What Is an "Area Plan"?

The short version

Site coverage is simply: how much of your block is covered by a roof, shown as a percentage. If your block is 700m² and your house plus granny flat together cover 280m² of it, your site coverage is 40%. Every zone has a maximum — go over it and the DA won't be approved as a simple proposal.

Gross floor area (GFA) is different — it's the total enclosed floor space inside the building(s), measured to the outside face of the external walls. A granny flat's GFA also has its own cap (90m² in most residential zones), separate from the site coverage limit.

The tricky part is that not every roofed square metre counts the same way toward these two numbers. An open-sided carport, for example, might count toward site coverage (it has a roof) but not toward GFA (it isn't enclosed living space). Eaves overhanging the walls usually count toward neither. So the area plan uses hatching — a diagonal-line shading pattern — to visually mark exactly which parts of the drawing are included in each calculation and which are excluded, so the assessor doesn't have to guess.