How to Tell if Your Floating Subfloor has Rot

Installing a piece of flooring
  • 1-8 hours
  • Intermediate
  • 0-100
What You'll Need
Face mask
Safety goggles
Pry bar

If you have a floating subfloor, you will need to give it a check up once in a while to be sure there is not damage. There are a few signs that you may have a problem, which we will explore here.

WARNING: Wear safety gear (gloves, safety glasses, face mask) any time you have to inspect for mold or mildew, to avoid inhaling particles or getting them into your skin and eyes.

1 - Check From Underneath

First, the best way to check your subfloor is from the underside. If you have a basement, you can inspect the subfloor from below by using a ladder and a flashlight to inspect it for damage. If you do not have a basement, you will have to go into your crawl space to check. You need to see the subfloor in order to make a determination as to whether you have a problem. If you are unable to access from underneath or from your crawl space, you will have no choice than to pull up an area where you can inspect it to see if there is an issue.

2 - Staining

You will check for stains on the subfloor. This can indicate that you have, or have had a water problem, which is a definite sign the subfloor is or will be rotting in that spot. This area will have to be repaired to stop further damage.

3 - Sagging

subflooring from the underside

If you see that the floor is sagging, or feel sagging while walking on the floor, most likely you have a rot issue. Stepping on the floating floor you should not feel it give way, or feel springy, in a specific area. This is a definite sign that there is a rot issue under that area of the flooring.

4 - Spots On The Flooring

Look at the floor surface in the room. If there is an area that has not had a spill which caused a spot, then it is likely that the wood in the subfloor is rotting. You will need to pull up the flooring and repair, or the spot will continue to not only spread on the subflooring, but also damage the flooring itself.

5 - Mold Or Mildew

If you find that you are having a mold or mildew issue in your room, and cannot find where it is coming from, many times it is caused by moisture in the subflooring which causes the wood to rot quickly, not to mention the health concerns. This will have to be dealt with by a professional.

6 - Cracked Drywall

Look around the bottom of your drywall, for cracks or an uneven surface. If you have obvious damage occurring just at the bottom, it is a sign that your subfloor has rot. This can mean that there is also rot in the joists which is causing a shift in the drywall. If this happens, you will not only need to replace the subfloor but also repair the joists and drywall. Keep in mind that any visible damage on the interior floor means that it is much worse underneath and needs to be addressed promptly.