Slab insulation at sliding door junction

[junglejim]

Not sure the best way to approach this so advice appreciated.
 

option A: The standard approach as per guidance from screed company is to put the foam edge strip on the door edge and screed right up to it. As per picture A.

 

In my mind that’s potentially a cold bridge point so…

 

option B: I was thinking about putting structural foam perimeter (grey) along the door edge and then the foam strip (photo B) the down side is that the slab will finish inside of the structural foam so the foam won’t have any compression from the slab and the flooring will overlap it. Potentially it’s not very tight and may need trimming down which will be tricky in situ but gives the edge of the slab extra insulation
 

Any advice appreciated 

[Nickfromwales]

Adding the upstand does add some additional thermal break, but any decent door threshold will already be reasonably well thermally broken, plus the foam gives immediate separation from the screed and the threshold / frame. 
 

Have the yellow foam against the frame, as expansion (should you actually need it) needs to be at the perimeter.

 

You then fit the grey stuff with foam, so it doesn’t move, then trim that to be the exact height of the screed, so the screeders have a target to lay to. 
 

After the screed is dry, you then cut the yellow foam to the screed height.

 

You could just double up on the yellow foam, but it looks like you already have the grey stuff so crack on. 
 

Stop and start the yellow foam in the internal corners to prevent gaps from forming a continuous radius, just apply duct tape to the back of the foam to create a hinge, then once fitted tight do the same to the front to keep it liquid proof. 

[junglejim]

17 minutes ago, Nickfromwales said:

Adding the upstand does add some additional thermal break, but any decent door threshold will already be readily well thermally broken, plus the foam gives immediate separation from the screed and the threshold / frame. 
 

Have the yellow foam against the frame, as expansion (should you actually need it) needs to be at the perimeter.

 

You then fit the grey stuff with foam, so it doesn’t move, then trim that to be the exact height of the screed, so the screeders have a target to lay to. 
 

After the screed is dry, you then cut the yellow foam to the screed height.

 

You could just double up on the yellow foam, but it looks like you already have the grey stuff so crack on. 
 

Stop and start the yellow foam in the internal corners to prevent gaps from forming a continuous radius, just apply duct tape to the back of the foam to create a hinge, then once fitted tight do the same to the front to keep it liquid proof. 

Thanks Nick. My logic was because the bottom of the screed is pretty much level with the bottom of the frame so not particularly well thermally protected from the concrete upstand. At the usual wall edges I have a 30mm pir upstand so seems to make sense to extend continue that in front of doors but given its a threshold figured it needs to be load bearing as pir would likely damage. My understanding was that screed needs to go up to the yellow edge strip hence putting that inside the grey foam. Perhaps an alternative is to use pir upstand as per external wall edges but trimmed so that screed can still go over the top but at half depth (3cm) but I’d worry this might be too thin and vulnerable to cracking.

Edited 7 hours ago by junglejim

[saveasteading]

16 minutes ago, Nickfromwales said:

fit the grey stuff

Something robust there are all sorts from very squidgy to almost solid.

[Nickfromwales]

16 minutes ago, junglejim said:

Thanks Nick. My logic was because the bottom of the screed is pretty much level with the bottom of the frame so not particularly well thermally protected from the concrete upstand. At the usual wall edges I have a 30mm pir upstand so seems to make sense to extend continue that in front of doors but given its a threshold figured it needs to be load bearing as pir would likely damage. My understanding was that screed needs to go up to the yellow edge strip hence putting that inside the grey foam. Perhaps an alternative is to use pir upstand as per external wall edges but trimmed so that screed can still go over the top but at half depth (3cm) but I’d worry this might be too thin and vulnerable to cracking.

I’d go with my above, simple, robust etc, and leaves a completely flush surface to lay flooring to. 

[Nickfromwales]

Leave the yellow foam about 10mm higher than top of screed, to deal with any splashing of screed or a ‘wave’ accidentally going over the upstand. 
 

Cut it back after the screed has dried. 

[junglejim]

11 minutes ago, Nickfromwales said:

Leave the yellow foam about 10mm higher than top of screed, to deal with any splashing of screed or a ‘wave’ accidentally going over the upstand. 
 

Cut it back after the screed has dried. 

Thanks. Really helpful. Can I ask why put the yellow behind the upstand when on the other edges it goes in front? I thought it was to decouple screed from insulation etc? Attached is how the other external edges are done where there isn’t a door.

Edited 6 hours ago by junglejim

[Nickfromwales]

1 hour ago, junglejim said:

Thanks. Really helpful. Can I ask why put the yellow behind the upstand when on the other edges it goes in front? I thought it was to decouple screed from insulation etc? Attached is how the other external edges are done where there isn’t a door.

Not life or death. Carry on as you are sir. 

 

Just gives a splash back at these doorways which saves cleanups or disasters if screed gets into the running gear of a slider.