What areas were tested? Were these airborne tests or were there samples taken from multiple surfaces such as drywall, studs, joists, subfloors?

The biggest/most expensive issue is removing the infected plywood (could be that you need BOTH layers of your subfloor removed) and then reinstalling just to get you back to square one.

Your home insurance should get involved at this point. Mold remediation should be part of your insurance package which means you can utilize the funds available through a claim. If it is approved, then remediation is the way to go. Once surfaces have been infected, they stay infected until remediation is done. And once an infection is present there is no way to get rid of it without remediation.

At this point, you will need to bring you home insurance on board to find out what funds can be made available to you to help with this situation. But the bottom line is you will be looking at removal of the subflooring (possibly down to the joists). If the joists have been infected as well (most likely they have been) then remediation is the only way to stop the infection from reintroducing itself into the new subfloor material.

Let us know how/what was tested and what the insurance company says.

"...came up through the slab over time..."...?

Are you saying there is plywood sitting on top of concrete and then laminate sitting on top of that?

Yes, the slab has plywood on top of it, and then the laminate is on top of the plywood. To save money and not rip out tile that was under the flooring, the prior owners just put plywood down to make the floor level.

The bigger issue is that you need to resolve the moisture coming up through the slab. Removing the damp/moldy plywood is not that big of a deal.

We're going to put a plastic barrier down under the new flooring. I was told that once the flooring and wood is all taken up, the mold spores will go everywhere and that we will need to pay thousands to remediate before proceeding with the floor. I'm wondering whether the mold remediation is necessary.

I would apply concrobium (available at Home Depot in the paint department) to the moldy material before removal and call it good enough myself.

Try cleaning with non-diluted laundry bleach and allow it to dry overnight. It should kill off the mold.

So you all would do that, even though the moldy material (wooden boards) is going to the dump? We are going to remove the boards and throw them out and then put the new floor over the slab.

Are you leaving the old tiles in place? How old is the house? The issue of the damp slab is still an issue. Technically a vapour barrier (like 10mil polysheeting) will stop most dampness....but it will not stop mold from growing UNDERNEATH the plastic. This normally isn't a concern, but if a slab is old enough, and wet enough and has had PREVIOUS mold growth then you are almost guaranteed to have more problems in the future.

My concern becomes what does the drywall look like at the 'floor level'? If the two layers of wood-like stuff has been soaked and contaminated, does the drywall (at the floor level) have issues as well? If the drywall was, in anyway, TOUCHING either the plywood OR the laminate, the soaked wood will have sponged water onto the drywall = soaking = mold growth.

It is possible to deal with the wet floor stuff with a SHEEP load of bleach (please be careful with bleach...in it's pure form it can cause breathing difficulties and nausea...and even damage lung tissue if not used with HUGE amounts of ventilation)...but once the mold spores start crawling up the walls, you will want to look at investing in the mold remediation.

Sadly you won't know until the wet plywood (bad former-homeowner bad! No biscuit for you!) has been removed and you can take a hands-and-knees-with-flashlight look at the base of the walls (use a screw driver to poke at the bottom of the drywall...if the screw driver pokes through without any pressure, you have more issues than you thought).

Make your decision once you have the ability to assess the walls at floor level.

You said you were concerned about mold spores getting into the air. That is why I would use the concrobium. Which is better at killing mold spores than bleach. Bleach mostly bleaches the mold. It doesn’t really do much to actually kill the mold.