Strengthen Attic Floor 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.

Strengthen attic floor joists.

Now it is time to use some wood and screw it into place on the original joist as well as the cross beam. 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. Sistering is the process of adding a new joist next to each existing joist. Plywood firmly fastened to the undersides of joists helps prevent this side to side bending and stiffens the floor.

Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall. 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. They create the structural strength of the attic floor. 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.

Jacking them up too fast may cause cracks in the walls and floors overhead. 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. Squeaks in a floor usually mean that the subfloor has loosened from the joists. 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.

A layer of 3 4 in. For this fix to work well the upper edges of the joists must be solidly fastened to the subfloor above. Gluing and screwing a 3 4 attic subfloor and providing solid bridging should also be considered. A steel plate can be used the same way.

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. A day until they re level. In my 80 year old house the attic had 2x6 floor joists about 16 oc. I recommend three gusset pairs per joist at the quarter points one about every 3 feet.

This is a great answer.