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blake floyds · 7 Apr 2008

Hello can you help

building an extension have my bricks up to damp course

can you tell me what i need to do for the floor I can not get in touch with my building inspector

dose it go like this

Hardcore

blinding

sand

200 mm insulation (this is what I been Told , I thought it was 100 mm )

100 mm concrete slab

screed floor[/u]

^woody^ · 7 Apr 2008

Hardcore - minimum 100mm

blinding sand - 25mm

DPM

Insulation - 150mm polystyrene or 80mm Kingspan/Celotex

100 mm concrete slab

70mm screed (optional)

Don't forget 25mm thick insulation upstand around the edge of the slab where it butts up to an external wall

GaryinAshby · 8 Apr 2008

My BCO also told me to put in a polythene membrane (just standard stuff, not a DPM) between the Celotex & concrete slab.

^woody^ · 8 Apr 2008

There is no need for that, did he say why?

GaryinAshby · 8 Apr 2008

No, just told me there had to be a barrier between the insulation & concrete, despite there being a full DPM under the insulation. As I had a lot of large polythene sheets lying around I didn't question it.

noseall · 8 Apr 2008

they insist upon this method in Staffs also.

Shytalkz · 8 Apr 2008

It's to stop screed/concrete getting between the sheets and causing cold bridging. It's not an extra dpm.

^woody^ · 8 Apr 2008

Well surely its better to have no gaps between the sheets, then nothing falls through!

Shytalkz · 8 Apr 2008

Indeed. If you use the stuff with the membrane already on the top and taped joints, there isn't a problem. If it's just EPS or somesuch, then that's when the BCOs insist on it.

^woody^ · 8 Apr 2008

"Yeah, of course I'll put it in " he thinks while waving the BCO goodbye

What a waste of time

blake floyds · 10 Apr 2008

can I put my insulation on top of the slab so i can put under floor heating on it

Deluks · 11 Apr 2008

In a word, no. Follow the advice given, and use insulation board for underfloor heating in addition to the celotex. Belt and braces, very warm floor, will save you dough. If you mean wet underfloor heating, then this goes into the floor screed anyway and won't need any other insulation.

^woody^ · 11 Apr 2008

A wet system should be fitted on top of the insulation and then screeded

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