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Bearers (single span / continuous span)

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  1. #1
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    Dec 2007
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    Default Bearers (single span / continuous span)

    All,

    I have bought the book Decks and Pergolas Construction book which everybody advises to read however when trying to calculate what sizes I need for the Ledger, and bearers I am somewhat confused by the terminology "single span or continuous span". Can somebody please advise as to what is meant by this.

    Furthermore, can somebody confirm the following is correct. The proposed deck is approximately 13 metres long (running parrallel and joined to the house) and depth 5.2 metres into the garden. The posts I intend using will be 100x100 and spaced in a line at intervals approx 1800mm from the wall up to the 5.2 metres and no more than 1500mm from each other. The bearers and joists would be sized upon somebody advising what the difference is regarding single and continuous spanning.

    Really would appreciate some help.

  2. #2
    Senior Member
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    Single span is when you have only 2 supports, one at each end of the bearer/joist - something like a post and lintel structure (e.g. stonehenge). Continuous spanning is when the bearer/joist is supported by more then 2 posts.

    For example, if I had to span a 3 metre distance and I had 2 posts, say 2.8 metres apart, and I used a single 3 metre bearer - this would be single span. If I now put a post in the middle, so each post is 1.4 metres apart and still used the single 3 metre bearer - this would be continuous span. Note that in the second example with 3 posts 1.4 metres apart if I used 2 bearers, each 1.5 metres long - this would be 2 separate single spans.

    I also struggled with this idea and the above is my understanding... I'm not an expert (at this anyway) and I guess someone will correct me if I'm wrong.

    Cheers,
    Adam

  3. #3
    1K Club Member
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    Default

    spot on chumley

    Tools

  4. #4
    Apprentice (new member)
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    Feb 2010
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    portland
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    Question

    old thread but thought i would toss this in.
    if i have a bearer 4m with 4 supporting post under it can i use two peices of 190x45 f7 laminated together. over the whole 4m

  5. #5
    4K Club Member ringtail's Avatar
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    yes. I dont know my pine span tables but I would think a 190 x 90 anything would easily span 4 mt continuous

  6. #6
    Apprentice (new member)
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    Default

    Thanks yeah you would think so but was told it would only be good for 3.6 Does anyone out there know i cant understand the span tables.

  7. #7
    4K Club Member ringtail's Avatar
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    According to my Hyne program you can do that with just about anything. 2 x 90 x 45 MGP 12, 1 x 190 x 35 MGP 12, and too many more to list. What you have there is overkill.

  8. #8
    Apprentice (new member)
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    Nov 2010
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    New Zealand
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    Default

    DIYGUY - 4 posts supporting a beam 4M long gives you a span of only 1.4M way less than the 3.6M noted above. Your beam is way overspec.

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