Strengthen Attic Floor Joists

They create the structural strength of the attic floor.

Strengthen attic floor joists.

A layer of 3 4 in. 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. 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. In my 80 year old house the attic had 2x6 floor joists about 16 oc.

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. For this fix to work well the upper edges of the joists must be solidly fastened to the subfloor above. This is a great answer. 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.

Gluing and screwing a 3 4 attic subfloor and providing solid bridging should also be considered. A day until they re level. 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. Plywood firmly fastened to the undersides of joists helps prevent this side to side bending and stiffens the floor.

Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. Now it is time to use some wood and screw it into place on the original joist as well as the cross beam. Jacking them up too fast may cause cracks in the walls and floors overhead. I recommend three gusset pairs per joist at the quarter points one about every 3 feet.

Sistering is the process of adding a new joist next to each existing joist. A steel plate can be used the same way. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall. Tack a beam under the sagging joists.

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.