UFH screeds - Flowing, Flexidry or sand cement?

[thompo]

Hello

We are renovating and are putting a new concrete floor down throughout the house.

Spec was to have subfloor laid to allow 100mm insulation and 50mm Ultraflow screed to improve UFH response etc.

Due to crappy job on the subfloor (localised bumps, dips causing rocking insulation - sorted with lots of grinding, self leveller and cut insulation. Now discovered its all out of level) were actually left with 50-100mm for Screed!

Given that i will now require a thicker screed for the majority of the floor (65mm over about 60%), is there much point in using liquid screed vs sand and cement?

Ive seen Flexidry, amongst other things such as very rapid dryout, reduced shrinkage etc it claims to give better compaction around the heating pipes and increases heat conductivity?

Is flexidry just an additive to sand and cement? if so i cant see how it gives better compaction, surely thats down to the screeder?

Anyone think there would be a noticeable difference in performance of sand/cement vs liquid screed at the same depth? All the comparisions ive seen compare 50mm of liquid screed vs 75-100mm of sand cement so its pretty obvious which one will heat faster lol.

cheers Neil

 

[Norcon]

Have no idea what flexidry is but assume its a chemical additive that the snake oil salesman will swear is the best thing since sliced bread.

Your best bet is to contact the screed supplier if you want to go gypsum based and see what they tell you.