Crosswater shower tray installation in U shape space

[Ash Gall]

I am installing a very heavy stone resin shower tray Crosswater Linear 1500x800 in a u shaped 1500wide x800 deep space plasterboard walls in upstairs bathroom with P5 flooring.

Instructions insist on setting tray on mortar 5:1 ratio with a plasticiser my questions are:

1 )do I need any form of additional waterproofing 

2 )how much plasticiser do I use in the mortar mix

3 )how much sand do I need for this area 10mm thick

4) plan to use my mate and glass suckers to lift onto mortar difficulty in u shape area is there a simple trick alternative 

[Russell griffiths]

You will need to waterproof the whole shower wet area 

tanking membrane with specific waterproof corner sections and details. 

 

Do not be thinking you can just tile the plasterboard, that’s a disaster waiting to happen. 

 

Lots of posts on here about bathroom tanking @Onoff is the man who likes taking lots and lots of pictures. 

[tonyshouse]

I do floor first with semi non slip vinyl coved up walls 150mm and then wet wall 50mm downlap 

= failsafe 

 

[Ash Gall]

What do you think of the Mappei waterproofing kit ?

[Ash Gall]

2 hours ago, Russell griffiths said:

You will need to waterproof the whole shower wet area 

tanking membrane with specific waterproof corner sections and details. 

 

Do not be thinking you can just tile the plasterboard, that’s a disaster waiting to happen. 

 

Lots of posts on here about bathroom tanking @Onoff is the man who likes taking lots and lots of pictures. 

What about the Mappei kit ?

[Russell griffiths]

Yes it’s good stuff, look at their website and study the tech drawings of how to instal properly, 

you will need to tank well as you haven’t used moisture resistant plasterboard, but you should tank well regardless of what board you use

 

do not scrimp on this stage, your expensive tray will be worthless if water is getting around it. 

[wozza]

I used Abacus Elements boards around both of my trays and also their tanking kit so I didn't have to tank the whole boards - just the joints and fixing screws / washers.

 

I also used a Mappei kit that the plasterer had left over from a job and he gave to me.

 

I preferred the Abacus kit - but the Mappei kit was ok - the Primer G seems good stuff.

 

Are you using tiles or shower panels?

 

Edited November 27, 2020 by wozza

[Ash Gall]

3 hours ago, Ash Gall said:

I am installing a very heavy stone resin shower tray Crosswater Linear 1500x800 in a u shaped 1500wide x800 deep space plasterboard walls in upstairs bathroom with P5 flooring.

Instructions insist on setting tray on mortar 5:1 ratio with a plasticiser my questions are:

1 )do I need any form of additional waterproofing 

2 )how much plasticiser do I use in the mortar mix

3 )how much sand do I need for this area 10mm thick

4) plan to use my mate and glass suckers to lift onto mortar difficulty in u shape area is there a simple trick alternative 

Thanks for your help on tanking but anyone got an answer to the mortar questions 

[PeterW]

About 15 litres of mortar needed so that’s about half a bag of sand if you buy a maxi bag from

Wickes and you won’t need much cement. Worth buying Mastercrete as it already has a plasticiser in it. No need to add anything else. 

I would put the tray in place and lift it from the front and prop it then spread the sand and cement and drop the tray gently onto it. @Nickfromwales advises scouting the bottom of the tray first as otherwise the sand and cement doesn’t bond well. 

[Bonner]

Bodge alert! My mate who is a plumber put my shower tray on a bed of decorators caulk (3 tubes if I remember). No movement in the 12 years I had the house. Lay it down on 2 thin battens then pull them out.

[Onoff]

See this video. For a start the bloke has used the green moisture resistant plasterboard. People do use standard pb but then tanking is even more important:

 

 

Then this one:

 

 

Same kit as I used. I went mad and did a huge area, used 2 kits.

 

 

[Ash Gall]

10 hours ago, PeterW said:

About 15 litres of mortar needed so that’s about half a bag of sand if you buy a maxi bag from

Wickes and you won’t need much cement. Worth buying Mastercrete as it already has a plasticiser in it. No need to add anything else. 

I would put the tray in place and lift it from the front and prop it then spread the sand and cement and drop the tray gently onto it. @Nickfromwales advises scouting the bottom of the tray first as otherwise the sand and cement doesn’t bond well. 

Do you mean the Major bag 

[PeterW]

39 minutes ago, Onoff said:

 

 

Same kit as I used. I went mad and did a huge area, used 2 kits.

 

 

Yep same one as I use - now branded EverBuild Tanking Kit and usually cheapest on Amazon. 

[PeterW]

10 minutes ago, Ash Gall said:

Do you mean the Major bag 

 

Yep same difference - a 25kg bag. 

[Ash Gall]

10 hours ago, PeterW said:

About 15 litres of mortar needed so that’s about half a bag of sand if you buy a maxi bag from

Wickes and you won’t need much cement. Worth buying Mastercrete as it already has a plasticiser in it. No need to add anything else. 

I would put the tray in place and lift it from the front and prop it then spread the sand and cement and drop the tray gently onto it. @Nickfromwales advises scouting the bottom of the tray first as otherwise the sand and cement doesn’t bond well. 

Never realised Mastercrete actually has plasticiser it only mentions improver in their tech note. Did everyone know that ?

[PeterW]

All plasticisers are is additives to make the mortar more workable. It adds nothing to the finished product. I’ve laid big shower trays on cheap tile adhesive before now as it sets just as quick and is easier to level as it is slightly more fluid. 
 

 

[ProDave]

2 hours ago, Bonner said:

Bodge alert! My mate who is a plumber put my shower tray on a bed of decorators caulk (3 tubes if I remember). No movement in the 12 years I had the house. Lay it down on 2 thin battens then pull them out.

I will admit to doing the same but with a proper waterproof sealant, Stixall i think was the one.

 

You don't actually need much, usually only a small area of the shower tray touches the floor. Measure and mark out what bits actually touch the floor.

 

17 years later no movement no leaks.

[Vijay]

2 hours ago, PeterW said:

All plasticisers are is additives to make the mortar more workable. It adds nothing to the finished product. I’ve laid big shower trays on cheap tile adhesive before now as it sets just as quick and is easier to level as it is slightly more fluid. 
 

 

 

So is there any reason to add more when laying bricks/blocks if it's already in there?

[Oz07]

@Vijay brickies would prefer it as creamy as possible I reckon. Only problem is too much is not good for the compo. 

 

I've used foam for a tray before. 

[PeterW]

2 hours ago, ProDave said:

 

You don't actually need much, usually only a small area of the shower tray touches the floor. Measure and mark out what bits actually touch the floor.

 

17 years later no movement no leaks.

It is also supposed to be there to support the tray overall so it doesn’t flex. 
 

40 minutes ago, Vijay said:

 

So is there any reason to add more when laying bricks/blocks if it's already in there?

 

Yes as it can alter the cement bonding if there is too much and cause issues if you add too much. Additives need tiny amounts. 

[Ash Gall]

23 minutes ago, PeterW said:

It is also supposed to be there to support the tray overall so it doesn’t flex. 
 

 

Yes as it can alter the cement bonding if there is too much and cause issues if you add too much. Additives need tiny amounts. 

exactly the Crosswater tray is stone resin completely flat underneath and they warn you to make sure all the area is in contact otherwise there is a risk it will crack in in supported areas. I have noticed it I quite thin in places

[Pocster]

I thought as advised by the welsh wizard just tile adhesive under the tray ......