How to Fix a Sloping Floor – A Guide on How to Level a Sloping Floor

The use of self leveling compounds is one solution for fixing a slightly sloped floor, however they should not be used for slopes that are in excess of 1/8 inch per foot. They are easy to apply. Simply mix and apply to the sloped floor per the manufacturers instructions.

Shimming to Level a Sloping Floor

Fixing a sloping floor by shimming it works if the slope is relatively minor, e.g. 1 inch over a 12 foot span. Shimming a floor over a greater slope, however, will present other visual and physical problems, such as the ceiling height being markedly different from one side of the room to the other. Likewise, windows may look crooked when viewing from the shimmed floor upwards.

To shim a sloping floor varying lengths of 2×4 strips are attached to the subfloor. The thickness of the 2×4 strips will vary from one side of the room to the other depending upon how much of a slope there is. For example you may need a 1 inch thick 2×4 strip on one side of the room and gradually thinner strips as you work your way towards the opposite end of the room.

At the far opposite end of the room a shim should not be required, assuming it represents the final desired floor height. 

To determine how thick of a maximum shim will be required, find the highest floor height in the room, and then using string, nails and a level, run this max height to the opposite end of the room with the sloping floor.

With the level string attached to the side walls you should then be able to determine the necessary 2×4 shims required along the length of the sloped floor. Make sure to attach the 2×4 shims directly over floor joists.

Raise the Home to Level a Sloping Floor The other alternative to fixing a sloping floor is to raise the home off of its foundation and to repair the damaged sill plates or foundation wall. This process is expensive, but in the end it’s a better solution to fixing a sloped floor than shimming it, particularly if the slope is significant. Besides fixing the sloped floor issue, repairing the home’s sill plates or foundation walls will also make the home more structurally sound.

The home’s sill plates are often damaged by water or insect infestation and if left unchecked the home could at some point come right off of its foundation walls.

Likewise if the foundation walls have settled or crumbled, such as may be the case if the foundation was made out of stones, the home could also come off of its foundation.

If you decide that repairing the sill plates or foundation walls is your best alternative for fixing your sloped floor issue find a contractor who has expertise in doing this type of work. The home will need to be jacked up and temporarily supported while the sills and/or foundation walls are repaired. It takes precision and solid engineering to do this correctly, and to prevent wall cracks and other structural problems in the home.