Screed Floor and Insulation Upstand

[itsfhome]

About to lay a screed floor and have read I need to put an insulation upstand around the perimeter of the screed floor.

Is this really necessary? The screed floor is 65mm so I will need to place a strip of 65mm x 20mm insulation around the room. Is there a place I can buy this in strip form or is the only option cutting the excess celotex rigidboard insulation I have?

Also, the screed is to be laid on top of the insulation? What's the views on this, should I lay a secondary DPM before the screed so the floor will be slab/DPM/Insulation/DPM/Screed? Seen mixed comments on this.

Thanks in advance

Adrian

 

[RedHerring2]

Yes, you'll need to cut your strips of insulation for the upstand.
Yes, you should put another polythene layer over the insulation but it doesn't have to be a proper dpm. It's just to stop the screed losing too much water into the insulation gaps, thus allowing it to cure properly.

Incidentally, I usually cut the strips of insulation before laying the floor so that the floor insulation holds the perimeter insulation in place.

 

[itsfhome]

Thanks. Looks like I'll have to cut out the upstand then. Do I need to remove the foil on the insulation in the area of the upstand?

It's going to be fun cutting that beastie.

Regards

Adrian

 

[RedHerring2]

Why would you need to remove the foil? It'll be installed in exactly the same way as the floor insulation, i.e insulation, then the thin sheet of polythene to cover the whole, so your screed will not be in contact with it.

Another reason for cutting the upstands before you install the floor insulation. You're not cutting strips 65mm wide, but strips 150mm wide or so. It matters not whether you cut them from the length or the width of a sheet.

 

[jeds]

Just buy a sheet of 20mm insulation and cut the upstands from that. A poly membrane over the insulation is a good idea. This is a vapour barrier to eliminate the possibility of condensation beneath the insulation.

 

[itsfhome]

Thanks for the info. I had 20mm tick insulation left over from the ceiling and used that. My concern was I did not have enough and would have to cut up the 100mm stuff.

RedHerring- thanks - my question about the foil was just about the contact with the side of the existing insulation. Just didn't want a d'oh moment.

Insulation went down this weekend and now awaiting BC inpsection and the delivery of the sand/cement for screed mixing/laying.

Regards

Adrian