What the best way to run the waste for this shower?

[OldKettle]

Hi,
I am looking to install this shower and tray in a bathroom that I am refurbishing.

Mode Hardy 8mm easy clean shower enclosure and stone shower tray

Click here to read more about the Mode Hardy 8mm easy clean shower enclosure and stone shower tray from Victoria Plum.

victoriaplum.com

I'll be replacing the sink and toilet too, but I am keen to get the shower installed first.

The rough dimensions of the shower tray are marked out on the floor in duct tape, and the location of the shower drain is marked with the star on the piece of paper.

The black line of tape, in the centre of the photo, indicates the planned location of the new shower unit.

I will be removing the floorboards in the shower area and replacing with a single piece of 18mm marine ply.

As you can see there is a long waste pipe (outside diameter 36mm) for the sink, which has been run through the joists, and which connects to a perpendicular 42mm pipe which runs to the soil stack. There is also a 42mm waste, which was installed above the joists, for the old bath.

I originally hoped to tee the shower waste to the long pipe, but 36mm is undersized. I could still tee to it, but would have to expand the pipe to 42mm downstream of the tee.

Attaching it to the old bath waste, will either involve cutting into the joist, or raising the height of the floor under the shower, to accommodate the pipe above the joist. I would not be attaching to the 42mm pipe at the current height but would be looking to run a new 42mm pipe as close to the top of the joist as possible, and connecting to the vertical section of the 42mm pipe. I suspect that I will need to place minimum 50mm timbers across the joists and then the ply above that, to give me a sufficient drop to the vertical waste.

I have also included a shot which shows that all of the cables from the consumer unit enter the house right next to the area around the pipes, which would complicate running brand new pipes in that area.

I have a few questions that I am hoping to get some advice on, please.

1) Is raising the floor and connecting to the existing 42mm vertical waste the best option, or should I tee into the 36mm pipe, expanding it to 42mm downstream of the tee?
2) The tray is 1400x800. If I raise the floor, should I create a raised area which is exactly that size or should I go larger?
3) Can I and should I install the tray rotated 180 degree so that the waste is in the location of the orange spot?

Any advice on the above and any other thoughts would be much appreciated.

 

[Jackrae]

Those shallow shower trays are a right pain for overflowing is there's any restriction in the drain line, such as air, hair or conditioner build-up

 

[Madrab]

One main concern - notches for joist should be no more than 1/8th of the depth of the joist, that 36mm basin waste pipe should not be notched into the joists. Current specifications state that the max notch in a joist should be no more than 0.125 of the depth of the joist or 35mm as the max.

How to get it right: Notches & holes in solid timber joists | LABC

When installing pipework or cabling, floor or ceiling joists may need to be notched or drilled. But this could weaken the floor to such an extent that it becomes structurally unsound. To find out if this might be the case, you can find guidance on notches and holes in solid timber joists for use...

www.labc.co.uk

Do not reduce the shower waste from it's 40mm starting point, if anything you increase it to 50mm. I'd raise the tray and then connect it intop the current bath waste, also allows a suitable fall to ensure the outflow from the tray is the best it can be.

1 - Best option
2 - Creating a plinth that is the same footprint as the shower tray topped with 18mm WBP ply/OSB3 would be fine
3 - If you are doing 1&2 then no reason not to rotate the shower as the waste can flow from that point as easily as the first position IMO.

The tray will need to be raised around 90-100mm above the current floor to allow for the shower waste to fit correctly and allow and adequate run to the waste outflow.

 

[OldKettle]

One main concern - notches for joist should be no more than 1/8th of the depth of the joist, that 36mm basin waste pipe should not be notched into the joists. Current specifications state that the max notch in a joist should be no more than 0.125 of the depth of the joist or 35mm as the max.

How to get it right: Notches & holes in solid timber joists | LABC

When installing pipework or cabling, floor or ceiling joists may need to be notched or drilled. But this could weaken the floor to such an extent that it becomes structurally unsound. To find out if this might be the case, you can find guidance on notches and holes in solid timber joists for use...

www.labc.co.uk

Do not reduce the shower waste from it's 40mm starting point, if anything you increase it to 50mm. I'd raise the tray and then connect it intop the current bath waste, also allows a suitable fall to ensure the outflow from the tray is the best it can be.

1 - Best option
2 - Creating a plinth that is the same footprint as the shower tray topped with 18mm WBP ply/OSB3 would be fine
3 - If you are doing 1&2 then no reason not to rotate the shower as the waste can flow from that point as easily as the first position IMO.

The tray will need to be raised around 90-100mm above the current floor to allow for the shower waste to fit correctly and allow and adequate run to the waste outflow.

Thanks Madrab.

I was a bit surprised to see the notches so deep in the joists. I was aware that they were too deep, but thanks for confirming what the max depth should be. I certainly won't be cutting into them at all.

They were supporting a cast iron bath previously so, although they have been cut too deep, I am working on the assumption that they will support the shower tray. I think the saving grace is that they are only spanning a gap of around 1 metre, as the ground floor external wall actually runs through the middle of the bathroom (just to the right of the black pipe in this photo) . The other end of the joist is anchored to the upstairs external wall, which is supported by a concrete lintel, so the shower will actually be above the porch area (which will make maintenance access much easier).

Thank you for the other points. I will now plan to raise the area as you suggest, and will also rotate the tray to the "orange dot" position. I can't quite picture how to best seal the gap between the tray and the vertical tiles with the plinth being exactly the same dimensions as the tray, but will try to figure it out. Would the vertical tile be flush with the side of the tray, or just proud?

Also, is that black pipe possibly lead?

 

[Madrab]

My process would be -

1. Run a couple of supports into the floor between and level with the joists (dwangs) where short ends of plinth frame will sit, don't leave it just on floorboards as they will deflect
1. set out the waste pipe run with shower waste attached.
2. Build the plinth (over engineer) with the long lengths sitting over the joists, around waste run
3. Top with 18mm ply/osb cut out to suit the waste run/ shower waste/trap
4. Tank the wet area and leave to dry properly
5. Fit the tray tight to the wall and corner, sealant/adhesive underneath and along long and short edges @ wall and push in, seal along top edge and then leave 24hrs
6. Tile down to the edge of the tray and leave normal setting time/grout and silicone seal the tile at the tray.

The black pipe (in the floor?) doesn't look like lead, given the fittings on it, looks like old old copper, rub some 80grit over it and see what colour it comes up, if it comes up silver then it'll low carbon steel, copper coloured then.....