Many ordinary Kenyan prefer brick built houses because of their relatively low prices and durability. However the processing of manufacturing bricks -whether manual or automated -is an expensive affair in the sense that it is time consuming and is likely to test the patient of anyone.
In Kenya, the process is largely a manual. However there are a few clay works companies with highly automated and controlled bricks manufacturing operations.Between this two extremes are entities that making interlocking bricks using semi-automated machines sold under Makiga brand name.
Bricks are made by molding wet or moist clay into desired shapes and then left in an open sheltered space to dry for a few days. The green bricks normally reduce in size during this drying process. Once dry, the bricks are subjected to a firing process. The firing temperature is set high (between 940° C to 1200° C)to vitrify the clay or change it into glass like material that is durable and maintenance free.
Generally speaking bricks can be grey, yellow, blue, red, and black in color. This color depends on type of clay used, firing conditions and whether the clay went through artificial pigment addition process. For example higher temperatures and low oxygen in the Kiln will produce blue bricks. On the slip side High temperature and high oxygen will produce red bricks. The explanation is simple-there is enough oxygen in the kiln to work on iron oxide in clay which changes it to a red color.
The standard bricks sizes are (a) 6 inches by 6 inches by 12 inches, (b) 5 inches by 6 inches by 12 inches and (c) 4 inches by 6 inches by 12 inches. These brick sizes weighs between 2 and 4 kg, can easily held by hand and sell at between Kshs 6/ and Kshs 12/.
There are five type of bricks, namely
- Common bricks-These are used for general building work
- Facing bricks-These are given a finishing that make them look extra appealing than common bricks. The surface of these bricks maybe given a designed rough texture, sand faced or smoothened.
- Engineering bricks-they are dense with high load bearing capacity and low water absorption. They are more expensive because they require very high firing temperatures.
- Standard special bricks-This bricks are designed into special shapes to improve the quality of building works. Examples are bullnose and radial bricks.
- Concrete bricks-Manufactured from a mixture of cement, sand and iron oxide pigments under high pressure in steel moulds. They harden and increase in strength with age.
When using brick on a construction project the following points should be borne in mind
- Bricks absorb irreversibly moisture from the air after firing and as result may balloon in size slightly. It’s advisable then, that you should not use bricks within two weeks after firing.
- Common bricks absorb water. You are well advised again not to use them in damp, soggy grounds or for damp courses. Instead use building stone or concrete blocks for the foundation and then revert to your bricks for constructing the wall above the ground.
- Mortar used as a sealant between bricks in courses should be weaker than the individual bricks. This is to prevent cracking of bricks in the event of slight movement of the building.
Common uses of bricks and price
Bricks are excellent materials for constructing foundation and walling of buildings. Also they are used as cladding material to give building an appealing brickwork finish. Lastly they are also used to create brick pavements and sidewalks around buildings.
In Kenya, the prices you are likely to pay for bricks will depend on demand and supply conditions, brick size and the location of the supplier. This price will range between Ksh.6/ and Ksh.12/per piece. Comparing this price with that of building stones or Concrete blocks, its obvious bricks relatively cheaper.
Sources:Materials for Architects and Builders by Arthur Lyons PhD.