I am about to undertake various jobs round the house - the wife's bought me a round to-it, so no excuses now. In the bathroom we are going to have a shower cubicle and basin in a corner that currently has no water supply. The supply is diagonally opposite the new position. To get the water over there will mean passing pipework through
5 or 6 floor joists (it's a first floor bathroom, no water in attic). Is it ok just to cut a series of 1" depth slots to take the pipe? Will I need to strengthen the joists when doing so (I was thinking of screwing a 12" sheet of 3/4 ply below each slot, but wondered if this is necessary?). Drainage is not a problem - they will be on an outside wall. Thanks Paul
Best to route pipes like this close to lines of support (where the joists rest on internal support walls or close to external walls). At these points the joists are least stressed by bending/flexing loads. Also a good idea to centre these under a floor board and clearly mark the top of the board for future reference. Shouldn't need reinforcing if these rules are followed.
notching out and using copper tube is old and busted. drill through the joists with a 20mm flat bit and use plastic pipe and push fit fittings for the supply pipe to the shower.
remember: /always/ drill the hole for the pipe a few mm /below/ the bottom of the screws / nails you intend to use to refix the floorboards as you don't want to do what I once did, 11pm in someone else's house, last floorboard to be replaced, I smacked a nail right through a copper pipe.
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
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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.
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.
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