Hello. Could someone direct me to where I can get information about "floating" concrete basement floors? *or has anyone ever heard that term used before? I have been told it is OK for my basement floors to have broken away from the walls because it is a "floating" concrete basement floor. The house is about 18 months old and I am not sure how to research this. Thanks. :-)

This message has been edited. Last edited by: Emily,

Hi, Emily

Any concrete flatwork slab is said to be "floating" if it has no foundation beneath it. For instance, a concrete patio in your back yard is usually a "floating slab" as are sidewalks, etc. while the floor slab of a tract home rests at it's edges on a block wall or grade beam that supports it and protects it from frost heave. If your basement slab appears to have "broken away" from your basement walls it is because concrete shrinks slightly as it cures and pulls away from the basement walls that contain it, which are actually shrinking slightly as well. Actually, your basement slab technically doesn't "float" either because it's edges are supported by the footings under your basement walls. In the Midwest a typical 16" wide footing is under your 8" thick basement walls leaving a 4" ledge both inside and outside the basement wall. Your basement floor slab was poured on granular fill that is level with the top of the footing which supports the outer 4" of your floor slab. Confused yet? What it amounts to is that the pulling away of your basement floor slab from the basement walls is normal and the "floating slab" bit doesn't really explain it.

Hello Monz. Thank you so much. Your explanation makes sense to me. I had heard that in Springfield, Ohio a certain type of basement floor with gravel trenches around the perimeter is also sometimes refered to as a "floating basement floor" and I became very confused.
The company that poured the basement floor also said they had put too much water in the cement mixture. Do you know if too much water in the concrete will cause any long term problems/concerns? And if so, how should I proactively address the situation? (sealers or something?)
Again, thak you so much. All of the help is appreciated more than you can know. -Emily in Ohio :-)

Glad to share what I've picked up from 30 years of building houses. Most folks don't realize how much science is involved in concrete. It's not just a matter of dumping it on the ground and letting it dry. When water is added to the other components of concrete - sand, aggregates and Portland cement - a chemical reaction occurs. Too much water in the mix does weaken the resulting concrete. In big projects like highways, bridges, buildings, etc, constant testing of the "slump" is done to prevent this - and if it does happen, it's a big problem. In a residential basement floor slab the strength requirements are less, of course, but a weakened slab will result in excessive cracking and surface problems - scaling, spalling, etc.
The bad news is that there really aren't many good ways to "repair" concrete. The only solution is usually to tear it out and redo it. This is a particularly lousy option for a basement floor. The good news is, as long as it's not so bad that the slab literally crumbles, there are things you can do to minimize the problem. Caulk the cracks and consider a concrete floor paint to minimize problems like excessive "dusting" of the surface. I see several brands of garage/basement floor epoxy coatings at the home centers. They might be a good idea.
Don't worry too much if a few extra cracks are the only problem. The only way to make it totally right isn't really an option. Good luck.

Thanks for the well wishes. And once again, I sincerely appreciate the advice and help.
Have a great day! :-) -Emily