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water damaged floor joist


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  • water damaged floor joist

    I have started a bathroom remodel and discovered a water damaged floor joist under the front edge of the bathtub. This joist is sistered by 2 others. My question is whether I can remove the damaged joist and not replace it since there are still 2 stable joists and then run supports from the adjacent joist to the remaining 2 joists. This is a 1960's home and the old tub was metal surrounded by tile and the old floor was tile with about 1-2in. concrete substance underneath. The new tub and wall surround are acrylic and the floor will be swiftlock laminate, all of which will be considerably less weight than the previous. Help!!!!!

  • #2
    The sistering of those joist provides alot more strength than just the single joist alone, and even though you are not gonna have the same weight to support, I think it would be a bad idea to leave it out and not replace it. You could end up with alot of bounce and possibly it could sag. Plus you will not own this home forever and the next owners will be in the blind. You should be able to cut a new joist and hammer it up in between the two stable joist. Then drill holes through all 3 joist and insert screws with bolts and washers every 1 foot or so and cinch up tight. Here's a link to show the details

    Just a note on your laminate, be very caustious of installing laminate in a bathroom. It is easy for water to seep beneath and the particle board that is under the laminate will swell and pop up the flooring.


    • #3
      since the joist needs to be repaired, can I remove the water damaged section (approx. 6.5ft.)from the 16ft joist and then place 2x8 cross pieces attatched to the adjacent joist and the remaing joists at each cut end to support the sections of old joist. I could also run bolts through the joist I am going to repair before I cut the damaged section out.Then replace the damaged section with a new 2x8 between the cross pieces and bolt this new piece to the 2 old joists? will this give enough stability. I would replace the entire length, but plumbing and manpower are in the way.


      • #4
        I'm not going to take the time to make structural calculations, but the following should be economical and work safely.

        The amount of lumber needed for reinforcement is about 1/3 of the length of the joist plus the amount of damaged wood. If you have a 15’ joist, the replacement piece of wood should be at least 5’ plus the damaged wood. (e.g., if the last 3’ are damaged, the sister joist should be a minimum of 8’ long). Use the same size lumber (e.g., 2" x 8"’s should reinforce 2" x 8"s, etc.).

        1. Install new sections of joists from the end of the existing to the far side of the support beam. Be sure that the mating ends are in contact from top to bottom.

        2. Place a jack under a 4 x 4 and raise the end of the first joist so that it is level.

        3. Apply construction adhesive to a 2 x 8 x long splice piece, place one end on top of the beam, and clamp it in place.

        4. Drill pilot holes or through holes in the splice piece or both pieces as required for the screws or bolts used to fasten them together. Make the holes as small as possible.

        5. Place a staggered row of fasteners near the top of the joist and another near the bottom. If you use regular screws, place them about 3" apart. If you use 3/8" to 1/2" lag screws or bolts, use washers and space them about 8" apart.