Bi-folding door frame over cavity

[shbrooks]

I have a situation where two bi-folding doors form the corner of my rear extension - one will have a low threshold with the patio, the other (around the corner) will step down to the garden.  In order to keep the corner post to a minimum, I would like to set the door frames back, which means they sit over the cavity.  I've therefore worked up the following details using Warmotech Phonotherm (RG550) and Marmox Thermoblock to bridge the cavity and would appreciate any comments/feedback.

 

[Nickfromwales]

All seems kosher to me. 
 

Why the overlay UFH? You can just put the UFH pipes onto the insulation, adding 20(?)mm more slab insulation to boot. Then just pour the screed / concrete as your finished slab. 
 

Flooring then goes directly on to the heated slab. Cheaper and better, just takes a little longer to warm up but a good setback timer will deal with that. 

[shbrooks]

Thank you for your comments. The overlay UFH is a continuation of the existing UFH in the main house, so seemed sensible to carry it through for continuity and levels.