Stud wall in bathroom

[Sikes]

Hi

I have bathroom walls back to brick (solid no cavity). I'm planning to stud the bathroom walls out. I had planned to do option 1 below (image is if viewing from above). Ensuring an air gap to keep it dry. I've had a builder in for another job who says I'm over complicating it and could do option 2. No air gap with studs fixed to the wall, with the vapour barrier between the studs and the wall. What do others think? The squiggly lines are meant to be insulation

 

[worms]

What sort of insulation are you using? When I insulated my external bathroom wall (rubble construction rather than brick), I did more or less as your version #1, but that doesn't mean it was correct!

 

[Sikes]

What sort of insulation are you using? When I insulated my external bathroom wall (rubble construction rather than brick), I did more or less as your version #1, but that doesn't mean it was correct!

I was thinking of using wool batts. But budget may dictate otherwise. What did you use?

 

[worms]

I’m afraid I went for Kingspan and foil-backed bubble wrap, so no breathability. This piece of exterior wall was only a couple of metres wide, with good air movement along the back of the new studs and insulation, so it should hopefully stay dry.

In your case, there will be next to no permeability through the tile backer board and tiles, so I would think that you need that air gap behind the insulation. And if there is no air flow through the new internal lining, I struggle to see the advantage in going for the added expense of breathable insulation. You will get cold damp air at the foot of the exterior wall, so some form of exterior ventilation might be needed.