How To Jack Up A Sagging Floor

The jack should be placed directly beneath the center joist.

How to jack up a sagging floor.

The solution to sagging floors or the damaged sills and joist ends that contribute to them often involves jacking. Underneath the floor in a crawl space or basement position the floor jack or jacks and place the beam in position. Raise each jack by 1 8 inch at a time this will help to reduce any damage to window frames and plaster or drywall walls above the floor. Make sure that the lumber or lally posts are perpendicular when jacking or they may slip out of position.

Carefully hoist the jack until the beam reaches the floor underneath. Pour self leveling underlayment in the problem area. Compound can correct sags and dips as deep as 1 1 2 inches. Stand your floor jack between the two beams on top of the one that s on the floor and turn the thread on the jack until it wedges under the top beam.

Secure the jack to both beams top and bottom putting screws into the holes on the flat steel plates that are pressing against the wood. The 4 inch lally posts can be replaced by 6 x 6 inch lumber. When this happens stop hoisting the jack and lock it in place. Continue to raise the jack until you feel some resistance.

A common scenario is to install temporary jack posts and support beams then permanent posts and beams over new footings. If you have access to the basement or crawlspace it is possible to jack up saggy joists until they are level and then sister them so that they remain straight after the jacks are removed. You ll need to hire a structural engineer or foundation specialist to jack up and level the house and then shore up your home with pilings beams or even put new footers on the foundation.