Should You Consider a Concrete House?
Long since popular in Europe, the concrete house now makes its way to American soil.
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.
“The biggest misconception is ‘I’m going to live in a cave.’ The reality is if you were to drive past concrete homes, you couldn’t tell any difference. They can be finished to look like any other house on any other street,” says Donn Thompson of the Portland Cement Association.
Concrete has numerous options for home design. Since it is the structure material not the style, concrete homes are not limited in how they appear. Plus, owners of a concrete home typically can save money on their insurance policy because of fire resistance alone. “If an insurance agent understands construction, the savings may even be higher because of disaster, termite, and pest resistance,” says Thompson.
Benefits of Concrete Construction
Here are a few of the other benefits all concrete forms provide:
- Greatly diminished outside noise
- Resistance to fire
- Able to prevent damage from subterranean termites and dry wood termites.
- Stronger than wood framing and able to resist wind-blown debris
- Reduced HVAC loads because their continuous wall assemblies reduce air infiltration and have inherent higher levels of insulation
Also, concrete can incorporate recycled content in the mix, earning added support from those interested in building green
Types of Concrete Building Systems
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.
Best for: Homes in high wind areas; areas of wide acceptance such as Florida.
PROS AND CONS
- 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.
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.
Best for: Homes in high wind areas, especially with designs that employ concrete floors, ceilings and walls.
PROS AND CONS
- 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.
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.
Best for: Homes of contemporary design in flat-site open settings.
PROS AND CONS
- 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.
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 Thompson of 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.
Best for: Homes in which insulation is important, since this system offers the most insulation with inside and outside layers in the fewest steps.
PROS AND CONS
- 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.
Autoclaved Aerated Concrete
This concrete system is popular in Europe but still relatively unknown in the United Sates. The material was used in the New American Home featured at the 2008 International Builders’ Show in Orlando, FL. The precast structural mix is an air-tight, non-organic material. When applied, the concrete mix expands and entraps small air pockets for a lightweight product.
The material has superior fire resistance and, according to PCA’s Thompson, can be molded and cut into precise units. While block-size is most common, the product can also be cast into reinforced panels for walls, floors, and roofs.
Best for: Homes in warmer climates that will benefit from the air pocket insulation and not require supplemental insulation.
PROS AND CONS
- Pros: Superior fire resistance; able to be cut into precise units.
- Cons: Limited U.S. suppliers; home designs with significant point loads (such as supporting a long floor beam) may require special engineering because the product’s light weight may not have sufficient load-carrying capacity.
Costs of Concrete Construction
Concrete systems are more expensive at the outset. Typical concrete systems generally add about three to five percent on average to the price tag of a home, says Thompson. “Keep in mind that this is a one-time financial hit but the savings is perpetual. The resulting energy efficiency more than offsets this increase.”
When checking on relative costs, it’s important to compare apples to apples. Some factors influencing costs include:
- Price of concrete in your area
- Price of the concrete system in your area
- Local labor rates
- Competitiveness of the local marketplace
- Experience of the crew
- Design of the home
- Local building codes
“In Florida, where you have strict building codes due to wind activity, wood-frame construction can cost a lot more to meet those requirements,” says Thompson. “When the cost of the wood-frame home goes up, concrete construction can be equal to or even less than an identical wood-frame home.”
Consider the Possibilities
Here are some tips to keep in mind if you are considering concrete for your next home.
- Visit construction sites in which the contractors you are considering are using the various concrete wall systems. Talk with them about which system makes sense for your site.
- Interview builders that use the system you want. Ask for references and talk to those homeowners about whether the builder was on time, early or late with their project, and whether the project was on budget. Ask about their experience of living with that type of concrete system home.
- Know that good planning is essential. It “eliminates all of the problems and headaches of construction,” says Friemoth of Walls Are Us Inc. He says it is important to have subcontractors, such as plumbers or electricians, familiar with or open minded to concrete construction methods. Coordinate with your builder. Make sure you take the time you need to be comfortable with the designs and options you have chosen. Outlets, windows, utility runs and rough openings need to be factored in at the design stage.
- Be aware that future remodeling is possible but does get a bit more complicated. Because concrete is stronger, more steps will be involved. However, says Thompson, an addition, even a wood-framed one, will be stronger because it will get lateral support from the concrete systems. Remodeling most interiors will be similar to other homes since interior walls are usually wood framed.
- Remember that if you have chosen a home design based on wood frame construction but want to go with a concrete wall system, the thickness of the concrete wall, which may be six inches in difference, will affect the plan.