Why Use Concrete Masonry?

Concrete masonry has evolved into a functional and beautiful building material that gives designers the artistic flexibility to create strikingly beautiful single and multi-family residences, office buildings, warehouses, municipal buildings, manufacturing facilities, learning institutions, hospitals and much more. Concrete masonry is now the worldwide preference in terms of all masonry requirements. Travel to the U.S.A. or Australia, most of Europe, in fact just about anywhere except South Africa, and you will find concrete masonry to be more abundant than any other walling material. So what is different about South Africa? The answer is that although concrete masonry has been around since the 19th century, relatively speaking it is the "new kid on the block" in the South African market. Many specifiers and contractors adopt the "stick with what you know" attitude and continue to use the variety of older products available on the market instead of educating themselves as to the benefits available through the use of this more modern building material.

What Are The Benefits Of Concrete Masonry?

1.Dimensional Accuracy & Symmetry - concrete masonry is batch produced moulds and therefore the size can vary in only one plane, usually the height, as opposed to other products on the market that can vary in length, width and height. The SABS 1215 allows for a variation of +/- 3mm on the specified height. Concrete Masonry is also symmetrical, so the units are rectangular and not wedge-shaped or bent. No more "banana" bricks…

2.Consistency - because concrete masonry is batch produced, the quality of the units is consistent within a particular batch. There are no issues with some bricks being hard and brittle, others being soft and crumbly. All units are manufactured to the same high standard. It is also smooth and lends itself to fairface and bagged applications.

3.Versatility - concrete masonry is probably the most versatile masonry product available. It offers the designer a rich variety of dimensions, aspect ratios, textures, colours and profiles as the basis of wall design. There is an almost limitless palette of possible colours. It can be made almost totally waterproof. The size and shape of units available is only limited by having the correct mould. It can be made to have special textures. The units can be fluted or plain. The list of possibilities is almost endless.

4.Energy efficiency - concrete masonry is also naturally energy efficient, the secret being in its mass. The thermal mass of concrete slows down the passage of heat moving through a wall and allows the masonry structure to absorb heat instead of passing it through to the inside of the building, keeping the inside cool. As the wall is cooled by nightfall, the absorbed heat is released, gradually warming the inside. Likewise, this thermal barrier helps to keep a concrete masonry structure warmer in the winter months. This effect of ensuring that buildings stay warm in winter and cool in summer lessens the need for artificial climate control and therefore wasted energy. From manufacture to transport to construction, concrete masonry is modest in its energy needs and generous in its payback.

5.Modular system - another major architectural benefit of concrete masonry is the modular masonry design concept. The modular system of concrete masonry allows for efficient design co-ordination of sizes of building components, such as door and window frames. Units such as bricks and blocks are the dimensions which permit other components to fit into the space provided in a controlling reference system in a particular direction. Modular co-ordination enables components to be built on site without modification, as well as reducing the range of sizes required. Large savings arise from the ease of building in units which fit into the space provided without having to be cut or modified.

6.Thermal & Acoustic insulation - the thermal insulation properties are covered above under the heading Energy Efficiency. Concrete masonry is a highly suitable material for attenuating noise as it is an extremely dense material which reduces the transmission of airborne sound. Resistance to sound transmission will obviously increase with wall thickness. It is also important to remember that the acoustic performance of a building is related to the capacity of all the elements in the building to reflect, absorb or transmit sound.

7.Resistance to cracking - all masonry units of whatever type are subject to some degree of movement... Masonry derived from fired products such as clay tends to expand over time and concrete masonry tends to shrink over time. The degree of movement in a particular masonry unit is regulated by the SABS, and can be controlled to some degree through the use of control joints. Where concrete masonry has the advantage is that the contraction rates for concrete masonry and concrete are very similar. Since the foundations are concrete, the slabs are concrete, the reinforced walls or frame structures are concrete, the lintels and decks are concrete, not to mention the mortar and plaster covering the masonry, the use of concrete masonry will result in a harmonious relationship within the structure and help in eliminating the cracking problem so prevalent in today's buildings.

8.Fire resistant - concrete masonry is fire resistant. The SABS 0145 Tables 4 & 5 specify the fire resistance ratings for load bearing and non load bearing walls constructed from concrete masonry walls. Obviously the thicker the units the higher the fire resistance rating will be, with the exception being that solid units have a higher rating than hollow units. The class of mortar used will also impact on the fire rating as it is the performance of the wall that is important, not just the materials contained therein.

9.Weatherproof - concrete masonry can be manufactured almost totally waterproof with the addition of specialized admixtures. This is not usually necessary since quality concrete masonry is usually manufactured to a "low suction" tolerance due to its high density. Water penetration of a wall is usually through fine cracks at the interface between the masonry unit and the mortar, and only rarely through the masonry unit or the mortar. The greater the bond between mortar and masonry, the greater the resistance to leakage. The bond depends largely on the "waterproofness" of the brick and the water retention properties of the mortar (which can be improved through the addition of lime to the mix).

10.Availability in Winter - concrete masonry does not have to be baked, but cures naturally over time. The winter rainfall is a much lamented fact of building in the Western Cape, and often leads to a shortage of fired products. Concrete masonry is generally freely available throughout the year, allowing for shorter lead times and better stock control on site.

11.Cost Effective - when looked at from an overall perspective, concrete masonry is completely cost effective. When the initial cost of the masonry, the maintenance cost of the building, the cost of heating and cooling the building, as well as the final salvage value of the building are taken into account, concrete masonry is arguably one of the most effective materials used in construction.

 12.Compatibility - concrete masonry is highly compatible with cementitious products, including most paints and sealants.

 13.Durability - concrete masonry is a highly durable material, and is manufactured to resist local exposure conditions for the intended life of the building. Durability is generally related to compressive strength, which in turn is related to density. Surface protection such as paint and plaster adds tremendously to the durability of any walling material.

14.Environmentally friendly - the use of concrete masonry also benefits the environment and promotes sustainable building practice. Not only is concrete masonry fully recyclable, but leading manufacturers such as Cape Brick are using recycled crushed aggregate in the manufacture of their products. This has major advantages in terms of lessening environmental impact and gives rise to a truly green building product. Concrete masonry manufactured using RCA has possibly the lowest embodied energy of any masonry product available in the Western Cape today.

Myth versus Reality!

1.Concrete bricks cause cracking… MYTH - Cracking in buildings can be caused by a myriad of reasons. The use of uncured products, products with differential movement rates, incorrect mortar mixes, as well as normal settlement of the slab and foundations will all cause cracking. In fact, as has been mentioned above, concrete masonry actually has the advantage in that the contraction rates for concrete masonry and concrete are very similar. Since the foundations are concrete, the slabs are concrete, the reinforced walls or frame structures are concrete, the lintels and decks are concrete, not to mention the mortar and plaster covering the masonry, the use of concrete masonry will result in a harmonious relationship within the structure and help in eliminating the cracking problem so prevalent in today's buildings.

2.Concrete products allow moisture penetration… MYTH - Water penetration of a wall is usually through fine cracks at the interface between the masonry unit and the mortar, and only rarely through the masonry unit or the mortar. The greater the bond between mortar and masonry, the greater the resistance to leakage. The bond depends largely on the "waterproofness" of the brick and the water retention properties of the mortar (which can be improved through the addition of lime to the mix). Concrete masonry can be manufactured almost totally waterproof with the addition of specialized admixtures.

3.Buildings built with concrete products are cold… MYTH - This is a wide spread perception often caused by the fact that concrete masonry is gray (cold) and fired masonry products are red (warm). The truth could not be further misrepresented. Due to its density, concrete masonry has excellent thermal insulation properties. The thermal mass of concrete slows down the passage of heat moving through a wall and allows the masonry structure to absorb heat instead of passing it through to the inside of the building, keeping the inside cool. As the wall is cooled by nightfall, the absorbed heat is released, gradually warming the inside. Likewise, this thermal barrier helps to keep a concrete masonry structure warmer in the winter months.

4.Concrete bricks are only for low cost housing…MYTH - Concrete blocks have been a basic building material for hundreds of years, but those gray building blocks of yesteryear have evolved into a wide variety of sizes, shapes, colours and textures. Some of the finest residences and office buildings are built from concrete masonry.

For further information please contact Cape Brick. 

Tel: 021 690-2020