Joist maths check ;)

Discussion in 'Carpenters' Talk' started by SparkyAnt, Apr 22, 2021.

  1. SparkyAnt

    SparkyAnt Member

    Hi there!
    I’m building a 4.8x3.6m shed (16x12)

    For the base, Im looking to have 3 skids 100x100 on top of concrete blocks x6 per row/3 rows.
    Each row spaced at 1480mm centres
    Each of the skids will run horizontally the full 4.8m length ( front/middle/rear)

    Noggins will be 16inch/400 cent

    Going off the very highest kN/m2 weight on the span tables 1670mm is the max unsupported span for a 47x97 c16 , c24 apx 200mm more

    My original plan was to use 6x2 but if I’m interpreting the table correct and my “skid design plan” is sound supporting fully in 3 places with 1480mm being the max span , 6x2 is massive overkill and 4x2 would be ideal???

    Could someone please let me know if I’m right. I’m looking to order the timber this week

    EDIT—- I’ll be using 18mm OSB for the shed floor on top of the joists ...if that makes any difference/advance in strength also
    Last edited: Apr 22, 2021
  2. warcs

    warcs Member

    My span tables from building control show the max span at 400ctrs of 97x47 to be 1.93m, for 450ctrs 1.82m and 600ctrs is 1.47m this is for C16 timber, you will be fine.
  3. Severntrent

    Severntrent Screwfix Select

    Use of all those noggins is also overkill. TRADA tables also relate to Service conditions 1 and 2, your timber is condition 3 ( not in warm and dry environment)
  4. SparkyAnt

    SparkyAnt Member

    Brilliant! Thanks for backing that up mate appreciate it
  5. SparkyAnt

    SparkyAnt Member

    Ahh ok, I didn’t realise there were different tables for different usages/environments.
    I’m just happy I can get away with 4x2/47x97 as that’s saved me over £100 on the timber cost. Cheers mate
  6. I-Man

    I-Man Screwfix Select

    Brilliant series of videos i've just discovered where he builds his garden room from scratch. Captures every step from planning to building.

    May be of use!
    SparkyAnt likes this.
  7. SparkyAnt

    SparkyAnt Member

    Thanks mate :) appreciate that

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