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Pre-design: Site & Context

Four pieces of site information drive almost every later design decision: climate zone, wind region, BAL, and soil classification. Nail these before you draw.

Overview

Before any framing, slab or cladding decision can be made, the site itself has to be characterised. The NCC and its referenced standards select different deemed-to-satisfy provisions depending on these four inputs. Getting them wrong means redesigning later.

01Climate Zone

Australia is divided into eight climate zones in NCC Schedule 1. The zone drives insulation R-values, glazing energy requirements, condensation management, and the NatHERS pathway under Section 13.

Find your zone via the ABCB climate zone map or NCC Schedule 3 (state appendices).
Canberra and the ACT sit in Zone 7 (cool temperate).
Zone affects: insulation, glazing, sealing, ventilation, condensation.

02Wind Region

Wind classification per AS 4055 (housing) or AS/NZS 1170.2 (engineered). Determines bracing, tie-down, roof fixing and cladding selection in Section 6 and 7.

Regions A, B, C, D — most of inland southern Australia is A.
Terrain category and topographic multiplier matter as much as region.
Output is a wind classification like N1–N6 or C1–C4.

03Bushfire Attack Level (BAL)

Assessed under AS 3959 for sites in designated bushfire-prone areas. Drives the construction requirements in Section 9 — windows, decking, cladding, subfloor and roof.

BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40, BAL-FZ (Flame Zone).
Most state planning portals will tell you if your site is in a bushfire-prone area.
BAL above 12.5 escalates costs significantly — flag early to client.

04Soil / Site Classification

Per AS 2870. A geotechnical report classifies the site, which sets the footing and slab design in Section 4.

Class A (stable rock/sand) → M (moderately reactive) → H1/H2 (highly reactive) → E (extreme) → P (problem site).
Reactive clay sites (H, E) need stiffened raft or piered footings — major cost driver.
Required before any footing design is signed off.

On-site Checklist to expand

Climate zone confirmed from official map
Wind classification documented (AS 4055 or AS 1170.2)
BAL assessment (if in bushfire-prone area) on file
Soil/site classification (AS 2870) from geotech report

Common Gotchas to expand

Assuming BAL-LOW without a formal assessment.
Missing the difference between wind region and wind classification.
Ordering the slab before the soil report is in hand.

Notes & Examples to fill in

Add worked examples, diagrams, photos and project-specific notes here as you accumulate them.