Preparing sub floor for Screed

[Paulymase21]

Hi, I’m currently trying to rectify a lot of poor workmanship and corner cutting by our previous builder.
In the attached photo I have removed poorly laid DPM and insulation boards with a view to starting again.
Also there is no DPM under the slab.
What I am considering is rather than attempt to notch out the back of the insulation boards over the multitude of pipe work is to lay an extra deep

sand blinding layer over the pipe work and rule it off level, then lay my DPM over the sand followed by the insulation boards. I will then be installing a wet underfloor heating system followed by the appropriate screed.
Would that be an acceptable procedure??
Many Thanks

 

[bobasd]

Is there enough depth for what you propose - why not make a drawing of a full scale section view using the next room FFL as a benchmark?
Maybe there's ample hot water piping in that compartment already?
I cant see the whole floor or the depth at the threshold but you might be better off constructing a suspended floor with a 3/4" ply surface?

 

[Paulymase21]

There’s plenty of depth. I Just wanted to see if anyone would flag a reason for not using compacted sand over the pipe work?? As long as I use a DPM on top of the sand I can’t really see an issue. Appreciate your feedback though, Thanks.