Suspended Floor

Discussion in 'Getting Started FAQ' started by Russel Green, May 20, 2020.

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  1. Russel Green

    Russel Green Member

    Hi All,

    first post, so take it easy on me... just replacing floorboards in a suspend wood floor and notice a lot rubble and sand. So I need too remove as some is only 10cm under the joists? Also can I move it to the middle where the void is three feet down or should I skip it? Also the room smells damp but not had heating in this room and no air vents under flooring. Plan was:
    Put in several air vents
    Replace two rotten joists.
    Place dpm under current joist in contact with the bricks.
    Insulate between joists with rigged kingspan.
    Lay down chipboard flooring.
    And then new flooring.

    should I put a damp membrane above the insulation? Or should I leave it as we would rather the room breathes?
    Should I spray down any mould under the floor to kill before doing the work?
    Should I wrap the ends of the joists with dpm or just put it under them?
    Do the treated joists also need me to treat with anything?
     

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  2. Abrickie

    Abrickie Screwfix Select

    No need for dpm
    Yes, treat any mould
    Yes, wrap the joist ends
    Treat any cut ends, with a suitable timber treatment

    Minimum 150mm required under the joists, so you can move the excess to the middle ;)
     
    WillyEckerslike likes this.
  3. Russel Green

    Russel Green Member

    Thank you very much.

    will the damp smell go once everything is sorted?
     
  4. Abrickie

    Abrickie Screwfix Select

    You may want to consider spraying the rubble with either a bleach or disinfectant solution, whilst treating the mould ;)
     
  5. D
    Do the job properly and put timber floorboards back.
    The only thing chipboard flooring is good for, is lining the sides of a skip to get a bit more in, it is then consigned to the dump which is the best place for it.
     
  6. Russel Green

    Russel Green Member

    thanks for the advice
     
  7. WillyEckerslike

    WillyEckerslike Screwfix Select

    I completely forgot about that one in my recent list...
     
    Deleted member 11267 likes this.
  8. As well as Dot and Dab Willy, also the work of the Devil.
     
    WillyEckerslike likes this.
  9. Russel Green

    Russel Green Member

    hi Abrickie,

    can I ask as well can I just lay the new joists on top of the bricks the same as the old hoist or do they need fixing/brackets
     
  10. Abrickie

    Abrickie Screwfix Select

    Just the same as the old ones, although your new ones may need wedging up a little ( metric v imperial sizing) broadfix packers are your friend for that :)
     
  11. Russel Green

    Russel Green Member

    thanks pal that’s what I thought

    Yeah the new joists are slightly smaller 100mm by 75 and the old ones 100mm x 80. Will that be fine and should I go with C24 or C16 treated.
     
  12. Abrickie

    Abrickie Screwfix Select

    C24 , without knowing the span you may be ok with c16 but there’s no difference in cost, don’t worry about 5mm just pack up ;)
     
  13. Russel Green

    Russel Green Member


    Another couple of questions. If only half a joist is rotten can I cut it back to the dwarf wall up the middle of the room and then run a new joist beside it from the dwarf wall To the other side? Would I need to join them or have them overhand a certain amount.

    also if I’m only replacing a limited amount of joists do I need to inform building control?

    I’m planning to insulate as per regs?

    cheers again
     
  14. Abrickie

    Abrickie Screwfix Select

    Yes you can just do half a joist, as long as they are sitting over the full width of the dwarf wall that’s good enough. No need for BCO for only a couple of joists :)
     
  15. Russel Green

    Russel Green Member

    whats bco?
     
  16. Abrickie

    Abrickie Screwfix Select

    Building control
     
    ElecCEng likes this.
  17. ElecCEng

    ElecCEng Screwfix Select

    *officer :D

     
  18. Russel Green

    Russel Green Member

    Ha ha ha

    of course... so no need? Someone said if doing more than 25%
     
  19. Abrickie

    Abrickie Screwfix Select

    Are you replacing 25% of your joists ?
     
  20. Russel Green

    Russel Green Member

    about 4 out of 11
     

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