Water from Exterior Damages Floor Covering Q&A


“I live in a 4 year old townhouse and I have vinyl floor covering installed in the kitchen and eating area. A few months after I moved in, I noticed some faint discoloration and staining on the floor covering near the outside wall. It appears to be on the underside of the flooring because I could not clean it. I contacted the builder and he said that it was probably a manufacturing defect and he had the vinyl replaced. Lately I have noticed that the staining was coming back. Do you have any idea why the staining is occurring? My house is built on a slab so there is no way to look underneath the floor.” – R.K., Alameda



Staining on the underside of vinyl floor covering is usually the result of moisture infiltration, and before the floor covering is replaced, it is important to locate and eliminate the source of this moisture. If you don’t, the staining will continue to re- appear no matter how many times you replace the floor covering.

The most common example of this type of staining occurs in bathrooms, usually near the base of the toilet or adjacent to the tub or shower pan. While moisture cannot permeate the surface of the vinyl floor covering, it can seep underneath at joints and edges that are not fully sealed.

If the joint between the vinyl floor covering and the face of the tub or shower pan is not kept properly sealed, it will be exposed to moisture that can collect there from tub or shower over spray. People do not realize how much water can collect at this location just from stepping in and out of the shower or tub.

Water that collects at this area can then wick under the vinyl floor covering, making the back side of the vinyl wet. Over time, this moisture creates mildew growth which starts out as a light gray stain and then turns black. If the staining or discoloration that you see on the floor covering won’t come off, chances are it is coming from the underside, and it is probably moisture related.

The staining that you are describing in the kitchen and eating area also sounds like it is moisture related because it has re-occurred. What you need to do first is to find out where the moisture is coming from. The fact that your house is built on a slab, limits the possible sources of the moisture to three things; a leaking water line in the slab, water being sprayed at, or pooling at the face of the concrete foundation, or finally, sub surface water wicking up through the underside of the slab.

If it were a leaking water line, the staining would be more or less in one area (near the break in the pipe and the slab would be wet or damp. This would have been discovered when the floor covering was first replaced.

If there was sub surface water wicking up through the slab, it would mean that there was a break in vapor barrier beneath the concrete that is allowing the moisture to pass through. This commonly occurs during periods of heavy rain, or over-watering. My guess is that your particular situation is the result of water either pooling or being sprayed at the face of the foundation.

This could be the result of heavy and /or continuous rains or possibly from the sprinklers. Sprinklers spraying against the house allow water to run down the face of the foundation and then pool at the base. The surfaces of the concrete foundation can absorb tremendous amounts of moisture when exposed to water.

When this source of moisture is allowed to occur on a daily or every other day basis, (such as with sprinklers that are on timers), there would be enough moisture for it to travel in towards the interior of the house two to three feet.

If you find that the sprinklers are not spraying directly at the building, check the drainage to make sure all water flows away from the house. This is particularly important if your property has an up slope on one side of the house. If water cannot be drained away from this area, you may need to install a drainage system to carry the water somewhere else.

Remember, when water is allowed to pool adjacent to a foundation for long periods of time, it can do a lot more than cause staining to floor coverings. It can be one of the biggest contributing factors to building settlement and foundation failure. Water and moisture also have the capability to destroy wood members throughout the house if left unchecked. It pays to eliminate sources of moisture infiltration and improper drainage before they have a chance to become bigger and more expensive problems.

Experience: Condo Roof Leak

AAH was retained to evaluate roof leakage and provide litigation support regarding defective construction, and management services for the eventual repairs of the defects.