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Insulation under screed


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#1 bmc

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Posted 21 October 2005 - 12:18 PM

I am raising my floor level by about 100mm, at moment just concrete slab. Dont know if there was any insulation under slab. Can I put polystyrene sheets in now under screed? Will screed work ontop of polystyrene sheets ok?
What is the minimum thickness of screed so wont crack, haven't had a look yet but assuming sheets will be about 25mm??
Any advice appreciated.
Cheers

#2 Guest_cwatters_*

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Posted 21 October 2005 - 06:30 PM

I think 65mm is the norm for reinforced sand cement screed. I think I read that some liquid screeds could be used down to 40mm but you would need to check.

Screed on top of insulation is normal. For example it's the way most Under floor heating systems are done.

#3 regs_guy

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Posted 21 October 2005 - 08:10 PM

current regs would require 100mm polystyrene or 70mm celotex/kingspan. but unless you are doing say a garage conversion or conversion you dont have to meet this reg

polystyrene is more compresible than celotex/kingspan hence more prone to cracking

50-75mm screed with a light reinforcement (e.g chicken wire) is common

#4 cideredd

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Posted 29 August 2006 - 09:20 PM

Chicken wire ?
Have you ever tried laying a 50mm floor screed on insulation with chicken wire as reinforcement?
In the good old days maybe ,but not on insulation!

#5 griffinsa

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Posted 30 August 2006 - 07:38 PM

could you use d49 mesh?