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Default insulation under screed - best insulation ?

On 15 Nov, 21:35, wrote:
Thanks for the speedy responses - much appreciated.

So I have a max of 135mm between floors and you are recommending a
70mm min screed which leaves me with the following options:

70mm screed -- 65mm insulation
75mm screed -- 60mm insulation
80mm screed -- 55mm insulation
85mm screed -- 50mm insulation

I guess I can look for some 65mm or 60mm insulation but doubt I will
find it.

Am I ok with 50mm insulation ? (Regs are a bit different here in
Channel Islands to UK so I am not required to put any in - I just
wanted some to take the chill off a bit).

I'll use some offcuts to go round the perimeter but just cut them to
20mm and go full screed depth. Is there a max on this perimeter
insulation? ie would you gain by having it 50mm? Or is this determined
by the plaster and skirting board width/depth? ie a limitation of
about 20mm.

As for the fibromesh - haven't heard of this so will have to
investigate locally.

Chicken mesh or a thicker gauge mesh? Local builders don't sell D49
(2.5mm bar with 50mm squares) but do sell either chicken mesh rolls or
A142 (6mm bar and 200mm squares)

Was in two minds whether to screed with a mate (and get mix delivered
by big mixer or dumped into the back of his truck - he is a stone
mason and has done floors before). Or to pay some plasterers to do
it.

I understand the wood and bay approach but am not convinced I can get
a decent floor with no dips or hills. Did the slab and blocking
previously myself.

Thanks for any help.
Ed


Dear Ed
About 10% of the heat loss of an average uninsulated house goes
through the floor so the other poster is quite right that the gain is
small but as we find the cost of energy going up and up and you are
not going to be re doing this and the building is to last at least 100
years design life it would be good for you and those that follow you
to put in more rather than less. This is a personal view and dependant
on the prediction that energy costs will continue to rise
exponentially - any normal payback calculation would probably opt for
lesser amounts.
Fibromesh is a white cottonwool-like / fluffy material that you mix
with the dry pack and comes in 900g bags and acts like the horse hair
in old fasioned coarse stuff (lime putty/sand mixtures for plastering)
- it is a binding agent providing tensile strength. It is not that
expensive but you may have to get it posted over.
Keep the edge insulation to 20/25mm - just covered by the plaster (but
leave a gap vertically! - and the skirting. Any more is a waste of
time and has practical problems you have spotted.
Pre mixed screeds come with the properly formualted fibromesh but
normally come in minimum quantities of 4 tonnes
I doubt you could do that yourself in a day! remember you have to get
it off the lorry onto a platform/tarpaulin etc outside your house,
barrow it in, lay screeds (dont forget the roof battens for this) to
correct levels - fill in between and it is quite a big area. I reckon
you will need the two of you as plasterers and a couple of guys to
barrow it in for you to do it in a day
Chris G