How To Brace Up A Floor

Bridging braces the joists against each other with diagonal metal bars or wooden boards between the joists.

How to brace up a floor.

Cross braces may be installed during the construction process or added to older homes and it involves nailing small wooden braces from the top of one floor joist to the bottom of the next joist and vice versa to form an x. When you add the new screws do so at an angle and make sure they attach to the subfloor. As you add the screws the gap between the subfloor and the joist will close up. The sagging floor was the symptom and somewhere under the house there had to be a cause.

Jacking them up too fast may cause cracks in the walls and floors overhead. Working your way across the floor add the braces between adjacent joists one at a time at eight foot intervals. Finally cut and install new columns to fit between the beam and the new footing. With all the braces together these form a sort of truss like structure to stiffen up the floor.

As a test firmly push a metal probe or screwdriver into the post at the floor line. As the posts slowly rot and melt into the floor the house settles accordingly bottom to top. Use post shore jacks screw jacks or hydraulic jacks to lift the new beam into position beneath the joists. Tack a beam under the sagging joists.

Either way you can reinforce each joist or specific joists by doubling or tripling them. Floors bounce because the joists are either too small or they span too far. Install bridging on either end of the joists at a distance of of their total span. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.

A bridge runs from the top of the first joist to the bottom of the second and from the bottom of the first joist to the top of the second to form an x. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. If your floors are 15 feet 4 6 m long for example you would position a brace 5 feet 1 5 m from either end. A much better truss like structure would be achieved if there was another member along the bottom so that they form a sort of cross lattice girder.

Well after doing the navy seal crawl up under the house we found that the joists that were supporting that floor were not actually attached to the sill plate any longer as seen in the photograph below. And this was my strategy for stiffening up this floor. A day until they re level. You can also slide several shims between the subfloor and the joist and then add the screws to brace the joists.

Next snap a chalkline across the underside of the joists in the middle of the span to help align the new beam.