“Conventional” Concrete Block
Although the word conventional describes grey concrete block, homes build with these units are rarely conventional. Architects and homeowners striving for a modern or industrial look find that grey blocks blend well with glass and metal finishes typically found in this type of home. These block homes, cropping up everywhere from urban infill projects to rugged desert and mountain environments, often feature uncommon uses of one of the most common materials. Not only does grey block provide the desired aesthetic, it provides a healthy environment by reducing the potential for mold, pests, fire, and chemical off-gassing. Owners are often wowed by the combination of beauty, durability and energy efficiency.
When an architect in Queen Creek, Arizona built his own home, the design was born a passion for modern architecture and from inspiration found in the natural, rocky beauty of the surrounding preserve. The objective when designing this project was to create a structure that would “blend” into its surroundings and maintain the integrity of the natural surroundings. And on the practical side, the owners decided that a concrete based material would provide the proper insulation against the brutal heat.
In the design, they chose to showcase the raw beauty of the concrete block…leaving the majority of walls exposed within the project. Steel, glass and exposed concrete floors were also utilized to give the project a loft-type feel. This will withstand the test of time…visually and structurally. The high walls and ceilings allow for an open feeling and bring the outside beauty inside. Staying with grey block, the owners accent the home with bright accessories to bring in color to the home.
Single wythe walls offer the economy of providing structure and an architectural facade in a single building element. They supply all of the attributes of concrete masonry construction with the thinnest possible wall section. For those who wish to expand beyond the look of “conventional” grey block, architectural blocks can be produced in a wide range of colors and styles. Architectural units are available with many finishes, ranging from the rough-hewn look of split-face to the polished appearance of ground face units, and are produced using local materials in many colors and a variety of sizes. To enhance the performance of this wall system, two areas in particular need careful consideration during design and construction—water penetration resistance and energy efficiency. The major objective in designing dry concrete masonry walls is to keep water from entering or penetrating the wall. In addition to precipitation, moisture can find its way into masonry walls from a number of different sources. Dry concrete masonry walls are obtained when the design and construction addresses the movement of water into, through, and out of the wall. This includes detailing and protecting roofs, windows, joints, and other features to ensure water does not penetrate the wall. Figure 1 shows the typical single wythe wall construction and figure 2 shows recommended flashing options. Integral insulations result in excellent thermal mass benefits and are typically molded polystyrene inserts, expanded perlite or vermiculite granular fills, or foams. As for the studs used for interior insulation, the thermal resistance of the concrete masonry webs, and any grouted cores, should be accounted for when determining the thermal performance of the wall. When using integral insulation, the insulation should occupy all ungrouted core spaces. Granular fills are placed in the masonry as the wall is laid up. Usually, the fills are poured directly from bags into the cores. A small amount of settlement usually occurs, but has a relatively insignificant effect on overall performance. Granular fills tend to flow out of any holes in the wall system.
The terms cement plaster and cement stucco are used interchangeably. They both describe a combination of cement and aggregate mixed with a suitable amount of water to form a plastic mixture that will adhere to a surface and preserve the texture imposed on it. When freshly mixed, plaster is a pliable, easily workable material. It can be applied either by hand or machine in two or three coats, although two-coat applications are more typical when plaster is applied to newly constructed concrete masonry. Figure 3 shows the typical CMU and stucco finish wall construction.
While plaster may be used as an interior or exterior finish for most building materials, some type of metal reinforcement or mechanical keying system is usually required to effectively attach the plaster to the substrate. Concrete masonry, however, provides an excellent base for plaster without the need for reinforcement. Since block is manufactured of the same cementitious material as that in the plaster, the two have a natural affinity.
When Don Alward, a North Carolina mason, built his home he wanted a sturdy, safe, efficient, economical home that could fit in “Anywhere, Any Neighborhood, USA.” He worked with Architect Carlos Baldovinos to design a traditional three bedroom, 2 bath ranch-style stucco home. The two decided to construct the walls of light weight 8 inch concrete masonry units (CMU) with steel reinforcement. The interior walls are framed using light gauge metal framing with a ½” airspace built in to decrease thermal transfer through the studs or fasteners. The foamed in place insulation on the exterior CMU walls help to maintain a constant temperature in the house and therefore lower utility costs for the owner. A hard-coat stucco was applied to the exterior walls and synthetic stone trim was applied around doors and windows to create a cottage feel for the residence.
Multi-wythe masonry walls can take one of several forms: composite, non composite or veneer walls. The primary differences between these wall systems are in construction details and how applied loads are assumed to be carried and distributed through the load bearing system In a veneer wall, the backup wythe of concrete masonry is designed as the load bearing system, with the veneer providing the architectural wall finish. Veneers are available to complement any type of architectural style. The primary advantage of using multi-wythe construction is in applications where different architectural features are desired on each side of a wall. Greater flexibility in moisture control and insulation, as well as increased fire resistance rating and sound transmission class, can also be realized. Clay or concrete brick veneers are connected by wall ties and wood or vinyl siding is typically attached using exterior wood furring strips which have been nailed to the masonry. In either case, the design possibilities are endless.
The Allen residence is encircled by the rocky hillside slope of Troon Mountain, Arizona. The lot offers dramatic views, but lay vacant for many years because of the logistical impediments to development. The owners needed a structure with the strength necessary to rise up out of the sloping rock and withstand the elements. The compromise was found by Knoell & Quidort Architects of Phoenix. They used a wall system with load bearing CMU and a veneer of natural quarried stone to blend in with the rich textures of the surrounding environment. The architects also decided to embrace the unusual lot shape and characteristics--600 hundred linear feet of street frontage, setbacks that reduced the buildable area to 25% of the total lot,and a 20% slope. Concrete masonry structure is the unsung hero of this stunning home that wraps the contours of the hillside and takes advantage of prominent views.
Something for Every TasteConcrete masonry's mass provides many consumer benefits. It has a high sound dampening ability, is energy efficient, fire and insect proof, durable and can easily be designed to resist hurricane force winds and earthquakes. It is an extremely flexible building material that provides beauty, security, strength, and durability. CMD
Project: Private Residence, Queen Creek, AZ
Architect & General Contractor: Home Owners
Masonry Contractor: Stoll Masonry, Inc. Chandler, AZ
Masonry Supplier: Quality Block Company, Inc., Phoenix, AZ
Project: Alward Residence, Concord, NC
Architect: CSCAMY Architecture, Charlotte, NC
General & Masonry Contractor: Don Alward, Rockwell, NC
Block Producer: Johnson Concrete Company, Concord, NC
Project: Allen Residence, Scottsdale, AZ
Architect: Knoell & Quidort Architects, Phoenix, AZ
Masonry Contractor: Randy Gregory Masonry, Phoenix, AZ
General Contractor: G.M. Hunt Builders, Cave Creek, AZ
Block Supplier: Superlite Block, Phoenix, AZ
Click on each figure to view a larger version.