Text 2. MASONRY

Definition of masonry, its main characteristics. Masonry is the building of structures from individual units laid in and bound together by mortar, and the term "masonry" can also refer to the units themselves. The common materials of masonry construction are brick, stone such as marble, granite, travertine, limestone; concrete block, glass block, and tile. Masonry is generally a highly durable form of construction. However, the materials used, the quality of the mortar and workmanship, and the pattern the units are assembled in can strongly affect the durability of the overall masonry construction.

Brick Laying. Bricks are laid flat in rows called courses, exposing either their sides (stretcher) or ends (header). The pattern of overlap created by the course is called a bond. There are several different kinds of bonds, including Stretcher (most common), Herringbone, English, Basket and Flemish. With all bonds, the vertical joints between each course of bricks must not line up or the structure will be weakened.

Bricks are usually held together by mortar. The mortar consists of sand, a binding agent (traditionally lime but these days more often cement) and water, which is then mixed to a thick paste. It is applied to a brick, which is then placed onto another brick and allowed to dry.

When building a structure, a bed of mortar is laid on top of the foundation, and the structure's ends are built up first. A string is then stretched between these ends to ensure each row of bricks stays level. Two layers of brick are used to create a stronger structure, with a gap left in between for insulation purposes.

A wide range of structures including arches can be built using bricks.

Advantages. The use of materials such as brick and stone can increase the thermal mass of the building, giving increased comfort in the heat of summer and the cold of winter and can be ideal for passive solar applications. So, masonry is very heat resistant and thus can provide good fire protection, too. In appearance, especially when well crafted, the construction has an impression of solidity and permanence.

Brick typically will not require painting and so can provide a structure with reduced life-cycle costs, although sealing appropriately will reduce potential spalling due to frost damage. Non-decorative concrete block generally is painted or stuccoed if exposed.

Disadvantages. Extreme weather may cause degradation of masonry wall surfaces due to frost damage. This type of damage is common with certain types of brick, though relatively rare with concrete block. If non-concrete (clay-based) brick is to be used, it should be suitable for the climate in question.

Masonry tends to be heavy and must be built upon a strong foundation (usually reinforced concrete) to avoid potential settling and cracking.

Differences in styles. The selection of the brick used, especially for color, will affect the appearance of the final surface. In buildings built during the 1970s, a high degree of uniformity of brick and accuracy in masonry was typical. In later periods this style was thought to be too sterile, so attempts were made to emulate older, rougher work. Some brick surfaces are made to look particularly rustic by including "burnt" bricks, which have a darker color or an irregular shape. Sometimes new bricks may be artificially aged by applying various surface treatments.

Stonemasonry. Stone blocks used in masonry can be "dressed" or "rough." Stone masonry using dressed stones is known as ashlar masonry, whereas masonry using irregularly shaped stones is known as rubble masonry. Both rubble and ashlar masonry can be laid in courses (rows of even height) through the careful selection or cutting of stones, but a great deal of stone masonry is uncoursed.