SuperJohnG Posted January 17, 2021 Share Posted January 17, 2021 (edited) I'm pretty well ahead with the soil pipes and runs, however the downstairs WC shower tray is causing me major headache. I want to keep the tray on the floor (doesn't need to be flush). But haven't chosen the tray, and need to put in stacks this week. How do I deal with this? See images below, rigth most stack comes from the 1st floor, the furthest left is for toilet and basin. I was going to possibly put one in the middle, that I could maybe shutter around so that I can use a low level shower trap and figure it out later. But how do I know how much to shutter? and what depth? also as I don't know which tray Ill end up I could end up with a tray with a drain in the corner. It all seems to be a right PITA - but I have to develop a plan quite quickly. Any help / steer much appreciated. All the soil pipes are hidden in a fake stud wall. (Or should be If we put them in the right place!) Edited January 17, 2021 by SuperJohnG Link to comment Share on other sites More sharing options...
Russell griffiths Posted January 17, 2021 Share Posted January 17, 2021 Why not get rid of the tray and just tank it and tile. Link to comment Share on other sites More sharing options...
willbish Posted January 17, 2021 Share Posted January 17, 2021 Wet room as per @Russell griffiths certainly seems easier Or buy the tray and trap this week Or bring the soil pipe up in the centre of where the tray will be (tray wont have hole in the centre) then before concrete pour make a box out of OSB to create a void in the concrete 100mm deep surrounding waste pipe and reaching to one corner of tray. Link to comment Share on other sites More sharing options...
SuperJohnG Posted January 17, 2021 Author Share Posted January 17, 2021 3 minutes ago, Russell griffiths said: Why not get rid of the tray and just tank it and tile. Not a fan of wet rooms, much prefer a tray and full screen. Link to comment Share on other sites More sharing options...
tonyshouse Posted January 17, 2021 Share Posted January 17, 2021 If tray, it absolutely must have upstands, = failsafe and can’t leak Link to comment Share on other sites More sharing options...
James94 Posted January 17, 2021 Share Posted January 17, 2021 If you have your eye on a certain tray there may be some dimensions with it and some fitting instructions, but personally wouldn't fit anything without having tray to put in place. Regards James 1 Link to comment Share on other sites More sharing options...
TonyT Posted January 17, 2021 Share Posted January 17, 2021 Shutter out for the whole tray area if not sure and concrete it separately once decisions have been made.. far easier than digging out concrete. +1 for the upstands. 1 Link to comment Share on other sites More sharing options...
SuperJohnG Posted January 17, 2021 Author Share Posted January 17, 2021 26 minutes ago, tonyshouse said: If tray, it absolutely must have upstands, = failsafe and can’t leak 3 minutes ago, TonyT said: Shutter out for the whole tray area if not sure and concrete it separately once decisions have been made.. far easier than digging out concrete. +1 for the upstands. By Upstands you guys just mean like a normal tray? I'm not sure I can shutter the whole area as it is in the ring beam and 40mm down it will have reinforced mesh. Link to comment Share on other sites More sharing options...
TonyT Posted January 17, 2021 Share Posted January 17, 2021 https://www.mirashowers.co.uk/shower-trays/mira-flight-low-rectangle-1200-x-800-4-upstands/ upstands on the shower, the waterproof covering/ wet wall goes inside the shower tray Link to comment Share on other sites More sharing options...
TonyT Posted January 17, 2021 Share Posted January 17, 2021 3 minutes ago, SuperJohnG said: By Upstands you guys just mean like a normal tray? I'm not sure I can shutter the whole area as it is in the ring beam and 40mm down it will have reinforced mesh. Use a tin of expanding foam, spray it over the reinforcing to make a dam. Dig out later Link to comment Share on other sites More sharing options...
Russell griffiths Posted January 17, 2021 Share Posted January 17, 2021 Just run your 100mm pipe up but set off to one side from where you think the waste will be, cut a block of polystyrene 400mm square and use this as shuttering, pour your slab and you will be left with a 400mm void, this will give you the room to fit your trap and connect up to the 100mm, when all done concrete in place. Link to comment Share on other sites More sharing options...
SuperJohnG Posted January 17, 2021 Author Share Posted January 17, 2021 7 minutes ago, Russell griffiths said: Just run your 100mm pipe up but set off to one side from where you think the waste will be, cut a block of polystyrene 400mm square and use this as shuttering, pour your slab and you will be left with a 400mm void, this will give you the room to fit your trap and connect up to the 100mm, when all done concrete in place. I can't get it deep enough in the slab though as the mesh will be 40mm below surface? Also - 100mm?? you mean 110mm right or have I missed something? Link to comment Share on other sites More sharing options...
TonyT Posted January 17, 2021 Share Posted January 17, 2021 Cut the mesh! add it back in later. 1 Link to comment Share on other sites More sharing options...
TonyT Posted January 17, 2021 Share Posted January 17, 2021 And yes it 110mm 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted January 17, 2021 Share Posted January 17, 2021 2 minutes ago, SuperJohnG said: I can't get it deep enough in the slab though as the mesh will be 40mm below surface? Also - 100mm?? you mean 110mm right or have I missed something? Can’t get what deep enough? the block of poly ? cut it. 200mm poly under reinforcement 40mm on top. Fill it with concrete dig out poly and your left with a big void work out tray location and trap, cut out mesh that is in the way fit trap to the 110mm pipe with a bit of 50mm between the two 1 Link to comment Share on other sites More sharing options...
Temp Posted January 18, 2021 Share Posted January 18, 2021 (edited) Have done two trays in screed floors. This is what I've done.. Shutter the area under the tray full depth of the screed. Arrange for waste pipe to enter void as far away from likely waste position as possible. I suggest near a back corner but not right in the corner. Say 2" away. Low as possible. Have it enter at 45 or 90 degrees to the side of the tray not some random angle (to avoid needing a flexible pipe). McAlpine have a range of top access traps that have different minimum depths for the pipe and different flow rates. Use the diagrams to see how far down the pipe must be. I would use 50mm pipe. https://mcalpineplumbing.com/traps/shower-traps-accessories Pour screed to top of shuttering. Later when you have the tray you will make a timber frame with WBP on top to support the tray in the void. When you have the tray.. Take waste trap apart so you are working with just the bit that goes below the tray. Trial fit the waste pipe work to get trap in right place and height. Construct timber frame to support tray. Add >12mm WBP on top with oversize hole for waste. Top of waste should be flush with top of WBP or a few mm above it to allow for mortar bed. It helps if the pipework allows the trap to move up and down say 10 mm and a few mm in other directions. But do not allow it to fall down too far. Put a small block under it if necessary. Thus is to ensure the top part of the trap will reach it. Trial fit tray and top of waste and check tray level. When 100% happy take it all apart. Solvent weld the waste plumbing and recheck position. If you use a lot of solvent adhesive you get a few seconds to twist joints to get correct alignment. Test for leaks. Screw down WBP. Double check waste position. Do all this next bit in one go... Mix mortar for bed. Lower tray in place on mortar and check level. Run bead of sealer around waste hole in tray. Insert top of trap through hole in tray and screw into lower part of the trap. Tighten but don't over tighten. Wipe up any sealer that squeezes out. Recheck tray is level. Let mortar set. Before laying the tray inspect the bottom of the tray around the trap area. It should be smooth and flat so the sealing washer on the lower part of the trap works. If not then may need sealer on washer before laying tray as well as around the hole on top. If the timber frame is resting on insulation I would put WBP down on bottom as well to spread load. Forgot to say all timber should be pressure treated. Edited January 18, 2021 by Temp Link to comment Share on other sites More sharing options...
Temp Posted January 18, 2021 Share Posted January 18, 2021 Dont know why I didn't think of this before but.. If you make the shuttering from pressure treated timber with strips of 12mm WBP on top the shuttering could be left in place and form part of the timber frame supporting the tray. Just remove the 12mm WBP strips and replace with the 12mm WPB panel. Link to comment Share on other sites More sharing options...
Onoff Posted January 18, 2021 Share Posted January 18, 2021 (edited) Though I cast my shower corner floor to falls for a wet room corner, I did the main slab, with mesh in first. I just shuttered off the for the shower corner (and part sunken bath): I did though remove the red Polypipe panel in this area to get a consistently thicker, stronger slab. What a mission that was cutting it up in bits. Similar fun was had then fitting a bit of DPM with the mesh in situ! My SBR heavy, 10mm pea shingle, concrete mix: A few on here have just left in a bit of EPS level with the FFL that you dig out later. You can decide on your trap position later. Edited January 18, 2021 by Onoff Link to comment Share on other sites More sharing options...
tonyshouse Posted January 18, 2021 Share Posted January 18, 2021 Upstands are not at all like normal trays, they additional little wings that are part of the tray that stand up behind the wall panels or tiles to form a failsafe waterproof seal Link to comment Share on other sites More sharing options...
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