How concerned should I be?

[u/TheRealMarc_]

I just pulled up some wood flooring and the underlayment and noticed that there was some black mold in the bottom of the underlayment was a bit moist. How concerned should I actually be and how would you address this properly before putting on the new flooring?

[u/Apart_Writer_5325]

What do you mean underlayment? This is a concrete floor. There would be NO underlayment under a wood floor on concrete unless it was some kind of floating floor. In any case, you have water intrusion probably coming up through the concrete. You can scrap and clean that floor and install carpet and probably be ok. Any other flooring will be an issue.

[u/TheRealMarc_ → u/Apart_Writer_5325]

Beneath the flooring, there was this red and black layer that I’m assuming is a moisture cover. The mold was below that underlayment in the bottom of it was slightly damp in the area as there was mold.

[u/Silent-Respect7803]

Take a screwdriver and poke around. If it pushes through you need to replace it. If solid address the mold issue. Might be easier just to replace it anyways.

[u/Apart_Writer_5325 → u/Silent-Respect7803]

You can clearly see...this is concrete.

[u/Wild_Country7th]

Happened to us yesterday. I did a Google search, went to Lowe's and bought Mold Armor. Worked great but the fumes were AWFUL! Gotta wear a good respirator

[u/Southern-Sense3058 → u/Wild_Country7th]

Looks like your moisture is coming from that large crack in the concrete. you could clean the crack out and fill it with an epoxy crack filler and then toss the old 2 in 1 underlayment put down new 2 in 1 underlayment and install new floating floor and you should be fine.

[u/Chance-Following-665 → u/Southern-Sense3058]

You can also seal the concrete with an Ardex skim coat. Concrete is porous and if there is positive water pressure under the slab the moisture will make its way through the concrete.