Wet underfloor heatin

[Rslee]

I have a floor depth of approximately 120-140mm below finished floor level. The floor is block and beam and we are putting in Robyn's pipes in screed. Can you please tell me if the floor construction is correct going from top to bottom:

porcelain tiles
flexible adhesive
debonding layer
adhesive- what sort?
60mm screed with wet underfloor heating pipes in
50mm celotex
block and beam floor

Do you know how thick the adhesives and debonding layers should be?
Does anyone have any product recommendations for these layers - I know nothing so am starting from scratch as I need to tell the builder everything
Do you need to add anything to the screed to stop it from cracking - building inspector mentioned chicken wire as celotex is compressible layer?
Do fibres in screed prevent cracking? Is this special screed or do you just add something to it?
Do you need a membrane between the celotex and the screed? Builder is using xtratherm (it's actually not celotex) and has reluctantly agreed to use foil tape to seal the joints.

 

[Chalked]

Starting from the bottom up.

Block and beam.
100mm insulation
Vapour barrier. ( visqueen)
Underfloor pipework.
50mm screed ( use anhydrate liquid screed) don't use a hand laid screed.
If it's not a large floor, use a gypsum based powdered tile adhesive and prime the screed with accrilic primer.
If it's a large floor, use a anti crack membrane like "ditra" use gypsum based adhesive to lay this, them flexible powder adhesive to tile.
You will have then a finished depth of 165-175mm finish.
You should use 100mm insulation, but may have to drop to 75mm.

 

[Worcester]

Chalked solution is correct.

75mm of insulation probably won't meet Building Regs, so you will need a specialist insulation panel if needs to go thinner.

 

[mutley racers]

I just had a company design a layout for me in 100mm joists. It goes 25mm battens, 50mm insulation and then 25mm screed

 

[ShaunCorbs]

I just had a company design a layout for me in 100mm joists. It goes 25mm battens, 50mm insulation and then 25mm screed

screed on a wooden floor?

 

[Worcester]

I just had a company design a layout for me in 100mm joists. It goes 25mm battens, 50mm insulation and then 25mm screed

Depends upon what work is going on.. As OP is having a non-habitable room converted, it would be subject to building regs, as such the insulation requirements will be different.

Even so 50mm insulation is a lot of downward heat loss compared to current regs, it'll be cheaper to spend more on insulation, you'll need less ufh pipe as the pipe spacing will be greater and and you'll save forever on reduced fuel costs.

 

[tolly]

screed on a wooden floor?

They probably mean a pug/biscuit screed, just there to give thermal mass for suspended floors.

 

[Ermintrude]

I just had a company design a layout for me in 100mm joists. It goes 25mm battens, 50mm insulation and then 25mm screed

Hope u didn't pay for that design I've been doing it for past 8 years