Warm flat roof and ewi

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b123b

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I am building an solid brick extension and have a warm flat roof . The joists overhangs a bit. Then there is a fascia board. The plan was to put ewi all the way up into the fascia boards in between the joists ( in hindsight I should have built it differently to avoid joists and cold bridge - but this is my first project so please go easy on me ! I'm feeling pretty annoyed about it so I'll just make the best of a "bad" situation)

I think I will also spray foam from the inside the area between the wall plate and the joists . Is this sensible, to insulate both inside and outside the fascia board area ? Do I need to install any vcl on the wall or wall plate? I was told by ewi company I don't need vcl for phenolic wall insulation .

Thank you!
 
b123b said:
I am building an solid brick extension and have a warm flat roof . The joists overhangs a bit. Then there is a fascia board. The plan was to put ewi all the way up into the fascia boards in between the joists ( in hindsight I should have built it differently to avoid joists and cold bridge - but this is my first project so please go easy on me ! I'm feeling pretty annoyed about it so I'll just make the best of a "bad" situation)

I think I will also spray foam from the inside the area between the wall plate and the joists . Is this sensible, to insulate both inside and outside the fascia board area ? Do I need to install any vcl on the wall or wall plate? I was told by ewi company I don't need vcl for phenolic wall insulation .

Thank you!
Click to expand...
Have you bricked-up between the joists?
For future reference - cavities are a great place to fit & forget the insulation. (y)
 
No. There is timber noggins between the joists at the edge. It's a small flat roof with 100mm x 47mm joists on top of a wooden wall plate .

There is no cavities as it's a solid wall with Kingspan k5 on the exterior.

I think I'm going to have to apply liquid membrane to make it all airtight (maybe not as rest of internal wall isn't meant to be airtight as k5 will make it airtight)
 
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b123b said:
There is no cavities as it's a solid wall with Kingspan k5 on the exterior.
Click to expand...
Yeah I got that. I'm saying that builders and designers choose a cavity construction because it's simpler in the long run to achieve modern standards.
 
Do I need foil tape or is it sufficient to foam the joists at the edges? I imagine it's a bit of a faff to foil tape all the way around each joist.
 
Does the type of foam matter ? There's such a bewildering choice ....
 
Hello

I am still unclear if I need to make the space between the roof and the brick wall airtight? Do I paint some kind of liquid VCL membrane on the joists on the inside in this space?
 
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