how do I reinforce a cracked floor joist?

Question

A hole made for a plumbing pipe pass-through had weakened the joist whish is about 3" by &7" so that the bottom portion of the joist has fully cracked but the is little sagging, perhaps 1/2 inch.

Answer 1

If the plumbing can be removed, rent barrow or buy a Tele-post( a type of post that can be adjusted to size an then extend to jack up the joist. Lowes or Home Depot will have them) Jack up the joist until the crack is tight and turn an additional 1/2 turn. Use 3/4" plywood cut to the same width as the joist and a minimum of 48" in length, the longer the better. Using a good quality construction adhesive (Liquid Nails etc..) glue the pl wood on both sides of the joist. Complete the job by nailing the plywood with a nail which is long enough to go through the pl wood and as much of the joist as possible. In your case a 16d (penny) common or sinker nail would be great. Remove the post after a day or two. it may settle just a bit, but that is what the extra 1/2 turn is for. The hole can be redrilled for the plumbing.

This really works well.

Jumbo

Answer 2

Half an inch of sag is pretty bad, and should be corrected. I used two methods in my old 1913 house.

The broken floor joists in the kitchen I removed and replaced, because that area would see so much traffic, the load the floor would see was unpredictable, and it was easily accessible since I was tearing the floor up for other reasons.

The cracked floor joist in the back bedroom we braced. We used hydraulic jacks to jack the joist up into the correct position and then took 2x4's about 4 feet long and nailed one on each side. This was strong enough to handle having a huge steel file cabinet sit on it without a squeak for the years I lived there.

Answer 3

Your repair needs to be as strong as the original joist. Sister a 2x8 at least 6' long, the longer the better. You need to jack it back into position, with construction adhesive glue then nail the new joist into position. Drill holes and install carriage bolts 2 every 8-10". Don't skimp on the wood or the glue.

Answer 4

A remedy an architect friend gave me for same problem
for a long diagonal split......
No fancy tools reqd .
Took up the sag w/ a scissor jack from the car & a 2x4 extension.
The pipe centered itself in the original hole.
Notched 3/4 " plywood for pipe which was close to underside of floor at that point.
Glued & nailed to both sides of the joist.
Went a little more than length of crack in each direction from hole
(He said many nails would hold better than bolts ).
Took out jack & it did'nt budge,
Good luck

Answer 5

Is the plumbing pipe still there? If it is you will have to reroute it and then do as suggested above

Answer 6

Scab 2 boards next to it. One on each side and run several bolts through them to secure it.

Answer 7

Sister...Sister....J