I have constructed a wetroom on timber floor, which is subject to natural movement from heating etc, approx 6 months ago.
Floor make-up - WPB onto joists, Tilesafe membrane, pre-formed tray with linear gulley, SLATE tiles, unsure of grout/adhesive as "professional" tiled it.
Blockwork walls, plastered & tanked with BAL WP1 Slate on walls.

I have noticed water coming up through grout in 2 different areas on floor, close inspection has shown floor / wall joints failing due to expansion of building, type of house is notorious for movement.
Ideally I would like to use a silicone type sealant to seal the failed joints, silicone
not recommended with Tilesafe memebrane ?
Rake out failed grout joints and replace with new grout / flexi additive?
Movement can be several between 2-4mm in this house

dont quite understand why a movement joint would effect membraine were tiles or slate meet in internal corners (floor to wall internal wall corners) should be siliconed the same color as grout to allow mevement maybe a pic would help

Hi Barbelbob, welcome to the forum, before the wpb was installed, what was the measurement between the joists? Did you add extra noggins to stop any deflection? Can you get in touch with the tiler and find out what was used to fix the tiles because if the wrong adhesive/grout was used then that could be a fundamental part of your problem.

just read tech sheet on tilesafe memb and it does state that silicone should not come in contact with memb //////// mixing flex add to grout will not give enough movement in joints recomend you contact tilesafe and ask question

Jay,

I don't know the products sold in the UK, but I find it hard to believe that any of them would NOT want a soft joint at the changes of plane. Like you said, grout with super-flex additive still won't allow for enough movement. The tech sheet for that product doesn't mention anything about this eh?

if it was tanked properly, 2-4 mm should not break it down !!!

Originally Posted by diamondtiling

Hi Barbelbob, welcome to the forum, before the wpb was installed, what was the measurement between the joists? Did you add extra noggins to stop any deflection? Can you get in touch with the tiler and find out what was used to fix the tiles because if the wrong adhesive/grout was used then that could be a fundamental part of your problem.

JOISTS HAVE BEEN NOGGINED OUT SUFFICIENTLY, 22mm WPB SCREWED AT 300mm CTRS. VERY SOLID FLOOR, MEMBRANE INSTALLED WELL, IT'S THE GROUT WHICH IS FAILING, DUE TO EXPANSION OF BLDG STRUCTURE, IT'S A WEIRD SIXTIES HOUSE, WHICH EXPANDS AND CONTRACTS TOO MUCH.
I'M GOING TO RE-GROUT USING BAL SUPERFLEX WIDE JOINT. WILL LET YOU KNOW OUTCOME

Originally Posted by BARBELBOB

JOISTS HAVE BEEN NOGGINED OUT SUFFICIENTLY, 22mm WPB SCREWED AT 300mm CTRS. VERY SOLID FLOOR, MEMBRANE INSTALLED WELL, IT'S THE GROUT WHICH IS FAILING, DUE TO EXPANSION OF BLDG STRUCTURE, IT'S A WEIRD SIXTIES HOUSE, WHICH EXPANDS AND CONTRACTS TOO MUCH.
I'M GOING TO RE-GROUT USING BAL SUPERFLEX WIDE JOINT. WILL LET YOU KNOW OUTCOME

The outcome will be that your new joints fail as well. You will need to use a "silicone type" flexible jointing product some how. Maybe make sure it doesn't fill the full depth of the joint so it doesn't affect the membrane?

Thanks for advice, I will re-grout affected areas adding GT1 BAL additive to grout, then
silicone over for NOW!

Originally Posted by BARBELBOB

Thanks for advice, I will re-grout affected areas adding GT1 BAL additive to grout, then
silicone over for NOW!

DO NOT ADD GT1 to Superflex grout! it is not designed to have an additive mixed with it and you may well get very unpredictable results!