Article No: 205
By: Article reprinted with permission from the National Concrete Masonry Association
Photography reprinted with permission from the National Concrete Masonry Association
More Northern designers and builders are learning what their Southwestern and Southern counterparts have known for decades: concrete masonry makes for good, sound residential construction. While defining the built vernacular in other parts of the country, concrete masonry’s toehold in colder climates has traditionally been second to stick-built homes. Fortunately for consumers, you will find intrepid builders like Pat McDonell of McDonell Construction, Inc., in Hudson, Wisconsin, educating the public and building industry on the virtues of concrete masonry in residential building.
McDonell has created a system for his homes that involves foam insulation and geothermal heating and cooling systems that make his designs—when combined with the versatile qualities of concrete masonry—particularly effective for the severe winters and hot summers of northern climates. Given the systematic innovations at work here, the use of concrete masonry over wood is not merely substituting one material for another in terms of preference, but creating a more effective machine for living.
“Spray foam, geothermal heat systems, and decorative concrete are all upgrades from stick-built homes but now standard with my masonry homes,” says McDonell. “The foam and geothermal systems compliment each other with the masonry shell.”
While McDonell’s homes are slightly more costly to build than traditional wood-frame built construction—by as much as five percent—several factors help to mitigate this higher initial investment. In Minnesota and Wisconsin, where McDonell builds his homes, weather impacts not only the cost of heating and cooling a home but also maintenance and damage because of severe weather and high winds. Heating costs associated with concrete masonry can be reduced by up to two-thirds—masonry homes are virtually maintenance free, and high winds won’t wreak havoc with exteriors as they do with siding. There is a sense of safety and solidity to these homes that can’t be replicated with more traditional building methods.
Additionally, concrete masonry homes provide quiet from outside noises, as well as superior fire protection.
McDonell says that his clients have three main concerns when it comes to the homes he designs for them: aesthetics, energy, and air quality—or the dangers to structure and health associated with mold. “My clients are savvy. They know what they want. It’s usually aesthetics, energy efficiency, or mold protection—the others are byproducts. They’ve usually owned three to four homes, and consider the masonry home their last.”
McDonell’s homes have a superior method of exterior wall construction, which addresses these criteria. He employs a bar-reinforced rock face masonry block in three color blends. The block is 6 inches wide by 16 inches long by 4 inches high. “Most commercial buildings use an 8-inch high block, which can have too much of a commercial building look for some residential designs,” says McDonell. The 4-inch-high unit lends itself well to residential application.
Interior sheetrock is applied to a stud wall behind the exterior masonry wall with stucco wrap and closed-cell foam insulation filling the void. “It locks everything in place,” McDonell says of the spray foam insulation. A closed-cell spray foam is used since it is impervious to moisture. He points out that there are “no fibers in my system that can mold.”
McDonell scoffs at the notion that houses create conditions for mold because they are built too tight. Rather, he cites the problem in wood-frame construction. “My masonry homes are very tight. This is a good thing. My wall system keeps cold air out and warm air in, vice versa in the summer, where the block meets the foam. It doesn’t allow for the climates to meet at the vapor barrier standard with wood-frame homes. This is where condensation can occur. Our foam acts as a vapor barrier. We have a 1- to 2-inch airspace between the foam and the sheetrock.”
Conventional wood-frame houses, on the other hand, create problems by virtue of their systems. “With siding, sheeting, 2-by-6 studs, fiberglass insulation, vapor barrier, and sheetrock, cold air can penetrate to the vapor barrier where condensation occurs,” McDonell says. “There’s a dead air space. Fiberglass can mold, and as it gets wet, it loses its R-value.”
There is a crucial lack of information regarding the merits of residential concrete masonry, given the standards that have prevailed in the northern building industry for decades. “The biggest hurdle for a new builder coming from a different background—concrete masonry—is that wood frame builders have the framing and siding industries on their side and get more exposure. It’s a stick-built mindset. There are small things about concrete masonry that people don’t understand. You have to teach people new techniques and methods, and not just clients; there are others in the industry you have to educate.”
McDonell has created some beautiful and beautifully functioning homes. Among them is the Glenview home, in Somerset, Wisconsin, which involved moving a 167-ton limestone cottage built in the 1860s from its existing location on the property to the lakeside. This cottage was incorporated into the new structure.
“The foundation for the existing home was 24 by 26 feet and was a two-story,” says McDonell. “Once we cut the foundation off, we rolled it down the hill. The walls were 2 feet thick, so we had to build two 12-inch block walls to support the home—all while underpinned. We put the old house within 12 feet of the new home and had it perfectly aligned. It took about four hours to move the home about 200 feet and down about 25 feet in elevation.”
McDonell created a home with many windows that attaches to the old cottage, matching its warm hues, but contrasting building and rooflines. With 2,380 square feet of living space on the main floor and 1,800 square feet of finished basement, the Glenview home required 10,000 Concrete Masonry Units (CMUs) to construct. McDonell used steel truss hangers to hold floor trusses locked in with several courses of core-filled CMUs. On the exterior, an 8-inch CMU was turned “inside out to give it a break with a ‘band.’” In-floor heat was used under the upper level sub-floor.
For a 3,636 square-foot custom home in River Falls, Wisconsin, A.H. Bauer Design of Hudson, Wisconsin, assisted McDonell in designing a residence. A mold engineer was also brought on board. The owners had experienced severe mold-related complications from a recently built wood-frame house.
“We made sure it was a one-level home,” McDonell says, “to avoid any possible issues with moisture below grade. It should be noted that we designed a lower level mechanical room below grade to help with pitch for plumbing and to isolate noise. The home has geothermal heat; and in-floor heat is the primary heat source. We used an anti-microbial duct for our air exchange system and mini-split systems for air conditioning. We used these to keep the cool and moist air out of the duct system.”
Particular care was taken to ensure that mold issues wouldn’t arise because of the sensitivity of the new home’s owners. “We patterned random CMUs out of the wall to give it a shadow effect and used gray concrete block behind the stucco areas. This allows us to have stucco without having fibers in the wall system. Putting it against block will avoid the potential to mold. The house sits on a hill so the backside is actually unevenly backfilled to complement the landscape. We reinforced the concrete block in order to hold the load with core fills and bond beams.”
Additionally, McDonell was attentive to other aspects of moisture penetration that could occur with settlement. “We applied a stucco wrap on the interior face of the masonry shell. This offered our walls an additional barrier, which is flexible and durable, to moisture penetration.”
While it is difficult to change habits of an entrenched building industry, McDonell appears determined to win his uphill battle. “I don’t think people understand that mold and energy efficiency can be controlled with attention to detail and specific building methods,” he says. “We need to educate consumers. It’s hard because engineers, architects, builders, lumberyards, and framers are so accustomed to wood-frame building methods. They don’t seem to want to look out of the box. I’d love to build masonry structures for other general contractors. I am confident that the more builders and designers who are exposed to the beauty and benefits of my masonry homes, the more success we’ll have.”
For more information, visit mcdonellmasonryhomes.com.