Creating fall with tile adhesive

[tidemaster]

Hello all, I am wondering if you can use tile adhesive to create fall instead of a screed mix, ( I know more expensive but have plenty of bags left over from prev job). I was thinking of say 5mm up to 20mm. If so is any one familiar with 'keraflex' by Mapei .Anyone know of other brands that can be built up which also allow for flex.
Another quick question, can you use tile adhesive directly over a pvc water proof membrane? Mine is a orange rolled out sheet.

[autogenous]

Given the nature of screed mix and what you want to achieve, screed serves a purpose of being able to "screed" the mix flat but on a fall. With tilers glue the straightness is very hard to achieve. It drags and being required is very claggy and high slump.

At best there is a chance that you maybe able to mix a "little" tile glue with the screed but remember you are scraping the fall to the drain hole.

You are using plastic sheet as a damp proof membrane? Your better off using a proper paint on damp product such as Dampfix. Once you have done that you could use some watery tile glue mixed neat as a binder of the screed to the damp covered floor, brushed on prior to spreading and screeding the screed.

What is the floor medium you are laying on? Concrete? Compressed Fibre Cement (CFC)?

What type of structure is the bathroom in? Brick render? Stud frame? Tilt slab concrete?

[tidemaster]

Thanks auto.g,
It is for a veranda so no drain hole, just some fall away from house is req'd. The waterproof membrane is already down,(pvc orange sheet).
The veranda is 19mm cement sheet over timber joists. I have a slight bit of bounce on floor thats why I thought Flexi glue built up would be better than screed,(also a lot less weight). Is there a flexible tile glue that would let you build up to approx 20mm that would stick to waterproof membrane

[RPMT]

i agree with autogenous... tile glue is very dificult to screed. not to mention it slumps some what.

your better off with sand and cement screed of 4 to 1 mix.


i also agree with autogenous on the waterproofing

[autogenous]

The fall probably should have been created with the CFC then hydrocrete or similar mixed with neate GP cement brushed then screed dropped on while hydrocrete mix still damp. Hydrocrete dries fast do it as you go. Hydrocrete is acrylic based and creates a water based barrier. You can mix a "little" bit of water with the HC mix to make it paint like.

Then the best rubber flexible tile glue used you can find.

Any movement in the CFC may crack the screed. I wouldn't use anything less than about 20mm high screed on the CFC, even then its borderline.

You don't want movement in the CFC sheet which is probably 18mm?

Maybe a flexible additive to the screed but its going to be gluggy and non screeding.
A glue based screed will not end up flat and wont screed.

The plastic sheet will allow the tiles to move like a slip joint. Not ideal I think.