From the wiki:
Have I missed a(nother) change of regs?
Not that I am aware of, there are restrictions as to where (between 0.1 and 0.25 x span) and how deep (no more than 0.125 x joist depth), but other than that nothing is still permitted (unless you are using some composite joists made with stringers and web).
I can see why it would be prohibited in the central half of the joist length. but why is it prohibited at the ends of the joist? Surely that's the palce where it would have least effect on the strength.
BTW, how DO people install central heating pipes now? Do they have to use flexible ones and drill through the joist centre?
Robert
I take it you mean "notching" and not "nothing" ..lol
I would imagine that notches anywhere would affect the allowable deflection of the joist, to some extent. After all, the joist depths are calculated from tables to meet the requirements of the span. But you are right - how to get around the problem of CH pipes? I suppose that the only practical solution is to notch at the ends, with shearing force being the only real factor there as opposed to deflection. In my house, there are quite a few cases of joists notched in the centre and electrical cables run on top. I've re-routed most of the electrical cables but haven't bothered to strengthen the notched places with plywood (and probably never will since the joists are not deflecting too much!).
Maris
It is the place that is least affected by any bending forces on the joist, but *most* affected by any shear forces, since it is immediately adjacent to the point of support (via hanger, wall etc). Notches here could enable the joist to split at the end.
In an ideal world, you can still use notches - just be a bit choosy where you notch. In the real world most plumbers seem to hack lumps out any place they fell like it!
Yup, sorry!
OK I own up. I wrote this section.
Well this is part A of the BR and has been for some while. I have at least one gas fitting book that covers this matter.
But the shear stresses are highest at the ends.
OK I think I over stated the case here. Although much of the text is probably still OK.
Do you have a section number in the BR document? I could not find anything in the latest (2004) edition (which is odd because I am sure I have seen reference to it somewhere).
On Sat, 10 Mar 2007 02:47:04 +0000, a particular chimpanzee, John Rumm randomly hit the keyboard and produced:
The old span tables (including the notching diagrams) were removed from the 2004 Approved Document A, and section 2b just refers to the TRADA document or BS 5268-2 and BS 8103-3, both of which are available for a fee[1]. The guidance hasn't changed from the 'old' 1992 AD A which can still be downloaded from the Planning Portal website.
Notching outside these parameters is not 'prohibited'; these are 'rules-of-thumb', and if you wish not to take advantage of them, you will need to demonstrate by calculation that the member is still adequate for the loads upon it.
[1] The TRADA tables were removed, as I understand it, at the request of TRADA because either the Government didn't want to pay the fees to TRADA for reproducing them, or TRADA thought they could earn more by publishing them themselves.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.