How to Replace Double Floor Joists

Gain access to the base of the double joists through the basement or crawlspace beneath the floor. This will remove the need to take up the flooring in order to reach the joists for the replacement process.

Set up pole jacks beneath the joist that runs nearest the double joist that you’re removing. Place the jacks beneath both ends of the joist and adjust the height of the jacks so that the tops are fully beneath the base of the joist to provide additional support.

Measure the boards that you’re replacing and cut replacement boards of the same dimensions and length to fit with a circular saw.

Cut through the joint along the ends of the original boards with a reciprocating saw equipped with a metal blade. This blade type should smoothly cut through the nails that hold the double joist in place. Have an assistant hold the joist in place, as you cut, to avoid having it fall suddenly. Lower the joist to the floor and set it aside.

Position the first replacement joist in the same place as one of the double joists you just removed. Secure the joist to the frame along the wall with 8d nails driven in at an angle through the board and into the frame. Use at least two nails for each board, extending from the base of the board into the frame and from the outside edge of the board.

Spread a layer of construction adhesive along the face of the board where you intend to place the second board. The adhesive will help the boards bond together and reduce future squeaks. Place the second board into position secured tightly against the side of the first board. Secure the board to the wall in the same method used for the first board.

Nail the two boards together with 12d nails driven along their length. Space the nails at 16-inch intervals and use three nails driven in vertically down the height of the boards.

Lower the tops of the pole jacks and remove them to allow the newly placed boards to support the floor.