I’m about to embark on a mission to tile the upstairs bathroom and en-suite floor in a new extension. I’m not a tiler but I am a builder’s son and would be ashamed if I didn’t at least have a go on smaller of the two rooms before employing a tiler!

The problem I have is a combination of conflicting information from the adhesive / tanking membrane manufacturers and the composition of the floor.

The two rooms in question are upstairs in a newly built extension, the joists are 9” x 3” joist covering a relatively short span, set between the joists is a wet underfloor heating system set in to 50mm insulation panels provided by Wavin. The floor comprises of 22mm T&G caberboard flooring, fully supported on all short edges and at the extremes, glued along all joins and screwed at 200mm centres.

Cut into the floor is an Impey Aquadec GRP 22mm shower tray insert, supported on the underside by 18mm plywood battened to the joists and screwed down (leaving the floor level with no steps).

My intension now is to prime the floor and cover the entire surface with the Impey Tilesafe membrane provided as part of the Impey wet room kit and then tile the surface with 50mm x 50mm travertine mosaic tiles.

The problem I have is that many of the adhesive manufacturers are recommending the use of a two-part tile adhesive (i.e. powder and binding agent) given the floor type, however Impey say that this cannot be used as it ‘eats’ the Tilesafe membrane which is bitumen based but the adhesive manufacturer are wary about recommending one-part adhesive as it may not be flexible enough….. !!?!??!

So, after the epic intro…. My questions to the professionals are as follows….

1. Should I change the floor construction? (i.e. add 15mm ply, or similar, under the shower tray and over the caberboard)
2. If I don’t change the floor construction, which adhesive should I use?

Sorry if this is a repeat of a commonly asked question, but I’ve been searching around and haven’t been able to find a consistent answer so I thought I would put my precise situation out there and see what people think.

Thanks in advance for any assistance and be nice… I’m new to tiling and my enthusiasm might not last

Impey Tilesafe - Impey Technical Information

You can get a single part S2 adhesive.. will work the same as a 2 part..

Mapei S2 quick is a great one..