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Would inserting a 152 x 89 x16 ub strengthen this adequately... Advice very much appreciated

Discussion in 'Building' started by rustyjaz, 20 Feb 2020.

  1. rustyjaz

    rustyjaz

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    Hi, I understand the need for calculations but also understand the difficulties when the lintel is cast in place?

    I would like to remove the single brick partition to the left. This is the old pantry. The lintle is holding the side of the house (3 bed semi detached) the pantry is part of a flat roof extention beside the house. The lintle is fairly hefty. It is 200mm high apart from on the left where an extra layer of bricks reduced the hight to 150mm (it must have been cast in place) it is 300mm wide. The reduction in hight is not through the whole lintle only 100mm (of the 300mm wide lintle)
    The length is 2.84m.

    The lintle spans both the interior and exterior brick work. Looking at it from the exterior side (from within the pantry) the lintel is rectangular, however, from the interior brickwork (due to the extra course of bricks) the lintel is not rectangular and reduces down to 150mm at one side.

    My original intention was to to get rid of the left side brickwork leaving 200mm bearing. The neighbours have done the same with no known issues. But due to the 'nitch' I am wondering whether to add a 152x89x16 above. That way I could leave the concrete I place and have extra peice of mind.

    Please see pictures. Does this sound correct or am I completely off? Kind suggestions very much welcome.

    Cheers
     
    Last edited: 3 Mar 2020
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  3. rustyjaz

    rustyjaz

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    Anyone?
     
  4. JobAndKnock

    JobAndKnock

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    On the kind of jobs I work on (more and more listed building refurbs/repurposing) you no longer see cast in place lintels simply because it is almost impossible to do accurate calculations for them (according to an S/E I'm friendly with), so I'm not surprised nobody has answered this. You are asking for an opinion on a significant structural change without a site visit. In other words you really do need a Structural Engineer to do the calcs. Anyone answering this may well be making themselves liable in the event of a structural failure
     
    Last edited: 21 Feb 2020
  5. rustyjaz

    rustyjaz

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    OK, fair point. May be I should be more specific, is there a way of calculating the strength of the lintle if cast in place? As no way of knowing if steel rods inside, and unknown strength of concrete.

    Secondly if a rsj was placed above the exciting lintle, would that reduced the load placed upon the lintel under it? To me it makes sense but physics do no always make sense to me.

    I am trying to gauge if this is a possibility, not wanting someones approval and certainly not to later claim against if there was a problem.
     
  6. JobAndKnock

    JobAndKnock

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    According to an S/E I know, not really. Pre cast lintels are manufactured in a controlled environment with proven raw materials where periodically a sample is taken and destruction tested. This isn't possible for a one off, hence the reluctance to do the calcs one one offs with uncontrolled materials any longer
     
    Last edited: 21 Feb 2020
  7. rustyjaz

    rustyjaz

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    Would having an rsj above the pre cast lintel reduce the load below?
     
  8. JobAndKnock

    JobAndKnock

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    Surely any UB (universal beam - you no longer hear the term RSJ) would need to be big enough to span the same distance as the existing cast Iintel and would therefore need to be able to support the entire load of the wall would it not? In which case you'll still need to do the calcs in order to size it correctly. The other thing you seem to be missing is that this sort of structural work is generally notifiable (to Building Control), in which case that would also necessitate the structural calcs....
     
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