Steel beam sizing

Discussion in 'Engineers' Talk' started by spud_nuts, Dec 3, 2021.

  1. spud_nuts

    spud_nuts New Member

    We're looking to remove a load bearing wall, which is supporting one wall of a gabel, the floor above, ceiling above and roof above. I've sent our structural engineers calcs to my dad and we're both a bit concerned.

    Screenshot 2021-12-03 at 15.10.58.png

    The above image shows the wall (and chimney to be removed). The wall is supporting the joists from Room 2, and the section of Room 1 to the right of the existing steels (supporting another gable).

    The values the engineer has used for his calcs is here:
    Screenshot 2021-12-03 at 15.12.32.png
    And he has come up with requiring a 203x203 UC46.

    Some of my/our worries are:
    - The floor loads only take in to account the floor for Room 2, and not the section of Room 1 who's joists are supported between the existing steels and the wall to be removed.
    - The wall dead load is for a 2m high wall. The wall is at least 2.5m tall above the steel.
    - There are no calculations for the chimney. He has stated that gallows brackets are fine.
    - The roof load is for just the width of the room, and doesn't take in to account the steep pitch of the roof.
    - Ceilings and stored items in the loft havn't been taken in to account.
    - My old man thinks the weight required for the roof is too small.
    - He's calculated the span as 5.2m, when it's clearly more than that.

    Now I'm no structural engineer, but some of the above points seem quite worrying, and I wouldn't imagine they're included in the 1.4 and 1.6 safety factors that are used in the calculations.

    Is anyone able to put my mind at ease and let me know what steels they used for their houses? Or if any structural engineers know that the specified steel is roughle correct?

    Obviously I'll follow up with the engineer, but the fact that he's clearly missed some stuff is pretty worrying.

    Any help is greatly appreciated.
  2. Bob Rathbone

    Bob Rathbone Screwfix Select

    Did the SE visit the site and take his own measurements and observations, or did you provide any information? If you provided any information then you may be in trouble as the SE will claim that that is 'What the customer told me'. Something of this size and complexity requires a site visit by the SE and the SE must take all measurements and observations.
  3. Severntrent

    Severntrent Screwfix Select

    Size and span looks OK to me
  4. Jord86

    Jord86 Screwfix Select

    An 8 inch square quarter tonne lump of steel over 5m long is a very large, very painful item to install which will take a massive amount of weight. Did the engineer come out to the job or just calc it off plans? How do you know he's missed stuff and not just lumped it in with his loading figures, a four foot overhang of joist and floorboards isn't much weight and should be propped if required, likewise the storage items on the loft floor and the pitch of the roof being steeper doesn't really make a difference in your scenario. Gallows brackets generally are ok for supporting chimneys however some Building Control officers or councils don't like them, checking first would be wise. No offence, but your father saying the roof loading is wrong doesn't mean anything unless he can explain why, or is an engineer himself. Just ring the bloke to clarify.
  5. stevie22

    stevie22 Screwfix Select

    As you've drawn it the "span or EFFECTIVE LENGTH should be 5.7 so that's a massive worry. As to the rest nothing looks obviously wrong but we don't got a full picture here.

    He should have done his own survey.

    Personally I would have spec'd a pair of UBs if I could make them work as it's a much more efficient section and the pair are a whole lot easier to install.
  6. spud_nuts

    spud_nuts New Member

    Thanks all for the advice.

    Thankfully, with how the garage and doors line up (not pictured in the floor plan), it's a straight line to get the steel in. The builder came round with his steel installer and he had a look at the plans and whilst the steel will be heavy, he was happy that it will be easy to install with two lifts (genies I think he called them).

    The engineer did come out to the job. I'd pre drilled holes in the ceiling for him to see joist directions etc, but he seemed very relaxed about the whole thing and has evidently gone off old plans from an extension 25 years ago. He didn't even get a tape measure out!

    I've submitted the whole thing to building control with the calcs and engineers drawings, and explained the use of gallows, and they've given approval to go ahead, so hopefully it should be all good to go with the gallows.

    The worry with the roof load was that he uses 0.75 regardless of the pitch or material of the roof. As we've got a very steep roof pitch, we didn't know whether that was sufficient.

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