Thanks for all the replies. Just one more question.. if there was to be a stud wall perpendicular to the direction of the joists in about the middle of the span, would that be considered to 'break the clear span'? Or not be part of any calculation with regard to the trada span tables?
Choosing lowest profile floor joists - On Trada limit with this - Help please :)
- Thread starter lordgaz
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It would add a small point load at mid-span of each joist, which is where you could do without it, as it will increase bending stress and deflection.
As your joists are fairly near the limit, there is a small chance it would take you technically over the limit. But in practice it will probably not make much difference, as people rarely load the floor up to the maximum 1.5kN/m² anyway; the floor certainly won't collapse! (the standard tables factor in an allowance for poor workmanship and materials, and slight overloading).
Suggest not losing any sleep over it.
As your joists are fairly near the limit, there is a small chance it would take you technically over the limit. But in practice it will probably not make much difference, as people rarely load the floor up to the maximum 1.5kN/m² anyway; the floor certainly won't collapse! (the standard tables factor in an allowance for poor workmanship and materials, and slight overloading).
Suggest not losing any sleep over it.
What's the layout on the floor beneath that? You'd need the floor beneath to be constructed of floor joists that are deep enough to carry the extra load, or for the ground floor to have a structural wall in the same place so that the loadings can carry though.
Do they also assume you've notched the joists as per the guidelines in Part-A? i.e. would a structural engineer be able to prove a size based on the joists never being notched anywhere, or would building control argue that that's not realistic and there's no way of controlling what subsequent owners do?
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If we have the stud wall, it will be built onto the screeded slab - So I see it adds issues rather than solve them (I was thinking it would add to the support, but I am wrong - so in that respect, in theory it would be better to build a stud wall that makes no contact with the joists then? (not that I would do that!)
I think the joist sizes given in the table allow for notching/drilling as long as these follow the guidelines for spacing/position/size etc.
It could be argued then that if the joists were not to be notched or drilled - ever - then theoretically a smaller section would do.
But in the real world, these things happen, so have to be allowed for.
In practice, the one thing which kills domestic floor joists is deflection and bounce and it is really down to how much deflection we are prepared to tollerate.
If there is a plaster ceiling below, the amount of deflection allowed is less than if there were no ceiling.
The Codes usually stipulate the maximum deflection allowed - the BS Code states domestic floors should deflect no more than span x 0.003 - this ensures that plaster ceilings below don't crack.
Think Tony1851 may have assumed the stud wall was going to be above your new joists not below it! If your plan is in the shaded bit (on the TRADA tables) and you've got a nice solid (4 x 2 studs) partition wall underneath that would certainly stiffen the floor up. Stud walls can be considered as structural but there'll be design detailing necessary that I don't know about. You could always put a 4" block wall in.....
Yes,sorry, I was not clear where this wall would be. Block wall would be ideal, but we need to use a pocket sliding door in this wall so I am not sure it would be suitable (unless you have thoughts) .. again, space is at a premium and thicker walls would steal into room size
Hmm. Looked at pocket doors myself a while ago, ran away from the cost & that was a non-structural wall. If headroom downstairs permits you could run a steel beam or lintel above your partition wall- that'd break the span upstairs for definite (and avoid any compression problems on your sliding door). But putting a lintel in would have its own costs and problems.....party wall possibly.
Sounds to me as if you'd be well off finding a structural engineer to sort a bespoke solution to your problems- once you get an SE on board they can design to your spec and (as long as they're prepared to sign off on the design) outside the advice in TRADA tables and approved documents and the like.
Sounds to me as if you'd be well off finding a structural engineer to sort a bespoke solution to your problems- once you get an SE on board they can design to your spec and (as long as they're prepared to sign off on the design) outside the advice in TRADA tables and approved documents and the like.
I've asked a SE now - I will let you know the reply if possible,
Yes, I misunderstood; you can have a structural stud wall designed which would enable you to reduce the depth of the joists considerably.
This is assuming there is a reasonable thickness of concrete on the ground floor.
This is assuming there is a reasonable thickness of concrete on the ground floor.
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