Bathroom stud wall gap from external no-fines wall

10 Dec 2023
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United Kingdom
Hey all,

Currently undertaking a complete bathroom renovation, stripping everything back and starting from the bottom up. It's an older wimpy no-fines house so the walls/structure isn't the typical brick or blockworks. The plan is to take down all of the plasterboard walls (the horrific honeycomb/paramount stuff) and replace in its place with a proper stud wall to allow running services through and a place for fixtures etc.

As the walls were removed I saw there was a 30-40mm gap between the external no-fines wall and the plasterboard (some pictures included to show the gap for context).

The main question is, when building out the stud wall, should this gap be maintained or can the gap be reduced to a few mm/practically up against the wall?

The house has got those external insulation cladding attached so the wall isn't directly exposed to the outside and my thought was that the gap was initially there to maintain an air gap insulation to go along with the other air insulation methods typical of these house builds (no fines wall and paramount plasterboards).
But since there's external insulation, assuming this would remove the need for the gap?

Bonus questions, if you're up for it:
- Would look to put insulation in between the stud walls, again should this insulation be pushed up against touching that external wall?
- The side of this wall will also be where the bathtub be installed and planning to use insulated tile backer boards for the walls plus tanking the joins, would any vapour barrier be needed for the walls or ceiling additionally?

Thanks in advance.


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