Hi one and all,
I built an extension and now need to screed the floor.

There is 135mm to play with between the old floor line and the current
concrete slab top.

I was planning on insulating above the slab and under the screed. (No
underfloor heating, just hoping to improve insulation and maybe gain a
bit of heat from passive solar gain) The room is a kitchen and
measures about 4.7m by 5m. The walls are block with a 70mm plus cavity
(fullfill eventually) and there is a floor above - ie two storey
extension).

I was planning on putting 70mm of insulation in and a 65mm screed but
have just had a crisis of indecision since getting quotes from the
local builder.

They recommend Kingspan TP10.
I thought that this was for roofing and having used it in the roof I
know that it is pretty weak and I would have thought not ideal in
compression.

They have given me prices for the following:

Kingspan Kooltherm K3 (50mm)
Jabfloor 70 (50mm)
Kinspan TP10 (70mm)

I haven't seen the K3 but from the online literature from KSpan it
looks like I can use K3 or TF70.

Is TP10 the wrong material ?

Whatever insulation I end up using I was hoping to avoid cracking by
using mesh.
I was going to add some wrapping mesh (D49) or chicken wire at the
bottom of the screed.

However I read that it is a good idea to stop cold bridging by using
20 to 25mm of perimeter insulation.

I would have thought that this will lead to more compression of the
insulation ? THen you have a floating layer of screed with insulation
all around.

I want to lay tiles and don't want to find a floor cracking and
sinking after a few years....

Any thoughts on this ?! Help ! What is the standard way of doing
this ?

Thanks for any help.
Ed