Stud wall centres. Residential vs Commercial

Sorry if in wrong forum but its for a bathroom so....
I'm building a stud wall in a large garage to section off a new bathroom and office space. My sister in law is designing the renovation and she is a very experienced retail architect having worked extensively in Europe and Australia. She is insisting that we can build the stud wall (not load bearing) with studs on 900mm centres (she says 918mm is her exact number she uses regularly). Australian 'code' for residential says 450 or 600 centres. We are not required to get a planning or building permit for this. Wall will be just under 2600mm high. She also says we can achieve good insulation qualities using 75x30 studs and that we don't need 90x35 which I was leaning towards. Garage will see minimum temps of about 1-2 deg C on the absolute coldest of winter nights.

Anyone have any thoughts on these dimensions? We will be doing all the work ourselves.

Code say max 600mm between centres. And I’d presume thicker walls allow better insulation. Why try and penny pinch on what will be a small extra cost. I’d probably use 90x35 at 450 centres for a bathroom to allow for any heavy cladding like tiles you or a future owner might install. Go 90x45 if you’d like the leeway it offers you putting sheet joints over studs or just making it easier to hit studs with fixings.

What wall sheeting is to be used and what does the installation guide for that sheeting advise ?

Thanks.i would definitely be adding more studs where needed but I do like the idea of 450 centres in the bathroom area for extra support.
I hadn't thought about the weight of the cladding .

Will ask her for the specs of the sheeting thanks too

Insulation batts come in specific sizes. You might want them to fit neatly.

Consider some brace board where you are likely to fit towel rails or even toilet roll holders. Makes a difference unless it is fully tiled.

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Originally Posted by Handyjack

Consider some brace board where you are likely to fit towel rails or even toilet roll holders. Makes a difference unless it is fully tiled.

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Thanks guys

This is a good heads up Hj

Watching Grand Designs [ UK version] those 900mm stud centres seem to be used with 120*45 studs and 16mm OSB exterior bracing, but for a non loadbearing wall inside an existing structure I don't think it makes much difference to structural integrity and the design requirements of the internal cladding is what is important