Basement Floor Feels Uneven

Question

I recently purchased a home with a full finished basement. The home was built in 1988. No foundation or structural concerns were noted during the home inspection. There is carpet in the basement. The few visible locations of bare concrete (exterior, mechanical room) show no signs of distress.

However, when I walk around the carpet in the basement without shoes on, I feel a few places where it’s uneven: a ridge, a bump, etc.

Is this a cause for concern? Should I pull up the carpet to check for cracks?

Update,

I pulled a piece of carpet over one of the offending areas and this is what I found. There is a crack, and also what looks like a purposeful control joint. This isn’t the entirety of the areas I was worried about. However, for discussions sake, if all of the unevenness in my basement is due to features like this, should I be concerned?

A deeper inspection of visible, vertical concrete surfaces continues to indicate no cracks in the foundation walls. All windows and doors in the home function properly.

Answer 1

Two things here:

1. If a basement is poured right it will all slope to the floor drain. This sometimes is noticeable because not all guys pouring a basement floor are artists, so their flow to the drain might not be as even as you would want (being nice). Maybe sometimes the exterior walls will slope in if there is an extensive weeping system - that flows to sump pit(s).

2. Very normal for a basement to have 1 major heave line. This is basically the concrete buckling on itself. This has nothing to do with your foundation is in essence cosmetic. To fix these there are a number of products but basically you chisel out the line (in reality hammer but giving you a visual) and then install some sort of flexible substance (you can just use caulk on smaller heaves) and then reseal it with concrete. It is basically the same way you fix drywall that has seasonal heaves with just slightly different materials.

If you are alarmed pull up the carpet, take some pictures and post them on here. You really can't tell with carpet there. My gut reaction is that you are probably just fine. Sometimes these heaves are caused by once in a lifetime events (a summer of 100 degree days 40 days in a row without rain - happened to two of my properties that summer) or that's just what the basement was going to do no matter what (not enough stress reliefs during pour). Either way this is usually not a big deal or a big risk to home owner unless you are feeling the unevenness next to walls which could effect footings.

Note based on added picture: Your basement has heaved right at the joint control - which is by design. It looks like the joint cut was slightly small for the amount of movement. This is neither a problem or even a tad alarming. If you don't like it, grind down the ridge flat. You could even chisel a "V" in that ridge and fill with something more pliable than concrete. On the scale of being an issue this is a .5 out of 10.

Also the crack is because the heave point pushed out. Again not a big deal. Given the house was built 35 years ago, it is probably settled in. So it is basically as bad as it is going to get. Remember basement floors almost have nothing to do with the foundation of your house (except in rare cases which I don't think yours is).

Answer 2

Large slabs usually have “crack lines” or expansion joints built into them. Expansion joints are just about always noticeable. Crack lines under carpet may be noticeable. In basements carpets are often glued down. pulling them up can be a chore. My dad always said there are 2 types of concrete. “The kind that has cracks and the kind that will crack”. Concrete continues to harden as it ages so it gets more brittle. Is this something to worry about? I would say no. See the 2 kinds of concrete above. Also if that area is on a crack line designed to crack there and not spider crack everything is normal.