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What Is a "Section"?

A section is one of the most important drawings in your DA — and the one full of unfamiliar height terms. Here's what each of them actually means.

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The short version

Imagine slicing straight down through your granny flat like cutting through a layer cake, then looking at that slice side-on. That's a section. Where a floor plan shows the layout looking down from above, and an elevation shows what the outside looks like from the front or side, a section shows the building's heights — how tall the floor slab is, how tall the walls are, how high the roof goes — all stacked on top of each other.

Every one of those heights has to be pinned to a fixed reference point so the numbers mean the same thing to everyone: your drafter, the certifier, and the Territory Planning Authority. That reference point is the Australian Height Datum (AHD) — a nationwide "sea level zero" that every height in Australia is measured against. Instead of just saying a wall is "2.4m tall" (tall compared to what?), a section states everything as a number of metres AHD, e.g. "finished floor level 582.10m AHD" — an exact, unambiguous height above mean sea level.

Who works this out? Your surveyor's detail survey provides the real AHD ground levels for your block, and your drafting team uses those to calculate and draw every other level on the section.

Reading a section

Building envelope (max height limit) Natural ground level (NGL) Finished ground level (FGL) Ceiling level Finished floor level (FFL) Australian Height Datum (AHD) — the fixed "zero" every level is measured from
AHD

Australian Height Datum

The fixed, nationwide "sea level zero" that all heights in the section are measured against — so a stated height means the same thing everywhere in Australia.

NGL

Natural ground level

How the ground actually sits right now, before any earthworks — the real, existing slope of your block as recorded by the surveyor.

FGL

Finished ground level

The ground level after any cut or fill reshapes it for the build — what the ground will look like once construction is complete.

FFL

Finished floor level

The height of the top surface of the floor slab or deck — where you'd actually stand inside the granny flat.

CEILING

Ceiling level

The height of the underside of the ceiling, measured the same way — sets the internal room height.

ENVELOPE

Building envelope

An invisible "box" in the sky defined by your zone's rules that the entire building must fit inside — the section proves the roof doesn't poke through it.

This is one of the core documents required for almost every granny flat DA. See the full DA Documentation Checklist for everything else you'll need.

Let your drafting team calculate the levels

Canberra Drafting manages our DA & BA paperwork end to end — call us and we'll walk you through exactly what your block needs.

Call: 0403 370 551