Help needed regarding rsj 8m ceiling joist

Discussion in 'Builders' Talk' started by Ipatel369, May 14, 2020.

  1. Ipatel369

    Ipatel369 New Member

    Thank you for taking time to read.

    I am not builder neither expert but no one seems to give correct and clean answer.

    Basically we live in a bunglow that's 8 meter wide and 20meter long approximately.

    We thinking to get ceiling joist down so we get more space on the loft thus we can create dormer upstairs. We know that we have to change all our joist to bigger one to have dormer.

    However we want to remove most of the brick internal wall downstairs and make them as stud wall. As we have disability thus we want to have flexibility to move walls of bedroom if situation changes for us with minimal cost.

    Is it possible to have rsj 8meter long for this purpose? we do not want any box in ceiling or floor bcz we use ceiling track hoist.

    From my initial research I got impression that it is possible but we will have box in ceiling or upstairs floor. However most of thos answers were for house that have load bearing walls upstairs.

    Regards
    Stay safe
     
  2. DannyDoLittle

    DannyDoLittle Active Member

    Yes it's more than possible to get the RSJ to 8mtr but using an RSJ that size comes with added complications... weight, maneuverability (getting it in place)

    See the picture attached.. that's 2 x 8.6mtr RSJ's bolted & plate welded together. Was not an easy task getting them in place.

    You'll need to get a Structural Engineer to calculate the amount of steel needed.

    You say you want to drop all internal brick walls and make them stud walls so you can move them around... You do know that stud walls are fixed to?? You're better leaving the brick internal walls and opening up the door frames to make them bigger for ease of access, but might need to chance the lintels above the doors to.
     

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  3. Abrickie

    Abrickie Screwfix Select

    “I am not builder neither expert but no one seems to give correct and clean answer.“

    How do you know then ?

    The answer is obviously yes you can put a dorma in and replace all the internal wall with studwork.
    Firstly employ a structural engineer. Then be prepared to move out while your roof comes off and the internal is taken back to a shell. Pretty much anything is possible if you throw enough money at it, which takes you back to needing a SE to work out how to support the roof you want.
     
    WillyEckerslike likes this.
  4. Mr Rusty

    Mr Rusty Screwfix Select

    Definitely a SE for an 8m span. For a short span of a couple of meters the risks are low and good builders will have done it many times. 8m is a big span, and you not only have to think about the strength of the beam, but also the fact you end up concentrating all the upper loads into point loads at the ends of the beam so the bearing down to the foundations becomes important.
     
  5. A steel beam with an 8m clear span will be quite deep and would almost certainly be deeper than your new floor joists resulting in a downstand/bulkhead. Or the other option is to have a lower flush ceiling but if too low in an open plan space will feel quite chlastrophobic.

    Another thing to bear in mind is the possible Planning implications. If the proposals do not meet the PD guidelines, you may have to submit a HH application. If your LPA decide that due to the amount of existing walls being removed, they’d actually consider it as a knock down and re-build, which would require a Full application. I’ve just had this recently where we left up three walls and the LPA only just agreed it can be dealt with as extensions/alterations via a HH application.
     
  6. stevie22

    stevie22 Screwfix Select

    Abrickie and Mr Rusty make very good points.

    8m is a killer: we usually wind up having to size beams for deflection rather than strength in domestic situations and the beam span is multiplied by itself 4 times to calculate it so a span of 4m would need only 1/16 of the stiffness in the beam: much smaller.

    I think your concept is sound: take the pain now to give simple flexibility down the road but if a support somewhere in the middle is possible then things would be a lot easier. You will have a staircase somewhere and you wont want to be moving this so maybe this could be made to work. A lot depends on you roof headroom. I think what you need is a good designer who does his own calcs so a technician rather than an architect (they typically think space and aesthetic without practicality) or an SE who typically work solutions to constraints imposed by Architect.

    I think if push came to shove you could perhaps get away with a small (50 or so) downstand as any hoist track could pass under it.

    Good luck with project.
     
    WillyEckerslike likes this.

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