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Strengthen a floor joist

Discussion in 'Building' started by m0t, 11 Apr 2021.

  1. m0t

    m0t

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    We've recently had an extension finished and the builder has left a new joist fixed in a way that makes me slightly uneasy.

    It's a dormer and one of the new joists couldn't be sat on the top of the existing wall plate on the internal wall because an existing floor joist from the next room was directly in line with where it needed to sit, an existing ceiling joist was directly on one side and an old chimney breast on the other.

    The builder cut the joist short and bolted it to the chimney breast.

    The bit that has made me uneasy is that he has made a bit of a hash of the bolt holes and as a result the bolts are sitting at an angle and the heads aren't flush to the joist. The builders view is that the BCO saw it and passed it so there isn't any problem.

    The chance of anything going wrong is pretty small but the bolts being at an angle does increase the risk of a failure and I've got a bath sitting on this one.

    I've been trying to think of options for strengthening it a bit without pulling the whole thing out.

    The front runner at the moment is to take a spare bit of joist about a metre long and cut out a rebate for the ceiling joist (ceiling joist is about 1/3 the height of the 145mm new floor joist). This would then be glued to the ceiling joist, then to the new joist that's bolted to the chimney and the old floor joist in the adjacent room. I'd then bolt everything together with coach bolts and timber connectors. I've got everything in the shed to do this so it would also benefit from being free.

    Any problems with this approach or something better to try?
     
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  3. Bouy

    Bouy

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    "The chance of anything going wrong is pretty small but the bolts being at an angle does increase the risk of a failure"
    Why? The area of the bolt at the joist/brick interface is if anything increased so shear failure is increased and as long as the bolt heads are tight against the joist there would be no slackness so again no issues?
     
  4. m0t

    m0t

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    Coming back to this I had a more detailed look and the two bolts were some kind of hex headed concrete screw. Both were loose in the block and couldn't be tightened properly.

    I filled the holes with resin and then replaced them. I also did attach an extra length of joist alongside to connect it to the wallplate for good measure.
     
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