Repairing uneven or heaved concrete basement floors can be a challenge. In some cases the “repair” for the problem may be the removal of the floor and pouring a new slab. Smaller heaves can be repaired in other ways. The first step is always to determine the cause and implement a solution to the heaving problem.
String a line across the basement from wall to wall at the point of the concrete floor. If the concrete is higher than the string, it has been heaving upward. If not, portions of the slab are sinking.
Install drain tiles and/or sump pumps to reduce moisture content in the soil below the slab. Drain tiles are installed in a trench either just inside or outside the foundation wall. Sump pumps are placed in sump holes at a level below the concrete floor. Concrete heaves when the soil moisture below it freezes and expands. Providing drainage will reduce future heaving but will not alleviate heaving that has already occurred.
Measure the amount of the heaving. Small differences in levels can be evened out by pouring an overlay across the existing slab. The Concrete Resurfacing Network suggests overlays of 1/16 to 3/8 inch are possible. Mix a mortar-type cement mix with mall or no aggregate and spread it across the old slab. Slabs where the heaving exceeds 3/8 inch are likely a candidate for slab removal and replacement, according to Service Magic.
Solve the problems that caused the heaving before repairing the concrete. This reduces the likelihood of recurring problems. If the uneven floor is caused by portions of the floor sinking rather than rising, it can be jacked into place. Specialised equipment is used to pump mud under the floor to fill in areas where erosion or compaction has created voids, allowing the floor to sink.
Removing a concrete slab from a basement is hard and difficult work. Break the slab into small pieces to make moving them out of the basement easier. Add underfloor drainage tiles before pouring the new slab.