not cost effective.

Slapping a 3/8" layer of plywood on top will leave a spongy spot. 1/2" would be the bare minimum and you may still notice it flex a little. 3/4 much better but now you are significantly eating into the CCC of the RV particularly if it wasn't large to begin with when there is a cheaper viable solution. Also, any of these can be much more challenging if you have a slide that needs clearance over the flooring.

I think before I would mess with drilling holes and injecting epoxy, since you’re going to have to replace the floor covering anyway I’d just cut out everything down to the bottom ply of the subfloor and replace it with plywood subfloor material. I would confine the cutting to the open/walkable floor area unless there was water damage that needed to be fixed.

:):)

valhalla360 wrote:

Gdetrailer wrote:
Doubt it would work for long, resins without some reinforcements like fiberglass tend to be brittle and will just crack and shatter under the flooring.

The fix would be in compression, so it shouldn't crack or shatter (or if it did it won't matter).

The issue with coming up from the bottom is stopping it from draining back out before it sets. You can't thicken it because you want it to flow into the voids which are likely quite narrow. Also, you need somewhere for the air to escape.

By going from above, gravity tends to keep it in place and allows it to find the voids. The other holes allow the air to escape.

All "depends" on the thickness of the void you are dealing with.

Pretty much any modern RV uses the same foam core sandwich floor with a thin plywood or strandboard bottom and top layer, random reinforcement cross studs and foam insulation laminated in between.

The problem however, manufacturers to save weight and money have shifted to using thinner layers of bottom and top plywood or strand board that flexes much more. This additional flex over time breaks down the wood and the foam..

Adding something that turns solid as it cures in the middle while it can help short term, in the long run eventually is going to fail as the other foam beside the resin degrades. That failure will be the weakest component in the system.

Drilling holes also compromises strength in a laminated system and drilling on the underside will weaken wood that is not in compression..

I know folks tend to gravitate to the "easiest" way which is to drill bunches of holes then fill with a liquid fix but it only fixes a symptom of an inherent problem.

New floor coverings are not all that expensive so one could easily lay a new subfloor over all the floor areas you walk over and floor areas where movable furniture may be. Done correctly you will never notice a 3/8"- 1/2" floor height change. Even in the largest RV you would be talking less than 200 square feet.. Will not add all that much weight, will not cost all that much and in the end a long term fix.

Gdetrailer wrote:
Doubt it would work for long, resins without some reinforcements like fiberglass tend to be brittle and will just crack and shatter under the flooring.

The fix would be in compression, so it shouldn't crack or shatter (or if it did it won't matter).

The issue with coming up from the bottom is stopping it from draining back out before it sets. You can't thicken it because you want it to flow into the voids which are likely quite narrow. Also, you need somewhere for the air to escape.

By going from above, gravity tends to keep it in place and allows it to find the voids. The other holes allow the air to escape.

Yes I have fixed a foam core floor in our 87 Award. I drilled from above and below just through the ply, then injected foam conpatible adhesive. Worked good, but we did have to refloor inside.
You could try doing it by drilling up through the bottom ply and foam then injecting, wait to set then drill again only through the underside ply to inject again. A nozzle to make certain the adhesive goes up to the top, and does not spread into the lower area is something to consider.
Test --- Try your adhesive on samples so you know amount and compatability. Cant have a adhesive that foam does nt like. Too much adhesive could cause the floor to swell. A flexible urethane minimal expansion foam should do. Small squirts, close together. Get some 1/4" ply, foam and experiment before you try it out on the camper.

Doubt it would work for long, resins without some reinforcements like fiberglass tend to be brittle and will just crack and shatter under the flooring.

I suspect, if you plan to keep the trailer for a long time, doing it right the first time by removing any weakened damaged material and replacing with new heavier material will be much better in the long run.

You have to start with a good "foundation", weak foundation will simply fail again and with resins it will make the next repair more difficult to do.