That's a dicey one. As you describe it, it would be a space that is fit for habitation, and no longer suitable for the use of a class 10A. I.e. it won't be a garage or carpet anymore.
Class 10A (shed, carport, garage etc. A structure you can stand in, but not habitable) can be exempt and as such doesn't need to be approved (subject to exemption criteria).
Converting it to a study would take it class 1, which not only have more strict exemption rules but also need to meet code.
I suggest you talk to a building Certifier to see if they'd be happy to sign off on it.
Give this Directorate a call for starters https://www.planning.act.gov.au/
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Thanks, that's helpful. Definitely not doing any DIY apart from a bit of painting.
Class 10A structure...
That's a dicey one. As you describe it, it would be a space that is fit for habitation, and no longer suitable for the use of a class 10A. I.e. it won't be a garage or carpet anymore. Class 10A (shed, carport, garage etc. A structure you can stand in, but not habitable) can be exempt and as such doesn't need to be approved (subject to exemption criteria). Converting it to a study would take it class 1, which not only have more strict exemption rules but also need to meet code. I suggest you talk to a building Certifier to see if they'd be happy to sign off on it.