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  1.  
    I've just written a free extension to the Sketchup 3D app which aims to help novice builders create the frame for garden offices, workshops, studios (and "Tiny Houses") up to 30m2 floor area using the Segal-method of post and beam timber framing.

    http://extensions.sketchup.com/en/content/segal-method-timber-frames

    It can create mono-pitched (shed) and dual-pitched (gable) roofs with specified maximum/eaves heights for avoiding the need for planning permission in the UK. Rafters can be solid timbers or engineered timber I-beams. Metal fixings are included in the model, such as M12 bolts and truss clips. Floor joists at 400mm or 600mm centers can be added, as can wall studwork.

    It also saves out a spreadsheet listing all the components used, as standard length timbers, etc. to make it easier to cost & order the parts.

    It is still an early version of the extension, and I'm sure there is lots of room for improvement, so I would dearly love to hear any feedback - positive or negative! Ideas for new features, things I should be doing differently, etc.

    I think I've made a mistake by having the floor joists resting across the sills of the bents (and having the bent tiebeams underneath the topplates) ? It does simplify the design (e.g., no need for joist hangers) but it drastically reduces the headroom, which is a big problem if you are building under permitted development and the eaves height can't be more than 2.5m :(

    Many thanks
      screenshot-dimensions.png
  2.  
    Posted By: sheffieldnickI think I've made a mistake by having the floor joists resting across the sills of the bents (and having the bent tiebeams underneath the topplates) ? It does simplify the design (e.g., no need for joist hangers) but it drastically reduces the headroom,

    The headroom can be increase by moving the ceiling joists (tie-beams) up to bisect the rafters. This will still stop the roof spreading the walls and gives head room in the middle of the shed where it is needed most.
    • CommentAuthorMikC
    • CommentTimeMar 13th 2017
     
    You could get around using joist hangers by sitting the floor joists on a batten which is fixed to the side of the green cross beam. Just make sure the batten ( or other size timber depending on space) is properly fixed with glue and mechanical fixings directly below each joist. This was my workaround when I encountered the very same trying to make a suspended timber floor within permitted development . It might not pass building control but I wasn't fussed.

    I have a model on my laptop which I'll post up when I get a chance.

    I look forward to having a look at your extension.
    • CommentAuthordjh
    • CommentTimeMar 13th 2017
     
    Posted By: MikCYou could get around using joist hangers by sitting the floor joists on a batten which is fixed to the side of the green cross beam.

    I don't understand. Yes, you could sit the joist ends on a ledger beam that was lower than the cross beams, but how do the joists cross the intervening cross beams?
    • CommentAuthorMikC
    • CommentTimeMar 13th 2017 edited
     
    Posted By: djh
    Posted By: MikCYou could get around using joist hangers by sitting the floor joists on a batten which is fixed to the side of the green cross beam.

    I don't understand. Yes, you could sit the joist ends on a ledger beam that was lower than the cross beams, but how do the joists cross the intervening cross beams?



    Ledger beam, that's a better description. The joists would butt up against the intervening cross beams, so lots of small joists rather than one long one.

    Would there be any issue with that approach?
  3.  
    Posted By: MikCWould there be any issue with that approach?

    Extra work/cutting and extra materials (2 x ledger beam per joist)
    • CommentAuthorMikC
    • CommentTimeMar 14th 2017
     
    Posted By: Peter_in_Hungary
    Posted By: MikCWould there be any issue with that approach?

    Extra work/cutting and extra materials (2 x ledger beam per joist)


    true, but cheaper than joist hangers and quicker too, i would have thought
  4.  
    Posted By: MikC
    Posted By: Peter_in_Hungary
    Posted By: MikCWould there be any issue with that approach?

    Extra work/cutting and extra materials (2 x ledger beam per joist)


    true, but cheaper than joist hangers and quicker too, i would have thought


    I'd originally planned to use ledger beams to support the floor joists on my own build, but I was advised against that approach because of the extra work involved, and also that softwood deforms under compressive point loads. In the end I went with Simpson LUP230/50 joist hangers which were only £0.47/each and very quick to fit with the recommended 3.75x30mm square twist nails.

    For the Sketchup extension, I've considered running the floor joists the opposite way, which would mean fewer joists to cut, and fewer joist hangers. But you'd need beefier beams and joist hangers for long unsupported spans, which would end up costing more...
    • CommentAuthorEd Davies
    • CommentTimeMar 14th 2017
     
    Posted By: sheffieldnickand very quick to fit with the recommended 3.75x30mm square twist nails.
    Sorry, bit off topic but while we're here, anybody know if those can be put in with a nail gun?
    • CommentAuthorcjard
    • CommentTimeMar 14th 2017
     
    Yes, but you need a positive placement nailer
    • CommentAuthorcjard
    • CommentTimeMar 14th 2017
     
    or a spare pair of eyes
    • CommentAuthorEd Davies
    • CommentTimeMar 14th 2017
     
    Because of ricochets if you miss the hole?
  5.  
    Another question: my extension currently uses the same size of beam for the bent sill (supports weight of floor + building contents) as it does for the bent tiebeams (under tension only, to stop the roof from spreading?).

    Can I get away with never having more than 100x47mm for the bent tiebeams? I don't know if I'm reading this table correctly, but I think for C16-graded timber under tension parallel to the grain, it should take 3.2N/mm2 so that is 15kN / 1500kg ? That would allow for cheaper tiebeams, as well as (slightly) more headroom.
    http://www.roymech.co.uk/Useful_Tables/Timber/Timber_design.html

    Thanks
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