"jim_in_sussex" wrote in message
oups.com...



rules for notching & drilling joists are in the building regs - notches
must be in a zone between 0.07 & 0.25 x clear span of the joist away
from either end: for holes the zone is 0.25 to 0.4 x span. Notches may
not be more than 1/8 (0.125x) joist depth & notched on the top of the
joist, not the underside.. 90deg square cut notches are considered
weak - use a drill to make a rounded hole & cut down from the joist top
to obtain a rounded base.

Holes must be not over 1/4 of the joist depth & drilled on the centre
line. IIRC regs also state a 75mm minimum distance between any two
notches/ holes. Also IIRC NHBRC make that 100mm instead of 75mm.
Drilled holes must have a 50mm clearance of solid timber above and
below (allows for standard 65mm flooring nails)..

If at all possible you'd do far better to route the water pipe along
the wall above the floor and box it in. Water pipes looping down under
the floor and up again are a PIA.. If you intend to use Cu on this job
that's another PIA. Passing Cu thru several joists almost inevitablly
involves multiple solder joints which are amongst the weakest part of
an installation. Granted, if they are going to fail it usually happens
within a few days, but solder joints can still fail after years. If
you are going to use pushfit plastic, would you trust those joints
under the floor? Condsider carefully what happens if it there is a
difficult to access leak.

If you notch, you'd be also well advised to protect the pipe in the
notch with steel plates: often used for electrical work: (available
from www.tlc-direct.co.uk).

Last a word of caution: this sounds as if it could be a job notifiable
to Building Control. If you are going to ignore that, at least find
out the ramifications of ignoring - google on this group for more info:
basicaly you have to wear dark glasses for 6 months and keep everything
under wraps for 12 months.

HTH

Thanks for that. The intention is to bring the pipe up through an internal
plasterboard wall to the shower controls. the shower will be fully tiled. I
have my concerns that any leaks will be buried in the wall or under the
floor (also to be ceramic tiled!) May have to look at alternatives.