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climbinggeorge

Beam and block to insulation

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I've got a little conflicting info on the appropriate layers for our ground floor so I wanted to check in with the buildhubmind.

We have a builder that is completing our house to shell, they are handing it over to us with a beam and block floor with a membrane on it (all pressure tested at this point)

I had planned, and the architect's spec had said to put insulation, then clip UFH to it and pour the screed.

The screed supplier had suggested another membrane over the top of insulation to stop any reaction between screed and foil, and stop any extra screed pouring down cracks.
A potential UFH installer had said putting a layer of sand and another membrane on the existing one.  The logic being that the single membrane is our only defence against damp so it adds redudancy wither another layer and the sand protects from any sharp bits from the beam and block floor.

Just looking for an idea on usual practise, if such a thing exists

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I'd go block+Beam, DPM, insulation, Membrane, UFH, Screed

 

Clean up the block and beam, and grout it, sweep/Scrape it so no nasty sharp bits or lumps of gobbo left behind from the builder, when happy lay down the DPM, insulation nice and tight, tape up joints, next layer of plastic sheet then clip in the ufh. 

 

Oh and Perimeter insulation needs adding in too. and someone told me to add some expansion strips in doorways for some man made breaks in the screed.  Need further advice on that as unsure.

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I’m always amazed when “experts” tell you that you’re going to get damp coming into a building through an air gap, a beam and block floor and then 100mm of impervious insulation and finally into a screed later …

 

Unless the floor is very uneven, the sand shouldn’t be required but should be on top of the beam and block and below the membrane. In reality if you sweep and clean the block surface there will be no issue. 
 

Should be :

B&B

DPM

Insulation (with edge insulation) 

Slip membrane

UFH Pipes

Screed

 

 

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14 hours ago, climbinggeorge said:


The screed supplier had suggested another membrane over the top of insulation to stop any reaction between screed and foil, and stop any extra screed pouring down cracks.

 

Its mainly to stop the screed loosing water. Helps prevent cracking. Some recommend putting a temporary sheet of plastic on top of the screed as soon as you can walk on it to control the drying process for same reason. 

 

I recommend expansion gaps in the screed at doorways. Otherwise when the screed in each room shrinks towards its centre you can get a curved crack where they meet at the doorway. Can be a problem if tiling. 

 

 

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Thanks all, will go straight down with insulation (plus edge insulation), tape the joints then extra membrane, UFH then screed.

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