New bathroom layout & plumbing routes

[Addlepate]

Hi all,

Trying to work out the layout for a new bathroom and struggling a bit because of plumbing routes. Room is 2.75 metres x 3.3 metres, with the window and door in the short walls and the joists running longways, i.e. from door wall to window wall. Existing (which was lashed in) looks like this. The dog leg top right is the boiler cupboard, and I'm worrying about it now as we're having a new boiler fitted on the 10th and I want to make sure it's going in the best place:

I'm looking to get a shower in as well, and I've experimented with various layouts, but all the decent layouts end up with something - probably shower or sink - over on the top wall, creating a problem getting the drain across to the stack, which is on the outside wall bottom left, near the loo.

However, I'm wary of going through the joists with a drain, as they've already been notched out and it would take a lot of strength out. The only ways I can think to do it are to put the sink there, which at least means the drain can be reasonably high and can be boxed in on the wall, or to put the shower there and take the the drain out through the right hand wall and into a downpipe outside; this would be OK, as we have a combined drain, but would be a lot of work as it would mean going into the roof space of the extension, which is to the right below the window.

I was wondering if anyone has any ideas or suggestions I haven't thought of, perhaps the experienced trades here who might have come across a similar problem.

Thanks.

 

[RrogerD]

How about a shower above the bath, above the taps? You could put in one of those wider, 'P' shaped type baths.
Or, shower as you propose but run the waste out through the outside (window) wall and then around the back and side of the building into the soil stack?

 

[Hugh Jaleak]

I think you may have answered your own question, the only real option is to take the shower waste out and through the roof space of the extension.

 

[Addlepate]

@RrogerD thanks. I think a shower over the bath has been rejected by the boss, though we will have another run through it - she really wants a walk in shower, and I'd like to make it happen if I can.

I'll have a look at the shower waste run today, though I think going right round to the stack will be too long a run. Part of the problem with going outside is the pitch roof to the extension overlaps the bathroom wall - it comes to a couple of courses of brick below the bathroom window sill - so if we go out through the window wall, either round to the stack or to the downpipe, it will mean breaking into the roof space to install the pipework; do-able, but a pain.

The other alternative, I suppose, is a false floor, but that's not without work and issues either; or to put the sink on that wall, so at least the drain will be higher and could be boxed in, though that's not without problems:

@Hugh Jaleak thanks; you may be right, I was just hoping fresh eyes on it might spot something I hadn't thought of.

 

[trojanhawrs]

What depth are your joists?

 

[Addlepate]

@trojanhawrs good point - 8" (200mm) deep at 15" (380mm) centres

 

[trojanhawrs]

Is the door wall a supporting wall? I should say, does it have a supporting wall under it?

 

[Addlepate]

@trojanhawrs yes, supporting wall, though with a ground floor doorway directly below the first floor doorway. Joist ends built in to the wall. Should maybe also say the joists are 2.125" / 54mm thick.

 

[trojanhawrs]

Do you have notches or holes in the area between toilet and bath? If not and your joists are pretty level with each other you could probably get a waste in there if you're accurate

 

[Addlepate]

@trojanhawrs Joists are notched to 25mm deep for pipes at 150mm and 300mm centres from the window wall, otherwise clean. They are fairly level; there's a messy bit around where the shower is shown in the second image, as there was a chimney breast there that was obviously taken out many years ago.

Are you thinking of going across the room roughly at the joist centres, putting holes in using the D/4 rule? I hadn't thought of it, just assumed it wouldn't be a goer (and I hadn't remembered the permissible hole size as near that big), but you have set me thinking.

Assume it would have to be a hole rather than a notch given the size of a shower drain and the need for a fall along its length. Also wondering about the practicalities of drilling the holes accurately and feeding a pipe through as there is no space to feed it from ...

 

[matlob]

On your last pic you could you put the sink on the grey (shaded) wall and then most of the sinks pipework would be hidden behind the bath. I'd also go for as large a shower as you can as the cost is not a great deal more

 

[trojanhawrs]

Yep it'll have to be a hole, you said the soil stack is on that wall so I assumed you would have room to feed in from there. You'd want roughly a 30mm drop across that distance so you'll be flirting with the rules a bit but assuming 6 joists and a 5mm drop between each you'll not be miles off with a 44mm hole saw. I'd laser or use a long straight edge to mark across your joists and use an Arbor sized bit (6mm?), you can then feed through a cable rod or similar and check you've got the drop and the holes are lining up before you go mental. I'd then SDS a pilot from inside to out and core back in. Again, this is assuming your joists are pretty level

 

[trojanhawrs]

Sorry I'm talking pish, minimum fall is 20mm per metre so might be fairly far out at the extremes

 

[Addlepate]

Morning all. Thanks for your thoughts. Apologies for the delay replying; I had an eye procedure yesterday and couldn't see to type!

@trojanhawrs it was well worth thinking about, and I might take structural / building control advice, but I think as you say it probably doesn't work. As I read the regs the hole has to be on the centreline of the joist and maximum joist depth / 4 diameter, so I read it as having 25mm either side of the joist centreline to play with; I don't think that gives enough fall. In reality there might be reserve strength in the joists, particularly as they are slightly oversize for the span, but they've already been notched outside the proper zone so I'm wary of taking more out. The only other possibility is whether you can strengthen / stiffen joists by adding material or bracing plates but I don't see that option in the building regs.

@matlob the dogleg in that wall - the one with the grey / brown face - is the boiler cupboard. The grey / brown face is the one that would have to open (door) to give access to the boiler. Sorry, I should have made that clearer. Having said that, that is the reason for showing the sink where it is on the last picture, in that I could minimise boxing out / hide the sink drain by running through the cupboard and round behind the bath, particularly if the bath was built in. Good tip on the shower, and thats the way I hoped to go; I don't want to be banging elbows when showering and we can get in at least a 1000 x 900 if not 1200 x 1000.

There's another wrinkle in that the room is out of square by about five degrees - the whole house is - so putting the shower in that bottom left corner would mean a bit of angled studwork or drywall to square the corner for the shower tray and enclosure, but at the moment that feels like less work than the wastes.

The urgency at the moment is really to make sure we're putting the boiler in the right place - everything else comes later (slightly backwards, I know). From the discussion I think it has to stay in the corner it's in at the moment, top right, probably hung on the window wall to keep the possibility of option 2 with a shallow airing cupboard. or option 1 with a wide cupboard but slightly awkward access for servicing.

 

[trojanhawrs]

Where does your existing condensate drain for the boiler go?