Found a spongy floor that’s actually a total structural failure, how would you start?

That adjuster is dreaming if they think a patch is going to fix a structural failure of this scale. Spray foam is basically rot-accelerant when you trap moisture against wood. You’re looking at a total gut job. If five people have already fallen thru, the floor system has effectively zero load-bearing capacity left. You need to get some **adjustable jack posts** and 4x4s down in that crawlspace imediately to shore up the remaining good structure before the walls start to settle or the fridge ends up in the dirt. Four layers of subfloor means the previous guys just kept chasing the rot without actually fixing the source. That dead weight is likely what’s snapping the trusses now that the wood is compromised. Once those metal gusset plates lose their grip on the decaying wood fibers, the truss is effectively useless. It’s no longer a structural member; it’s just debris. You’ve got to strip it all the way back to the sill plates. If that rot has traveled into the rim joist or the bottom wall plates, the scope just doubled.

Stop work and document everything for that adjuster. They need to see the hidden damage that the spray foam was masking. Pull a piece of that wood out and show them how it crumbles in your hand like wet cake. If they still push for a patch, ask for a structural engineer’s stamped report taking liability for a partial repair. That ussually changes their tune. And don't let any more of your crew walk on that without a **temporary deck** of 3/4 inch plywood or heavy-duty planks spread across the good joists.

Watch out for the biohazard aspect too. Between the moisture, the mold, and the cat waste, you’re breathing in some nasty stuff. Get a proper respirator on and run a negative air machine while you're tearing it out. This is a full-scale remediation, not a simple floor swap. Hopefully you're on a **Time and Materials** contract becasue the surprises aren't going to stop til you hit the dirt.

Five people falling through is absolutely wild. I’m just getting into DIY, and I always thought spray foam was the fix-all for insulation and gaps. Does it always rot wood out like that if there’s a tiny bit of moisture, or was this just because they used it to hide a massive leak? Also, if the wood is basicly mush, where do you even put those jack posts? I'd be worried the jack would just push right through the rot instead of actually holding anything up. How do you find a solid spot to start the shoring when everything around the trusses is crumbling?

Man, those four layers of subfloor are basially acting like a giant, heavy sledgehammer just waiting for gravity to win. People forget that extra ply adds up fast. You're probly looking at 10 lbs per square foot just in layers of "fixes" that did nothing but accelerate the collapse. To the DIYer asking about the jacks—you gotta find the concrete footer or pour a temp pad. If you just crank a jack on soft dirt or trough mushy wood, you're just making a hole. Also, get ready for the stench. Once you peel back that foam and wet vinyl, that house is gonna be uninhabitable for a few days without some serious ventilation.

Seriously, get an engineer to sign off on a full demo before you touch anything else. Adjusters love to play detective to save the company a buck, but they aren't the ones who will be liable when the kitchen island ends up in the crawlspace.

Once those metal gusset plates on the trusses pull out from the rot, there is zero structural integrity left. You can't just patch a truss system once the tension is gone. I've seen guys try to sister LVLs onto mushy wood and it’s a total nightmare. It’s a complete gut job or you’re just asking for a massive lawsuit down the road.

Those gusset plates are likely toasted becuase the acids in decaying wood eat right trough the galvanized coating. Once that protection is gone, the teeth on the plates just dissolve. I’ve seen guys try to "sister" new lumber to rotting trusses as a "patch," but you can’t nail into mush. It’s like trying to screw into a wet brownie. Check the rim joist with a screwdriver. If it sinks in, that rot has wicked up into the wall studs. If the adjuster keeps playing games, use a moisture meter. Anything over 20% is a structural failure, but I bet your readings are pinned at the max.