Joist Sistering Question

I need to sister a bunch of 2x10 joists. The new joists will be the same size as the existing and span the entire length. In a couple places, this will repair sagging or cracked joists, but mostly this is for adding structural strength to the house. I would like to hear from some experts how they would go about doing this. I know I should use construction adhesive, screws or bolts to squeeze the joists together, and nails for shear strength. I haven't been able to find anything about what is and what is not allowed under the building codes for this job. However, I do know that you're supposed to use 16d nails for framing, which are 3.5", so they will stick out the other end quite a bit. I didn't really feel like bending them all over, but if that is the best way then I guess that's what I'll have to do. Some of these will be in the basement where I'll be running a lot of wiring eventually.

Thanks!

 

Building codes do not cover sistering joists, not that I am aware of anyway. But it is similar to creating a built up girder or beam (2 - 2x). (See line 27 at: TABLE R602.3(1). ) You do not need 3.5" nails. 3" (10d) nails suffice, or if you have a framing gun and or (12d) 3 1/4" nails, just drive them at a slight angle so they don't protrude. Glue is also not needed and fwiw, glue is not part of any building code either... but whatever floats your boat. If you glue anything, imo it would be the subfloor, to prevent squeaks. Run a bead on the subfloor about 1" away from the joist you are sistering before you tip the new joist up.

I would run a saw down the top side to create a bevel on about 2/3 of the top edge. That will make them a little easier to stand up. You will need a sledge to beat them until they are vertical. You can cut pieces of blocking to drive them over tight before nailing them... so bolts or screws really aren't needed. You should install tight blocking anyway. Ensure that if the new joists have any crown along their length that you turn them so the crown is up.

 

Nails have a very convoluted almost non-sensical designation. Your nails should be the same diameter as a 16p nail. They make shorter versions but they are harder to find. You can check in the special bracketry section at your local big box home center. They are often used with joist hangers and other specialty brackets. But, I just use regular 16p/d nails and drive them with a nail gun at an angle so they don't protrude. This is just to temporarily hold the joist in place. Then I follow up with structural screws or through bolting to provide the real strength.

 

Thanks for the responses!