Primer required?

Hi,
I have done a few tiling jobs for myself over the past few years and would rate myself as reasonably competent!
I like to ask questions before going in head-first so as to limit any avoidable mistakes.
So, first question for you hepful chaps is..... I am laying UFH in my flat (kitchen & bathroom) which is constructed with block and beam floor with 100mm polystyrene insulation and 22mm chipboard floor. I am using 6mm insulation panels which I believe need to be stuck to the chipboard floor with Rapid Set Flexible Adhesive.
Now, do I have to first prime the chipboard floor with acrylic primer before sticking the boards down and do I have to prime the top of the insulation board before applying the Adhesive for the tiles?
Finally, The UFH mat is 3mm thick, can I lay the mat within the wet Adhesive and lay the tiles directly on this or do I have to lay the mat on a thin bed of adhesive first and let this go off before the tile adhesive bed and tile!?
Hope I am making myself legible!?

clean the floor and check with the adhesive manufacturer if the substrate needs primed prior to laying boards.Once boards are layed and the ufh matt is positioned,you could use a slc then tile it?

Originally Posted by brian c

clean the floor and check with the adhesive manufacturer if the substrate needs primed prior to laying boards.Once boards are layed and the ufh matt is positioned,you could use a slc then tile it?

On the money Brian

Thanks guys, it's better to ask before getting stuck in than getting stuck in then getting stuck!

it sounds like a floating floor, hope you're not thinking of tiling it

Not sure if it's floating - all stud walls are wood framed and screwed to the floor?
And yes, I AM tiling it (on top of the fixed down warmup boards)
I will let you know in a year or so wether you can say I told you so!!!

if it's a floating floor, you won't have to wait a year!

The Chipboard will have to be very secure. I would use thicker contruction board than 6mm as well at the very least 10mm. Make sure contruction board is screwed as well as stuck down using a SPF. Also i would use a suitable levelling compound for the UTH and then use a 2 part adhesive and flexible grout.

As the other fellow says if its a floating floor be very careful

You need to have ZERO deflection to tile floating floors....and use S2 type adhesive..

Not something i would do lightly.

Doug,
Can you please define a floating floor?
Is this were the floor is not screwed to the base that it sits on?
The flat is 35 years old and the floors have no sags or creaks. Is it ok to use SLC on this then adhere the insulation boards to the SLC with 1 part Weber Flexible Rapid Adhesive? Would it make a difference to use a two part milk with the Flex?

if your chipboard is just sat on your insulation and there is no joists secured to your block and beam floor, and therefore no fixings in your chipboard to the joists to anchor everything to the b&b floor, then it's a floating floor, so you're going to get a lot of bounce and movement within the floor.This will lead to tiles cracking and de-bonding whatever adhesive you use imo

How did I miss that floating floor The man who never made a mistake, never made anything

So is there no deflection in Insulation boards used under the UFH? These are a polystyrene board so not solid by any means.
I am now really worried that I am doing completely the wrong thing having bought all of the kit!!!