Concrete Homes Side by Side Comparison: A Quality Concrete Home for Only 3% More



Building new concrete homes with concrete exterior walls will add roughly 3 percent to the sale price, compared to the same house built with conventional wood framing.

Research results showed this modest increase during the monitoring of the construction of three homes, built side by side by the same crew.

The exterior walls of two concrete homes were built with concrete, while the third was built entirely with wood framing.

What was studied?

Three homes were built on adjacent lots in a development near Chestertown, Maryland.

The exterior walls of two concrete homes were built with insulating concrete forms (ICFs) and the third was built with wood framing based on standard building practices presently used in the region. Each home was approximately 1,100 square feet.

The National Association of Homebuilders’ Research Center observed the same contractors build each house.

The framing crew that erected the exterior walls was experienced with both wood and concrete home building, having built numerous wood frame and over 40 ICF concrete homes in the past.

For one of the ICF concrete homes, they used the same ICF system they had used previously, a screen-grid block system, with modular 48-inch long by 12-inch high molded foam blocks.

These units stack and interlock like toy building blocks. For the second ICF concrete home, the crew used a flat wall system, consisting of narrow 96 inch long and 8-inch high foam planks, with flat edges that are wired together as the units are stacked.

The time and labor data presented here is not suitable for general estimating purposes, since not all components of each assembly is included in the figures.

Only the work impacted by the change in the materials used to build the exterior walls of the homes was compared.

How much labor was required?

The total productive labor hours used for each portion of each house related to use of ICFs and their assumed cost are identified below:

Total Labor Hours:

Screen Grid Block ICF SystemFlat Wall Plank ICF System Wood
68.28 total labor hours 96.91 total labor hours 60.70 total labor hours
12.49% longer than wood frame 59.65% longer than wood frame  

Total Labor Cost:

Screen Grid Block ICF System Flat Wall Plank ICF System Wood
$1,970.05 total cost $2,838.34 total cost $1.730.91 total cost
$1.32 per square foot of wall  $1.91 per square foot of wall $1.09 per square foot of wall
$1.80 per square foot floor area $2.59 per square foot floor area  $1.58 per square foot floor area
$.22 per sf flr. area higher $1.01 per sf flr. area higher   


Because homes in the Chestertown area are typically sub-contracted on a lump sum or piecemeal basis, actual hourly rates for home construction for this region did not exist. Instead, hourly rates were obtained from Means 1997 Residential Cost Data.

The higher labor costs for the house built with the Plank ICF System reflects the learning curve for the crew building their first home with this system. Experience has shown a crew will typically require a three home learning curve to become familiar and efficient with ICF systems. Far lower labor rates for the second ICF house demonstrate the greater efficiency the same crew had working with the ICF system they had used numerous times in the past.

What were the material costs?

The cost of materials to construct the exterior walls are identified below:

Above Grade Wall Material Costs:

Screen Grid Block ICF System Flat Wall Plank ICF System Wood
$3,572.75 $3,148.73 $1,249.74
$2,323.01 higher than wood $1,898.99 higher than wood  


What was the total cost difference?

The total cost of labor and materials related to the use of ICFs for foundation and above-grade exterior walls are identified below. The increase in cost between the ICFs and the wood frame home amounted to 3.5% of the sale price of the home, and 7.2 to 8.4% of the construction cost of the home.

Foundation and Above-Grade Exterior Wall Labor and Material Costs:

Screen Grid Block ICF System Flat Wall Plank ICF System Wood
$6,552.52 total $7042.72 total $3,760.52 total
$2,792.00 higher than wood $3,282.20 higher than wood  
3.0 % of $94,000 sale price higher 3.5% of $94,000 sale price higher  
7.2% of $39,000 construction
cost higher
8.4% of $39,000 construction
cost higher
 
$4.40 per square foot of wall total $4.73 per square foot of wall total $2.37 per square foot of wall total
$5.97 per square foot floor area total $6.41 per square foot floor area total $3.42 per square foot floor area total
$2.55 per sf flr. area higher $2.99 per sf flr. area higher  


What's the bottom line?

The developer of this subdivision realized the greater value he could offer homebuyers by switching to ICFs. His contractors were able to make the transition easily while adding modest additional cost to the new homes. 
You can build a high quality concrete home for only slightly more than conventional wood frame. The small additional cost is a small price to pay for the added comfort, quiet, disaster resistance and greater energy efficiency.

To view construction photos of concrete homes click here

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Paul@concretehomes.us

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