RSJ - where would it end?

Discussion in 'Builders' Talk' started by ynot2diy, Jun 2, 2021.

  1. ynot2diy

    ynot2diy New Member

    I would like to knockout a wall marked with green dots on the attached plan (and add a short wall marked in blue) and I am trying to estimate how complicated it might be before consulting structural engineers etc.

    The photo shows the original plan of the ground floor from when the house was built. There is an RSJ marked on the plan but it looks like it would only go towards the partition wall (point marked in red). My question is - is this likely that the RSJ would be so short and then the wall I want gone would be load-bearing? Or is it just how it looks on the blueprint? (I don't have a better resolution and the lines are a bit blurry). I thought RSJ would normally span all the way towards the other external wall (it would be 6 m in total).

    The floor joists on the first floor are perpendicular to that RSJ.

    Ultimately, I will be able to lift the chipboards on the first floor and check, but just wanted to get some opinions as I am not quite ready yet to rip out the carpets...
    ground floor.jpg
  2. jonathanc

    jonathanc Screwfix Select

    I doubt the shell would be longer than it needs to be so expect part of the wall to be load bearing. What’s it made from? Is it stud or block?
    ynot2diy likes this.
  3. ynot2diy

    ynot2diy New Member

    It's made from block. Would that be enough to support the RSJ and the joists above?

    Also, in this case, it looks like it would be really hard to remove that wall without leaving some kind of column to support the existing RSJ?

    And then the new RSJ would need to be boxed below the ceiling?
  4. stevie22

    stevie22 Screwfix Select

    Unlikely to be strong enough even if by some fluke it was long enough. You need typically 50% more strength in a beam to accommodate a10% increase in length.

    Putting your new steel under the existing will be far and away the easiest option.
    ynot2diy likes this.
  5. ynot2diy

    ynot2diy New Member

    So would these be my options:
    1) leave a column where the existing "embedded" steel ends and add new steel underneath the ceiling where the wall would be removed

    2) put new 6m steel supporting the existing one and replacing the support provided by the wall?

    In 1) the column would be in a an awkward place and I am not sure 2) would be feasible, so maybe another option:

    3) put new 6m steel and add additional supporting column somewhere in the area of the "current serving hatch" so that it is "out of the way"?

    Thanks a lot for your advice!
  6. stevie22

    stevie22 Screwfix Select

    You need someone to look at this for you and spec your steel. BC will want to see calcs.

    You may need a beam under the wall the hatch is in which would then bear on the new steel dependent on what's above it.

    You really don't want posts in midspan: at worst you might need one at the end if there isn't a suitable wall to sit it on
  7. ynot2diy

    ynot2diy New Member

    I will not be touching anything before I get the calcs, of course!

    A column at the back (top on the plan) is not a problem if needed, as there are some boxed pipes in that corner, so I was thinking to leave a short wall there anyway.

    The front end (bottom of the plan) is more tricky because the current RSJ is above the window, so I would not be able to put a post there.

    However, I did want to make that window bigger, so maybe I could try to get to structural engineer to do calcs for something like this?
    Does it look reasonable? front mods copy.jpg front mods copy.jpg front mods copy.jpg
  8. stevie22

    stevie22 Screwfix Select

    An SE will do whatever you ask him to.

    I'm not quite seeing how your elevations tie to the plan, but that may just be a blonde moment.
  9. ynot2diy

    ynot2diy New Member

    Sorry - I used the position of the existing RSJ as a reference (red in the front elevation, line in the floor plan), but it is a slightly larger section of the building, which made it all somewhat confusing!

    In any case, it looks like it is unlikely to be as easy as one could hope for (as all other things in life!) and I might need to prepare for the SE consultation, BC, and all the costs of a new 6 m steel beam, and possibly some support for it to sit on on front end...
  10. stevie22

    stevie22 Screwfix Select

    OK blonde moment it was: I was reading existing steel as side to side bit it's the chain dotted line running up and down?

    Probably the easiest way is a new steel middle to back in line with the existing and a cross beam picking up the end of new and old
  11. ynot2diy

    ynot2diy New Member

    Side view.jpg
    Yes - it is the dotted line...

    So now I'm confused again... The old beam is levelled with the joists, but the new beam would need to go below the joists, wouldn't it? So I thought you meant to run new long beam across the room (like on the left on this new sketch).

    If I were to use a new beam from middle to back, the cross-beam would run perpendicular to the old beam and span the whole room across (e.g. resting on external walls)?

    (Sorry, if that makes no sense, it's all new to me)
  12. stevie22

    stevie22 Screwfix Select

    Makes perfect sense. Either option would work structurally so the idea is to adopt the one that is either cheaper or easier.

    I normally try for the shortest span first but several factors need to be considered.

    Option 1 will look neater as it's a single box but it will be longer and therefore a bigger section. It may well need a new spreader beam over the window so there is an unknown.

    Option 2 will probably have less weight of steel overall but will need a joint. You could put the new green beam up in the floor thickness to match the existing. More work but perfectly do-able. You are then back to a single box.

    You also need to think about how the steels can physically be fitted in too.

    A good SE should take account of all these issues
    ynot2diy likes this.
  13. ynot2diy

    ynot2diy New Member

    OK - awesome.

    In Option 2, I would need the cross-beam even if the new beam is at level with the old one (both in the floor), is that right?

    If that's the case, option 1 might be "easier", as the cross-beam would need to rest on the party wall...
  14. stevie22

    stevie22 Screwfix Select

    Yes to cross beam for option 2 and yes you will need a PWA

    Option 1 will probably be the best in this case, but see how the numbers work,
    ynot2diy likes this.
  15. ynot2diy

    ynot2diy New Member

    Great - thank you!

Share This Page