I am a very new home owner (a few weeks) and I recently discovered a leak in my fully finished basement (discovered wet carpet). We had some concrete experts come inspect, $3800 quote later we will be getting some foundation work done.

The room that was moist, did not have sub floor. The room beside this one, has what I believe to be a plywood sub floor (~2 inches above ground). The concrete expert recommended I cut regions of the sub floor to inspect for moisture (so we know if we need to excavate a larger region). To do this, I need to first pull back the brand new carpet and underlay (recently renovated).

Can I simply cut anywhere? Or should I try and cut in certain regions (i.e. outer region of stud), so that I can simply re-screw the plywood down. I bought a circular saw for this reason.

I have minimal experience with anything house related, although I have been Google-ing the heck out of this.


Addition: If I remove an entire panel, should I expect it to be nailed and glued or just nailed down?

  • 1
    I would do this inside a closet inside a closet you won't be walking over so there would be less chance of problems in the long run.
    – Ed Beal
    Feb 24, 2017 at 21:02
  • 3
    You may be able to remove entire 4'*8' floor panels, which will be less destructive than cutting them. Feb 24, 2017 at 21:02
  • 1
    Is it common to have a raised basement floor like this? Seems to me the only reason that section of the floor is raise is because it takes on a little water? Feb 24, 2017 at 21:37
  • 3
    Another possibility is to buy a borescope, and look through small holes say 1/2" drilled into the subfloor. Or use a keyhole saw on a drill for larger holes then replace the drilled out plugs. Feb 24, 2017 at 22:43
  • 1
    Borescopes are cheap these days. I've seen $10 ones that plug into a smartphone. Feb 25, 2017 at 4:24

1 Answer 1


This is going to be complicated and expensive.

First, you need to determine if the leak is coming from the exterior or the interior. I'd check plumbing fixtures above the area and see if you can trace it down. It could be running down a wall and into the space under your subfloor.

Second, if it's coming in from the exterior, you need to know the extent of the damage. So, you will need to remove sections of the subfloor. (If you live on a slope, I'd start on the high side of the slope.) If you find a wet spot in one area, I'd move 8' -10' and remove another section. If it's wet you can assume it's wet between sections too. However, finding the point at which it's leaking into your basement is key. I'd assume the wetter the area, the more likely you're closer to the point of leak.

If it's coming from the exterior, Possible leaking points: 1) joint between concrete wall and concrete slab, 2) joint or crack in floor, we call this hydrostatic infiltration, (it gets pushed up from the sub-soil), 3) backfill against the outside wall that is placed too high on the wall. (Water could be coming in over the top of the concrete wall.)

There are other possible places where it could be leaking, (I.e.: roof flashing, downspout, stormdrain, expansion joint, etc.,) but I'd start with the 3 listed above.

Repair will depend on where the leak is occurring, of course. I'd let your contractor guide you on that.

Hmmm...so...when you bought the house was this leak disclosed to you? If not you probably have a claim back to the seller. I'm suspicious of the "new carpet" in the basement because I don't think most people refurbish their basement unless they're trying to cover up a past problem in hopes of a sale. So, be sure to document what you find, take lots of pictures, and get a written statement from your contractor on what he found and if it looked old or new. I've testified as an expert witness for buyers who found leaks, settlement, etc. covered up. A good professional can tell if a leak is new or old...usually.

  • Indeed, our concrete expert is positive the leak is due to broken / clogged weeping tile, there are also a few cracks around the leak in question. We chose a very reputable company to fix the issue. We know for sure it's an exterior issue. In terms of legal action, our lawyer is doing anything he can. As you were elluding to, it was likely covered up, given the recent renovation in the basement. We had a large snow melt the revealed the issue.
    – Shinobii
    Feb 25, 2017 at 15:17

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