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    • CommentAuthorEd Davies
    • CommentTimeMay 10th 2016
     
    My house needs some long joists. As specified by the structural engineer they're 220x45 C24 just over 7.2 metres long which is a pain as 7.2 metres is the longest the local big-chain timber merchant can do. They'd also be expensive per m³ I expect - my C24 posts are only a little cheaper than glulam on that basis.

    Said big-chain timber merchant's local manager suggested LVL (laminated veneer lumber - oversize plywood) from, I think, Crendon Timber. I asked if that had a “C” rating in the way that JJI glulam can be treated as C27 as an alternative to their normal calcs. He said it didn't work that way.

    I wonder if he's mistaken and that actually those beams can be used in place of C24 directly with no extra calculations. Alternatively, if there's another form of engineered timber that can be used directly that way.

    Weather's too good not to get on on site for a few days but I'll probably go chat to the timber people near Inverness airport that Willie suggested a while back about this. Any info might be very helpful for discussions, ta.

    (Going back to the SE is not really an option - I'd like to get this house built this year.)
    • CommentAuthorborpin
    • CommentTimeMay 10th 2016
     
    Posted By: Ed Davies(Going back to the SE is not really an option - I'd like to get this house built this year.)
    You will need to if you want him to sign in off I suspect :cry:
    • CommentAuthorEd Davies
    • CommentTimeMay 10th 2016 edited
     
    But why would I need him to sign it off if it's a direct substitution? Ie., something that meets the C24 specification.
    • CommentAuthorborpin
    • CommentTimeMay 10th 2016
     
    Posted By: Ed DaviesBut why would I need him to sign it off if it's a direct substitution? Ie., something that meets the C24 specification.
    Because he has given you a specific spec. I'd check personally but YMMV. Unless he looks or BC pick it up, it it unlikely anyone will notice. You could try the metal web joists as another alternative.
    • CommentAuthorEd Davies
    • CommentTimeMay 10th 2016
     
    Posted By: borpinBecause he has given you a specific spec.
    Right. That's why I'm asking about materials which are certified to meet that specific spec. Glulam is - I'm wondering if anybody knows of any cheaper alternatives which are, too.

    Metal web joists probably aren't certified in that way which is why I'm not thinking of them as an alternative.
  1.  
    Hi Ed, is there any reason why you can't just use multiple shorter joist lengths? The span for even that size of timber isn't huge so wherever they are supported you should be able to just overlap the shorter joists and nail them together or use tooth connectors & bolts. I'd do everything I could to avoid any kind of special ordering, 4800mm lengths are always off the shelf....
  2.  
    Posted By: willie.macleodThe span for even that size of timber isn't huge so wherever they are supported you should be able to just overlap the shorter joists and nail them together or use tooth connectors & bolts.

    Won't that have implications on the supporting structure? E.G. if you use an internal wall on top of which to make the joint then that wall becomes a supporting wall which may have implications on its construction and foundations. By specifying a full length beam I am presuming the SE did so to avoid intermediate supports
  3.  
    I am making the assumption that the engineer has specified the joists based on the longest unsupported span - there must be intermediate supports as even 220x45 joists will be trampoline like around 7m - I'm guessing the actual span is closer to the 4m mark, I'd be much happier with a single 4m odd length in the middle and two shorter joists either side if I recall Ed's design correctly. A quick call the engineer would confirm the suitability though.
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016
     
    Piccy:

    https://edavies.me.uk/2016/04/456-frames/dsc01780.jpg

    That's a view looking east. The joists are to go north/south from one stub post, across the two main posts to the stub post on the other side. One each side of each row of posts; there are to be 9 of those frames in total (six up in that picture), so 18 joists. Blocking between the joists between the main posts (3600 mm centres) so, yes, plenty to tooth and bolt to but very awkward to overlap. Still, the SE didn't give details for that so it might raise the BCO's eyebrows.

    Haven't looked at the original drawings but I suspect the SE originally designed them to be exactly 7.2 metres but when I asked for changes (long story of Chinese whispers between me, the house designer and the SE) he thought “sod him” and didn't bother to keep that.

    Agree about “off the shelf” but the local chain timber merchant said he can get the LVL stuff on the next lorry up (Thursday following order - so not this week :cry:) with delivery to my site within a few days. I've got plenty to get on with for now if I can get the process started.
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016 edited
     
    Posted By: willie.macleodA quick call the engineer would confirm the suitability though.
    That's the problem though - engineer didn't answer the phone last couple of times I called and only gave a one sentence reply (albeit a useful sentence) to the last few emails I sent. Even before he was paid he was very slow (three week turn-round on email exchanges).

    Last time I tried to call him it was on site with the BCO present for the founds inspection. BCO was quite sympathetic as he's having similar problems with his (different) SE for his own house project. In general the BCO has been helpful and sensible but, not unreasonably, wants a joined-up paper trail so I don't want to just make up a bolting scheme however sensible it might be in practice.

    The drawings specify bolting and staring for the east/west joists along the side of the house so the absence of equivalent specifications for the north/south joists across the house is a bit glaring.
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016
     
    SketchUp screenshot:
      sketchshot.png
  4.  
    I cross posted - you're using these timbers as ledgers, and hanging the joists off them. I couldn't understand how you were only going to need 18 joists otherwise!

    Shame you weren't given details for the post connections there. The engineer should have given you those really. If the cost is going to be much higher for an engineered solution I would personally just use shorter lengths and over engineer the join at the middle posts, possibly with a decent plate either side and through bolting. Though I'm sure you've had enough of drilling holes through heavy timbers by now..
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016
     
    Posted By: willie.macleodShame you weren't given details for the post connections there. The engineer should have given you those really.
    Actually, he did: two by M16 bolts through. Holes in most of the posts are already drilled for those which is part of my reluctance to change horses at this stage.
    •  
      CommentAuthordjh
    • CommentTimeMay 11th 2016
     
    Ed, I think glulams are graded according to GL numbers whereas C24/C16 is for lumber, including the timber the glulams are made from, though there is maybe a well-known correspondence?

    e.g. https://www.trada.co.uk/jail/downloads/dir/memberBrochures/8973D4F0-EC05-11D6-864C-00D0B7B8B494/Lilleheden_Technical.pdf

    LVL has ratings too, although I don't know what they are in the UK. I think what you might be able to do is supply the engineer's details using C24 to the firm supplying the LVL and ask their engineers to quote a size of at least equivalent ratings for stress, bending etc. The BCO ought to accept their engineer's statement that the LVL solution is at least as good as your engineer's C24 solution.

    e.g. http://www.woodworks.org/wp-content/uploads/2013-WS-Mar-Landreman.pdf for examples of what you seem to be doing.

    Alternatively, perhaps you could join two half beams in the centre. If I've understood your picture, there's loads of room between the two beams either side of the upright posts to put lapping lengths of wood to strengthen the butt joints. It would be at least as strong and stiff as a single length of wood.
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016
     
    Posted By: djhI think what you might be able to do is supply the engineer's details using C24 to the firm supplying the LVL and ask their engineers to quote a size of at least equivalent ratings for stress, bending etc. The BCO ought to accept their engineer's statement that the LVL solution is at least as good as your engineer's C24 solution.
    Yep, drawings are with the potential supplier but I'm a bit bothered they'll try to be “clever” and come up with a thinner design or something not realising the other implications. E.g., one of the iterations with the original SE was to make the floor thicker overall than the minimum required structurally as I wanted to insulate more than minimally.
    •  
      CommentAuthordjh
    • CommentTimeMay 11th 2016
     
    Posted By: Ed DaviesYep, drawings are with the potential supplier but I'm a bit bothered they'll try to be “clever” and come up with a thinner design or something not realising the other implications. E.g., one of the iterations with the original SE was to make the floor thicker overall than the minimum required structurally as I wanted to insulate more than minimally.

    They'll have more chance of realising it if you tell them :bigsmile:
    • CommentAuthorEd Davies
    • CommentTimeMay 11th 2016
     
    Posted By: djhThey'll have more chance of realising it if you tell them
    Trouble is, of course, the endemic lack of reading comprehension around (see above). E.g. earlier this afternoon I emailed who I think is the manufacturer of the beams being suggested to ask them similar to this for their product saying I want beams 7.2 metres long. Prompt reply (good) saying they can't do a clear span of 7.2 metres (not so good). I didn't say anything about spans - just the overall length. :devil:
    • CommentAuthorcjard
    • CommentTimeMay 12th 2016 edited
     
    Logical presumption though, that you're ordering a single length because that's what you want as a single span.. You can see why the manuf responded so, when in 99 percent of cases they'd be being asked for 7.2 solid because that's what joe blogs has down for the span.

    And faster to write an email back saying you don't want it for span reasons, than investigate another option?

    Phone call would be better, followed up by an email
    • CommentAuthorEd Davies
    • CommentTimeMay 12th 2016
     
    Posted By: cjardAnd faster to write an email back saying you don't want it for span reasons, than investigate another option?
    Indeed, an email back is what I did. It's just an illustration of how difficult it can be to communicate stuff, sometimes.

    Still, it turns out (thanks for the whisper DJH) that the company I thought were the manufacturers are likely only distributors, anyway.
    • CommentAuthorEd Davies
    • CommentTimeMay 17th 2016
     
    For anybody's future reference: the LVL the local supplier was thinking of is Ultralam-R. My structural engineer is happy with this as a substitute for the C24. He got back to me so quickly on it that it was obviously not something he had to think about too much.
    • CommentAuthorringi
    • CommentTimeMay 17th 2016
     
    How does it's price compare to C24 per m?
    • CommentAuthorEd Davies
    • CommentTimeMay 17th 2016
     
    A lot more: for these 45x220s its £8.80/m vs £2.75/m for the softwood.

    That'd probably make more sense if you had a design intended to make better use of the properties of the LVL but such is history. E.g., I could probably save a bit on the ancillary softwood blocking here but not enough to justify the cost of getting it all re-engineered.
    •  
      CommentAuthordjh
    • CommentTimeMay 18th 2016
     
    Maybe the 39x220 would be enough if your SE is speaking to you again?
    • CommentAuthorEd Davies
    • CommentTimeMay 18th 2016 edited
     
    He actually got back very quickly which was good. Yes, that's the sort of saving you might make starting from scratch but, assuming you can just go on a m³ price, that'd save £150 so not really worth the cost and probable delay.

    Also, at the “eves” (or whatever you call them on an A-frame) the bolts attaching these beams to the little stub post will need to be counter-sunk as they're under edge beams. Dropping the thickness of the beam would disproportionally reduce the amount of material left.
      beam-overlap.png
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