Choosing the building materials is an essential part of building a house – but how do you choose what material to build your walls out of? Here is a performance summary of Brickwork and Blockwork to help you decide if you want to build your next house using these Building materials.
Clay brickwork is available in a wide variety of natural colours and textures derived from fired clay used in combination with cement mortar joints of various colours and finishes. The colour of clay bricks is a direct consequence of the clay they are made from and the process of firing. Bricks remain stable and colour-fast and do not need to be rendered or painted. Clay brickwork is most commonly used uncoated to display the richness and texture of the material.
The colour of concrete bricks and blocks — light to medium grey — is a consequence of the cement used in their manufacture. Other colours from pigments added to the concrete mix are subject to changes from fading and weathering.
Clay and concrete bricks are manufactured under close controls to the requirements of AS/NZS 4455:1997, Masonry units and segmental pavers; AS/NZS 4456:2003, Masonry units and segmental pavers and flags — methods of test; and AS 3700-2001, Masonry structures. These provide the means for determining the strength of clay brickwork walls when subjected to horizontal loads resulting from wind, earthquake or fire.
Concrete blocks come in a variety of densities, and should be matched to the required application. High density blocks are generally made from cast concrete and aggregate, whereas lower density blocks may use fly ash or cinder.
The voids in hollow concrete blocks can accommodate reinforcement rods (a typical detail for retaining wall construction) or be filled with a variety of insulating materials to improve their thermal resistance.
Although traditional brickwork often included the use of partial or full arches, these forms are rarely used structurally in modern construction.
Toxicity and breathability
Similarly, concrete bricks and blocks are inert, do not give off volatile materials and are non-toxic once manufactured. The same provisions apply to safe handling of cement and cutting procedures.
Durability and moisture resistance
Although not completely waterproof, clay brickwork is extremely durable.
Although not completely waterproof, clay brickwork walls resist the penetration of rainwater, including wind-driven rain. Some moisture may eventually soak through the mortar joints. For this reason external brickwork is generally constructed with a space separating it from the internal leaf in the form of brick veneer or cavity walling.
Clay bricks can be subject to fretting where the surface of the brick progressively spalls off. This is caused by water migrating in the wall and transporting salt to the brick surface where it forms crystals that grow in voids in the brick and break off from the brick surface as they expand. Appropriate use of damp courses and good detailing to avoid moisture penetration and build-up can eliminate most of the risk of fretting.
Concrete bricks are designed to perform in a similar way to clay bricks and have a surface finish that resists the penetration of rainwater. As with clay bricks, general detailing and construction should seek to eliminate moisture penetration, typically with cavity walling.
Concrete blocks are porous and need to be treated, coated or covered to prevent moisture wicking through the material.
Detailing for brick and blockwork needs to incorporate:
• damp-proof courses
• weep holes.
Clay bricks can often be reclaimed for reuse when a building is demolished. After cleaning they can either be directly reused as bricks or crushed for making path and road surfaces. Because of their inert, inorganic nature, crushed clay bricks may also be used as part of the growing medium of extensive green roofs.
The use of fly ash in some concrete block manufacture replaces the energy-intensive material of cement with a waste product from power stations.
Buildability, availability and cost
Clay and concrete bricks are manufactured throughout Australia and are available at competitive prices. Even in remote areas, bricks and blocks can be supplied at moderate prices due to the wide availability of truck transport and back-loading opportunities. Consider transport energy costs for any long-distance movement of heavy material.
Brick veneer — the construction system of choice for most domestic builders — is one of the most economical ways of building in Australia.
The prevalence of brick veneer construction means that the availability of the materials and skills to build brick veneer is generally very good; it is the construction system of choice for most domestic builders and this contributes to it being one of the most economical ways of building in Australia. Lightweight framing is the main structural part of brick veneer construction. It is quick, uses no wet trades and allows roofs to be erected early in the building process.
Double brick or double masonry typically requires that the inside leaf (in an equivalent position to studwork in a lightweight frame structure) is structurally sound before roof framing can begin. Double brick construction thus takes longer than brick veneer.
Reverse brick and masonry veneer uses trades and techniques that are familiar to the domestic builders but arranged in a different configuration. The external, lightweight leaf requires waterproofing treatment and the building’s openings require slightly different detailing. As a result, reverse veneer is generally more expensive than conventional brick veneer and there may be some differences in the building program that slightly extend construction time.
Solid brick and blockwork walls are mostly used for internal walls and generally the only buildability issues arise from their connection with other components of the building and impacts that may have on the construction program.