Ceiling Joist Span

Discussion in 'Carpenters' Talk' started by Simon Harrison, Oct 14, 2022.

  1. Simon Harrison

    Simon Harrison New Member

    Hi all,

    First time here so go easy on me.

    I recently purchased a 1930’s semi detached house and have been doing works upstairs.

    The ceiling joists are 3x2 (at 350mm centres) and I can’t find any info relating to maximum span for 3x2 although it seems nowadays, 3x2 is not sufficient for ceiling joists.

    Anyway, I guess I have 2 questions.
    1. Can anyone help me with the maximum span of 3x2’s?
    2. If I add extra wooden “joist hangars” from the rafters to the ceiling joists, is this acceptable and does this in effect, “extend” the maximum span?

    thanks in advance
    Simon
     
  2. Severntrent

    Severntrent Screwfix Select

    Google ,ceiling joist span, for tables, 1.3m ish span is about max for c16, hangers from rafters is recognised way to extend span but rafters must be designed for extra loading
     
  3. Rosso

    Rosso Screwfix Select

    Ok. Span in feet, divide by 2, plus 1.
    So for 12' span =12/2=6 +1=7inch, or 175mm, except irmts not 175, its 170.
    What is your span?
    Theoretically, a 2 by 3 should only manage a 4' span, but somehow, in the old days......
     
    Last edited: Oct 14, 2022
  4. arrow

    arrow Screwfix Select

    For rule of thumb in feet it is half plus 2. A 12' span would be 8x2
     
    Jord86 likes this.
  5. Jord86

    Jord86 Screwfix Select

    As arrow said it’s plus two, similarly the metric equivalent is twice the span plus one, so a 3m or 10’ span would require a 7x2 for floor joists. Ceiling joists were sized to carry much lighter loads and act as ties back in the day.
     
  6. Severntrent

    Severntrent Screwfix Select

    Forget rule of thumbs, go www.timberbeamcalculator.co.uk and with a bit of interpolation between centres and sizes you can see what max span can be
     
  7. big all

    big all Screwfix Select

    just checking its 350 centres and not 350 between timber faces as that would actually be 400 centres [406/16"]
     
    Simon Harrison likes this.
  8. stevie22

    stevie22 Screwfix Select

    Is the ceiling sagging? Not sure why you're worried when it' been there near on 100 years.

    Timber quality back then way better than modern stuff
     
    Simon Harrison likes this.
  9. Simon Harrison

    Simon Harrison New Member

    Good point. It’s 400 centres.
     
  10. Simon Harrison

    Simon Harrison New Member

    So the plan is to remove this and rebuild something similar but obviously the opening is wider than the NHBC recommended 600mm. The previous owner took the original wall down to build the cupboard and that was how they supported it. Without the cupboard today the 3 x 2 wold be running its full length (3 ish metres, to where it’s joined to the next joist that runs to the rear across the bathroom ceiling. That span would be far too big.
     

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  11. Rosso

    Rosso Screwfix Select

    True. Absolutely true. I was comfortably on the ouyside of a few bottles of McEwan's Champion, and really shouldn't have been posting
     

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