Do I need a primer for SLC onto a slip membrane?

[Great_scot_selfbuild]

We’re covering a small area of UFH (which was too shallow to lay the dry screed) with self levelling compound. In searching about SLC I’ve seen mention of a primer - is this always needed? The SLC will be onto a slip membrane which is over the pipes.

This is the stuff I’ve been recommended to use. 

[Russell griffiths]

The primer is for priming up the surface if you are putting the SLC onto another concrete or screed surface. 

If you are going over a plastic membrane nothing is going to stick to it, your SLC will always be an independent slab on top of the ufh. 

[Nickfromwales]

How thick (or thin) is this going to be?

 

Also, you cant use primer over a membrane.
 

I can’t recall your foundation type, but if theres a DPM under the slab you should cut the slip membrane out and put the SLC down without any such decoupling.

[torre]

Isn't the membrane usually laid below the pipes?

[Great_scot_selfbuild]

33 minutes ago, torre said:

Isn't the membrane usually laid below the pipes?

@torre The vapour membrane is below the pipes, the slip membrane on top.

[Great_scot_selfbuild]

4 hours ago, Nickfromwales said:

How thick (or thin) is this going to be?

 

Also, you cant use primer over a membrane.
 

I can’t recall your foundation type, but if theres a DPM under the slab you should cut the slip membrane out and put the SLC down without any such decoupling.

probably end up being about 30-40mm.

Foundation is a suspended beam & block floor, DPM, 150mm PIR, Vapour membrane, UFH, slip membrane.