Answer: A basement floating wall is a construction technique used in basements, particularly in areas where expansive soil conditions exist.

Expansive soil can swell and shrink with moisture changes, causing the foundation of a home to move slightly. To accommodate this movement and prevent structural damage, floating walls are installed. For example, I build in Colorado, and soils in Colorado tend to be expandable—meaning they gain volume, or “swell” when wet or frozen. This swelling is very strong, and can shift entire foundations of even the largest homes (though usually only by an unnoticeable amount.)

You can see a photo of a floating wall from a previous project of mine above.

Key Features of a Basement Floating Wall:

• Bottom Plate Attached to the Floor: In a floating wall, the bottom plate (the horizontal board at the base of the wall) is not rigidly attached to the floor. Instead, it is anchored with nails or bolts that allow slight vertical movement. This is crucial for areas where soil movement could push up on the basement floor.
• Gap Above the Bottom Plate: A small gap is left between the bottom of the wall studs (the vertical boards) and the top of the bottom plate. This gap allows the wall to “float” and move up or down slightly without transferring pressure to the wall or the structure above.
• Vertical Movement Accommodation: By allowing for vertical movement, floating walls help prevent damage to the wall structure, such as cracks in the drywall or damage to the framing, that might occur due to the shifting or heaving of the basement floor.
• Flexible Construction Materials: Sometimes, more flexible construction materials, such as certain types of insulation or flexible drywall tape, are used in conjunction with floating walls to further absorb and accommodate movement.

In Conclusion:

Because basement walls sit directly on top of the home’s foundation, this makes them susceptible to moving when the ground becomes saturated with rain or when temperatures dip below freezing. Floating the basement walls allows the soil to expand without adversely affecting the home. This method, while effective, is not entirely fail-safe, and even if your basement walls are floated, the ground can still move enough to make small cracks appear in the drywall or in the floor tiles. However, these are just cosmetic concerns, and generally don’t affect the overall integrity of the structure.

You may or may not be qualified to build your own floating walls in your basement, but make sure understand what the permitting requirements are before you get started.

If this was of value to you, feel free to read my other posts in our blog. I also cover more pointed questions like this in my FAQ. 

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