Insulation Required - Mansard loft conversion

[JohnMarsden]

Hi - I haven't found this answer searching the forums and I'm therefore wondering if it's a stupid question.

 

We are having a loft conversion done. Part of the new roof is mansard.

 

Does the mansard wall count as a wall or a roof for insulation purposes?

 

Edit: I should say, the loft conversion has mansard 'walls' leading up to a flat roof. 

Edited August 23, 2024 by JohnMarsden
Clarification

[Dave Jones]

is the outside covering tiles or brick ?

[Redbeard]

Not quite an answer to your Q but I always try to achieve more-or-less the same U value for all elements of rooms-in-roofs, so never mind that stud *walls* only need 0.3. I look to achieve 0.16 or less over the entire envelope (apart from the windows which are not very see-through at 0.16!)

[JohnMarsden]

2 hours ago, Dave Jones said:

is the outside covering tiles or brick ?

 

Slate tiles

[Dave Jones]

1 hour ago, JohnMarsden said:

 

Slate tiles

 

think BCO would treat that as roof.

[Mike]

From memory, it's treated as a wall if >70°, as a roof if <70°. But do verify that - I may be wrong / it may have changed.

[DevilDamo]

5 hours ago, Dave Jones said:

is the outside covering tiles or brick ?

Why does that make a difference? A slate or tile hung dormer is a wall and that’s not brick.

 

@JohnMarsden It would be treated as a wall.

[JohnMarsden]

18 hours ago, DevilDamo said:

Why does that make a difference? A slate or tile hung dormer is a wall and that’s not brick.

 

@JohnMarsden It would be treated as a wall.

Thanks!

 

For anyone in the same position, the legislation is here:

 

 

It is also reflected in the fire regs - essentially, the definition of what constitutes an "external wall" is quite clear now.

 

cheers