Far from the misconceptions of dark, damp, musty-smelling structures, today’s concrete homes can be designed to stand up to extreme weather, rising heating and cooling costs, and growing noise pollution — and look good doing it.
Concrete building systems are of five main types: Concrete block, ICF or Insulating Concrete Forms, removable forms, panel systems, and autoclaved aerated concrete.
The familiar rectangular blocks are a traditional construction material and the most widely used concrete building system, particularly in Florida, where they provide an affordable defense against hurricanes. Today’s concrete blocks now work with improved insulation and building techniques for cost-effective results.
According to the Portland Cement Association, blocks now incorporate insulation in several ways, from mixing it into the pre-molded cement to filling a block’s open cavities with loose fill or foam inserts. The insulation and the continuous barrier raise the R-value, or measure of resistance to heat flow, by preventing air leakage.
Pros: Sturdy in high-wind areas; familiar product for local crews and to local code officials; and a modular product that allow homes to be designed in standard dimensions reducing construction waste.
Cons: Regional preferences may make this product not as readily accepted in some parts; the standard dimensional aspects of blocks may mean that some of the more exotic home designs will take more time and may impact the productivity of construction crews.
Best for: Homes in high wind areas; areas of wide acceptance such as Florida.
In this system, insulation and reinforcing steel are placed inside removable wall forms made of aluminum, wood or steel. Concrete is then poured into the forms. Once the concrete has cured, the forms are removed.
Walls Are Us Inc. of Waterford, WI, uses two variations. In one, removable forms are poured for walls and, in the other, concrete is poured for the floors and ceiling as well “to form a monolithic envelope,” says Randy Friemoth, the company’s president.
Pros: Exterior and interior walls can all be poured at the same time; concrete interior walls can be textured or furred out for drywall; wind-resistant; forms can make exterior wall look like brick or textured paint.
Cons: Regional preferences and familiarities with this system may make it not as readily available in some areas.
Best for: Homes in high wind areas, especially with designs that employ concrete floors, ceilings and walls.
There are two panel systems: precast concrete and tilt-up concrete. With precast, a home’s exterior walls with rough openings are produced at the concrete plant. Foam insulation is installed, steel reinforcing embedded and electric wiring added. The panels are transported to the site, lifted by cranes and attached to the foundation and to each other.
With tilt-up concrete, the wall panels are also cast, but the casting is done on site. This method required a fairly wide-open site that can accommodate tilting the walls into place. Once properly positioned, the walls are connected to the rest of the structure.
Pros: Creation in a factory setting ensures a high level of quality, unaffected by job site conditions and weather; wind-resistant; quick set-up possible if site properly prepared for either system; both systems able to accommodate curved panels; on-site system eliminates the cost of transporting panels.
Cons: Accessibility to precast plant may limit availability; tilt-up option works best with large, flat, open site; site must be able to accommodate large cranes.
Best for: Homes of contemporary design in flat-site open settings.
Insulating Concrete Forms (ICFs)With this system, concrete is poured into permanent forms. The forms are made of insulating material, either interlocking blocks, panels, or planks. The panel and planks are interconnected with plastic or metal ties and the blocks with special grooves or interlocking teeth.
Early ICF systems, often for differentiation, used forms that allowed varying thicknesses of walls. But the industry is moving as a whole toward uniform thickness, says Donn Thompson, Director of low rise buildings for PCA.
“Pick your peril of mother nature. Nearly 90 percent of us have one to consider fire, wild fires, seismic, or severe winters. ICF and concrete can beat them all,” says Scott Sundberg, P.E., structural engineer and sole proprietor of Category X Coastal Consulting, Pass Christian, MS. Sundberg believes in the power of performance-based designs. His ICF home in Harrison County, MS, survived the 28-foot storm surge and 125-mile-per-hour winds of Hurricane Katrina when the house was only 85 percent completed.
Pros: Highly energy efficient; storm resistant; good flexibility for designs because the polystyrene forms can easily be cut for custom designs; forms are lightweight and easy to work with; does provide some flexibility after the concrete is poured for additions of electrical and some small plumbing runs due to the thickness of foaming materials.
Cons: Using ICFs for curved and more elaborate walls takes longer; can not be used for basements in areas with heavy termite infestation unless the product has a termiticide incorporated into the foam.
Best for: Homes in which insulation is important, since this system offers the most insulation with inside and outside layers in the fewest steps.