Bricks

A brick is a block of ceramic material used in masonry construction, usually laid using mortar. The oldest shaped bricks found date back to 7,500 B.C. They have been found in Çayönü, in the upper Tigris region, and in south east Anatolia close to Diyarbakir. Other more recent findings, dated between 7,000 and 6,395 B.C., come from Jericho and Catal Hüyük. From archaeological evidence, the inven­tion of the fired brick (as opposed to the consid­erably earlier sun-dried mud brick) is believed to have arisen in about the third millennium BC in the Middle East. Being much more resistant to cold and moist weather conditions, brick enabled the construction of permanent buildings in regions where the harsher climate precluded the use of mud bricks. Bricks have the added warmth benefit of storing heat energy from the sun during the day and continuing to release heat after sunset.

The soft mud method is the most common, as it is the most economical. It starts with the raw clay, preferably in a mix with 25-30% sand to reduce shrinkage. The clay is first ground and mixed with water to the desired consistency. The clay is then pressed into steel moulds with a hydraulic press. The shaped clay is then fired ("burned") at 900-1000 °C to achieve strength.

With extruded bricks the clay is mixed with 10-15% water (stiff extrusion) or 20-25% water (soft extrusion). This is forced through a die to create a long cable of material of the proper width and depth. This is then cut into bricks of the desired length by a wall of wires. Most structural bricks are made by this method, as hard dense bricks result, and holes or other perforations can be produced by the die. The introduction of holes reduces the needed volume of clay through the whole process, with the consequent reduction in cost. The bricks are lighter and easier to handle, and have thermal properties different from solid bricks. The cut bricks are hardened by drying for between 20 and 40 hours at 50-150 °C before being fired. The heat for drying is often waste heat from the kiln.

The thickness of brickwork is casually quantified in units of brick referring to the length of a brick. A double-skinned wall will have some bricks laid across both skins or courses and therefore the wall will be as thick as the length of the brick. Because most typical bricks are roughly twice as long as the are wide, a single-skinned (or single course) wall with bricks laid end to end will be as thick as the brick is wide, which is roughly half the length of the brick; it is called "half brick" thick. Simply put, single-skinned walls are expediently or casually referred to as "half brick" thick and double-skinned walls "full brick" thick even though technically this is only an approximation relevant to bricks roughly half as wide as they are long.