Tiles falling off inside new shower cubicle.

[Josh77]

Im a DIY'r and wanted to give it a go, now im wishing i hadnt.

I framed out a 3 sided walk in shower, insulated it with 100mm celotex, lined the area with 12mm marine ply, primed the ply with weber primer 360, i used a unibond readymix bathroom tile adhesive, 150x150x5 basic white tiles from B+Q (i buttered every tile) then grouted the lot with Mapei Flexible wall and floor grout for kitchens and bathrooms.

8 months on i saw i little movement on 1 tile and decided to investigate!

i pulled the first tile off and there was thick black mold behind it, which lead to the next tile and the next etc, ive had to remove the bottom 7 rows on all 3 sides because of this black mould. even the ply was soaking wet ive removed that too.

the plan is to dwang the joins and patch in with new marine ply after that im stumped! i dont want this happening again!

Where did i go wrong?
Dont use ply?
Dont use a readymix adhesive?
Are B+Q's tiles so cheap they are porous?
Was the grout to blame?
Should i have primed the tiles?

Any help with this matter would be greatly appreciated.

 

[PrenticeBoyofDerry]

latex based primer and cement based adhesive, is required.

 

[vinn]

In my way of doing things I never tile onto ply or OSB and avoid tiling on plaster board if possible.
The odds are that for various reasons you will continue to have problems. Maybe it would be best to remove all the tile and boards and start again.