Q & A: Why Is My Floor Swelling?

By Mosby Building Arts

I have a brick ranch house on a slab. A section of floor in the hall, outside the bathroom, has suddenly raised into a mound the width of the hallway, like a hump in the floor. This first happened about 14 years ago and I had to shave the bath door for it to close, but it eventually leveled itself out. Why is it doing this?

It sounds like you have excessive moisture either under the concrete floor slab of the house, or between the concrete and interior flooring material.

Because the concrete slab is heaving that far inside the house, it may be a water leak from nearby water pipes that have finally caused the soil to swell and heave.  It is a big issue if your slab home has a water leak in the pipes below the concrete, so you need a savvy consultant with some high-tech tools (like a thermal infrared camera) to locate the exact problem point. You can’t afford to have floors and slab torn up as an exploratory mission – you need accuracy.

Another cause could be excessive moisture that causes the floor material to swell and mound. High humidity around and below the area can cause swelling and buckling.Check the humidity in your home and try to keep it at 30% to 50%. This keeps your home comfortable and lessens the expansion and contraction of the building materials. Also, using a dehumidifier in the area may bring you some quick results.

Hardwood floor buckling can also happen if it is not installed with the proper gap between the floor edge and the perimeter wall framing.

If  your wood floors are properly installed, then you have some type of moisture problem, for which the the mound is merely the symptom.

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