water proof shower area before tiling ?

[shardy]

Hi all,
we are about to get our shower area tiled and wondered about waterproofing.
The loft company fitted normal ply to the shower area, not marine ply. We requested hardiebacker. I wondered if it is advisable to waterproof the ply with something like the BAL WP1 waterproofing kit?
Also there are a couple of big holes in the ply filled with silicon as the original holes for shower valves needed moving.
Their plumber fitted the shower tray but the gap between the tray and walls is 5 mm in the corner and up to 15 mm at the edge. This is because the walls of the house are not square and the walls of the new loft conversion are built exactly on top of walls below hence are also not square. There is a steel just below the shower area and new joists and thick chipboard floor so very solid I think.
As the ceramic tiles we bought are 1 cm thick, we will need to ask the tiler to make the adhesive more than 5 mm thick so that the tiles overlap the tray. Is that advisable? We bought BAL waterproof adhesive. The builders say the adhesive can be up to 2.5 cm thick
I've attached pictures. many thanks in advance for any wisdom shared

 

[it's not that hard]

I would put up plasterboard,then you could pack it out

 

[jeff the gasman]

Hi all,
we are about to get our shower area tiled and wondered about waterproofing.
The loft company fitted normal ply to the shower area, not marine ply. We requested hardiebacker. I wondered if it is advisable to waterproof the ply with something like the BAL WP1 waterproofing kit?
Also there are a couple of big holes in the ply filled with silicon as the original holes for shower valves needed moving.
Their plumber fitted the shower tray but the gap between the tray and walls is 5 mm in the corner and up to 15 mm at the edge. This is because the walls of the house are not square and the walls of the new loft conversion are built exactly on top of walls below hence are also not square. There is a steel just below the shower area and new joists and thick chipboard floor so very solid I think.
As the ceramic tiles we bought are 1 cm thick, we will need to ask the tiler to make the adhesive more than 5 mm thick so that the tiles overlap the tray. Is that advisable? We bought BAL waterproof adhesive. The builders say the adhesive can be up to 2.5 cm thick
I've attached pictures. many thanks in advance for any wisdom shared
View attachment 96808 View attachment 96809

Look at Mapeigum. It's the dogs wotsits.

 

[Madrab]

I don't understand, if there is a 5mm gap at the inside corner and 10 and 15mm respectively at the outside edges then if the tray is pushed tight into the inside corner then the outside gaps would reduce by 5mm unless there's a waterproofing strip in there but from the pic there doesn't seem to be one. That and if the fitters knew that a shower was going in there then the boards could have been fitted square with some packers...anyways.

Jeff's Mapegum is great stuff, used it a few times, mucho expensive the thicker you go tho. Ideally the tiles will need to be built out but again that means a whole lot more expensive adhesive over the whole tiled area to keep it flat. As long as he has sealed the shower well then a good quality shower seal could be an option.

 

[DH6]

Don't put ply anywhere near a shower, it a recipe for disaster

 

[shardy]

thanks for replies folks. I wondered about that Madrab. I thought there must be a reason why he didn't push the tray tight into the corner, but maybe he just didn't notice it wasn't square.
Why no ply DH6? Is it because wood contracts and expands more than concrete based boards?

 

[WabbitPoo]

Could you not cover all with a layer of hardiboards, packed to get them square?

 

[WabbitPoo]

Or better still, get what you think you're paying for and get them to replace the ply with cement boards

 

[shardy]

well I bought a Mapei showerproofing kit to tank the plywood walls, but when I stood on the tray to begin tanking the walls, the tray moved, ha ha. so I just lifted the tray and we decided to replace ply with hardiebacker. It was only the silicon round the edges holding the tray in place. Some type of bonding had been placed under the tray but just around the front curved edge of the quadrant, and a little bit at the back corner. The bonding was dry and brittle and just snapped in your hands. It wasn't sticking the tray at all. I think because the chip board floor hadn't been PVA'd the bonding dried out too quickly. The plumber told us he didn't need to cement the tray in place as the floor was perfectly level. What a lie. He had leveled the tray by using one small piece of squashed copper pipe and a small splinter of wood. You can clearly see how uneven the floor is now the tray is not there. So walls completely out of square and a sloping floor, perfect.
I've PVA'd the walls and floor, We are wondering now if we should tank the floor under the tray using the mapegum, or cement the tray in place and just tank the walls.
We bought BAL max flex fibre to do the tiling, can this also be used to fix tray in place?
I've attached some pics of bodged job for your amusement, plus a picture of showerspace with hardiebacker in place.
Thank you so much folks for the excellent advice, if it wasn't for these forums, I don't know what we would do :-0

 

[Agile]

There must be thousands of jobs done well.

But if you only see what is written about here you would think that there are no plumbers able to do a good job.

 

[Madrab]

Oh dear, what a waste of time that was, is this guy a bathroom fitter or actually a plumber? What was he thinking

Obviously you need to secure the shower, you want to ensure the floor is clean and dust free, run over it with a mop. Needs to be levelled of course. Needs to use a non water based adhesive to lock it down on that floor type if you can, moisture resistant flooring is notoriously difficult to key to with water based adhesives.

Sorry to say it but you shouldn't really have PVA'd the backer boards, all they need is wipe down, no need to seal. PVA isn't ideal, it's water based and can interact with water based tile adhesives or cause problems if it ever gets damp later. Also worth a thought is using an upstand seal that connects the shower to the wall. Then silicone along the bottom edge and sides of the tray that contact the wall too before sealing along the top edge prior to tilling.
You can tank the floor area egdes/corners where the tiles will be if it's liable to getting wet if you have spare, no point under the tray as there's a dirty great hole for the waste anyway.

Did you remove the ply before adding the backerboard if not is there enough play in the waste position?

 

[shardy]

thanks for replies. sorry when I said PVA I meant the primer that comes with the shower tanking kit. we had some left over after doing the walls.
We removed the ply from the wall before installing hardiebacker
I'll use the spare tanking gum to do the wall floor junctions as suggested. The instructions with the shower tray say fix in place with at least 15mm thickness of weak cement mix 5:1 sand cement ratio. Hopefully this will work on a moisture resistant chipboard floor. I rang the shower tray manufacturer to check and he wasn't sure. Its a Sheet Molded Compound tray (SMC) which is fibre strengthened polymers apparently.
is an upstand seal the pvc quadrant type trim? Can we use this as well as the mapei tanking fibre tape?

 

[Madrab]

A tray upstand seal, is a pre-adhesive rubberised tape, you peel half of it off and stick it to the edge of the shower tray that touches the wall, you then install tray and use a good quality silicone on the back of the seal and stick that to the wall, then tile down on top of that to the shower tray, it provides a waterproof seal from wall to tray edge. It can be used with the tanking.
http://aquastrap.com/
A PVC quadrant seal is different, that's a PVC plastic seal, as you say, it sits on top of the tray edge and is used more when bridging larger gaps if a tray isn't square to the walls for tiling to.
http://www.sealux.com/
The trick to bedding the tray in cement is to compliment the other fixing methods, that's using enough good quality silicone onto really clean surfaces at the contact areas on tray to the floor and walls and around the edges to seal in the whole shower outline. The cement in the middle will give it a bed to stabilise the tray and helps to level it rather than the main way of 'glueing' it into place with that type of flooring, I tend to suggest sinking the tray when I see P5.
If it was going onto a concrete floor or ply then it's got a higher adhesive grab, so a mortar mix grips better.

With the tanking primer down it may allow the cement to key to it better tho, make it quite wet.

The tanking tape is usually used on the walls down the inside corner(s), along floor edges and around pipes as a catch all and then use a seal for the tray, can never have enough sealing layers when it comes to showers on wood IME.

 

[shardy]

thanks for help Madrab. I used the mapei gum and tape to seal junction and create an upstand between tray and tanked backer board. at the widest point the tiles will only overlap tray by 1 or 2mm even with thick tiling adhesive. i suppose it would be advisable to use Sealux in this situation?

 

[Madrab]

If you have that size of gap then yes, a trim like the sealux will help a lot.

I'm confused though, you removed the ply and replace with backerboard and the walls still aren't square?? Surely once it was realised that the ply wasn't square, then the stud work would be packed out to square up the new boards? How far out are the walls compared to the pics on your original post?