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Odd size for main beam?

Discussion in 'Building' started by martysmarty, 25 Aug 2020.

  1. martysmarty

    martysmarty

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    Hi guys.

    I am really pulling my hair out here guys. Help me out as i think i am just seeing things now!

    My SE has spec'd a 203 x 203 x 46 UC beam to support the opening to our house. 4m span. We have a 1940s build with a cavity. On the drawings the walls are detailed 230mm overall thickness incuding cavity.

    So how can there be a single 203mm x 203mm beam holding both inside and outside skins there would be brick overhanging? or am i missing something.

    I only noticed as my builder said usually they are singles bolted together. If its wrong i have a good mind to ask for a refund as nothings been right yet.
     
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  3. sircerebus666

    sircerebus666

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    Have you asked for clarification from your SE?
     
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  4. noseall

    noseall

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    I'm pricing one up at the moment whereby the pair of beams (165mm wide each), even if bolted together and touching will be sticking past the 300mm wide wall. The SE has actually positioned the beams so that the webs are central to the brick - meaning they protrude even more.

    Someone will need to be creative with the plaster finishes.:unsure:
     
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  5. ^woody^

    ^woody^

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    A UC is stronger than a beam, so is used when UB is not feasible or practical.
     
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  6. kingandy2nd

    kingandy2nd

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    I have a 203 x 203 x 46 UC to support my 4m opening, which supports both skins on a 280mm wide wall. SE spec'd a 260mm wide 8mm thick plate to be welded onto the top of it, so seems to me like an element of overhang is ok.
     
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  7. martysmarty

    martysmarty

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    So we sre saying 47mm roughly of brick left unsupported is ok, and thats if the wall is straight. I get that more steel overhang is fine but not the other way around. I have floor joists on the one side.

    So i am.over thinking it then
     
  8. frutbunn

    frutbunn

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    This only gives an overhang of 13.5mm. If I remember correctly you are allowed 1/3 overhang. If I get time I will have a look at the latest BS just to make sure this is still correct. Personally I'd have designed or insisted the engineer calculate for 2 smaller section UB's.
     
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  9. kingandy2nd

    kingandy2nd

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    Your maths is wrong - 27mm of overhang, or 13.5mm on each side as fruitbunn has said.

    Speak to your SE to get comfort - don't be demanding your money back though :)
     
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  11. martysmarty

    martysmarty

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    Your right sorry. Did overlook that i even said 230mm details for walls. I guess 13.5mm dont sound too bad after all. Guess i need to sit this one out. We have had so many things wrong maybe i am just overlooking it a little now.

    Thanks guys my minds at rest
     
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  12. AS-Kent

    AS-Kent

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    I'm in a similar situ myself - have plans for a single storey flat roof extension with approx 7m external opening for sliding doors; SE has spec'd the same UC 203*203*46 as OP which is obviously way short of the approx 300mm cavity.
    There's 'nothing' (brick-wise) above this so it's only taking the flat roof/joist load, but I notice there's a small note saying 8mm thk *300 wide top plate required to beam supporting the wall above, so it seems to have been taken account of if required, because the overhang would be more significant than yours.
    However assuming this was intended to sit central to the cavity (on spec'd padstones) at the supporting ends, this would give a similar problem in that it's perched on the inside ~50mm of each padstone rather than spreading the load right across, is this normal too?
    Wondering if UC 203 is the 'go-to' beam for SE's which works well for them but leads to queries when somebody actually tries to build it?
    I'm on a tight budget so was hoping for a very simple build (with some DIY), so I was really hoping for standard practice rather than anything where a builder will be immediately factoring risk into his price because 'unfamiliar' materials are specified.
     
  13. martysmarty

    martysmarty

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    That was exactly my issue when the builder looked, he started being iffy as it wasnt his 'norm'. But i guess that dont mean its wrong either.

    I checked all my notes on the calculations and theres definitly nothing else added. Il do a physical measure of blockwork just to be safe. If it seems to far out il give him a ring.
     
  14. ^woody^

    ^woody^

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    Its not that straight forward, as a column (as a beam) has different properties to a beam, this means that there may be some specific loading that requires those properties, and one which would mean an impractically deep beam, or two beams both of which are too wide to sit on the wall they will bear on.

    Also a cavity wall lends itself to two beams due to uneven loading of the leafs, whereas solid walls (even with overhang) can be on a single central beam.

    The biggest problem with SE's is that inexperienced ones will just throw numbers into software with no consideration as to practicality.

    In practice, with a typical domestic loading arrangement for probably 95% of UK houses there are a very limited number of beam sizes that will cover all situations. I know several councils near me will not require calculations for beams in typical situations and spanning set distances.
     
  15. frutbunn

    frutbunn

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    I've worked at 4 LA's only at one did we always insist on calcs. If it was a straightforward UDL etc using an over engineered approach we would accept that.
     
  16. AS-Kent

    AS-Kent

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    Thanks for the replies guys - so I now have the added comfort of thinking I might have paid a SE good money for something that might not have been required, and might indeed be impractical or more expensive to build, D'oh! :) This was exactly why I tried to talk to some builders beforehand about the proposed job but none of them were willing to engage in any kind of detail without drawings - and getting drawings has led to SE calcs. Now when I go back to the builders, I can see me getting 'why didn't you get the normal XYZ arrangement drawn up?'!
    Having said that I'm fairly sure calcs are expected in my locale, will have to see as things progress.
     
  17. ^woody^

    ^woody^

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    Builders will always say something like "What? I never did that/did not use one of those on my last job", but most don't actually know why they never did, or why it is required on their next job. That's why there are builders and there are designers.
     
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