Does my roof cavity constitute a third leaf (photos)

tombarton

New member
I'm building my studio inside a shed structure. The original owner built an office space with framing and sheetrock inside the shed, as in this crude drawing (blue box = office/studio): studio 3.png

I'm wondering now, if the metal roof - above the space above the studio ceiling - will end up acting as a third leaf? Or more to the point, if it'll be detrimental.


Photo of space above office (sheetrock -> insulation -> yellowtongue wood boards):
studio 2.jpg.

The photo from the side shows one external wall of the office space, which is within the shed structure:
studio 1.jpg.


For isolation, I'll be hanging two greenglued layers of sheetrock from isolation clips, with standard fluffy insulation in the wall and ceiling cavities. Furthermore, I'll be adding mass to the extrnal walls/ceiling yellowtongue wood sheets with drywall in between stud spaces. The shed's external plywood walls will be removed, a sealed permeable vapour membrane added, and walls replaced with blueboard/cement sheeting.


My assumption is that the spacing between the wooden yellowtongue office ceiling and the metal roof is large enough not to act as an immediate third leaf (over 1.5 metres to the apex of metal roof above the current studio ceiling / wood top).

Thanks in advance for any advice!
 
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