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Solutions to 800mm floor joist centres

Discussion in 'Floors, Stairs and Lofts' started by Danj4, 20 Apr 2017.

  1. Danj4

    Danj4

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    Hi,
    I would like to lay a new floor covering in the first floor bedroom in our victorian terrace. The problem is that the floor joists (120mm x 60mm) are at 800mm centres with no noggins, spanning roughly 3.4m.

    Ideally I would make the structure better in order to accommodate a standard 18mm chipboard or floorboard covering. Will adding noggins suffice or will this put too much stress on the existing undersized joists?
    Should I add more joists to the structure - which would be quite labour intensive and disruptive and involves cob walls?

    What would everyone suggest.?
     
  2. endecotp

    endecotp

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    60mm wide joists at 800mm centres are in some sense equivalent to 45mm wide joists at 600mm centres.
    A 120 x 45 joist can span about 2m, according to modern rules.
    So 3.4m is a long way beyond what would be allowed today.
    Does the floor bounce much?
     
  3. Danj4

    Danj4

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    That's what I thought, however, there is a beam beneath the joists which would make the span around 2.4m and this means that there isn't much bounce. I think any bounce there is is due to the current 18mm t&g boards flexing.
     
  4. endecotp

    endecotp

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    So it was a complete waste of my time looking up the max span for a 120 x 45 joist, then?
     
  5. Danj4

    Danj4

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    Well its helpful to know that you think the joists as they are (taking into account the 2.4m span) seem to be ok to support the weight.
    So my next question is how to make it suitable to accept a new floor covering as most floor coverings are designed to span a maximum of 600mm?
     
  6. tony1851

    tony1851

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    Run 4" x 2"s at 400 centres the other way- fixed with joist hangars to the sides of the existing joists.
     
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  7. HawkEye244

    HawkEye244

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    I noticed the OP is thinking about chipboard but another member suggested ply instead.

    What are the pros of ply over chipboard?
     
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