Good idea to tank walls over a shower bath?

[mabealyv]

Hello everyone - first question, so bear with me; I have tried to look through the wealth of info you have already posted, so apologies in advance if I have simply looked in the wrong places!

Trying to re-fit bathroom in son's 'new' house, and have replaced plasterboard but not yet 'skimmed'.
He wants a shower over bath, this will be from domestic hot water system, 'combi boiler' so I don't think will be as agressive as a 'power shower', but was considering using a Mapei kit from screfix straight onto boards before tiling. Am just confusing myself with sequence:

Was planning to use a waterproofing kit , down to below level of bath edge, then tile, then fit bath. Now understand I should fit bath, apply waterproofing down to and onto edge of bath, then tile and grout.

My questions are

Given advice to fill bath with water before using Silicon, in case of bath movement, won't this bath movement negate/damage the waterproofing there? (and given lack of right angle at edge of bath, should I fill that gap before waterproofing?).

Should I leave a gap, say 6mm, between bottom edge of tiles over bath and edge of bath, so that a reasonably thick bead of Silicon is formed? I can't help thinking that a 'tiny' bead of silicon is being asked to do too much - i.e. 1mm thick plus 1mm movement = 100% stretch!

Have already learned that I should NOT use pre-mix - tiles are ceramic, 500x250 mm, 9mm thick. Am looking at Weber Set plus on price grounds. For plasterboard not covered by waterproofing kit, planned to prime with a couple of coats of diluted emulsion before tiling. Finally - how do you decide the size of the tile trim?

Any and all advice/recommendations will be gratefully received!

 

[Perry]

If the bath moves you have a problem, old wives tale by plumbers who havent fitted it corectley. If you use paint you will then have to then remove it before tiling, So i wouldent. A 2mm gap would be fine. Trim the thickness of the tile Plus, so I would think 10mm, but without the tile its hard to say.

 

[mabealyv]

Thanks, pjc - so it's ok to use the tile cement straight onto the plasterboard?

 

[cam_low]

when fixing the silicon bead I always fill the bath full of water, seal, then leave over night to set.

 

[Qwerty]

Do not paint anything you intend to tile. You will need to prime the boards you intend to tank using the Mapei primer from the kit. You can use this (or any other acrylic primer) to prime any new plasterboard prior to tiling if you wish. Some do, some don't. Tile adhesive straight onto paper face of plasterboard is fine, but can cause the adhesive to dry quickly so bear this in mind.
Only a few mm gap required between bath and tiles

 

[Perry]

Thanks, pjc - so it's ok to use the tile cement straight onto the plasterboard?

Yes its ok. I always made sure my fitters had no movement on any baths we fitted. I used to run around the rims, jump up and down in the baths in my showroom to so customers could see they didnt move. The bath reps thought I was mad but never had a bath move that we fitted.

 

[mabealyv]

Guys - thanks for all your swift responses! I did think it was a good idea to make sure the bath was fixed in place, honest! have already got the wood to frame up, plus for fixing to the two walls the bath will be against. Had just wondered about the tanking stuff, as I didn't know if it had the 'give' in it that the silicon has . . . had just assumed there might still be some small movement given the need to fill bath with water.

I'm also guessing here, but presumably just run enough of the the tanking onto the bath edge such that it is hidden by the tile/silicon subsequently fixed?

 

[Qwerty]

I'm also guessing here, but presumably just run enough of the the tanking onto the bath edge such that it is hidden by the tile/silicon subsequently fixed?

You've got it!

 

[jollyroger]

Here's how I always fit a bath...Build a good solid timber frame around the walls for the bath to sit on. Screw the timber to the walls and fit vertical timber supports at the corners and 1 in the middle. Put a generous amount of Silicon all round the frame and sit the bath in position. At this point I keep the metal legs of the bath off the floor and leave overnight. In the morning I screw down the feet of the bath and tighten by hand, ( not too tight ). When tanking and tiling are complete, I then tighten the legs up fully......Do it like this and your bath will 100% not move or creak EVER.

 

[Stef]

^^^ that's how you should fit a bath ^^^
It's almost the same way I advise a bath to be fitted, I don't stick the support legs in though but if you do the bath will never bow in the middle.
Once that Silicon is set that bath is going nowhere.