1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Rafter size and ledger plate on single storey extension

Discussion in 'Building' started by xdrive, 24 Nov 2020.

  1. xdrive

    xdrive

    Joined:
    2 Mar 2019
    Messages:
    261
    Thanks Received:
    2
    Country:
    United Kingdom
    Hi.

    I have a 4 metre extension. I'm trying to work out rafter size. I'm trying to achieve a 15 degree slope.

    Will be using interlocking double roman tiles.

    The clear span from ledger to wall plate is 3.68 metres.

    I will be using c24 rafters with no purlin.

    There will be 2 sky windows.

    The ceiling inside will be lowered to 2.4m height and finished with plasterboard.

    The span table suggests 2x7 c24.

    1. Would the deadload be no more than 0.5 or between 0.5 to 1?

    2. Is 2x7 about right for that span and pitch? I've been told by a builder 2x6 would suffice.

    Will use 2x7 ledger plate also if 2x7 rafters.

    3. Is rafter span horizontal length from ledger plate to beginning of wall plate start of birds mouth? Or end of wall plate after seat cut?

    4. Do the rafter sit on top of ledger plate or sit in hangers? That would determine height of ledger.

    5. Are air bricks necessary on side of roof?

    Cheers
     
  2. Sponsored Links
  3. 23vc

    23vc

    Joined:
    17 Apr 2015
    Messages:
    2,478
    Thanks Received:
    394
    Location:
    Warwickshire
    Country:
    United Kingdom
    The top plate doesn’t need to be as deep as you birdsmouth the rafters onto it so most of the rafter plumb cut sits against the wall
    Span is distance along the pitch not horizontal
     
  4. tony1851

    tony1851

    Joined:
    23 Feb 2012
    Messages:
    10,271
    Thanks Received:
    1,549
    Location:
    Manchester
    Country:
    United Kingdom
    Open (vaulted) ceiling or conventional flat ceiling with separate ceiling joists?
     
  5. xdrive

    xdrive

    Joined:
    2 Mar 2019
    Messages:
    261
    Thanks Received:
    2
    Country:
    United Kingdom
    Conventional flat ceiling with separate ceiling joists
     
  6. tony1851

    tony1851

    Joined:
    23 Feb 2012
    Messages:
    10,271
    Thanks Received:
    1,549
    Location:
    Manchester
    Country:
    United Kingdom
    Your dead load will be in the 0.5-1.0 range; 7x2 C24 @ max 400 centres would be needed.

    6x2 would deflect too much.
     
  7. ^woody^

    ^woody^

    Joined:
    3 Sep 2006
    Messages:
    33,361
    Thanks Received:
    4,523
    Location:
    West Mids
    Country:
    United Kingdom
    Span is diagonal distance. Is your 3.68 "span" diagonal or horizontal?
     
  8. xdrive

    xdrive

    Joined:
    2 Mar 2019
    Messages:
    261
    Thanks Received:
    2
    Country:
    United Kingdom
    The above Span is horizontal. The diagonal clear span is 3.8m
     
  9. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
  10. Sponsored Links
Loading...

Share This Page