Joist replacement / repair

Discussion in 'Carpenters' Talk' started by Derek Beeton, Sep 22, 2016.

  1. Derek Beeton

    Derek Beeton New Member

    We have just purchased an approx 90 year old property. The home report picked up on a “slight slope” to a floor in a downstairs dining room. On closer inspection the whole floor has dropped by about an inch to inch and a half at one side, along the outside wall. The joists should be presumably resting onto a wall plate at this end, but are instead floating an inch or so above the wall. At the other end they are built into sockets that are sound and solid. The whole floor hangs above a two foot crawl space – earth / rubble base, good ventilation and all air bricks and vents are clear. The room is approx 4m x 4.5m, with the joists running front to back along the 4.5 m and a single joist spanning the width at the halfway point, onto which the joists rest. There is a single brick pier, pretty much in the centre of the room. There are no noggins or other supports between joists. The floor also has a bow to it width wise as well, with the highest point, and most stable, being above the brick pier. The joists appear to be dry and sound and are 7 x 2’s. A couple do look obviously bowed however. No sign of rot, crumbling or worm activity. The plan I have in my head is to frame around the outside of the whole room (apart from where joists are into sockets), sister up joists to either side of the single width wise joist and hang joists on hangers. Instead of resting on the supporting timber, they would hang from the newly attached joists either side, effectively splitting the job into two separate floors. To attach ledger boards for hanging I planned to use M12 170mm Rawlbolts at 400mm staggered centres. My queries are, 1. Are these fixings enough at this spread? 2. Is hanging from foundation walls, rather than setting onto / into putting any undue lateral strain onto the walls? Presumably not at this low level? I do plan to put in noggins or possibly herringbone strutting. Cheers in advance for any help or advice!
     
  2. sospan

    sospan Screwfix Select

    Why not remove all the old joists fit your frame/ledger board and then use joist hangers to fit the joists - reuse any that are worth saving any that are not can be cut down for nogging
     
  3. Derek Beeton

    Derek Beeton New Member

    Cheers sospan. Think that's probably the way I'll go. Will rawlbolts as above be enough for the ledgers or should I be thinking resin ?
     
  4. BMC2000

    BMC2000 Screwfix Select

    ...and use treated timber joists
     
  5. Derek Beeton

    Derek Beeton New Member

    Thanks BMC - Will do.
     
  6. sospan

    sospan Screwfix Select

    I would drill and use resin. I have never liked rawlbolts - some grip and some don't and there is always the danger of the bricks shattering especially with older houses.
     
  7. BMC2000

    BMC2000 Screwfix Select

    Used joist hangers bedded in anchorser resin and for new floor joists in my loft, they werent going anywhere. Used it for setting a bolt a washer to anchor he original wall plate too. Great stuff and fairly priced. http://www.everbuild.co.uk/Anchorset-Red-380P
     
  8. chippie244

    chippie244 Super Member

    Use multimontis or thunderbolts.
     

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