wrote:
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

You need at least 70mm screed, with chicken wire.

For insulation, any PIR type (ie celotex or Kingspan) with a silver
foil backing will do. They will perform more or less the same.

I'm not sure that the Jablite product is as thermally good as the PIR
foams

They are designed to take the weight of floors, no problem

dg