Bracing a Sagging Floor Joist in a Crawl

Go into the crawl space and measure from the floor joist to the floor of the crawl space where the sagging occurs. Also, use the tape to measure from the joist to the floor where it is level and not sagging.

Use a table saw to cut a 2-by-10 beam to the measurement from where the floor was level and not sagging.

Identify the number of joints between joists in the area where the floor is sagging. Cut enough 2-by-10 beams to equal the number of joints.

Cover the ends of the beam with construction adhesive. Hold the beam at a vertical diagonal to the floor. Gently press the bottom end into the floor just under the floor joist joint. Slowly stand the beam upright between the floor and the joint. Use a hammer to tap the beam into place. You are lifting the sagging floor with these bracing joints, so it may take time to fit them into place.

Repeat Step 4 until all of the floor joints in the sagging area of the floor are properly braced.

Use a metal roofing brace to join the vertical brace beam to the sagging floor joist. Use wood screws to secure the metal plate to the beam and the joist. Repeat until all of the beams have a metal anchor plate in place.