Masonry
- The term masonry can also refer to Freemasonry
Masonry is the building of structures from individual units laid in and bound together by mortar. 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 laid in can strongly affect the durability of the overall masonry construction.
Applications
Masonry is commonly used for the walls of buildings, foundations, and monuments. Brick masonry is the most common type of masonry, and may be either solid or veneered. Concrete block masonry is rapidly gaining ground in popularity as a comparable material. Hollow-core block masonry offers various possibilities in masonry construction, generally providing great compressive strength, and is generally best suited to structures with light transverse loading when the cores remain unfilled. Filling some or all of the cores with concrete and steel reinforcement (typically "rebars") offers much greater tensile and lateral strength to structures.
Advantages
- The use of materials such as brick and stone can increase the thermal mass of a building, giving increased comfort in the heat of summer and the cold of winter and can be ideal for passive solar applications.
- Brick masonry will typically 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. Concrete block of the non-decorative variety generally is painted or stuccoed if exposed.
- The appearance, especially when well crafted, can impart an impression of solidity and permanance.
Disadvantages
- Extreme weather may cause degradation of the surface 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, care should be taken to select bricks suitable for the climate in question.
- Masonry must be built upon a firm foundation (usually reinforced concrete) to avoid settling and potentially cracking. If expansive soils (such as adobe clay) are present, this foundation may need to be quite elaborate and the services of a qualified structural engineer may be required.
- The high weight increases structural requirements, especially in earthquake prone areas.
Veneer masonry
Brick veneer construction has strength imparted by a framework of wood or a rough masonry wall of other material over which is placed a layer of bricks for weatherproofing and providing a finished appearance. The brick veneer wall is connected to the structural walls by "brick ties", metal strips that are attached to the structural wall as well as the mortar joints of the brick veneer wall. There is typically an air gap between the brick veneer wall and the structural wall. As clay-based brick is not completely waterproof, the structural wall has a waterproof surface (usually tar paper) and weep holes are left at the base of the brick veneer wall to ventilate the air gap. Veneered walls are often structurally superior to solid un-reinforced brick walls because the core can be constructed of steel reinforced block or poured reinforced concrete. Block may also offer opportunities to run utilities within the wall if some block cores can be left unfilled for this purpose.
Most insulated buildings that make use of concrete blocks, bricks, brick veneers, or some combination thereof feature interior insulation in the form of fiberglass batts between wooden wall studs, or rigid insulation boards covered with plaster or drywall. In most climates this insulation is much more effective on the exterior of the wall, allowing the building interior to take advantage of the aforementioned thermal mass of the masonry. This technique does however require some sort of weatherproof exterior surface over the insulation and is consequently generally more expensive.
Solid masonry
Solid masonry, without steel reinforcement, tends to have very limited applications in modern wall construction. While such walls can be quite economical and suitable in ALL applications, susceptibility to earthquakes and collapse is never a major issue. Solid unreinforced masonry walls tend to be low and thick as a consequence.
Brick
Solid brick masonry is made of two or more layers of bricks with the bricks running longitudinally (called "stretcher" bricks) bound together with bricks running transverse to the wall (called "header" bricks). Each row of bricks is known as a "course." The pattern of headers and stretchers employed gives rise to different bonds such as the common bond (with every sixth course composed of headers), the English bond, and the Flemish bond (with alternating stretcher and header bricks present on every course). There are no significant utilitarian differences between most bonds, but the appearance of the finished wall is affected. Vertically staggered bonds tend to be somewhat stronger and less prone to major cracking than a non-staggered bond.
Uniformity and rusticity
The selection of the brick used, especially for color, will effect the appearance of the final surface. In buildings built during the 1970's, 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. Others may use antique salvage bricks, or new bricks may be artificially aged by applying various surface treatments.
Artistic stylization
The attempts at rusticity of the late 20th century have been carried forward by masons specializing in a free, artistic style, where the courses are intentionally not straight, instead weaving to form more organic impressions.
Concrete block
Blocks of cinder concrete ("cinder blocks" or "breezeblocks"), ordinary concrete ("concrete blocks"), or hollow tile are generically known as "building blocks." They are usually much larger than ordinary bricks and so are much faster to lay for a wall of a given size. Furthermore, cinder and tile blocks have much lower water absorption than brick masonry. They are often used as the structural core for veneered brick masonry, or are used alone for the walls of factories, garages, and other "industrial" buildings where appearance is not a significant factor. Such blocks often receive a stucco surface for decoration. Surface-bonding cement is sometimes used in this application and can impart extra strength to a block wall.
Some concrete blocks are colored, and some employ a "break face", which allows the reproduction of an appearance similar to quarried stone, such as brownstone. For applications such as roadway sound control walls the patterns may be complex and even artistic.
Stone
Stone blocks used in masonry can be "dressed" or "rough." Stone masonry utilizing 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.
Sometimes "river rock" (ovate shaped smooth stones) is used as a veneer. This type of material is not favored for solid masonry as it requires a great amount of mortar and can lack intrinsic structural strength.
Structural limitations
Masonry is strong in compression (vertical loads), but is relatively weak when subject to tension or sideways loads, unless reinforced. Walls are often strengthened against sideways loads by thickening the entire wall, or by building masonry piers (vertical columns or ribs) at intervals. Where practical steel-reinforcement can also be introduced vertically and/or horizontally to greatly increase tensile strength.
Dry set masonry
The strength of a masonry wall is not entirely dependent on the bond between the building material and the mortar; the friction between the interlocking blocks of masonry is often strong enough to provide a great deal of strength on its own. The blocks sometimes have grooves or other surface features added to enhance this interlocking, and some dry set masonry structures forego mortar altogether.
Rocks
Stone masonry without the use of mortar was common in early civilizations, was frequently used for farmstead boundaries where rocks must be cleared from fields, and is sometimes seen today in primitive trail bulkheads and stream crossings. Owing to its poor performance in earthquakes, it is not used in modern buildings, although with careful use of mortar and stone selection its appearance may be emulated, especially when used as a veneer.
Gabions
Gabions are rectangular wire baskets, usually of zinc protected steel that are filled with fractured stone of medium size. These will act a single unit and are stacked with set-backs to form a revetment or retaining wall. They have the advantage of being both well drained and flexible, and so resistant to flood, water flow from above, frost damage, and soil flow. There expected useful life is only as long as the wire they are composed of and if used in severe climates (such as shore-side in a salt water environment) must be made of appropriate corrosion-resistant wire.
Bagged concrete
A low grade concrete may be placed in woven plastic sacks similar to that used for sandbags and then emplaced. The sacks are then watered and the emplacement then becomes a series of artificial stones that conform to one another and to adjacent soil and structures. This conformation makes them resistant to displacement. The sack becomes non-functional and eventually disintegrates. This type of masonry is frequently used to protect the entrances and exits of water conduits where a road passes over a stream or dry wash. It is also used to protect stream banks from erosion, especially where a road passes close by.
Serpentine masonry
A crinkle-crankle wall is a brick wall that follows a serpentine path, rather than a straight line. This type of wall is more resistant to toppling than a straight wall; so much so that it may be made of a single thickness of unreinforced brick and so despite its longer length may be more economical than a straight wall.