Choosing the right brick

Brick durability

Clause 2.3.1 of AS 3700 Masonry structures defines the durability of bricks as follows: 

“A masonry member or structure shall withstand the expected wear and deterioration throughout its intended life, taking into account the exposure environment and importance of the structure, without the need for undue maintenance.”

It’s important to be aware that traditional face brickwork is generally subject to natural weathering, such as rain, sun, wind, wind-borne sea spray and pollutants. This weathering will attack and deteriorate the brickwork as part of general ‘wear ‘n’ tear’. The main agents of this deterioration are salts and acids (generally found in industrial air-borne wastes such as vehicle exhaust fumes).

Sulphate salts can have the most severe impact on a brick’s durability. Sulphate and chloride salts are soluble in water, which means wind and rain can carry these destructive elements to exposed brickwork.

These salts attack bricks and mortar and cause the deterioration of the materials over time. Moisture enters the brick and then evaporates, forming crystals (i.e. salt crystals) that are left behind in the brick’s surface pore spaces. If not treated, the crystals will continue to expand, exerting pressure in these pores, causing the bricks to fret or exfoliate and leading to general deterioration.

AS 3700 specifies that masonry materials must be sufficiently durable for the exposure classification of the site. Table 5.1 of the Standard gives examples of typical exposure conditions.

Categorisation of bricks and masonry

Australian Standard AS 4455 states that bricks/masonry may be classified according to their durability in three categories: exposure, general purpose, and protected.

Bricks may be classified into these categories based on the supplier’s experience and knowledge regarding the demonstrated product history of surviving in the environment to which it is to be exposed – i.e. ‘fit for purpose’. 

Of these categories, exposure class is determined by laboratory testing. Testing for ‘exposure’ is referred to in AS/NZS 4456.10 Masonry units and segmental pavers and flags – Methods of test – Determining resistance to salt attack.

Matching bricks to site conditions

It’s important  to always match brick classifications to site exposure conditions, particularly when those bricks are to be located near, or exposed to, harsh elements. It is advisable that you consult your brick manufacturer or supplier, who can advise you as to the suitability of their product for your specific site conditions.