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Building Regulations and Standards: What's the cheap way to access BS6399?

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      CommentAuthorJustin
    • CommentTimeNov 15th 2008
     
    I want to look, at BS6399 part 1 to check out some straightforward rafter dead loads.

    I'm not in the mood for £80 to buy the BS document at the moment. Despite extensive looking, I can't find any on-line calculators, or documents providing rafter loading calcs. Are there worked examples, tables from the standard, or on-line loading calculators available for the amateur who wants to keep budgets tight?
    • CommentAuthortony
    • CommentTimeNov 15th 2008
     
    Yes, have a look at some old building regs docs

    I use span in feet/2 + one inch = timber size ... i.e. 10' span is 10/2 +1 = 6" or use 150 x 50 for rafter/joist and double one for a trimmer

    Rule of thumb but it is generally right.
    •  
      CommentAuthorJustin
    • CommentTimeNov 15th 2008 edited
     
    Thanks Tony.
    That in fact works out at exactly what was originally suggested for my span (assuming 400mm spacing). QED (possibly :), so a safe staring point.

    But I'd prefer to get down to the nitty gritty and work out what I'd require for 600mm versus 400mm spacing, knowing my tile load and the roof angle. (Hence I was kind of thinking of checking out BS6399). This is on the basis that I'd sooner use less rafters than more, not necessarily for economy (since increased depth may mean it's not so), but more importantly to mimimize insulation bridging (for a 100% fill roof, foam between and under).
    • CommentAuthortony
    • CommentTimeNov 15th 2008 edited
     
    Unbelievable now -- my rule of thumb for 400 vs 600 c/c is it makes no odds! bigger battens or with 400 35 instead of 50 rafters

    For fitting insulation between I cut the insulation first (352mm wide or553) then go wood/insulation/wood/insulation in that fixing order QVED
    • CommentAuthorsinnerboy
    • CommentTimeNov 15th 2008
     
    Justin - would you consider 225 x 50 at 600 c/c - to allow deeper cavity for insulation

    Also
    - battens and counterbattens over breathing felt and
    -vent above felt line
    - 25mm strip vents at eaves 5mm strip vents at apex
    all to facilitate future attic conversion ( assuming you are not actually doing one now )

    I find it easier to insulate , along slope , from wallplate up to apex back down to wall plate again . Changing planes of insulation along vertical "knee-wall" and small flat ceiling parts in the middle is akward and without a thermal imaging camera , it is difficult to check after if all insulations are in close continuous contact
    • CommentAuthorjon
    • CommentTimeNov 15th 2008
     
    "I want to look, at BS6399 part 1 to check out some straightforward rafter dead loads. "

    Dead loads are not given in 6399: 6399 is the code of practice for the use of Dead and Live but only provides live. Go to the library and get out an old copy of 648 if you want dead.
  7.  
    I have a pdf of the old Document A (1991) which has all of the old tables in it. Drop me an e-mail Justin
    •  
      CommentAuthorJustin
    • CommentTimeNov 15th 2008
     
    Thanks for the suggestions.
    Sinnerboy, that's useful but I need to minimize overall height as well (lIt's a lean-to beneath windows), so will be adding internal insulation too. Eaves strip vents, but not much chance at apex for lean-to. Was anticipating minimizing counter-batten thickness above sealed breather felt (Marley suggest as little as 12mm can be ok).
    Mike - thanks - I'll drop you my email
    Rgds,

    Justin
    •  
      CommentAuthorfostertom
    • CommentTimeNov 16th 2008
     
    Can I have one too, Mike? I have the 1992 one, 1994 revision - I'd like to check against older.

    Nowadays I generally get Struct Eng to size even rafters - and everything comes out surprisingly big. Haven't rules changed, since 1991?
    • CommentAuthorjon
    • CommentTimeNov 16th 2008
     
    There have been some changes fostertom. You should be able to get a good idea of requirements by using the 1994 version though.
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      CommentAuthorrichy
    • CommentTimeNov 16th 2008
     
    Good old Haringey Council have had this up for years, it's the full box of tricks, print before they hit delete! http://www.haringey.gov.uk/trada_span_tables.pdf
    • CommentAuthorwookey
    • CommentTimeNov 16th 2008
     
    At least cambridgeshire library provides online access to all British Standards. This is extreemly handy. Maybe yours has the same facilty. This lets you get PDFs of the standards. Hooray for libraries.
    • CommentAuthorFred56
    • CommentTimeNov 16th 2008
     
    Trada have recently published a new set of tables dated 2008. NBS have condensed and quoted them in a Shortcut 59. I think Justin is trying to calculate the minimum he can use rather than the quoted sizes from TRADA. My guess is that BC will ask for calculations to prove the application and they are usually unwilling to accept calculations unless they are from a qualified source. It may be easier to go to a Structural Engineer, one may have some fresh ideas you have not yet considered.
    If you library does not have online access to IHS or similiar, try befriending an egineering student with an Athens log-on, a bit naughty, but effective.
    • CommentAuthorwookey
    • CommentTimeNov 17th 2008
     
    Calculation are either right or wrong. Why should BC require the calculator to have a certificate? If they are right then BC should accept them.

    Is the problem that BC can't tell whether they are right or not (which would make BC a pointless beaurocracy - the whole point of them is that they should be capable of checking whether something complies with the regs, or near enough under the circumstances)? In which case quoting the relevant bits of BS648 might be necessary to explain to them.
    • CommentAuthorFred56
    • CommentTimeNov 17th 2008
     
    Wookey, I'm just remarking on what I have experienced and observed. BC does vary by local authority so your experience may differ.
    • CommentAuthorjon
    • CommentTimeNov 18th 2008
     
    Why should BC require the calculator to have a certificate?

    Try telling that to some BCs. It is sometimes unbelievable how much detail they require. Even if you are qualified.

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