How to Stabilize a Knee Wall

Remove the drywall, paneling or other type of wall sheathing with a flat bar to reveal the knee wall frame. A knee wall consists of a bottom plate, a top plate that sits on an angle and vertical wall studs between those two plates.

Secure the bottom plate to the joists by inserting two 16d nails through the bottom plate into every joist with a nail gun. Knee wall studs usually sit directly over joists. If they do in your home's knee wall, then insert the nails at an angle starting about 1/2 inch from the bottom of each wall stud into the joists. Space the nails evenly, but insert them on only one side of each stud. Do the same beside every stud.

Nail the knee wall's top plate to the rafters using the same method you used to secure the bottom plate to the joists. Insert two 16d nails in the top plate beside each stud, angling the nails to hit the rafters.

Hold a carpenter’s level along each loose knee wall stud, and ensure each is straight.

Secure the studs to the bottom plate by inserting two 16d nails on the side opposite from where you secured the bottom plate to joists. This process is called toe-nailing. Insert 16d nails into the studs starting about 1/2 inch above the bottom of the studs at a 45-degree angle. Each nail will clip the bottom corner of a stud.

Insert nails to secure the top of the studs to the top plate by using the technique you used in the previous step. Nail on the side opposite from where you nailed the top plate to the rafters.

Insert an additional 16d nail into the front of every stud. Because the top of each wall stud is cut at a downward angle to fit the slanted wall plate, the front of each stud is higher than the back of the stud. Place one nail horizontally 1/2 inch from the top of each stud to attach the stud tightly against the upper wall plate, or top plate.

Replace the wall paneling, or install new drywall or plywood to seal the space behind the knee wall.