The pages behind this answer, jurisdiction by jurisdiction:
What stays inside a lot
Inside the boundary of the lot is the owner’s ground: Queensland puts a lot owner as responsible for the maintenance of most things inside the boundary of their lot.
In Victoria the duty reaches the outside of it: a lot owner must keep the exterior of their lot in good and serviceable repair.
On a New South Wales floor plan the boundary is the inner surface of a wall whose base corresponds substantially with a base line, and the upper surface of a floor and the under surface of a ceiling that join a vertical boundary of the lot, or the boundaries the floor plan describes.
For a townhouse on its own land: an ACT Class B unit has a footprint on the ground, such as a townhouse, where the boundary is defined by a surveyed line around the land.
A balcony and a courtyard
| Place | Whose surface it is | What the official pages say about its upkeep |
|---|---|---|
| The balcony on lot 8 | On a New South Wales floor plan the boundary is the inner surface of a wall whose base corresponds substantially with a base line, and the upper surface of a floor that joins a vertical boundary of the lot, or the boundaries the floor plan describes. | New South Wales says the owners corporation is usually responsible for these repairs: balconies and balcony doors (except in pre-1974 strata plans). |
| The courtyard of townhouse T2 | Inside the unit: under the ACT’s Class B rule the boundary of a townhouse is a surveyed line around the land. | A different jurisdiction, South Australia: a body corporate can require an owner to keep their property maintained whether or not they agree, or do the work itself and bill them. |
By-laws that mention a balcony or a courtyard
A by-law can reach a balcony or a courtyard: Tasmania’s by-laws cover the use and enjoyment of lots and the common property, and exclusive use of common property, such as a garden given to one lot.
In Queensland an exclusive use by-law must be recorded in the community management statement to have effect, and South Australia says a unit holder needs permission before altering the outward appearance of a unit, for example external awnings.
What a by-law cannot do: Queensland says a by-law that only allows owners and not tenants to use the common property pool may be discriminating between different types of occupiers.
In a South Australian community titles scheme, a by-law that cuts a lot’s value or unfairly singles out its owner can be struck out by a court order.
What a body corporate can require of an owner
South Australia puts the requirement first: a body corporate can require an owner to keep their property maintained whether or not they agree, or do the work itself and bill them.
Victoria runs a written process: if an owner fails to keep the exterior in good and serviceable repair, an owners corporation can order the owner, in writing, to carry out the repairs.
If the repairs are not carried out within 28 days in Victoria, the owners corporation can perform the work without the lot owner’s approval and charge the owner for the cost.
New South Wales has its own recovery route: if an owner fails to carry out work required by a public authority’s notice, the owners corporation may carry out the work and recover the cost from the owner.
Where the rest of the question is answered
The boundary those rules rest on, drawn one wall at a time: Where does my lot end and the common property begin? Where the cost of the work is shared: Who pays for cleaning the common areas?