i'm getting UFH laid over 70m2 as per this diagram
the screed is only to transfer the heat ... but i've never used a weak dry mix (8:1 dry sand / cement) like this before and i'm wondering if it will set and be stable enough without crumbling for me to work on it ie to finish the refurb, plaster boarding, painting, wiring etc
or perhaps it would be better to use a stronger mix? or put down a temporary floor?