Wall floor junction advice

[Moggaman]

Hi guys.

advice re Airtightness please.

I am doing self build .

I am at concrete sub floor level. On that I will be putting 150mm insulation and then a screed. Walls are not plastered yet.

Currently the first fix electric is ongoing .

I am wondering about the need for wall floor Airtightness. It’s a block house.

If I get the ceiling slabbed out and the walls   And ceiling plastered first all the way down to sub floor, then lay insulation and pour screed…will that take care of Airtightness?

alternativrly , if I put in insulation and floor first ( like the Plasterer’s want), what Airtightness steps should I take .. bottom block will be unplastered..

thanks

 

[AliG]

It would be unusual to put wall in before the floor, although it would probably be better for air tightness. Someone may comment who has done that.

 

A couple of things I would recommend-

 

1. Put 25mm of PIR around the edges of the screed. We specified this in our build and the builders then used a roll of thin foam instead. The screed was down before I knew about it. You need insulation around the edge of the screed to stop a cold bridge between the screed and the block walls.

 

2. Are you planning to wet plaster the block walls or dry line them with plasterboard? If wet plastered then this will create airtightness and you won't have much to worry about. If dot and dab plasterboard then the best thing is to actually try and make sure the walls are airtight behind it and not use the plasterboard to create airtightness. I would recommend doing an air blower test before plastering the walls and sealing everything up then whilst it is still easy to get access.

[Moggaman]

4 hours ago, AliG said:

It would be unusual to put wall in before the floor, although it would probably be better for air tightness. Someone may comment who has done that.

 

A couple of things I would recommend-

 

1. Put 25mm of PIR around the edges of the screed. We specified this in our build and the builders then used a roll of thin foam instead. The screed was down before I knew about it. You need insulation around the edge of the screed to stop a cold bridge between the screed and the block walls.

 

2. Are you planning to wet plaster the block walls or dry line them with plasterboard? If wet plastered then this will create airtightness and you won't have much to worry about. If dot and dab plasterboard then the best thing is to actually try and make sure the walls are airtight behind it and not use the plasterboard to create airtightness. I would recommend doing an air blower test before plastering the walls and sealing everything up then whilst it is still easy to get access.

Thanks, I am wet plastering the walls..but I am wondering for the need for tape at the wall floor junction?

yes, 25mm PIR around the edge of the screed 

Edited November 18, 2021 by Moggaman

[Iceverge]

Tape is impossible to get it to stick to anything concrete related in my experience. 

 

We used airtight paint. First coat was very watered down, almost like a dust suppressant + primer. The second and third coats were neat. 

 

I bought my stuff from Philip in Prodomo in Tralee. He's a mine of knowledge too.

 

https://www.prodomo.ie/online-shop/#!/Belgacoat-Brush-dark-5-liter-air-tight-paint/p/137351991/category=109789652

[AliG]

If the walls are wet plastered and the floor is screed then I don’t see where air is going to come from at the wall floor junction.

 

It would have to be coming through any small area of unplastered wall which would be negligible.

[Dave Jones]

i would think the walls will be dabbed with boards first then plastered. You will then have a gap where both the board and plaster finish at floor level. 

 

Foam this up prior to skirting. same with any stud walls.

[JohnMo]

We had a air test prior to the plasterboard going on and had leak all around the building at the dpc.  Used blower proof liquid to seal.

 

May be worth a quick air test before you start fixing the skirtings etc, think it cost about £100.