Waste pipe through joists?

[Pete Verdon]

My bathroom plans include a recessed shower tray, whose trap will be in the void under the floor. I don't yet know which way the joists run (haven't taken up the old tiles) but it seems likely that one will be in the way between trap and soil pipe. What's the usual solution here? I'd be very wary of drilling a 40mm+ hole through a joist without some assurance that it's not compromising it structurally.

Any work would be near the end of the joist, no more than two feet from a supporting wall. Depending on which way the joists run, their span could be either 2m or so or considerably longer. The actual distance from trap to soil pipe is very short - one end of the tray will be up against the boxing-in that contains it.

Cheers,

Pete

[Tim S]

Pete Verdon coughed up some electrons that declared:

My IEE Build1) Max diameter of hole is 0.25 x joist depth

2) Holes on the centre line should be between 0.25 and 0.4 of the joist span from either end

3) Max depth of notch is 0.125 x joist depth

4) Notches between 0.07 and 0.25 of span from either end

5) Holes in same joist should be 3 diameters apart.

So in theory you can have a 50mm hole in the centre line of a 200mm deep joist, but only between 1/4 span to 0.4 (nearly the middle) of the span length.

How's your pipe position WRT to the length of the joist?

Cheers

Tim

[The Natural Philosopher]

likley its near the end.

What you could do is remove a section of joist completely, then bolt another section ACROSS the end of the cut part extending to adjacent joists This is structurally like making a false support for the shortened joist, by tying into teh other jots alongside it.

Thats OK over one joist, but Id be wary over cutting away two, though doubling up the joists you hang from would be a reasonable way to restore strength and rigidity.

Another possibility is to raise the whole shower tray on a plinth, so you step up into it, and then run the pipes over the joists.

In my case I had no other option, and the pipes run behind the bath and into a tiled, boxed off, section over the soil pipe where the bath, toilet and shower all meet.

[Pete Verdon]

[...]

Cheers. The distances from the end ring a bell, but I'm (pleasantly) surprised at the allowed size of hole. Is 200mm the joist depth you'd expect for a 1992 house?

I've measured the room, and found that it's 1700mm wide. I'm going to assume that the joists run across that span (both walls are solid) - can't see why it would have been done the long way. So I can drill my hole between 425mm and 680mm from the wall - not a lot of leeway, but luckily it's in about the right place. Just have to check the drain location on the available trays; if necessary I could get some extra flexibility by rotating the trap and using an elbow.

Cheers,

Pete

[David Hansen]

On Sun, 25 Jan 2009 12:48:17 +0000 someone who may be Pete Verdon wrote this:-

Run the pipe another way, perhaps to a different destination, though this may run into problems over the length of the pipe and the fall. Drop into the room below. Move the shower tray to somewhere the drainage is easier. Raise the shower tray so the pipes can be run above the floor boards.

If gravity drainage cannot be arranged then go down to 22mm diameter pipe via a Sanishower or similar.

[Pete Verdon]

I understand what you're suggesting, and I'm sure it could be done safely, but it still scares me :-). If I were doing it I think I would only need to be taking out one joist, but that's still something I'd rather not do.

That's pretty much what I have at the moment, together with a gungy, clattery, sliding-doored shower coffin^H^H^H^H^Hcubicle. The whole point is to eliminate this kind of suboptimal British contraption; I'd probably go for a pumped waste or one that went down through the floor to be dealt with below, rather than build another elevated plinth.

Hmm, actually, going down through the floor sounds like an interesting possibility. It would be above cupboards in an out-of-the-way corner of the kitchen. I'm planning a mid-life spruce-up (just a good clean, fix and paint, not a full refurb) down there in the near future.

Cheers for the train of thought :-)

Pete

[Steve Firth]

You're new around here, then.

[Pete Verdon]

Yep - an idea that occurred to me a few minutes ago responding to TNP. The more I think about it the more I like it. Could even fit a detachable access panel in the boxing down there - can you get rodding eyes for 40mm pipe? The current shower has a long and tortuous run, and is prone to blockages and hence overflows, so knowing I can always poke something through it if necessary is a good feeling.

Cheers,

Pete

[Tim S]

Pete Verdon coughed up some electrons that declared:

I'm afraid I don't know. I'd expect 200mm/8" in any house prior to about

1960. You could gauge this by measuring ceiling-floor thickness by the stairs, subtract 15mm for ceiling plasterboard and 20mm for floor covering - should give you a near enough indication.

You might have something funky instead of "normal" joists.

[Rick Hughes]

"Pete Verdon" wrote in message news:497c5f91$0$511$ [e-mail]...

a 200mm joist will allow for a 45mm clearance hole ... but this would have to be on mid point of joist and there are limits on length along joist depending on span etc. A better result is raise the tray up onto some 75 x 50 and fit a HepV0 trap with a 90 degree connector .... this requires only about 2" below the tray. I used HepV0 traps on all 3 showers in my place ... they are much neater.

They also meet requirements for AAV if that is an issue.

[RobertL]

What about a sump and a pump? then you can use much smaller pipe.

Robert

[Pete Verdon]

Nah - as posted elsewhere, it's highly likely that I'll be within the specs for drilling the joist, but in fact will probably go down through the ceiling below instead, where the pipe could easily be boxed in.

Pete