Can I Cut Out and Replace the Old Subfloor Under a Wall Sill?

Partition Wall

• If the damaged subfloor is beneath a partition wall, which is a non-load-bearing interior wall, you can cut out and replace the damaged section. The process involves loosening and rolling back the carpet from both sides of the wall, and then removing the baseboard and cutting away a section of drywall that allows you to access the area. You'll cut away the subfloor to the center of the floor joists just outside the damage, and you must cut through the nails attaching the wall sill to the subfloor. The new subflooring section slips beneath the sill. After screwing it to the joists and nailing the wall sill, you must repair the drywall, replace the baseboards and re-stretch the carpeting.

Load-Bearing Wall

• If the subfloor damage is beneath the sill of a load-bearing wall, call a contractor. Load-bearing walls support and disperse the weight of the structure above to the foundation beneath the house. Removing the sill beneath a load-bearing wall could cause damage to the structure above the wall if the wall settles during the process. The contractor might build a temporary support wall, or install other types of support, before cutting out and replacing the subflooring.

Tools, Materials and Supplies

• You'll need a circular saw to cut the old and the new subflooring and a utility knife to cut the drywall. A reciprocating saw that features a long narrow blade will slip between the bottom of the wall sill and the subfloor to sever the nails. Pull out loose nails from studs with a nail bar and use a drill to remove screws. A chalk line, popped over the joists and wall studs, serves as a visual guide for making accurate cuts. Use the drill to insert new screws, and a framing nailer for nailing down the sill. You’ll also need new drywall and drywall taping tools to repair the wall.

Considerations

• If you’re unsure whether the wall is load-bearing or not, call a contractor. Typically, but not always, a load-bearing wall will run perpendicular to the direction of the floor joists. If you have a basement or more than one aboveground floor, check the floor beneath the wall in question. If there is a wall directly below the first wall, it’s probably a load-bearing wall. If the first wall serves only as a divider, such as a short wall that frames a bathroom, it’s probably a partition wall.