When working on expansive soils such as clay and other soils that expand with moisture content, you must take special precautions to avoid structural damage to the foundation and basement walls. One of these precautions is floating walls. A floating wall is not attached at the top and bottom like most walls. Floating a wall can move with the house and prevents cracks from opening in the floor, foundation, and walls as the moisture content in the soil changes.
Floating basement walls are usually attached to the floor joists for the first floor and then nailed to the floor leaving a gap under the wall. This space is covered by the skirting boards and is not visible.
A reverse floating wall is attached to the floor. Lay the flooring on the base plate on the floor and nail it on the top so that the wall is stable but only sticks on the bottom. This is done on wet walls to keep the plumbing stable. The open space is at the top of the walls and is covered by trim. You can cover the entire wall with plaster, but you must be careful to leave the top open for movement. This means you cannot attach drywall to the wall all the way to the top or it will crack as the wall moves with changes in moisture in the floor.
For reverse floating walls, follow the basic instructions to float a wall, but instead of hanging the wall from the floor beam, you will be fastening the floor to the base plate and the tip to the top plate. Make sure your wall is vertical. If you don’t have the wall exactly square, it will cause problems. A 4 ½ inch gap is needed at the top of the wall. The wall should also have spikes in the same way as a normal floating wall, just on the top rather than the bottom. See the instructions for the floating wall for more information.
To cover the open area at the top of the wall, you can use moldings. Many people do not like the look of the trim around the ceiling. If you want alternatives, you can consider having a false ceiling that can be moved with the walls and the floor. You should fix the ceiling frame to the wall frames. When the house breathes, your whole room will move and you won’t notice it.