Do I need compacted hardcore, concrete subfloor & finished floor for TF build?

Hi, looking for some opinion. Just commenced a TF build & installing UFH prior to kit erection, thus requiring the finished floor to be in place now. When I fill & compact inside the rising walls with hardcore, do I then need to pour a certain depth of concrete for the subfloor prior to fitting dpc, insulation, UFH pipes & finally screed? Or have I an option to "skip" the concrete subfloor and just fit/install these over the compacted hardcore. Would appreciate any opinion. My architect is recommending the former, but I believe the latter is sufficient. Thanks in advance, apple1

no you cannot 'skip'....

generally the UFH company will have their own preferred detail here, but generally the construction would be:
floor covering on
75mm finishing screed on
UFH system on
insulation as specified on
100mm concrete subfloor, reinforced on
1200 gauge DPM on
Blinded, compacted hardcore.

Apple1,

Are you using strip foundations and blockwork rising walls?

Syd

Assuming strip foundation and blockwork rising walls to soleplate level.

Would you then generally pour the 75mm screed inside the structure once external walls have been erected?

Therefore the inner leaf deadwork and timber frame sole plate would act as a side shutter (+vertical insulation at the edge of the screed)?

no, personally i wouldnt....

i would have the UFC system installed and screed poured before TF comes on site....
use the inner 100mm block under the sole plate as the shuttering for the screed... and always incorporate 25mm vertical insulation between this block and the concrete...

This to me would seem to be the sensible option too. Its just that most timber frame standard details that i have seen show the top of the sole plate above the FFL. Indicating that you would need to side shutter the inside of the inner leaf in order to pour the 75mm screed before the external walls were in place.

(Hard to describe without a drawing)

I'm sure this could be designed out in the design of the frame itself though.

One question, where the 25mm vertical insulation is exposed at the perimeter of the finished screed, is it viable to to just cover this with the floor finish, i.e. tiles/carpet or would you need to put down an addtional surface e.g. ply etc.

Thanks All.

Garbow, yes, I'm using strip founds & block rising walls. Interesting point about how to cover the exposed insulation. Am curious about this also and looking forward to some replies.