i'm laying a new concrete floor we dug out 9 inches. i had planned to
lay 3" insulation, 4" concrete followed by 2" granolithic screed.
i've since decided against the screed so have an extra 2" to make up.
my first thoughts were to lay an extra 2" insulation, so 2 layers a
75mm layer and a 50mm layer then 4" concrete.

would this be OK... or am i better laying 6" concrete on the existing
3" of insulation.

can you have too much insulation and could there be any movement
causing the concrete to crack?

thanks

wrote:
i'm laying a new concrete floor we dug out 9 inches. i had planned to
lay 3" insulation, 4" concrete followed by 2" granolithic screed.
i've since decided against the screed so have an extra 2" to make up.
my first thoughts were to lay an extra 2" insulation, so 2 layers a
75mm layer and a 50mm layer then 4" concrete.

would this be OK... or am i better laying 6" concrete on the existing
3" of insulation.

can you have too much insulation and could there be any movement
causing the concrete to crack?

thanks

It depends what kind of insulation you are using - the cheapest is
polystyrene and regs now insist on 150mm, although for years and years it
was only 100mm and thousands of buildings have 100mm under them.
Kingspan is thinner but almost treble the price, the choice is yours - just
make sure you have 100mm (4 inch) of concrete (preferably readymixed) on
top, you'll also need 1200 gauge plastic membrane on top of your insulation
prior to pouring - some people put the plastic at the bottom, then the
polystyrene and then the cocnrete, but I've found that the concrete gets
under the slabs and lifts it up as it's being tamped.

In an earlier contribution to this discussion,
wrote:

i'm laying a new concrete floor we dug out 9 inches. i had planned to
lay 3" insulation, 4" concrete followed by 2" granolithic screed.
i've since decided against the screed so have an extra 2" to make up.
my first thoughts were to lay an extra 2" insulation, so 2 layers a
75mm layer and a 50mm layer then 4" concrete.

would this be OK... or am i better laying 6" concrete on the existing
3" of insulation.

can you have too much insulation and could there be any movement
causing the concrete to crack?

thanks

I think I'd go for 100mm (4") of rigid foam insulation and 5" of concrete.
That would give a good combination of thermal efficiency and structural
integrity.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

I would agree that extra insulation is fine, and would recommend
Kingspan. If in SW Scotland then I could do you a good price on 100mm
Kingspan.

The other thing to consider is what the surface is like beneath all
this. It is normal to put sub base down prior to the insulation to
give a stable platform to start with. Also, you can get away with less
than 100mm concrete if the mix is good, You can also get away with
150mm... you just need to advise the supplier so they can give you the
right strength of concrete for your job.

Calum Sabey
NewArk Traditional Kitchens 01556 690544

On 28 Feb, 00:50, " wrote:
I would agree that extra insulation is fine, and would recommend
Kingspan. If in SW Scotland then I could do you a good price on 100mm
Kingspan.

The other thing to consider is what the surface is like beneath all
this. It is normal to put sub base down prior to the insulation to
give a stable platform to start with. Also, you can get away with less
than 100mm concrete if the mix is good, You can also get away with
150mm... you just need to advise the supplier so they can give you the
right strength of concrete for your job.

Calum Sabey
NewArk Traditional Kitchens 01556 690544

Thanks for your replies. I had already laid 75mm polystyrene boards,
on top of 1200 visqueen. Base is solid, already compacted earth and
rocks. So I think I will just go ahead and lay more 50mm sheets on
top, giving a total of 125mm. Then 100mm of concrete. Checked this
out with BC this morning and they say its fine.

wrote:
On 28 Feb, 00:50, " wrote:
I would agree that extra insulation is fine, and would recommend
Kingspan. If in SW Scotland then I could do you a good price on 100mm
Kingspan.

The other thing to consider is what the surface is like beneath all
this. It is normal to put sub base down prior to the insulation to
give a stable platform to start with. Also, you can get away with less
than 100mm concrete if the mix is good, You can also get away with
150mm... you just need to advise the supplier so they can give you the
right strength of concrete for your job.

Calum Sabey
NewArk Traditional Kitchens 01556 690544

Thanks for your replies. I had already laid 75mm polystyrene boards,
on top of 1200 visqueen. Base is solid, already compacted earth and
rocks. So I think I will just go ahead and lay more 50mm sheets on
top, giving a total of 125mm. Then 100mm of concrete. Checked this
out with BC this morning and they say its fine.

Id lay some rebar in the concrete tho..just in case the compacted sub
base isn't..IYSWIM.

On Feb 28, 11:41 am, The Natural Philosopher wrote:
wrote:
On 28 Feb, 00:50, " wrote:
I would agree that extra insulation is fine, and would recommend
Kingspan. If in SW Scotland then I could do you a good price on 100mm
Kingspan.

The other thing to consider is what the surface is like beneath all
this. It is normal to put sub base down prior to the insulation to
give a stable platform to start with. Also, you can get away with less
than 100mm concrete if the mix is good, You can also get away with
150mm... you just need to advise the supplier so they can give you the
right strength of concrete for your job.

Calum Sabey
NewArk Traditional Kitchens 01556 690544

Thanks for your replies. I had already laid 75mm polystyrene boards,
on top of 1200 visqueen. Base is solid, already compacted earth and
rocks. So I think I will just go ahead and lay more 50mm sheets on
top, giving a total of 125mm. Then 100mm of concrete. Checked this
out with BC this morning and they say its fine.

I'd lay some rebar in the concrete tho..just in case the compacted sub
base isn't..IYSWIM.

All he needs is a screeding mix on top of the foam. It can be bought
ready mixed. Make sure it is not full of hard lumps and that the stuff
hasn't separated during delivery.