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RE: strengthening cut joist (Follow-Up #7)

posted by: brickeyee on 06.01.2011 at 10:53 am in Home Repair Forum

"sister the damaged joist full length. "

The full length does not require sistering, and unless you can move the drain lines you would still need to notch the new material for clearance.

Plumbers are well known for going at joists with a vengeance to run DWV lines.

It is not really always their fault though.
Carpenters seem to love placing joists under the middle of tubs (directly in line with the drain).

Add to that the 'designers' who never even consider how the DWV lines are going to need to be run and joists get hacked up.
Some sections of 2-3 inch angle fastened below the missing section on each side of the joist and extending at least as far as the missing section on each end of the cut should be adequate (so three times the length of the missing section).

The angle sections need tight bolt holes, and so does the joist.
I normally clamp the metal in place and then drill through everything.

Fasteners larger than about 3/8 inch do not get you anything extra (it is easy to exceed the crush strength of the wood if fewer larger fasteners are used).

The fasteners should be staggered up and down at least twice their diameter to avoid creating a 'zipper' line in the wood.

Having to hammer the bolts through the wood is NOT a bad thing (but watch out on the metal or you can wreck the bolt threads).

Nylon self locking nuts are better than lock washers.
The nuts only need to be snug to hold everything together, but not so tight as to start crushing the joist.

The angle does held spread the load out from the fasteners.


clipped on: 01.28.2014 at 11:02 am    last updated on: 01.28.2014 at 11:03 am