Another question on my shower tray

[Charles Middleton]

Sorry,,, another question....

I understand that the stone resin shower trays are very heavy. The position of where I want my shower will mean that I need to drill holes through the joists (estimated around 3 of them) to get the waste pipe through.

Will the drilled joists with what I believe to be 1.5 inch plumbing be strong enough to support the tray?

Also, from Googling I understand that I need to mount the tray on a mortar base. What I thought I would do is replace the current MDF floor boards with a suitable hard wood that I can tile on top of.

I presume then I just put my mortar mix on top of my new boards and set the resin tray into that.

My question is do I just put a flat layer of mortar on the floor or at strategic points?

Will the mortar make the shower tray higher than the tiles?

I presume I just scrape away the excess around the outside edge of the tray to make a neat finish?

Sorry for the beginners questions but I know nothing about this at all! I'm determined to learn and do this myself rather than get a plumber in - famous last words!

CM.

[Andy Hall]

This could be a bad idea. The waste plumbing for a shower tray is either 32 or 40mm so I would check. Also you have to have a reasonable slope for the water to run away. Drilling holes of this size in a floor joist can be a bad idea because of the weakening effect - I would seek professional advice on that.

Generally 18mm WBP ply (commonly available) is a good choice.

You need a mortar base for the whole thing. This is to take out unevennesses in the finish of the underside so that the load is spread evenly. The manufacturer's instructions will normally stipulate it and void the warranty if you don't.

It would do. I would suggest you put the tray in place and tile up to it. For other bathroom fittings like toilet and pedestal basic etc. then tile underneath - it's easier and better.

.andy

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[Charles Middleton]

Another badly planned project on my part then. I'm not sure what other options I have and the shower & tray is arriving tomorrow. I thought that it was safe to put holes in the joists providing that a) it was close to the supporting wall and b) the hole went through the middle of the joist and c) the diameter of the hole was no bigger than two thirds of the joist?

Also, I was planning to put a slight incline on the run through the joists to provide this.

So board the floor with 18mm WBP and then mount tray on motor base on top of that.

So the mortar really provides a base between the ply and the bottom of the tray which I presume doesn't touch the floor. Its likely in this case then that the mortar will be contained inside and underneath the tray - no problem.

CM.

[Andy Hall]

I am not sure on this. You could try pinging those in the know like Tony Bryer.

Yes.

Exactly. It needs to be under the central area and around the rim. The manufacturer's instructions should give details, but normally about 10mm or so is used.

Also you need to do some dry runs to align the waste plumbing. There are shower bottle traps with a mushroom lid where you can remove the strainer from the top. These have a rubber washer.

What I did was to do the alignment using wooden spacers to get the height right and then adjust the plumbing. When fitting, I used a smear of silicone under and above the washer and put it on the trap, then positioned the tray, applied more silicone to the top part of the fitting where it screws into the base and finally tightened it all.

.andy

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[logized]

I have just looked in a plumbing manual (from 1995) - it says holes cannot be bigger than 1/4 of the depth of the beam and the zone in which they can be made is between 0.25 and 0.4 of the length of the beam from wall. Also,the holes must not be below the centre of the beam or closer than 3 times the diameter to any other holes.

Dave

[Charles Middleton]

Thanks for the info. What's the typical depth of a joist? My house was built in 1995 if it makes any difference.

CM.

[Alan]

I had a similar problem where I needed to run a soil pipe through a joist, and remove all but about an inch of it. So, I made up a steel plate about a foot long, full joist height from 5mm steel, with a suitable cutout for the pipe. I then welded a length of 6mm x 50mm x50mm angle iron along the bottom of the plate for good measure. Added mounting holes and bolted the whole thing to the joist with coach bolts, BEFORE cutting the joist. Cut the joist with plate in place, and even if I jump up and down on it, it has no movement at all!

Took about an hour with a metal jigsaw blade and the welder to make out of scrap lying around the garage.

OK, so if you don't have a welder it may be a problem, but just a large steel plate will help put strength back into the joist that you need to cut out for the waste pipe....

Alan.

[Tony Bryer]

Generally not. You'll find a nice diagram of what is acceptable without calculations in a guidance note on the Tameside website -

holes max D/4 at between 0.25 and 0.4 of the span

Having said this, the usual practice in domestic construction is to make all the joists the same size, said size of course being determined by the longest span. If the bathroom is over the kitchen and you've got (say)

50x200 joists when you really only need 50x125 over this particular span then you can obviously chop a lot more out without causing problems but it would need to be verified by a structural engineer.

[logized]

I don't know what would be a typical depth of joist, I suppose it depends on the span length and building regulations. Here is a web page that agrees with the specifications for holes in joists in my plumbing manual -

[John Rumm]

between 175 and 220mm is common.

Have you considered building a platform to put the shower on? That would then let you run the waste above the floor level. Once boxed in and tiled it looks quite neat.

[Lobster]

You beat me to it, John; I'm doing exactly this at the moment (well, sort of - there's a heap in the corner of the garage comprising stone resin tray, shower door, some bits of 4x2, and a sheet of WBP ply, all gathering dust... SWMBO is not a happy cat)

Charles - providing you've got enough ceiling height I think this method is a no-brainer; just set your sheet of ply on top of 4 lengths of 4"x2" timber, pref arranged at 90 deg to the existing joists. You need a shallow trap for the waste (ie designed for a shower), and you should then be able to take the pipe through the floorboards. if need be, to wherever it needs to go, without chopping up any joists.

If you attach a removable panel on the front (ie twixt shower tray and floor) you'll easily be able to access the plumbing afterwards for maintenance purposes (with a shower tray lying flat on the floor, aften the only alternatives are trashing the shower tray or removing the ceiling below. Ouch, in either case).

David

[John Rumm]

;-)

Me too!

Just screwing on the plasterboards now - so not too long until I reach the new bathroom.

The annoying thing is, that I could have got away with running the waste under the floor since it would have been a straight run parallel to the joists. Only problem was it would have come our slap bang in the middle of the residual bit of pitched roof at the end of the dormer. I thought it would look a bit daft with a shower waste pipe emerging from a soffit, hence why I shall probably go for the "build a platform" solution like yours.

[Charles Middleton]

Hi, I assume that the platform would need to be slightly bigger than the actual shower tray (900mm x 900mm) which may pose some problems but I can look into that when I'm back home at the weekend.

How high would the platform need to be? I am assuming that I will also need a boxed in section down the one wall to run the pipe at floor level. Any ideas on the best way to construct this and how far it would need to come out from the wall?

Is it easy to tile onto wood and is there some sort of edging strip that I can use to make the edge between the sides and top of the platform nice and neat?

Thanks in advance,

CM.

[Charles Middleton]

Thinking about this a bit more I'm not going to be able put the shower on a platform. I am presuming the platform is square. This wont be any good as its the curved quadrant that's giving me clearance for something else - namely my feet whilst I'm on the bog! Putting in a square platform is going to remove that benefit.

Back to the drawing board - the worrying thing is that my plumber said it would have been fine to drill through the joists and after checking the diagram on the link provided logized no way is this the case!

CM.

[chris French]

In message , Charles Middleton writes

Then make a curved platform......

I put in 900 mm quadrant tray a few years ago.

I cut a piece of 18mm WBP ply to match the size and shape of the tray (actually a bit bigger on the wall sides as a bit went into the chopped out plaster of the wall.)

Supported the ply on 4x2's so arranged as to allow the waste to exit, and allow access from outside if necessary (though I used a top access waste) Tray bedded down on mortar as per instructions. Waste runs under the base to the wall then turns and runs along the wall to the outlet, - it's hidden behind built in cupboards, normal boxing in would be fine.

Fiddliest bit is cladding the curved open base.

In the end I cut pieces of scrap 2x1 to stand vertically under the ply flush with the front - spread along the curved front. - they fit tight, but I also glued them in place. Then I used a couple of pieces of white UPVC trim strip screwed to the timber (screws covered with white caps)

IIRC, I used two pieces of strip (one cut down) one above the other (total height is about 120mm I guess) as strip of the suitable size for one piece was not flexible enough.

I'm pleased with the final result.

[Charles Middleton]

This sounds like a good idea, especially it its only around 120mm of the floor (so it will look less when I have tiled up to it anyway).

Where did you get the PVC from?

How did you make the join between that and the shower tray nice and neat?

I would want to extend this in a box section down one wall - how far would I need it to come away from the wall for a shower waste and what's the best way to make the box section for tiling onto?

CM.

[John Rumm]

It can be the same size and shape if you want.

High enough to give you enough fall on the waste pipe. Hence it is dictated a little by the length of the horizontal run of the pipe. 4" to

6" would be about normal.

Either just enough to cover the pipe, or, some people like to make it bigger and taller so as to make a feature shelf of it.

You get the plastic tiling trims. These are fixed in place before you tile and have a neat rounded edge. You choose one that matches the colour of your tiles, or go for one of the more tarty ones like chrome or brushed ali effect.

[John Rumm]

You can make the platform curved to match the tray. If you then stick some uprights under the front edge along the perimiter of the curve you should be able to wrap some 1/4" ply round the quadrant. You can then tile along the curve using tiles cut into 2" wide vertical strips. Will probably look quite nice.

So much for the oft repeated advice to seek professional advice huh.

[chris French]

In message , Charles Middleton writes

IIRC, I bought it from Wickes. It's the sort of trims used around PVC windows, should be easy enough to get hold of.

The top edge of the trim has a rounded edge. I smoothed the edge of the ply base to match as much as possible the tray, and had to scrape away a little mortar as well (better forward panning would have helped here.) The trim fits quite nicely against the outer edge of the tray and I just sealed it with some sealant.

Not much, assuming 40mm waste, clipped to the wall - say 50 - 60 mm projection from wall. You just need to leave enough clearance for this Overall size say about 75mm? . Though you can make it wider and taller if you want to make it a shelf.

for something this small, I'd probably use ply 12mm would probably do, but if I had 18mm spare I'd use that. Say, fix a bit of batten to the wall above the waste pipe, either use another batten on the floor, or those plastic corner joiners to fix an upright strip of ply or suitable piece of wood to the floor, then make a lid from a strip of ply and screen it to the wall batten and upright. Prime and then tile.