Laying Marmox onto concrete floor ready for UTH and tiles

[jase the space]

I have a concrete bathroom floor. On the whole it is in pretty good nick but there are a few patches of dusty/crumbly areas.

I want to lay 6mm Marmox down before the tiler comes on Monday to lay the tiles.

The floor is not perfectly level as it is, there are a few humps.

Can I use flexible tile adhesive when I am laying the Marmox to make up for any difference in the floor?

Do I need to treat the floor with anything prior to this (I've seen mention of primer/bonfing agent - which one)?

If I can't go straight on with the Marmox could I use latex self levelling stuff and if I use this will it dry out in time for me to fit the Marmox and then the tiler to put the tiles on top of that?

Any help would be much appreciated (and fast!).

Thanks

 

[jase the space]

Oh and the area is only around 2.5m2 so not very big at all.

Any help much appreciated.

 

[jase the space]

OK I went to B&Q last night and picked up some "Unibond Ultra Rapid Set+ Floor Adhesive". This claims to be able to level and fix up to 20mm depth so sounds like it is just up my street.

The one thing that concerns me is that it does not say it is flexible BUT it does explicitly state that it is suitable for underfloor heating - one of the reasons I bought it.

I am only using this to fix the Marmox to the concrete subfloor - the tiler will then use flexible adhesive on top of this to fix the tiles and UTH to the Marmox. However, I have seen it stated that flexible adhesive should also be used for fixing the Marmox to the subfloor but I'm not entirely sure why as most of the heat should be on the upper side of the Marmox so why does the lower side interface need to be flexible?

Anyway, can anyone tell me whether this adhesive will be suitable for fixing the Marmox to the subfloor? Oh and my the way I have 10mm Marmox not 6mm - they sent me the wrong stuff!

I also picked up some PVA - I will use this in ratio 1:5 with water to prime the concrete floor first as stated on the adhesive packaging. Presumably I need to try and get as much dust up as possible?

Comments please.