Residential Concrete Masonry – August 2005
When Rex Bost of Bost Custom Homes in Cary, North Carolina was chosen to build the 5th Annual New Homes & Ideas Dream Home he chose concrete masonry construction to create a sound and quiet home. “Concrete masonry gives you a much stronger wall and when adding grout and steel reinforcement it provides even stronger support both laterally and vertically,” said Bost who began building concrete masonry homes in 1999. “Concrete masonry also makes a quieter house. A stick built house with brick siding will be quieter than a stick built house with siding. But when you increase the masonry to eight inches (203 mm) thick, the sheer mass absorbs more sound energy so it is much quieter”
Bella Casa, (the Italian words for Beautiful House) sits on one of 64 home sites in the 404-acre (163 hectares) gated community, The Hills of Rosemont in Chatham County, North Carolina. The 8,442-square-foot (784 m2), three-story home on four acres (1.6 hectares) incorporates concrete masonry to create a Mediterranean/Southwestern architectural feel.
Bost has been a leader in residential concrete masonry construction in an area of North Carolina where wood is the prevalent choice for residential construction. “In North Carolina, softwood lumber has more frequently been chosen as the structural system in residential construction, chiefly because of the availability of relatively inexpensive softwood lumber,” said Professor J. Patrick Rand, AIA at the School of Architecture at North Carolina State.
But over the past decade after several weather-related disasters, concrete masonry has begun to take hold as the material of choice for building safe and secure homes in Florida and in the southeastern part of the United States. “It is the product of choice in the high hurricane districts for a reason,” said Bost who builds more than half of all his houses using concrete masonry construction. “The benefits of concrete masonry are self evident. It is like the three little pigs story where the house out of brick was much stronger and withstood the force of the wolf. It is that simple of a concept.”
Yet in the Triangle area of North Carolina, concrete masonry construction is a concept that is just starting to take hold in residential construction. “It’s an emerging methodology,” said Rich Kearny, division manager with Johnson Concrete Products, the company that provided the concrete masonry units used to frame Bost’s home.
“You’re seeing more and more of it in residential construction.”
Besides building sound, secure homes, Bost also chose concrete masonry construction for this particular house because of its size, architecture, exterior façade and roofing materials. “The fact that it is such a large house with three-story walls on the back made concrete masonry the natural choice,” said Bost. With the entire structure tied together from the footings to the roof assembly with steel reinforcement it achieves a natural strength of 400 pounds (1779 N) per running foot compared to just 80 pounds (336 N) for wood framing.
It also allowed Bost to achieve the blended Mediterranean/Southwestern style on the exterior of the house. “Using concrete block exterior walls enabled us to use a true cement based stucco system over the masonry units so you get the true stucco look,” he said.
Though the roofing material looks like clay tile, it is actually a concrete product called Monier Life Tile.
Because of the additional weight it created, the design called for something more substantial than wood to hold the load. “With the sheer fact of the weight of the roof it was just the natural choice to use concrete masonry,” said Bost.
Bost began construction of Bella Casa with basement walls that step down with the grade of the home that sits on the side of a hill. The first and second floor exterior walls were then erected using 8 inch (203 mm) CMUs. Vertical columns were reinforced with rebar and then grouted solid for structural integrity at all point loads, on both sides of all window and door openings, at four feet on center around the perimeter of the home and on every corner. Vertical cells in the concrete block walls that were not grouted were filled with expanding foam insulation.
“The only place we did not use concrete block was one particular window wall where the windows were so close together we framed that in 2 x 6’s (51 x 152 mm),” said Bost.
Along with the exterior stucco application Bost also added another concrete product veneer called DUFFERIN Stone over parts of the concrete masonry. The “Chambly Beige” colored veneer, supplied by Adams Products Company, an Oldcastle Company, has a natural stone, antiqued finish appearance. “That is a concrete product made to look like stonework,” said Bost. “It is actually a four inch wide product and we used that in combination with 4-inch (102 mm) CMU concrete block units to create an 8-inch (203 mm) composite wall that was a load bearing wall.” Archistone, a cement based marble stucco application was used for the exterior trim.
Bost also used DUFFERIN Stone for the barbecue and fire pits outside the home, on the bridge entryway to the home and on an interior fireplace. “You get the look and feel of stone, with the ease of brick installation,” said Frank Werner, vice president of marketing with Adams Products Company.
To facilitate drywall installation on the interior walls of the home the framing contractor installed 2×4 (51 x 102 mm) studs at sixteen inches on center. The cavity created between the concrete block and the stud walls allowed the electrician and plumber to run most of the wires and pipes without having to pull them through the masonry walls. Once the mechanicals were installed, the masonry walls with wood framing were covered with drywall and finished just like typical walls in a home.
Concrete masonry construction was also a perfect fit on this Dream Home project because of its natural properties that provide privacy and quiet. The house was designed for privacy with the majority of the living space overlooking the backyard, swimming pool, four acres (1.6 hectares) of woods and a view of the 14th hole of The Player’s Club golf course.
Concrete masonry wall construction was also used to incorporate that same type of privacy in the interior of the house by blocking sounds such as traffic, lawnmowers and other outdoor noises. The sheer mass and weight of the concrete masonry walls reduces sound penetration through the wall by over 80 percent when compared to wood-frame construction. That means that only about one-quarter to one-eighth as much sound penetrates through a concrete masonry wall as it does a typical wood frame wall.
That, combined with the interior insulation (R-15 in the 2×4 (51 x 102 mm) walls, R-30 in the ceilings and R-19 in the floors) and the stucco coating applied directly to the home’s exterior provides superior sound-dampening qualities. “It is very quiet,” said Bost.
Other amenities in this award winning home include interior textured walls and rounded corners, a meditation room complete with yoga studio, an extensive home security system including a panic room with closed circuit monitors, a hidden elevator, home theatre, cigar room, wine cellar, nanny’s quarters, indoor sports arena and, a Koi pond in the front yard.
“This house was an exceptional showcase of everything you can do with concrete masonry from the wall construction to the roofing product, the stone exterior product and the concrete pavers around the pool and driveway,” said Bost, adding that although he was one of the first builders in his area to use concrete masonry construction, more builders are starting to catch on.
“We have shared with other builders how we do it and as customers see it more and more in our market we are getting more response from them about using it. We are considered the guys to come to for this type of construction in this market.”
Each year a new custom builder is chosen by New Homes & Ideas magazine to build the New Homes & Ideas Dream Home. That builder works with vendors and subcontractors to secure donations. Once the house is completed each room is decorated by local designers and featured on the Parade of Homes. The home furnishings are placed on silent auction with proceeds benefiting the NHI Dream Home project. In 2004 Bost Custom Homes teamed with the Chatham Development Corporation, developers of The Hills of Rosemont, and New Homes & Ideas magazine to raise $315,000 for the Leukemia & Lymphoma Society of Eastern North Carolina. The home also won Gold for Best Charity Event or Special Promotion in the nation by the Housing Guides of America.