Floor Joist Leveling By Sistering

How to sister a floor joist.

Floor joist leveling by sistering.

Sistering joists means beefing them up with additional material. You will have a level sound surface to lay your new floor on. Framing lumber is the typical. Then sister the joists will lvl joists at exactly the level you want.

When the sagging joists are level apply a generous bead of construction adhesive to the existing joist. Leveling the floor with shims is when you attach thin wedge shaped pieces of wood on top of the low areas of the joists to make the top joists even. Here s how we are correcting the problems. To permenantly secure the joist i will use 1 2 inch carriage bolts in sets.

Now that said when you have a major humpy floor you should bite the bullet and remove the subfloor planks down to the joists. You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings. My plan is to use construction adhesive and tack it into place with nails. But it s usually best to run the sister joist over the entire span.

This job can run you 1 000 and 5 000 depending on the extent of the job. Our 60 year old floor joists are showing their age. The amount of weight that each floor joist handles is pretty amazing. I have a floor joist that i noticed has several large knots that have split vertically through the joist.

Doing so strengthens weak joists and can help straighten sagging joists. Lay a new 3 4 plywood subfloor and bob s your uncle. Then attach the sister joist using three 16d common nails driven every 16 in. A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.

Driving 16d common nails in old hard wood is difficult. Sistering joists is a job for the pros who will bolt the new joists to the old joists and position the ends of the joists on the same sill plate that supports the original joists. When sistering these pieces together it is easy to put just a few nails in the boards and move on. On the top side of the floor another fix it idea to lay down new hardwood over the existing floor.

It is important to jack this end level to keep the floor from sagging any more and to keep the joists from splintering later. I am going to sister this joist with an identical sized joist 2x10 over its full length.