Exposure grade (brick)
Exposure grade (Exp) is the highest brick durability under AS/NZS 4455.1. Required within ~1 km of coast, below DPC, in saline soils. Salt-attack tested.
Ask Chalkline about this →Exposure grade (Exp) is the highest durability classification for clay and concrete masonry units under AS/NZS 4455.1. It is the rating required wherever masonry will be exposed to severe weather, salt, or aggressive ground conditions. Below Exp on the scale sit General Purpose (GP) and Protected (P), each suited to less aggressive exposure.
The three brick durability grades under AS/NZS 4455.1:
| Grade | Where to use |
|---|---|
| Exposure (Exp) | Within ~1 km of a marine environment, below DPC level, in saline or aggressive soils, retaining walls in contact with ground, freestanding walls in exposed locations, paving in coastal areas. |
| General Purpose (GP) | Above-ground veneer or solid masonry in most inland and protected urban locations. The residential workhorse grade. |
| Protected (P) | Internal walls only. Must never see weather, ground contact, or moisture. |
The test that distinguishes Exp. AS/NZS 4456.10 (Method 10: Determining resistance to salt attack) is the laboratory test that qualifies a unit as Exp. The test cycles the brick through brine immersion and drying; the number of cycles before deterioration sets the grade. Exp passes more cycles than GP.
Why this matters for builders. Three failure modes from wrong-grade selection:
- Coastal spalling. GP brick used within ~1 km of the surf line: salt-attack-driven face spalling appears within 2 to 8 years. The face delaminates in flakes, exposing the soft core. Rectification is full removal and replacement.
- Below-DPC dampness. GP brick used below the damp-proof course in a wet site: rising damp dissolves and migrates salt from the soil into the brick face, causing efflorescence then spalling. Worsens until the brick fails.
- Retaining-wall failure. GP brick used in a soil-contact retaining wall: aggressive sulfate or chloride attack on the bedding mortar causes the unit-mortar bond to fail. Wall lean and collapse over 5 to 15 years.
Where Exp is mandatory:
- Below DPC in any external masonry wall.
- Within approximately 1 km of the surf coast (the precise distance is a design call by the engineer or BAL-style assessor).
- In aggressive soil classified by the geotech (acid sulfate, saline, marine-derived fill).
- Below ground level in any retaining application.
- In paving subject to salt (de-icing salt is rare in Australia but coastal spray paving is common).
For builders. Specification of brick grade sits with the structural engineer or architect for the relevant location. The builder checks the delivery docket against the spec at unloading: Exp grade is stamped on the strapping and listed on the manufacturer technical data sheet. A mixed delivery (some Exp, some GP, same look) is a common defect; sight every pallet docket before the bricks come off the truck.
Also known as: Exp grade, exposure-grade masonry unit, salt-attack-resistant brick.
Category: Materials / masonry / durability.
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Last updated: 2026-05-14. Verified: 2026-05-14.