Article No: 44
The Concrete Combo
By: Carole McMichael
Most concrete home builders focus on trying one particular method, but Jim Steinberger, partner in Steinberger Construction Inc., didn't see it that way. He decided to use three methods: cast-in-place concrete, concrete masonry and precast concrete.
"We are third-generation design-build general contractors, located in Logansport, Ind.," Steinberger said, "long-established in the industrial/commercial markets. But recently, we have applied those skills and knowledge to the design and construction of a concrete home. My reasoning in choosing to build with a combination of methods is that I like concrete as a material itself — its properties; so why shouldn't I use what made the most sense for each component of the home, what seemed most appropriate or cost effective for each application. Also, I wanted to showcase concrete in its various forms."
Steinberger designed a single level, 2,876 square-foot, three-bedroom home, with a 1,092 square-foot, three-car attached garage, located on a 13-acre site. The project also included a safe room located between the house and the garage and 6,000 square feet of exterior concrete drives and patio.
"The first consideration was to emphasize the natural beauty of the site. We wanted to build a home with low, horizontal lines and a layout that would not disturb the original topography.
"Cast-in-place, which we chose for its strength, was used for the foundation and footings for all the walls," Steinberger said, "and because part of the house is earth sheltered, we used it for foundation walls on the below grade side. It was also used for the custom molded bond beam. For that, we took Styrofoam and cut scenes of nature — birds, animals and trees — to serve as molds for form liners, so when we poured, we got bas relief figures. That created a nice architectural effect and illustrated how fluid you can get with concrete. So many people see concrete as just a cold and rigid material. You can actually form it to any shape you want."
Steinberger used concrete masonry block for all the load-bearing walls (all exterior walls and two interior walls). All other interior walls were built using metal studs. Everything in the house was designed on module, so there was no need to cut the concrete blocks. All window and door openings were also designed on module. He chose masonry because it was more cost-effective than cast-in-place; also, masonry offered a broad selection in colors, stains, textures and types of block. He selected the split-face block, but stuck with the natural concrete color. The interior wall behind the wood burner retained exposed masonry because it was fireproof and could absorb heat. It brought the feeling of the outside inside, as well.
"Pre-cast concrete was used for the roof deck," Steinberger continued. "The ceiling of the house is the underside of the precast deck, so exposed painted concrete serves as the ceiling. The precast advantage for the roof was to complete the total envelope of concrete, which offers fire and termite protection, as well as soundproofing. It allowed us to design an open floor plan because it gives you long spans — in this case, long spans that are slender. An eight-inch panel is sufficient. I was trying to get a lot of horizontal lines without a lot of build-up on the roof. Precast also worked best for cantilevering an overhang to create the passive solar effect. Some overhangs went to five feet.
"A steel standing seam roof was a perfect match for a low slope precast concrete deck. We used galvanized steel framing for interior framing because steel framing was less costly and straighter than wood. Also, steel is 10 percent recyclable, and also indigenous, with Indiana being the nation's largest steel producing state. I didn't chose concrete roof tiles, which would be an option, because you need a steeper slope to the roof.
"Green construction was a key concern, in terms of energy efficiency and in the selection of materials used in construction. All structural elements are produced from local indigenous materials, including the cement and aggregate used for the ready-mixed, precast and masonry concrete. The local cement plant produces most of the energy required by burning hazardous waste products in their kiln. The process provides energy to manufacture cement while disposing of those wastes in the safest manner possible. Also, concrete is a natural and inert material, producing almost no potentially harmful VOC emissions, and is 100 percent recyclable."
Preparation and planning for a project that uses three distinctly different building methods is bound to take more time than when one method is used, but Steinberger's industrial experience routinely involved a mix of methods.
"We did the house on a pretty fast track schedule," Steinberger said. "From the time we decided to do it to the actual start was just a month. We kind of did it on the fly — which I don't recommend — but we are used to doing jobs on a fast track. We actually started on the foundation work before we had all the architectural stuff done."
The trickiest part of the project involved forming the bond beam that wrapped around the top of the masonry walls. It was a cast-in-place, molded bond beam, ranging from 18 inches to three feet high. Because of the broad spans, it served to hold together the lintels, wall openings and extended the corners to support the overhangs. Steinberger used off-the-shelf and custom-made form liners, which attach to the inside of the removable forms.
This operation was difficult, according to Steinberger. To get the nature scenes he designed, he had to have forms that were tighter than normal. The concrete had to be liquefied and almost over-vibrated to make sure it filled all the cavities in the mold.
"We had crews, concrete and masonry, that were used for our industrial projects, so we didn't have any trouble finding people with the skills we needed. In fact, I wanted to show off what they can do. We do a lot of complicated jobs, but people don't see the skill it takes. Our specialty is cast-in-place; we use subcontractors for masonry and precast, but any general contractor can put together a project like this."
Steinberger found that code inspectors were comfortable with his combination concrete construction. Code for residential building in his area is not a real issue. However, getting the necessary appraisal was a different story. The banker he worked with had a hard time doing an appraisal because this house didn't fit the established appraisal form and there was no history of sale to refer to.
Making the Sun Work
"An airtight concrete structure with rigid foam insulation, and no attic or crawlspace provides a tight, contained, high R-value envelope, which is well suited to using passive solar heat," said Steinberger. "The cantilevered beams and roof deck were calculated to shade the large south window openings in the summer, but provide full sun during the winter heating season. The solar heat is supplemented with an in-floor, hot water, radiant heat system and a wood burning stove. The concrete mass is a key component, serving as a heat sink that helps maintain comfortable temperatures without large daily fluctuation in the heat or cooling loads. Exposed concrete floors absorb and store solar heat, and the concrete floor, hearth and ceilings store heat from the wood burning stove."
The cost of the shell of Steinberger's home is comparable to high end stick built homes. "I wasn't trying to do affordable housing," Steinberger said. "When comparing costs, total costs throughout the design life of the home need to be evaluated. High energy efficiency and virtually no exterior maintenance will provide substantial long-term savings. In addition, the investment will be protected because of the extreme durability and long life of a concrete home, and life-safety benefits that will only be appreciated more as time goes on."
Steinberger believes the designer should spend the time necessary to learn about the site, the client and the client's lifestyle. "As the design concept grows, constructibility is considered every step of the way, so that the architecture is matched with methods and materials that are cost effective.
"There is more to the beauty of concrete than its strength and durability. Concrete offers an unlimited range of forms, textures, colors and shapes. These can be mixed until you are limited only by the imagination and creativity of you and your designer."
Photos by Rick Voorhees