Several other shapes are also available for specialty applications, such as bullnose blocks with one rounded end, jamb blocks which have an indentation where window and door jambs fit, partition blocks used to make interior partition walls, and lintel blocks used to make window and door headers. There are also architectural masonry units , which have textured faces designed for decorative use.
Characteristics of Load Bearing Masonry Construction - distworkdiscnachtla.ga
Virtually all walls built with CMUs share the same elements, although the application of those elements can vary considerably depending on the size, shape, and use of the wall. Most concrete block walls are single-wythe walls, which means they are constructed from single-wide rows of block stacked one over the other. Where greater structural strength is required, you can construct double-wythe walls , in which two courses of blocks are laid together.
The first step in building a concrete block wall is to lay out the foundation using stakes and masonry string. For a freestanding landscape wall, this involves creating a simple rectangular outline of the planned foundation. For building foundations, the layout requires a rectangular outline of the entire building, carefully adjusted to be perfectly square. After leveling the layout strings with a line level, transfer the location of the foundation onto the ground before beginning excavation.
Dangers from masonry walls on construction or demolition sites safety alert
The next step is to excavate earth for the foundation. The work involved here can vary considerably, depending on the required size of the foundation and the circumstances. If you are building a small landscape wall in a warm-weather climate, this can involve simple hand-digging with a shovel. For a building foundation or in a cold-weather climate requiring deep frost footings, excavation can be a major undertaking requiring earth-moving equipment. Either way, the goal is to create a flat-bottom trench to pour a concrete foundation for supporting the cement block wall.
Make sure to consult local authorities on the required depth and size of the foundation for the cement block wall you are planning. Any wall higher than 2 feet requires a frost footing that extends 8 to 12 inches below the deepest winter frost level in your region. Generally, the foundation should be twice as wide as the wall itself. The concrete foundation needed to support a cement block wall is usually created by pouring concrete into a hollow form lining the sides of the excavation trench, but the concrete can also simply be poured into the trench—a common scenario for construction of a freestanding landscape wall.
In this case, the top of the excavation is sometimes boxed with lumber to create a finished appearance. It is common for the top of the foundation to be kept slightly below grade, so that the foundation will be hidden when the wall is finished. Concrete for the foundation can be mixed by hand in a power mixer or mortar box, or it can be ordered from ready-mix sources and delivered by truck.
The top of the poured foundation should be perfectly level, but it does not need to be floated and troweled to a perfectly smooth finish. Make sure the foundation is fully hardened and cured before beginning construction of the wall. After the poured foundation has fully cured and hardened, mark an outline for the cement block wall onto the surface of the foundation, using a chalk line. Mix the appropriate mortar in a mortar box, then lay a 1-inch thick layer of mortar onto the foundation inside the outline.
Position the first course of cement block into the mortar and tap the blocks downward slightly to embed them in the foundation mortar. Begin the wall with a corner unit, then "butter" the flanges at the end of each subsequent block with mortar before joining it to the previous block.
This provides an optimal amount of strength. As you work down the first course, use a level to adjust the blocks so they are perfectly vertical, and use stakes and strings to ensure that the row of blocks remains perfectly straight. At the opposite end of the wall, end the course with another corner unit. Resources to the following titles can be found at www. For Instructors Request Inspection Copy. We provide complimentary e-inspection copies of primary textbooks to instructors considering our books for course adoption. Most VitalSource eBooks are available in a reflowable EPUB format which allows you to resize text to suit you and enables other accessibility features.
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The correct type and proportion of ingredients and the proper application of mortar are essential for the structural integrity of a block or brick wall. Mortar serves many functions:. It bonds the masonry units together. It assists in retaining a level wall, using the mortar bed as compensation for the small dimensional differences between one brick or block and another. It bonds installed wall reinforcement together into one structural unit. By varying the color of the mortar or the type of tooled joints, mortar provides an additional aesthetic appeal.
Figure shows a cross section of typical mortar joints in masonry walls.
Cross section of mortar joints in a masonry wall. Mortar is a mixture of cement, sand, and water, mixed to the consistency of a heavy paste.
This workability or plasticity of mortar provides both cohesive and adhesive properties. There are five basic type of mortar, each applicable to specific functions of the masonry wall:. Type M mortar is a high-compressive-strength mix providing greater durability, generally used on unreinforced masonry walls below grade. Type S mortar is also a high-strength mortar with slightly less compressive strength than Type M.
It has greater tensile strength and is the product of choice when reinforced masonry walls above grade are built. Type N mortar is a midrange compressive-strength product often used on interior non-load-bearing masonry walls.
TYPES OF WALLS
Type O mortar has lower compressive strength than Type N and is also used for interior non-load-bearing walls. Type K mortar has the lowest compressive strength and can be used for some non-load-bearing walls if local building codes allow.
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Mortar is similar to concrete and shares two basic components: cement and water. Like concrete, the rapid dissipation of water in hot weather and the freezing of water in cold weather must be avoided to provide a high-quality masonry wall. Most load-bearing walls above grade require reinforcement to provide the flexural strength required, as these masonry walls expand and contract due to temperature changes, loads imposed by strong winds, and the weight of the wall itself. Reinforcement also provides stability of CMU walls during seismic events.
Cavity wall construction often consists of a brick outer wall, an air space, and a structural inner wall of steel or wood studs faced with gypsum board.
These two wall types must be joined together to provide structural integrity and steel wall reinforcement. Reinforcements can be truss and ladur types or wall ties that tie the outer wall to the inner wall. Sections of masonry walls are known as wythes; a single wythe is one masonry wall thick, and a double-wythe wall consists of one outer and one inner wall, often of different masonry types: one brick outer and one CMU inner.
Mohiuddin Ali Khan Ph. London , in Earthquake-Resistant Structures , The devastating Long Beach earthquake in revealed that masonry construction was dangerously seismically inadequate. The California State Code made reinforced masonry mandatory. The Field Act introduced after the earthquake in banned unreinforced masonry construction. To achieve ductile behavior in masonry, it is necessary that the shear strength of the wall be greater than the tensile strength of the reinforcement so that the wall does not fail in shear first and to ensure a kind of bending failure by yielding of reinforcement.
Structural details are fundamental aspects in the mechanical response of masonry constructions. For example, the toothing between perpendicular walls, the junction with horizontal diaphragms, the interaction with adjacent buildings, etc. Often, the structural details are the results of the complex historical evolution of buildings, which may have altered the original configuration due to restorations, addition of parts, destination changes, damages and repairs, etc.
Structural details are, therefore, the result of a subsequent superimposition of modifications along with the centuries and their knowledge could be particularly complicated for historic structures. To improve the knowledge phase in masonry buildings, beyond the standards and guidelines Guide for the structural, ; Direttiva del Presidente, , recent scientific proposals have been developed Cattari et al. Dennis P. When fire pumps are provided in buildings, they should be of masonry construction with noncombustible roofs.