Floor to ceiling window, closing cavity (at floor level)

sydthebeat

https://www.boards.ie/discussion/comment/120994634#Comment_120994634

i said it "may" be sufficient, but personally i would prefer something wider. it really depends on the dimensions of the screed for which you are making the expansion allowance. Im not a structural engineer so i wont question whats specified in this case, but ill just make the point that the usual expansion joint cut into a concrete slab in large applications is 25mm.

on the 65mm edge insulation issue, this is why these details should be designed out prior to commencement. Theres nothing stopping you from attaching a L bead to the window frame to receive the laminate flooring if youre afraid of movement of the flooring, but ive stood on pieces of 50mm PIR on edge and they dont move.

SodiumCooled

Thanks, all these steps makes sense now overall. Ensuring airtightness did come to mind since the PIR will be butted to the cill and while the cill itself should be airtight but air could have a route up from the plywood but I thought that using airtightness tape between the cill and plywood and blocks and plywood at the sides should hopefully solve that.

I need to run all this past my architect anyway before I start work on it so will see what his overall feeling on it is.

sydthebeat

Also consider the air tightness detail under the concrete slabs.

SodiumCooled

https://www.boards.ie/discussion/comment/121015077#Comment_121015077

Are you referring to the airtightness for the ground floor under the hollowcore? The hollowcore has solid ends on all section connecting to an outside wall and the top block has been plastered up to meet the hollowcore above the metal ceiling to address airtightness here. Where the hollow core sits on an RSJ (so not plastered) I have sealed around it with airtight tec7 sealant.

sydthebeat

There will be V shaped gaps between the hollow core slabs over the block wall

There's need to be dealt with

SodiumCooled

https://www.boards.ie/discussion/comment/121015290#Comment_121015290

I also filled the majority of these with the airtight sealant, one or two bigger ones with expanding foam (which I will probably pair back and add sealant or airtight paint over when I have a chance).

I might add this was not something even suggested as being needed to be done I actually saw this as an issue myself. Plastering the top block was the only thing called out to be done.

I think the grouting of the hollowcore did a lot of the filling of these gaps which I guess is why no specific mention was made on filling it separately - I only needed a small bit of sealant in most places.

SodiumCooled

https://www.boards.ie/discussion/comment/120966951#Comment_120966951

Thanks for this suggestion as my architect was very happy with it and has approved it (though he said expanding metal would be fine rather than steel mesh if it was handier).

He did push back on the 65mm insulation you mentioned though and said he would not allow any more than 25mm against the cill as any more would have the screed floor finish too far back for his liking.