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Rotten Joist End

Discussion in 'Wood / Woodwork / Carpentry' started by CGORST, 26 Apr 2020.

  1. CGORST

    CGORST

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    Morning All!

    I had a rotted floorboard or two where a tumble dryer used to reside so I decided to remove it. However, when I removed the floorboards I found that the bottom of the joist had rotted where it met the wall and for about a foot inwards. I have removed the rotted wood and the top of the joist is sturdy and has no rot at all. Is there any alternative to removing and replacing the joist and if I do have to remove the affected part of the joist what is the best way to attach the new piece of joist?

    Thanks for your help!
     
  2. foxhole

    foxhole

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    Cut back and bolt on replacement section sistering the timber .
     
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  4. CGORST

    CGORST

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    Thanks foxhole!
     
  5. JobAndKnock

    JobAndKnock

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    There is no alternative. Rot has to be cut out to 1 metre beyond the rot point and the rotten wood burned. The joist is then sistered with one of the same size (e.g a 7 x 2 must be sistered with one of the same cross section), the minimum overlay is 1 metre and you need to use 3 no. coach bolts with star washers between the joists to resist movement (I suggest M10 or at least M8 in a domestic property). The timber should ideally be pressure treated and at least structural grade C16. Assuming that the existing joist end is pocketed into the masonry, where the end of the joist goes into the masonry it will be necessary to extend the existing pocket to accommodate the offset joist end. The end of the joist should be end treated with preservative and envelope wrapped with roofing felt in such a way that moisture cannot enter the timber (so all folds towards the bottom). The new joist must have at least 50mm bearing within the wall. It can be packed up to level using skate and mortar then the remaining hole around the end of the joist gets filled with bricks and mortar
     
    Last edited: 27 Apr 2020
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  7. CGORST

    CGORST

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    Thanks JobAndKnock!
     
  8. DIYnot Local

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