Tommy Mac Discussions Forums Fix-it Forum: Home Improvement & Do It Yourself Repair Forum Reinforcing Floor Joists – A puzzle for experts

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    • #48961

      I’m installing a new whirlpool tub (at least in theory, so far) and I’d like to double up a pair of 2×8 (x 10’4″) floor joists under the new tub. The problem is that I have electrical wires that run through the existing joists – making installation of sister joists something less than a slamdunk.

      Rather than re-running a bunch of wiring, I was wondering if I could simply build trussed joists around the wires. If anybody has any suggestions (and I realize that pharmaceutical suggestions might be entirely appropriate here) or references which might assist in this effort, I’d certainly appreciate it.

      In the alternative, if one was to notch a solid 2×8, could the cutout be filled and reinforced (by a metal plate, for example) in order to restore the strength of the joist?

    • #255551

      I think it would be better to drill holes for the wires in the sister joists and run the wires thru them. an alternate would be to make the holes, then split the 2×8 lengthwise, running the cut thru the wire holes, sister the split 2×8 pieces to the existing joist using construction adhesive and 5/16 carriage bolts every 2 feet in each half of the split sister joist. this should give about 95 percent of the strength of a true sister with another 2×8. also spend the extra bucks and buy #1 clear joists so that there is greater strenght due to no knots. You will have to go to a real lumber yard to get the clear joists.



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