Insulated kitchen floot

[Jase]

Hi all replacing our kitchen floor in the next week or two due to damp issues, 1880s house. Only got 450 mm to play with . i have dug a test hole to see how deep the foundations are .building inspector said i need 150mm of hard core 25 mm sand 100mm insulation then 100 to 150mm of concrete. Went to order the 100mm pir insulation on line spoke to the guy to make sure it was the correct stuff to put under the concrete slab and he said the insulation has to go on top of the slab then screeded due to weight issues on the insulation!  .Is this correct or have I got some of my wires crossed in conversation due the bloody stress of the house?. Or can it go under the slab, any advice would be greatly appreciated. Regards  stressed Jason. 

[Mr Punter]

The insulation can either go under the concrete or on top.  As it is a ground bearing slab the make up will depend on the ground conditions.  Double check with the building inspector as it is best to be on the safe side.

[A_L]

2 hours ago, Jase said:

Or can it go under the slab, any advice would be greatly appreciated. Regards  stressed Jason. 

 

It can go under the slab. In either case there should be a DPM somewhere below it and a slip layer immediately above it.

 

https://insulation-uk.com/floor-insulation/ground-floors/concrete-slab-floors

 

PIR for floors has a compressive strength of 140kPa for 10% compression, 1% compression (more realistic) will be around 45kPa (or about 4-5000kg/m²) so O.K. except for load bearing walls

 

https://insulation-uk.com/assets/5405_floors_bba-certificate_nov2018.pdf

[Jase]

Thanks both for your help so I'm not going mad after All?? Yes the hard core first sand ,DPM ,insulation DPM,SLAB, the concrete guys reckon they can get such a good finish I won't need a Screed!  What you reckon?  Allso does the insulation PIR have to be a certain spec?. Or just normal celotex or kingspan or simular?. Many thanks Jason.