Strengthen Attic Floor Joists

Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.

Strengthen attic floor joists.

Gluing and screwing a 3 4 attic subfloor and providing solid bridging should also be considered. Now it is time to use some wood and screw it into place on the original joist as well as the cross beam. You can however strengthen the joists by securing another length of wood to the existing joist called sistering or reduce wobbly floors with block inserts between the joists called. They create the structural strength of the attic floor.

A steel plate can be used the same way. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. For this fix to work well the upper edges of the joists must be solidly fastened to the subfloor above. Sistering is the process of adding a new joist next to each existing joist.

I went to get a permit from the city to finish the attic and they said i needed to reinforce the floor since for a live load it was not strong enough for our span below about 12. A layer of 3 4 in. Strengthening attic joists for live loads by sistering if the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. Where they connect to both the top and bottom joists each gusset pair will transfer approximately 100 pounds that s 50 psf of floor load times the 3 foot gusset spacing times the 16 inch joist spacing divided by the two joists.

Plywood firmly fastened to the undersides of joists helps prevent this side to side bending and stiffens the floor. Tack a beam under the sagging joists. Jacking them up too fast may cause cracks in the walls and floors overhead. Adding a 2 x 4 along the bottom chord of the 2 x 6 ceiling floor joist maybe helpful in stiffening the joist as well.

I recommend three gusset pairs per joist at the quarter points one about every 3 feet. If your attic joists won t bear the weight necessary to finish out a living space but the engineer cleared them to support floor decking for light storage you can install inch plywood or. Pretty sure you mean joists not rafters rafters are the sloped members that run directly under your roof whereas joists are the horizontal members that sit atop the ceiling of the floor below the attic. A day until they re level.

This is a great answer.