Architectural concrete unit masonry deserves special attention. Not only must it provide the stability and support of a normal concrete unit, but it also must also act as a design enhancement and a pleasant, eye-catching attraction. Architectural concrete unit masonry and concrete unit masonry have many similarities.

Architectural concrete unit masonry’s flagship unit is the architectural concrete block. This block is usually exposed to view, and thus, special emphasis is often put on its aesthetic and design qualities. It must provide the same qualities and strength that concrete block provides. Because the properties between architectural block and concrete block are essentially identical, aside from the design aspect of architectural block, many of the same types of blocks, such as insulated or sound-proofing can be utilized as architectural blocks.

Though it will vary slightly depending on the intended use, there are some core materials that are almost always used to form architectural concrete blocks. These include Portland cement, sand, water, and coarse aggregate. Other materials can be added to create desired effects, for example, color pigments for aesthetic properties. Glazed concrete blocks are a popular option for architectural concrete masonry. They are usually smooth and shiny in appearance, providing a pleasant effect. Also, as architectural concrete units are often in the public view and open to vandalism, these blocks are effective as they are highly water resistant and combat bacteria, chemicals, and graffiti well.

Even more so than concrete blocks, architectural concrete blocks are of concern in relation to the environment and outside forces, since they are often exposed. Concrete blocks themselves usually withstand outside forces well, but additional steps can be taken to enhance their abilities. These additional steps include adding flashings to protect from moisture penetration, and using types such as Glazed block which are usually somewhat resistant to bacteria and chemicals. As with nearly all masonry projects, special consideration should be taken with Hot and Cold conditions. Fire ratings for architectural concrete block can be calculated in a number of ways, including an online tool.

The most common size is 8″ x 8″ x 16″, similar in size to concrete unit masonry. An example of an enhancement is that of added cuts in sound or acoustic block, which act to absorb sound. Further details and designs for acoustic styles can be found on some manufacturer’s websites.

Project scopes and details with concrete block can vary from large projects such as structural units, to smaller tasks such as block retaining walls. Laying brick and laying concrete blocks is very similar, as the core ingredients are both a masonry unit and mortar. In some projects, however, like smaller retaining walls, railroad stakes or ties can be used to hold the unit together, in place of mortar.

With a wide range of applications, architectural concrete block can be used in a nearly limitless amount of ways. From arches, to fireplaces, to retaining walls, to exposed structural units, architectural concrete block is a popular option that adds design and style. Generally, any installation procedures that mention concrete blocks can also be applied to the installation of architectural concrete blocks. Overall, general instructions are available for an array of projects. Detailed installation instructions are available for projects like retaining walls and larger, structural walls.

Moisture penetration is always a concern with masonry. With architectural concrete blocks, however, it is a magnified concern as these units are exposed to the weather, and thus, moisture. Water proofing, or sealing, is recommended for these types of masonry units. Some blocks come with special repellents already applied to fight moisture. Other measures, however, can be taken, including adding flashings to prevent moisture from entering.

• Stretchers – The most common type used in laying walls. They are usually two-celled (or cored), and flat on their exposed face.
• Corner Blocks or Bull-Nose Blocks – A special type of stretcher, used to form corners. The bull-nose shape of the block allows it to have a rounded corner.
• Jamb Block – Used to form door or window opening areas. They are often grooved in order to fit with the edge of doors or window bucks.
• Partition Blocks – These are usually thin, sometimes less than half the normal thickness of a concrete block. They are non-load bearing, and are utilized for laying single-width partitions within a building.
• Beam Blocks or Lintel Blocks – These blocks are used at the top of an opening, and form a support beam overhead.
• Sound Blocks or Acoustic Blocks – Specifically made to act as sound-proofers by having specially designed cuts to enhance their acoustic abilities.
• Column Blocks or Flue Blocks – These blocks are hollow and are frequently used to lay columns.
• Insulated Block – Blocks made with additional thermal insulating properties, aided by polystyrene inserts.
• Glazed Block – These generally only stand apart for their aesthetic properties, as they can be colored or textured to add a design effect.
• Paving Block – Paving block is a special block commonly used for patios, walks, and driveways. It is solid, flat, and usually interlocking for ease and stability.

Though it will vary slightly depending on the intended use, there are some core materials which are almost always used to form concrete blocks. These include Portland cement, sand, water, and coarse aggregate. Other materials can be added to create desired effects such as color pigments for aesthetic properties. There are small differences in materials used to differentiate between light weight and normal or dense concrete blocks. Lightweight units will favor shale, slate, clay and ash, while the dense blocks more often will utilize stone, sand, and gravel.

Designs will vary somewhat, depending on the concrete block type. The most common size is 8″ x 8″ x 16″, though half block or solid blocks are usually sized at 8″ x 4″ x 16″. Specific design patterns are usually not applied, unless the block is to be seen in a public location. In this case, glazed block offers options for color and texture enhancements. One other example of an enhancement is that of added cuts in sound or acoustic block, which act to absorb sound.

Project scopes and details with concrete block can vary from large projects such as structural units, to smaller tasks such as block retaining walls. Laying brick and laying concrete blocks is very similar, as the core ingredients are both a masonry unit and mortar. In some projects, however, like smaller retaining walls, railroad stakes or ties can be used in place of mortar to hold the unit together.

With a wide range of applications, installations vary from project to project. Overall, general instructions are available for an array of projects. Detailed installation instructions are available for projects like retaining walls and larger, structural walls.

On the outside, ICMUs are composed of nearly identical materials as are conventional concrete blocks. Sand, gravel and Portland cement make up their composition. A layer of insulation within the block structure provides the means for high levels of energy efficiency. This “building within a building” creates interior walls with high insulated thermal mass, which absorb and store large amounts of energy. This increased heat capacity of the walls delivers unparalleled HVAC energy efficiency. As a result of the high thermal mass, or heat capacity, the effects of temperature variations and swings are lessened or delayed, resulting in an R-22 value of the block and less demand on HVAC systems. The most striking feature of the product is that it has no webs or connections between the faces. Even though the unit is webless, it has the cavities found in the conventional CMU that allow it to accept rebar, concrete, conduit and pluming that run through a standard brick wall. The blocks are also “finished” on the inside, eliminating the need for drywall and/or paint for the interior finish and making them less expensive and more environmentally friendly.

ICMUs are designed to have the outer appearance of traditional masonry units. On the exterior level, ICMUs are available in all masonry veneer finishes – brick, stone, etc. They can also be customized to fit the project needs for color and texture as well.

Insulated concrete masonry units were pioneered by NRG and are manufactured by A. Duchini, Inc. (insert link to sales sheet). NRG block allows for the installation of smaller HVAC units resulting in immediate savings and provides typical HVAC energy savings of over 60 percent, compared to same-size, common block buildings.

• Radiant – Radiant fireplaces heat by the emission of infra-red radiation. The fire heats the fireplace, which in turns heats the surrounding area through infra-red radiation. A typical design picture is available.
• Air Circulation – Air-circulation fireplaces work by heating the air that crosses the hot surface of the fire. This warm air then rises and, in doing so, attracts more air up behind it, creating a circulation effect. This method is achieved through the use of panels or ducts that are built into the fireplace. These ducts attract air from the area, and circulate it around a metal firebox, warming it. This warm air is then released into the area. Air-circulating fireplaces warm quickly and cool down even quicker.
• Metal Insert – Metal-insert fireplaces are relatively new and are installed in many newly built homes. Metal fireboxes are placed in the framing of the house and a flue is placed through the roof or side of the house. These fireplaces usually are made to work with gas logs only.
• Multi-Flue – Multiple-flue fireplaces have two or more flues. A flue, as elaborated upon in the “Methods and Materials” section below, is the duct or vent that rises from the fireplace hearth to allow the noxious gases from the fire to be released. Multi-flue fireplaces can also be radiant, circulating or metal insert. Sometimes more than one flue is utilized if the fireplace’s size is great, but more often multiple flues are strictly built for design purposes.

An understanding of the numerous components and terms applicable to masonry fireplaces is necessary to understand how a fireplace is built and designed.

• The hearth of a fireplace is the open recess of the fireplace.
• The firebox of a fireplace is the area within the hearth that the materials are gathered and set ablaze on the hearth floor.
• A mantel is the hood or decorative framework that surrounds a fireplace. It allows great leeway for design customization.
• A flue is the upward opening or duct that allows gasses from the fireplace to exit safely. It is the space within a chimney which carries the gasses upwards. Though they serve an important function in transporting noxious gasses away from the home, they can also allow much heat to escape when a fire is lit.
• A damper is the valve that regulates the flow of air and gasses within a chimney. It is a plate-like piece that can be opened or closed by the fireplace user. When the fireplace is not in use, it is useful as it stops air from escaping and stops rain or snow from entering the flue. When the damper is open, it allows for gasses to escape through the flue. Dampers should always be open when the fireplace is in use.
• The grate is the metal frame object within the fireplace and holds the materials that are set ablaze.
• Fireplace caps are the units which are placed atop the chimney, and directly over the flue. They usually consist of a screened siding to prevent animals from entering the chimney, and an overhead solid covering to prevent moisture or air infiltration. As they are usually visible along the rooftops, they are often times elaborately designed or decorated. They are most commonly made of steel, stainless steel, aluminum and copper.

Fireplaces are not load-bearing, structural elements. Instead, they are self supporting and spread on concrete foundations.

Fireplaces are not an energy-efficient way of heating. In fact, only 15-20 percent of the warmth a fireplace generates will actually circulate throughout the home. The rest escapes through the flue within the chimney and disappears into the outside air. Fireplaces are also prone to creative negative energy, as warm or cool air from the home can escape if the damper is not closed. One easy step to take to avoid the loss of air from your home is to have sealed-glass doors guarding the fireplace instead of a wire or mesh cover. If a masonry fireplace is to be installed in harsh weather conditions, special precautions should be taken.

Frequent and detailed chimney inspections are highly recommended for the safety of the homeowners and the structural integrity of the building. As parts of the fireplace unit are exposed to outside forces, this is of special concern. Any cracks or splits within the chimney should be reported to local fireplace and chimney inspection crews.

Components within the fireplace are designed with function and safety in mind. Dampers are designed to open fully and close tightly to ensure that gasses can escape and warm air can remain when the fireplace is not in use. It accomplishes this with a metal plate-like unit that has numerous bars within the middle section. These bars then pivot to the open or closed position.  A picture is available.

Fireplace caps are placed at the top of the chimney, and are designed to keep out animals and to prevent moisture from entering the fireplace and causing damage. Caps are made with a variety of materials, with the most popular options being stainless steel and copper. They consist of a screened siding and a solid covering above. Caps do not come in one standard size or shape, as they must be custom fit to be applied to the chimney they are covering.

In the case of extremely warm or cold weather conditions, some precautions should be taken. Masonry units used should be refractory, or appropriately fire-rated to withstand the heat from the fire. Charts and further information is available from the Masonry Advisory Council. Also, the mortar used should be appropriate to the project and should be able to withstand the high heat it must endure. These guidelines are designed to increase efficiency of the fireplace but, more importantly, to ensure the fireplace is able to operate safely.

Firebox walls, the surfaces that will come under the most scrutiny and intensity from the fire, should have the following composition: A 4″exterior brick layer, followed by a middle section consisting of 4″ concrete masonry units, and finishing with 2″ firebrick with ¼″ refractory mortar joints as an interior layer.

Dampers are required by building safety codes to be at least 8 inches above the top of the fireplace opening. They should be placed accordingly. Flues should be sized in cooperation with the size of the fireplace opening. The Masonry Advisory Council recommends the following guidelines:

The size of the hearth should also be carefully considered. It is recommended that the hearth should extend, from front of the fireplace opening to back, 16 inches if the opening is 6 square feet or less. If the opening is greater than 6 square feet, a 20-inch hearth extension should be constructed. The hearths width, from each side of the opening, should be 8 inches if the fireplace is 6 square feet or less, and 12 inches if larger than 6 square feet.

A multiple-wythe masonry unit uses the same materials as the single wythe it complements. As it is only a term that is directed at the format of the masonry units, the masonry units themselves are the same as applied to any other project.

The method backing multiple-wythe construction is that of increased stability and support. Multiple-wythe constructions also allow for increased insulation and efficiency properties, as emphasized within the section titled “Environmental Considerations.”

Multiple-wythe masonry units have some similar environment considerations as single-wythe units. However, multiple-wythe units have the advantage that one face, or wall section, is not exposed and thus, is not so easily affected by outside elements. The multiple-wythe construction generally means more efficient insulation, and the small gap often left between each wythe can be another opportunity to add insulation or flashing layers.

A multiple-wythe, by design standards, is more than one vertical section of a masonry unit, laid behind or in front of one another. The design of the masonry unit is identical to a single-wythe formation. For example, there is no change in the actual design of the brick; rather the format in which they have been laid is simply altered. To further increase the strength of the units, wire truss reinforcement is often used. Interlocking materials within the cavity between wythes are also commonly utilized, for example, insulation layers.

Preparation for multiple-wythe building is similar to single-wythe construction. Of course, additional masonry units are necessary as multiple-wythe construction uses double the units of single wythe construction. Additionally, any interlocking materials to be used between wythes must be prepared.

The installation of multiple-wythe units is similar to single units, but requires double the materials and double the time and effort. Most commonly, corrugated ties connect the masonry units to the structure; however, other anchorage units can be used. In the case of extremely warm or cold conditions, special precautions should be taken.

Refractory bricks consist of nonmetallic materials and are composed primarily of fireclays, hydrated aluminum silicates, and minerals with high aluminum oxide levels.

The mortar that complements refractory bricks is different from the substance used with traditional clay bricks. Fired brick requires a high purity mortar, primarily composed of alumina aggregate and calcium aluminate cement.

Refractory bricks are specially manufactured to be highly resistant to high temperatures and fires. Their special mortar only enhances this ability. Special considerations should be made when they are installed in cold or warm weather.

The visual appeal and aesthetics of refractory brick usually take a backseat to its functional design. It is made specifically to withstand heat in some very high pressure areas, and thus  it can be scorched and stained within minutes of its installation. Little attention is usually paid to its design for this very reason.

With the exception of a different mortar, refractory brick follows the same steps as traditional clay bricks do, see “Installation” within Clay Unit Masonry.

Safety is crucial on any job site. An employer needs to think not only of the rising costs of workman’s compensation and safety violation fines but, more importantly, of the lives of his employees and the general public around the job site. A safety program is usually required on all projects by all contractors. The mere weight of the material can cause injury if lifted improperly or stacked in an unstable manner. It is important to always wear the proper safety equipment so that eyes and skin are protected from flying debris while cutting, ears are protected from loud noises, and airways are protected from damaging dust particles.

Safety has two basic principles on any job site. The first is to keep the job sight safe from accidents, thereby keeping job productivity up and downtime to a minimum. The second is to keep the general public safe from falling debris and other job-site hazards.

All safety programs should be approved by the U.S. Department of Labor, Occupational Safety and Health (OSHA), State Bureau of Workers Compensation and the general contractor.  A Hazmat program will also be required for all jobs with materials having data sheets.

Proper safety equipment should be worn at all times while on a jobsite. Such equipment includes hard hats, eye protection such as safety glasses or face shields, a respirator or face mask when working with chemicals or cutting, ear protection, and protective clothing such as gloves, long sleeved shirt, pants and boots. Additionally, personal fall arrest systems may be necessary or the use of safety nets or other equivalent protection. For additional information on safety equipment, got to the International Union of Bricklayers and Allied Craftsmen Website.

Jobsites should be prepared with caution tape and barricades or proper signage to mark off restricted or limited access areas. All masonry materials should be properly stacked on the ground to avoid overturning or collapse and proper lifting techniques should be employed. Be sure that your back is straight, legs bent, and the weight between your legs is as close to the body as possible. Also, avoid twisting at the waist while lifting or carrying materials. Use ladders or scaffolding when necessary so that you are working at a safe working height and not lifting masonry materials above your head. . When working with reinforced masonry, all protruding reinforcing steel or rebar, onto and into which employees could fall, must be guarded to eliminate the hazard of impalement.

If scaffolding is being used, it must consist of at least two 2″ x 10″ planks and must overlap by at least 6″. They must support a minimum of 25 pounds per square foot over a maximum span of eight feet. All scaffold platforms should have guardrails, mid-rails and toe boards along all open sides and ends. If using walkway systems is not practical, employees must wear personal fall arrest systems, or employees should be protected by safety nets or other equivalent protection. For additional information on scaffolding, please go to Environmental Health and Safety Online.

Great care should be taken to protect occupational health and environmental quality when using any potentially hazardous and toxic chemical grouts, sealers or other potentially harmful material. Any unknown substances should be treated as potentially hazardous and toxic materials. The manufacturer’s recommendations should always be followed.  If there is a chemical spill, consult Material Safety Data Sheet, (MSDS).

In order to keep employees properly informed in the case of an emergency, safety and health trainings (such as first aid and CPR) should be offered along with trainings on proper lifting techniques. Additionally, weekly tool box talks on common safety issues can be conducted at job sites. Many insurance companies offer seminars on job safety. Training programs are also often conducted by local safety councils, trade associations or employee assistance programs. Check to see if onsite consultation programs by safety and health consultants are available in your area. Fines can often be avoided if safety violations are found and rectified prior to OSHA or government inspections.  Limited access areas should be erected to keep out the general public and unauthorized personnel. Be sure to check all equipment in advance to make sure is it functioning properly and dispose of and replace anything that is unsafe. Lastly, be sure to keep the job site picked up and organized so that materials and tools can be easily found when needed and to minimize hazards to workers.

It is necessary to analyze the worksite prior to beginning any job to check for potential safety hazards. A limited access zone needs to be established whenever a masonry wall is being constructed prior to the onset of the job. The zone must be equal to the height of the wall being constructed plus four feet and span the entire length of the wall on the side of the without scaffolding; entry should be restricted to employees actively engaged in constructing the wall. The limited access zone must be kept in place until the wall is adequately supported to prevent overturning and collapse, unless the wall is more than eight feet in height and unsupported, in which case it must be braced. Bracing must remain in place until the structure’s permanent supporting elements are in place. Barricades should be erected and caution tape put up to keep the general public and unauthorized employees out of the area.

If scaffolding is not being used or if scaffolding does not meet OSHA requirements, it is necessary for employees to wear a personal fall arrest system. It must have proper anchorage and connectors, a body belt or body harness and may include a lanyard, deceleration device, lifeline or a combination of these.

A variety of materials, or ingredients, are used to compose the right mortar mix as specified by its intended use. Though materials used in mortar mixes vary, there are some similarities in the core ingredients – cement, sand and water. Other materials are added when a desired effect or purpose needs to be achieved. To make the selection of the right mix easier, most mixes are available at large hardware or home-improvement stores. These mixes, named by code, include type N, type S, type M, type O, refractory mortar, and glass-block mortar. Each has a slight variation in terms of ingredients, and the most common mixes are listed in this section under “Design/Basics.”

Colored mortar is a popular option as a means of providing an aesthetically appealing effect and as a way to create harmony between masonry units. Colored mortar is achieved either through a premixed batch or through the addition of additives to create the desired color effect. Premixed colored mortars are popular because they remove another step in the process and, as the materials are added in controlled environments, there is usually a good consistency in the color. If the color mixing is to be done on site, this should be achieved through mixing additives or pigments in a large, controlled manner to achieve a uniform effect. The following pigments should be added to achieve the desired color effect:

Red – Red iron oxide

Brown – Brown iron oxide

Yellow – Iron hydroxide

Gray – Manganese dioxide

Blue Slate – Black iron oxide

White – White cement, white sand, and white stone.

Water penetration is the most important concern for masonry mortaring. Freezing and thawing, the direct results of water penetration, are most harmful and most common to mortar. The degree of which the masonry is able to protect against these issues is in large part determined by the workmanship or quality of installation. Because it is nearly impossible to prevent all water from entering, it is recommended to have a flashing to deter water. A flashing is a thin, impervious sheet of material used to absorb or re-direct the flow of water. Additional environmental considerations include the preparation and installation of mortar in extremely cold or warm conditions.

• Type N mortar is a medium-strength mortar that is recommended for use in above-grade projects including outdoor barbeques, outdoor chimneys, and exterior walls of structures that are susceptible to harsh conditions and forces. Its common composition is as follows: 1 part Portland cement, 1 part hydrated lime and 6 parts sand.

• Type S mortar is a high-strength mortar that is commonly used in applications such as foundations, brick and block retaining walls, patios, walks, and driveways. As it has great strength, it is a popular choice for outdoor projects that are subject to harsh conditions. Its composition is 1 part Portland cement, ½ part lime and 4 ½ parts sand.
• Type M mortar is a very high-strength mortar that is used in special applications to support exterior walls and stone retaining walls. Its composition is 1 part Portland cement, ¼ part lime and 3 parts sand.

• Type O mortar is a low-strength mortar that is recommended for load-bearing walls not exceeding pressure of 100 psi and is not subject to excessive moisture. Its composition is 1 part Portland cement, 2 parts lime and 9 parts sand.
• Refractory mortar is a calcium aluminate mortar known for withstanding high temperatures. Because of this ability to survive in such conditions, it is usually used in fireplaces or barbeques.

• Glass-block mortar is most commonly used for projects dealing with glass unit masonry. Its composition allows it to bond better with glass units, and thus it should not be used with concrete or brick units.

Many of the mortar types above are available pre-mixed at hardware or home improvement stores. If the mortar is being made from a scratch mix, however, it is important to note that some special accommodations must be made. The cement used should be Portland cement, the most common type of cement, while the sand should be screened, well cleaned, and free of any organic materials such as alkaline or salts.  Whether the mix is pre-made and bought, or composed from scratch, the water must be added by hand and this step is often more difficult than it may first appear. Adding too much water will make the mortar messy and weak, while not enough water means the mortar is thick and not easy to spread and utilize. Manufacturers will provide an estimate of the amount of water required, but some experimentation is usually always required. Spread small bits of the mortar onto the trowel and onto a test surface to see which composition of water is best.

Mixing of pigments to add color to the mortar is a popular choice. To do so, simply add the pigments into a large mix of the mortar. Color mixes often come with detailed directions, but to test out the color, simply spread a bit of it onto a test surface. If the color streaks, not enough pigment has been added.

Mortar can be mixed in either a mortar box, a large mixer or revolving drum. It should be noted, however, that mixing too much mortar at once is a common mistake. On hot days, mortar mixes can harden and be deemed useless in as little as thirty minutes.

Special preparations should be made for the use of mortar in extremely hot or cold conditions. In cold temperatures, the mortar and work area should be covered and protected. Until its ready use, store mortar in sheltered areas where temperatures do not dip below 70°F. When temperatures exceed 100°F, it is crucial to keep the mortar cool. This can be achieved by a simple squirt of water prior to application, along with covering the mixing area with a shade structure.

Mortar has a nearly limitless range of applications; it is used in nearly every project that falls under the concept of masonry. Because of the sheer number of applications it has, installation does vary from project to project. Generally, however, the mixing and application of mortar has some similarities and important steps that must be followed each time. After careful mixing (described in previous sections), the mortar is ready to be applied to bond the masonry units. This application of the masonry is achieved with a tool called a trowel that allows for quick mixing and placement of the mortar. Using the trowel, the mason can move from a mixing station to the application area to apply the mortar. The mortar should be spread generously and evenly on the surface in order to bond to each masonry unit which will be placed above or beside it.

Mortar and grout are often confused to be the same thing. In fact, each is different and has a different set of applications.  Grout generally has a much higher plasticity and fluidity than mortar. It is a popular option to fill cavities, small joints and floor tiles. Generally, mortar is used for much more complex and demanding structural projects than grout.