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Disclaimer

While the information in this document is believed to be accurate, neither the authors, nor reviewers, nor the U.S. Department of Housing and Urban Development of the U.S. Government, nor the North American Steel Framing Alliance, nor the National Association of Home Builders, nor the NAHB Research Center, Inc., nor any of their employees or representatives make any warranty, guarantee, or representation, expressed or implied, with respect to the accuracy, effectiveness, or usefulness of any information, method, or material in this document, nor assumes any liability for the use of any information, methods, or materials disclosed herein, or for damages arising from such use.

ABOUT THE NAHB RESEARCH CENTER, INC.

The NAHB Research Center is a not-for-profit subsidiary of the National Association of Home Builders (NAHB). The NAHB has 200,000 members, including 50,000 builders who build more than 80 percent of new American homes. The NAHB Research Center conducts research, analysis, and demonstration programs in all areas relating to home building and carries out extensive programs of information dissemination and interchange among members of the industry and between the industry and the public.

EXECUTIVE SUMMARY

Steel framing has been used for many years for interior non-load bearing and curtain walls in commercial construction. However, cold-formed steel members have only recently attracted attention for use in load bearing wall, floor, and roof framing applications in residential construction.

Despite the availability of cold-formed steel framing, there are still basic barriers that impede its adoption in the residential market. Probably the primary barrier is that the building industry is generally reluctant to adopt alternative building methods and materials unless they exhibit clear cost or quality advantages. A second barrier is how the thermal conductivity of steel affects energy use in homes. Given improvements in the technology over the past few years, it is not clear how steel compares with wood framing in terms of overall cost to the builder.

The scope of this project was limited to constructing two identical side-by-side homes at three different locations in the U.S. Each location had unique labor rates, material costs, size, shape and style of construction. The sites include Indiana, South Carolina, and North Dakota. Each site has a house framed with conventional dimensional lumber and a second one framed with cold-formed steel. Blower door tests are to be conducted for all demonstration homes to determine the levels of air infiltration for each house. Co-heat tests are also to be conducted at two sites (Valparaiso, Indiana and Fargo, North Dakota) to determine the energy consumption of each tested house.

A modified version of the Group–Timing Technique (GTT) was used to gather information for these houses. The GTT is a work measurement procedure for multiple activities that allows one observer using a stopwatch to make a detailed time study of an entire work crew at the same time. Continuous observations were made on a 15- minute interval and were recorded as tallies on a form that listed the elements of the job. Nonproductive time was also identified and removed from the totals to establish a normal time for each component of work. Time values were used to calculate the productivity of each of the houses for comparison.

This report is limited to the findings of the demonstration homes in Beaufort, South Carolina. Installed costs of the steel framing material were determined and compared with that of conventional wood framing. Results indicate that the cost of the demonstration steel-framed home is 14.2% more than an identical wood home, however, the framers’ labor hours for the steelframed home were only 4.3% higher than those of an identical wood home. The results also indicated that certain aspects of cold-formed steel (such as interior non-load bearing walls) are within the range that might be expected to be cost–effective with wood. An infiltration test was conducted for each home. Results indicated that both steel and wood-framed homes have approximately the same leakage (infiltration) rate.

When using the information in this report, extreme care should be taken in drawing comparisons with costs in a particular area, as local labor rates, availability of materials, and regional skill levels all influence a particular material’s final cost. The unit costs developed in this report were based on the data obtained from a small sample. This information does not include nonproductive time, builder overhead or profit. Results do not reflect a definitive study but rather indicate whether builders should consider cold-formed steel framing when searching for solutions to lumber problems and concerns. The reader should also be careful when using the cost data shown in Appendix B for a specific activity, as the data provided may not be representative of the true cost for that specific activity in another project, location, or circumstances.

1. INTRODUCTION

This report is the second of three reports of a multi–year study of cost and energy comparisons of steel and wood houses conducted for the U.S. Department of Housing and Urban Development (HUD), the North American Steel Framing Alliance (NASFA), and the National Association of Home Builders (NAHB). This study is conducted by the NAHB Research Center, Inc.

Steel framing has been used for many years for interior non-load bearing and curtain walls in commercial construction. However, cold-formed steel members are only recently attracting attention for use in load bearing wall, floor, and roof framing applications in residential construction.

Despite the availability of cold-formed steel framing, there are still basic barriers that impede its adoption in the residential market. Probably the largest barrier is that the building industry is generally reluctant to adopt alternative building methods and materials unless they exhibit clear cost or quality advantages. A second large barrier is the question of how the higher thermal conductivity of steel affects energy use in homes. Given improvements in the technology over the past few years, it is not clear how steel compares with wood framing in terms of overall cost for builders.

Little objective reporting exists comparing the total costs associated with framing with cold-formed steel versus conventional wood-frame homes. In addition, the labor component and impact of steel framing on other trades and systems in the home are particularly difficult to assess. This project helps address these concerns by:

  • determining the in-place labor and material cost for components of nearly identical homes built with steel and wood framing;
  • determining the impact of cold-formed steel framing on other trades; and,
  • determining the short-term energy consumption for nearly identical wood and steel homes.

The scope of this project was limited to three sites. The three sites are located as follows:

  • Valparaiso, Indiana;
  • Beaufort, South Carolina; and,
  • Fargo, North Dakota.

This report is limited to the findings of the demonstration homes in Beaufort, South Carolina.

2. OBJECTIVE

The purpose of this report was to compare the labor and material cost and energy performance (i.e., energy consumption) of steel-framed homes to those of nearly identical wood-framed homes. More specifically, the intent was to determine if the costs of steel-framed homes were “in the same ballpark” as wood-framed homes, realizing that local labor rates, material availability, and other factors will ultimately determine the cost in a specific area. None-the-less, results can be considered by builders when assessing the potential use of steel in their homes.

In order to assess the costs, an observer was sent to the job site where the materials were being used to frame the houses. The houses selected for observation are referred to in this report as the demonstration houses. To effectively make a comparison, both steel and wood houses were erected side-by-side in Beaufort, South Carolina. Framers, plumbers, and electricians were questioned in the field to provide input on the workability of each of the two materials and their practical applications. The in-place labor and material requirements and costs were monitored for both homes. Infiltration tests were also conducted to compare and contrast the tightness (leakage) of each house.

Each set of houses, to the extent possible, had nearly identical floor plan, dimensions, orientation, exposure, HVAC equipment. The demonstration homes were erected side-by-side.

3. COLLECTION OF LABOR HOURS

A modified version of the Group- Timing Technique (GTT) was used to gather information on each demonstration home. The GTT is a work measurement procedure for multiple activities that allows one observer using a stopwatch to make a detailed elemental time study on an entire work crew at the same time. Each activity performed at the job site was broken into components (e.g., floor framing, wall framing, and roofs), subcomponents (e.g., studs, headers, etc.), and tasks (e.g., measure, cut, brace, etc.) (see list of time and motion study categories for data collection in Appendix B). Continuous observations were made at fifteen-minute intervals and recorded as tallies on a form that listed the elements of the job. Nonproductive time (e.g., breaks, lunch, etc.) was identified and removed from the totals to establish a normal time for each component of work. The resulting numbers provided standard time values that were used to calculate the productivity of each of the two framing systems that were used for comparison. This technique was designed to simulate, as close as possible, a production setting and permits a comparison of the labor required to conduct a given task.

To the extent possible, all phases of construction that are directly or indirectly impacted by the framing materials were monitored and time and motion data were collected1. The data collection concentrated on the following components and subcomponents: Framing, Insulation, Sheathing, HVAC, Electrical, Plumbing, Drywall & Paint, Carpentry, Windows, Doors, Siding, Porch and Floor Covering.

4. SITE LOCATION

Beaufort, South Carolina: Habersham Development Habersham is a new waterfront community located on the banks of the Broad River in northern Beaufort County, South Carolina, and sited on a 283 acres former antebellum plantation. The demonstration houses are built on lots 113 and 115 across the street from the Mum Grace Park in Phase I of the Habersham development. The front doors of both homes face northwest. The average annual maximum temperature in Beaufort is 101°F (38°C); the average annual minimum temperature is 13°F (-11°C)2.

The address for each of the houses is as follows: Steel House: 113 Grace Park Rd. Wood House: 115 Grace Park Rd. Habersham, SC 29901 Habersham, SC 29901 Builder: Seaway Development Steel Supplier: Steel Framing Inc. Habersham Land Company Charleston SC. The approximately 1,428-square-foot (133 m2) homes were built with three bedrooms and two and a half baths over a crawl space (see Appendix A for plans). Both exterior and interior walls were built with conventional stick framing techniques. Builder: Seaway Development: A builder that builds single-family homes, town-homes, and condominiums in South Carolina. Seaway Development offers the option of either steel or wood frame houses.

5. CHARACTERISTICS OF DEMONSTRATION HOMES

All framing elements in the wood and steel demonstration homes were fabricated of conventional lumber or cold-formed steel members using local common practices. All framing materials were shipped to each site where all floors, walls, headers, and roofs were constructed. A 2x6 treated wood sill plate was secured to the top of foundation walls for the wood house. One-half inch (12.7 mm) anchor bolts secured the sill plates to the top of foundation walls. The bottom track was secured directly to the top of the foundation of the steel house. The roofs were framed using ceiling joists and rafters, and sheathed with ½ inch (12.7 mm) nominal OSB, and covered with asphalt fiberglass roofing shingles over 15-pound felt underlayment. The walls, ceilings and crawl space floors were insulated with R-19, R-40 and R13 fiberglass batt insulation, respectively. Wood siding was applied over oriented-strand-board (OSB) sheathing for the exterior finish of both houses.

Steel Demonstration Home:

Wall studs were spaced at 24 inches (610 mm) on center with load bearing studs located directly inline with roof rafters and floor joists in-line framing). All structural steel studs were 350S162-33 mil (0.84 mm) (2x4x33 mil) except studs under the main header and the stairs were 550S162-33. Non-structural steel studs were 350S162-27 (2x4x27 mil). All steel-framed members were designed using the Prescriptive Method for Residential Cold-Formed Steel-Framing3. All steel studs were delivered pre-punched with holes spaced at 24 inches (610 mm) on center. All steel members were precut by the steel supplier to the lengths required by the builder4. Exterior walls were sheathed with 7/16 inch (11 mm) APA rated oriented-strand-board (fully sheathed walls). The front porch of the steel house was designed with a gable roof to provide a slightly different appearance of that of the wood house (flat roof).

Wood Demonstration Home:

Wall studs were spaced at 16 inches (406 mm) on-center with load bearing studs located directly inline with roof rafters and floor joists. The 16-inches (406 mm) on center represent local practice in the Beaufort area for wood framing. All structural wood studs were 2x6 Spruce Pine Fir cut to length. Non-structural wood studs were 2x4 Spruce Pine Fir cut to length. Exterior walls were sheathed with 7/16 inch (11 mm) APA rated oriented-strand-board (fully sheathed walls). The front porch has a flat roof to provide a different architectural look than the steel house’s porch.

The homes were marketed for between $180,000 and $200,000 depending on the options selected. Table 5.1 summarizes the characteristics and geometry of each of the demonstration homes built at the Beaufort site.

Table 5.1 – Characteristics of Each Beaufort Demonstration Home1

Characteristic Steel House Wood House
House Orientation Front Door Faces Northwest Front Door Faces Northwest
House Type Colonial Colonial
Number of Stories 2 2
Foundation Type Crawl Space Crawl Space
Roof Type Steel Ceiling Joists and Rafters Wood Ceiling Joists and Rafters
Roof Covering Asphalt Fiberglass Shingles Asphalt Fiberglass Shingles
Roof Pitch 9:12 9:12
House Width 22 ft. 22 ft.
House Length 34 ft. 34 ft.
1st Floor Wall Height 9 ft. 9 ft.
2nd Floor Wall Height 9 ft. 9 ft.
No. of Bedrooms 3 3
Front Porch Size 8 ft. x 21 ft. 8 ft. x 21 ft.
A/C Unit Trane 16 RLA Compressor, 3-Ton Trane 16 RLA Compressor, 3-Ton
Thermostat Bryant Zone Perfect Plus Bryant Zone Perfect Plus
Furnace Trane 80% A.F.U.E. Gas Forced Air Trane 80% A.F.U.E. Gas Forced Air

For SI: 1 ft. = 305 mm

1 Refer to Appendix A for house dimensions.

6. TOOLS AND EQUIPMENTS

Common tools were used in the construction of both demonstration homes. Screws for the steel-framed home were driven using variable speed screw guns, provided by Dewalt (Black and Decker), with a clutch to prevent operator-induced fastening problems such as overdriving. Pneumatic pin drivers were used to fasten wood sheathing to steel wall studs. A chop saw with an abrasive aluminum oxide blade was used to cut steel members including studs, joists, and tracks (when needed). A standard circular saw with an abrasive blade and hand-held power shears were also used to cut steel members. Other tools for the steel house were used such as drywall screw guns, vise clamps, metal hole puncher, tape measure, felt pencil, etc.

Common tools for the wood house were used such as: hammers, nail guns, air compressor, circular saw, drywall screw gun, tape measure, etc. Table 6.1 provides a list of tools and other equipment used in the construction of the two demonstration homes.

Table 6.1 – Tools and Equipment Used for the Beaufort Demonstration Homes

Component Steel House Wood House
Tools Other Equipment Tools Other Equipment
Floor, Wall and Roof Framing 2 Screw Guns 2 Skill Saws Air Compressor 2 Nail Guns 2 Skill Saws Air Compressor
Roof Sheathing 2 Screw Guns Circular Saw Air Compressor Table Saw Forklift 2 Nail Guns Circular Saw Air Compressor Table Saw Forklift
Roof Covering Circular Saw Power Nailer Table Saw Air Comp. Miter Box 2 Nail Guns Carpenter Knife Air Compressor
Stair Framing Screw Gun Circular Saw Air Compressor Nail Gun Circular Saw Air Compressor
Front Porch Framing Nail Gun Screw Gun Circular Saw Jigsaw Air Compressor Nail Gun Circular Saw Air Compressor
Windows and Doors Hammer Nail Kicker Nails/Staples None Hammer Nail Kicker Nails/Staples None
Stucco Trowel Floater Scraper Scaffolding Trowel Floater Scraper Scaffolding
Kitchen Cabinets/Counter top Drill Jigsaw Clamps None Drill Jigsaw Clamps None
Trim Carpentry Baseboard Trim Power Miter Box Sander Jigsaw Nail Gun Kicker Air Compressor Table Saw Power Miter Box Sander Jigsaw Nail Gun Kicker Air Compressor Table Saw

Table 6.1 – Tools and Equipment Used for the Beaufort Demonstration Homes (cont.)

Component Steel House Wood House
Tools Other Equipment Tools Other Equipment
HVAC Tin Snips Circular Saw Clips Staples/Gun None Tin Snips Circular Saw Clips Staples/Gun None
Electrical Circular Saw Drill Puncher None Circular Saw Drill Puncher None
Plumbing Circular Saw Puncher Drills Pipe Wrench Teflon Tape Pipe Dope None Circular Saw Puncher Drills Pipe Wrench Teflon Tape Pipe Dope Bulldozer
Batt Insulation Scalper Blower Hoses Air Compressor Scalper Blower Hoses Air Compressor
Siding 4 Nail Guns Table Saw Power Miter Box Air Compressor 4 Nail Guns Table Saw Power Miter Box Air Compressor
Drywall Installation Screw Gun Drywall saw Tape Joint Compound Sandpaper None Screw Gun Hammers Drywall saw Tape Joint Compound Sandpaper None
Painting Sprayer Brushes Air Compressor Sprayer Brushes Air Compressor
Floor Covering Kicker, N G Circular Saw Table Saw Air Compressor Kicker, N G Circular Saw Table Saw Air Compressor
Fire Place Installation Circular Saw Hammer Screw Gun None Circular Saw Hammer Nail Gun None

7. HOUSE CONSTRUCTION

Table 7.1 provides a summary of framing details for each component of the two demonstration homes. Detailed floor plans are shown in Appendix A to this report.

Table 7.1 – Beaufort Demonstration Homes Framing Details

Component Steel House Wood House
Crawl Space Concrete Masonry Units Concrete Masonry Units
Floors Cold-Formed Steel Framing Lumber
Sill Plate/Bottom Track 350S162-33 2x12 Spruce Pine Fir
First Floor Joist Size & Spacing Trade Ready® 1200S200-68 @ 16” and 24” O.C. 2x12 Spruce Pine Fir @ 16” O.C.
Second Floor Joist Size & Spacing Trade Ready® 1200S200-68 @ 24”O.C. 2x12 Spruce Pine Fir @ 16” O.C.
Joist Fasteners No. 10 x ¾” Hex Head Screws 16d Nails
Rim Joist Trade Ready® 1200T162-68 2x12 Spruce Pine Fir
Floor Sheathing 23/32” x 4’x8’ T&G Plywood 23/32” x 4’x8’ T&G Plywood
Sheathing Fasteners No. 10 x 1-1/4” Hex Head Screws 8d Nails
Floor Headers Trade Ready® 1200S162-68 2x12 Spruce Pine Fir
First Floor Joist Insulation R13 Fiberglass Batts R13 Fiberglass Batts
Structural Walls Cold-Formed Steel Framing Lumber
Stud Size and Spacing 350S162-33 @ 24” O.C. 550S162-33 @ 24” O.C. 2x4, 2x6 & 2x8 Spruce Pine Fir @ 16” O.C.
Stud Fasteners No. 8 x 1/2” Pan Head Screws 16d Nails
Top Plate/Track 350T162-33 550T162-33 2x4 Spruce Pine Fir 2x6 Spruce Pine Fir
Wall Sheathing 7/16”x4’x8’ OSB (Huber) 7/16” x4’x8’ OSB (Huber)
Sheathing Fasteners ET&F Pins 8d Nails
Drywall Size 1/2”x4’x8’/12’ 1/2”x4’x8’/12’
Drywall Fasteners No. 6x1-1/4” Drywall Screws No. 6x1-1/4” Drywall Screws
Siding Material Wood Siding Wood Siding
Wall Cavity Insulation Type R19, Fiberglass Batts R19, Fiberglass Batts
Non-Structural Walls Cold-Formed Steel Framing Lumber
Stud Size and Spacing 350S162-27 @ 24” O.C. 2x4 Spruce Pine Fir @ 16” O.C.
Stud Fasteners No. 8 x 1/2” Pan Head Screws 16d Nails
Drywall Size and Fasteners 1/2”x4’x8’/12’/12’ w/Drywall screws 1/2”x4’x8’/12’ /12’ w/Drywall screws
Ceiling Joists and Roof Rafters Cold-Formed Steel Framing Lumber
Joist Size and Spacing 550S162-43 @ 24”O.C. 2x8 Spruce Pine @ 16” O.C.
Joist Fasteners No. 10 x 1-1/4” Hex Head Screws 16d Nails
Joist Top Sheathing ½” x 4’x8’ T&G Plywood ½”x 4’x8’ T&G Plywood
Drywall Size and Fastening ½”x4’x8’/12’ w/Drywall screws ½”x4’x8’/12’ w/Drywall screws
Rafter Size and Spacing 550S162-33 @ 24” O.C 2x8 Spruce Pine Fir @ 16” O.C.
Rafter Fasteners No. 10 x 1-1/4” Hex Head Screws 16d Nails
Ridge Beam Nested 800S162-43; 800T162-43 2x10 Spruce Pine Fir
Roof Sheathing 7/16”x4’x8’ OSB 7/16” x4’x8’ OSB
Roof Insulation Type and Thickness R40 Cellulose, Blown in R40 Cellulose, Blown in
Rafter Insulation R30 Fiberglass Batts R30 Fiberglass Batts
Component Steel House Wood House
Front Porch
Bottom Floor Joists 2x8 Spruce Pine Fir @ 16” O.C. 2x8 Spruce Pine Fir @ 16” O.C.
Top Floor Joists 2x8 Spruce Pine Fir @ 16” O.C. 2x8 Spruce Pine Fir @ 16” O.C.
Ceiling Joists 800S162-43 @24” O.C. None
Rafters 800S162-43 @ 24” O.C. 2x6 Spruce Pine Fir @ 16” O.C.
Roof Sheathing 7/16”x4’x8’ OSB 7/16” x4’x8’ OSB
Roof Covering Fiberglass Roofing Shingles Fiberglass Roofing Shingles
Miscellaneous
Wall Headers 550S162-33, 1200S200-68,1200S200-54, 1000S162-33 2x14 4-ply Main Header (First Floor)
Collar Ties 550S162-43 2x6 Spruce Pine Fir
Facia 33 mil Brake Shape 2x4 Spruce Pine Fir
House Wrap 9’x150’ TYVEK Roll 9’x150’ TYVEK Roll
Flashing Tape 6”x100’ Roll, Self-Stick W/P Tape 6”x100’ Roll, Self-Stick W/P Tape
Roof Covering Fiberglass Roofing Shingles Fiberglass Roofing Shingles

For SI: 1 ft. = 305 mm, 1 inch = 25.4 mm.

8. AIR LEAKAGE TESTS

Air Leakage Test (Blower Door Test)

Natural air infiltration into and out of a house is a critical component in a home’s energy performance and durability. Air infiltration comprises a large portion of the overall heating and cooling load in a home.

Blower door testing is used to quantify how much fresh air enters a building with all exterior openings closed. The results of a blower door test indicate how leaky a house is, where the major sources of air leakage are located, and how the house compares to other homes of similar size and type.

Test Method

A blower door test is performed in accordance with ASTM E7795. The results of the blower door tests are shown in Section 13 of this report. Results of blower door testing are presented in several ways, including Air Changes per Hour (ACH) value. An Air Change occurs when a building has its entire volume of air replaced with new air. The length of time required for this to take place is the infiltration rate of a building.

An ACH50 value is often used to relate a home’s blower door results because the value is directly obtainable from the test and does not require any assumptions about the building’s performance under natural (i.e. not under artificially elevated pressures) conditions. Results may also be presented in terms of airflow at a pressure differential of 50 Pascal, or CFM50.

Interpretation of blower door results usually involves a reference to some allowable leakage level. Many energy programs specify a maximum allowable ACH50 value. Others approximate a natural infiltration rate by dividing the ACH50 value by a factor that typically ranges from 17 – 20. These natural infiltration estimations are often criticized for being inaccurate. Other performance criteria may relate leakage to the square footage of the house, like CFM50 per square foot of living area.

9. FACTORS IMPACTING CONSTRUCTION AND COLLECTED DATA

It is important to address the factors that could have significant impact on the data collected. These factors include trained supervision, availability of skilled labor and stud size and spacing.

Trained Supervision

Construction on the steel house began with an experienced lead framer (steel supplier). This lead framer and his crew left shortly after the floor was framed. This caused some delays and nonproductive times in framing the rest of the house because the remaining crew was left without direct supervision for some time. This issue was not a factor at all in the construction of the wood house. Availability of trained supervision is an issue that must be considered when using an alternative material such as steel, as such, no adjustment factors will be used on the steel house.

Availability of Trained Labor

Experienced wood framers framed most of the steel home. The steel supplier (lead framer) brought his crew to train the wood framers. The training went on throughout the floor construction, but stopped after the steel framer and his crew pulled out. The wood framing crew on the other hand was relatively stable throughout the construction period. No adjustment factors for the steel house will be used here also, as lack of trained labor is another issue that must be considered when using an alternative material such as steel.

It is to be noted that the framing crew for both homes made several costly mistakes, especially in framing floor headers and the front porch. Furthermore, the framers installed an unnecessary (and time consuming) header in a non-load bearing wall in the first floor of the steel house. The header is needed for the wood house but not for the steel house. No adjustments will be made for this framing errors do happen.

Stud Size and Spacing

The wood house uses 2x4 exterior wood studs spaced at 16” (406 mm) on center while the steel house uses 350S162-33 (2x4x33) exterior steel studs spaced at 24” (610 mm) on center. Local practice in Beaufort is to place 2x4 wood studs at 16” (410 mm) on center. This is done because of the difficulty in drywall installation for 24” (610 mm) on center wood stud spacing and the need for stronger studs due to the location of the house in a high wind region (90 mph exposure C). The steel studs were selected from the Prescriptive Method, which specifies 350S162-33 (2x4x33) studs spaced at 24 in. on center for the specified design wind speed. Although the practice is to place wood studs at 16” (406 mm) on center, value engineering analysis could show that a 24” (610 mm) on center stud (wood) spacing can be structurally satisfactory. If engineering can show that wood studs can be placed at 24” on center, the difference could have a significant impact on the material cost of the steel house. The impact of the stud spacing will be addressed in the conclusion of this report. However, for this report, no adjustment factors will be used for these differences.

10. PRODUCTIVITY COMPARISONS

The two-story wood and steel demonstration homes were approximately 1,428 square-foot (133 m2) each. Floor plans for the demonstration homes are shown in Appendix A. The Beaufort site presented several regional conditions that make steel framing a particularly attractive alternative:

  • a fast growing area that is receptive to new and advanced technologies;
  • a mild-semitropical climate with an average yearly temperature of 65°F (18 °C)
  • abundant suppliers of steel framing materials in the region;
  • steel framing is accepted by the local building officials;
  • engineering is required for both steel- and wood-framed homes (high wind area). Although the Prescriptive Method was used in the design of the steel house, engineered drawings were still required similar to those of the wood house.
  • local code does not require steel homes to have exterior foam sheathing. This provides a good candidate for long-term energy monitoring of both similar houses in a relatively warm climate.

Framing for both houses began in mid August 2000. The framing crews for both houses include: (see Table 10.1)

  • a steel lead framer with experience of more than 10 years using cold-formed steel framing for residential construction. This framer acted as the initial trainer for the builder’s crew. The framer also supplied the steel (for the demonstration home) that he purchased from another supplier,
  • a steel framing crew who exclusively frame with steel, but previously framed with wood, trained (on steel) wood framers by the steel lead framer,
  • two wood framers with combined experience of more than 24 years using conventional wood framing construction. The framers worked for the builder; and,
  • a wood framing foreman who exclusively frames with wood.

A NAHB Research Center engineer monitored the construction process for both wood and steel homes from start to finish. The site engineer was present during every aspect of the construction process. A modified version of the group timing technique was used to document the time to build each of the two demonstration homes. The activity of each crewmember was recorded at 15-minute intervals. Data were collected and coded for each component of the house (walls, floors, roofs, etc.) and sub-component of the framing (studs, sheathing, etc.). Nonproductive time such as breaks or idle time was separated from productive time. Increases in time for personnel, fatigue, and delays were not added to productive time.

Table 10.1 – Crew Composition for Beaufort Demonstration Homes

Component Steel House Wood House
Carpenter/
Foreman
Helper Laborer Carpenter/
Foreman
Helper Laborer
First Floor Framing 1 4 1 1 4 1
Second Floor Framing 1 5 1 1 5 1
First Floor Structural Walls 1 5 1 1 5 1
Second Floor Structural Walls 1 6 1 1 6 1
First Floor Non-Structural Walls 1 6 1 1 6 1
Second Floor Non-Structural Walls 1 7 1 1 5 1
Ceiling Joists Framing 1 5 1 1 5 1
Roof Rafters Framing 1 4 3 1 4 3
Roof Sheathing 1 2 - 1 2 -
Roof Covering 2 1 - 2 1 -
Stair Framing 1 2 - 1 2 -
Front Porch Framing 1 2 - 1 2 -
Windows and Doors 1 2 - 1 2 -
Stucco 1 1 - 1 1 -
Kitchen Cabinets/Countertop 1 1 - 1 1 -
Trim Carpentry 1 1 - 1 1 -
Baseboard Trim 1 1 - 1 1 -
HVAC 1 1 - 1 1 -
Electrical 1 1 - 1 1 -
Plumbing 1 4 - 1 4 -
Insulation 1 1 - 2 1 -
Siding 2 5 - 2 5 -
Drywall Installation 2 2 - 2 2 -
Painting 1 2 - 1 2 -
Floor Covering 1 1 - 1 1 -
Fire Place Installation 1 1 - 1 1 -

Summary of Data Collected

Appendix B contains a detailed breakdown by component and sub-component of the labor man minutes from the time and motion study conducted at each site. Appendix C contains normalized labor man-minutes for each component of the house. The normalization was done based on the size (such as square footage of floor, walls, roofs, etc) for each of the framing components and based on the living area square footage for the sub trades. The normalization procedure assumed that all activities not involving the framing material should be the same (e.g., cutting OSB for the floor framing or installing furnace in the basement). This way, the activity that has a direct impact on the framing material or that is directly impacted by the framing material is identified. Appendix D contains detailed material take off and costs for each of the two houses.

Table 10.2 provides a list contractors and sub-contractors for each of the demonstration homes. Table 10.3 summarizes the dimensions of the different components for each of the demonstration homes as obtained (measured) from each site. Table 10.4 provides a detailed summary of the total 12 man-hours for each component of each of the demonstration homes, based on the normalized man minutes from Appendix C.

Table 10.5 provides a summary of fasteners cost (nails, screws, … etc) as paid by builder. Table 10.6 provides a summary of material and labor cost for each of the demonstration homes. The costs in Tables 10.5 and 10.6 were taken directly from the builder’s invoices and budget reports. Table 10.7 normalizes the material costs shown in Table 10.5. Material costs that are not impacted by the framing material were set to be equal (such as fireplace, siding, plumbing, etc.)

Table 10.2 – Contractors for Beaufort Demonstration Homes

Component Steel House Wood House
Floors, Walls, and Roof Framing Seaway Development Seaway Development
Roofing Admiral Roofing Admiral Roofing
HVAC Bootle Air Bootle Air
Electrical Foster Electrical, & Beever Services Foster Electrical
Plumbing Vic's Plumbing Vic's Plumbing
Insulation Advanced Insulation Company Advanced Insulation Company
Siding Maro Lack Siding Company Maro Lack Siding Company
Drywall Installation Unit Drywall Unit Drywall
Trim Carpentry The Carpentry The Carpentry
Drywall Finishing Unit Drywall Unit Drywall
Painting Singleton Paint Company Singleton Paint Company
Windows and Doors Seaway Development Seaway Development
Kitchen Cabinets Looper Looper
Floor Covering The Carpentry The Carpentry
Front Porch Framing Seaway Development Seaway Development
Stucco Quality Stucco Quality Stucco
Stairs Seaway Development Seaway Development
Fire Place Installation Seaway Development Seaway Development

Table 10.3 - Dimensions of Beaufort Demonstration Homes

Component Steel House Wood House
Floor Area
First floor 748 ft2 748 ft2
Second floor 680 ft2 680 ft2
Total Floor Area 1,428 ft2 1,428 ft2
Load-Bearing Walls (linear footage)
First story load bearing walls 123 ft 167 ft
Second story load bearing walls 160 ft 166 ft.
Total load bearing walls 283 ft 333 ft
Load-Bearing Walls (square footage)
First story load bearing walls 1107 ft2 1503 ft2
Second story load bearing walls 1440 ft2 1494 ft2
Total load bearing walls 2,547 ft2 2,997 ft2
Non-Load-Bearing Walls (linear footage)
First story non-load bearing walls 108 ft 64 ft
Second story non-load bearing walls 85 ft 77 ft
Total non-load bearing walls 193 ft 141 ft
Non-Load-Bearing Walls (square footage)
First story non-load bearing walls 972 ft2 576 ft2
Second story non-load bearing walls 765 ft2 693 ft2
Total load bearing walls 1,737 ft2 1,269 ft2
Roof Area
Ceiling 748 ft2 748 ft2
Roof (surface area) 1060 ft2 1060 ft2
Porch Area
Top and bottom porch 352 ft2 352 ft2
Porch roof (surface area) 176 ft2 240 ft2

For SI: 1 ft2 = 0.093 m2, 1 ft = 305 mm.

Table 10.4 – Normalized Labor Hours for Beaufort Demonstration Homes

Framing Component Total Labor Man-Hours (Hours)
Steel House Wood House
Floors1 80.50 74.00
First Floor Framing1 31.00 26.75
Second Floor Framing1 49.50 47.25
Structural Walls1 137.75 127.75
First Story Structural Walls 83.75 78.25
Second Story Structural Walls 54.00 49.50
Non-Structural Walls 41.00 43.00
First Story Non-Structural Walls 14.75 16.25
Second Story Non-Structural Walls 26.25 26.75
Roof1 96.25 95.00
Ceiling Joists 28.50 26.25
Rafters w/Decking 67.75 68.75
Front Porch Framing2 155.00 153.25
Stairs 24.75 24.50
Total Framing 535.25 517.50
Total Framing without Porch 380.25 364.25
HVAC 55.00 56.25
Electrical 58.50 53.50
Plumbing 56.75 55.50
Insulation 51.75 41.00
Siding 122.75 121.75
Drywall Installation, Finishing & Painting 173.75 177.00
Windows and Doors 39.25 39.25
Kitchen Cabinets 8.25 8.00
Baseboard Trim 112.00 111.50
Floor Covering 31.75 31.75
Roof Shingles 21.50 21.50
Fire Place Installation 9.50 9.50
Vinyl Facia 3.25 3.25
Apply Stucco 38.75 38.75
Install Felt Paper 5.00 5.00
Chimney Installation 41.50 41.50
Total Hours 1364.50 1332.50

1 Hours include sheathing. 2 The front porch for the steel house has a gable roof while the porch roof for the wood house is flat.

Table 10.5 – Fasteners Cost Paid by Builder

Fastener Steel House Wood House
AB-66 6x6 Adjustable Post Base $35.07 -
LUS210-3 2x10 TRPL JST Hanger $21.56  
LUS28-3 2x8x10 Joist Hanger $18.60  
NUTS-Bolts Screws -Washers $11.98  
NUTS-Bolts Screws -Washers $11.98  
1 1/4" Self Drilling Screws $11.20  
1" Self Drilling Screws $10.10  
1/2" Self Drilling Screws $11.20  
16D CC Sinker Nail 50 LB $17.57  
8D GALV Common 5LB $5.32  
BOX 2 1/2" Self Tapping Screw $18.98  
BX 1 1/4" TEK Screw $179.90  
BX 1 3/4" Paslode Coil Nail $578.00  
N8DB 1LB 1-1/2" Hanger Nail $14.95  
Self Tap DW Screw 5LB $14.99  
No. 6x1-1/4” Drywall Screws (1) (1)
LuS28 2x8 & 2x10 Joist Hangers   $21.24
2x2 Square Washers, 1/8”   $13.00
Hanger Nails   $20.00
SIM TIE DOWN H-5 (TECOJR)   $36.00
Adhesive Const 29 oz PL 400   $41.88
16d Galvanized Common 50 lb.   $64.64
Nails 50# cc Sinkers 8d   $30.02
Nails 50# cc Sinkers 16d   $14.74
8d Galvanized Common 5 lb.   $5.32
Total $961.40 $247.02

1 Cost of drywall screws is included in the drywall material cost.

Table 10.6 – Total Material and Labor Cost Paid by Builder

Component/Trade Total Material Cost from Builder’s Invoices Total Labor Cost from Builder’s Invoices
Steel House Wood House Steel House Wood House
Framing Materials $ 9,618.26 $ 7,125.51 $ 15,892.69 $ 11,220.27
Fasteners $ 961.40 $ 247.02 ? ?
Exterior Trim $ 7,992.33 $ 10,693.91 $ 10,151.08 $ 8,487.00
Interior Trim $ 5,781.36 $ 3,313.91 $ 5,065.92 $ 4,410.31
Interior Doors $ 815.30 $ 815.30 (1) (1)
Exterior Doors/Windows $ 10,209.41 $ 10,209.41 (1) (1)
Plumbing $ 7,500.00 $ 8,085.00 (1) (1)
HVAC $ 6,546.67 $ 6,547.62 (1) (1)
Electrical $ 4,992.36 $ 3,152.82 (1) (2) (1)
Drywall $ 5,238.84 $ 4,827.14 (1) (1)
Roofing $ 2,207.20 $ 1,921.25 (1) (1)
Insulation $ 2,542.00 $ 2,542.00 (1) (1)
Siding $ 2,097.36 $ 2,097.36 (1) (1)
Stucco $ 1,649.46 $ 1,489.30 (1) (1)
Fireplace $ 1,093.17 $ 1,080.73 (1) (1)
Kitchen Cabinets & Counter Top $ 5,640.92 $ 6,098.87 (1) (1)
Painting $ 10,521.01 $ 11,309.13 (1) (1)
Floor Covering $ 8,790.89 $ 7,515.83 $ 1,119.25 $ 1,119.25
Supervision $ 3,249.58 $ 2,517.27 ? ?
Total $97,447.52 91,589.38 $32,228.94 $25,236.83

1 Labor cost included in the material cost.

2 The electrician cost appears higher because two different electricians were sued for the steel. No credit was given to the builder for the work that the first electrician had done.

Table 10.7 – Normalized Material and Actual Labor Cost Paid by Builder

Component/Trade Total Material Cost from Builder’s Invoices Total Labor Cost from Builder’s Invoices
Steel House Wood House Steel House Wood House
Framing Materials $ 9,618.26 $ 7,125.51 $ 15,892.69 $ 11,220.27
Fasteners $ 961.40 $ 247.02 ? ?
Exterior Trim $ 10,693.91 $ 10,693.91 $ 10,151.08 $ 8,487.00
Interior Trim $ 3,313.91 $ 3,313.91 $ 5,065.92 $ 4,410.31
Interior Doors $ 815.30 $ 815.30 (1) (1)
Exterior Doors/Windows $ 10,209.41 $ 10,209.41 (1) (1)
Plumbing $ 7,500.00 $ 8,085.00 (1) (1)
HVAC $ 6,546.67 $ 6,547.62 (1) (1)
Electrical $ 4,992.36 $ 3,152.82 (1) (1)
Drywall $ 5,238.84 $ 4,827.14 (1) (1)
Roofing $ 1,921.25 $ 1,921.25 (1) (1)
Insulation $ 2,542.00 $ 2,542.00 (1) (1)
Siding $ 2,097.36 $ 2,097.36 (1) (1)
Stucco $ 1,489.30 $ 1,489.30 (1) (1)
Fireplace $ 1,080.73 $ 1,080.73 (1) (1)
Kitchen Cabinets & Counter Top $ 6,098.87 $ 6,098.87 (1) (1)
Painting $ 11,309.13 $ 11,309.13 (1) (1)
Floor Covering $ 7,515.83 $ 7,515.83 $ 1,119.25 $ 1,119.25
Supervision $ 2,517.27 $ 2,517.27 - -
Total $96,461.80 $91,537.06 $32,228.94 $25,236.83

1 Labor cost included in the material cost.

11. ANALYSIS OF DATA

Available house plans and framing plans are shown in Appendix A. Material invoices and builder’s budget reports were used to allocate material and labor cost for each framing component.

Tables 11.1 and 11.2 summarize the total labor hours and material cost for each framing component of the steel and wood demonstration homes in Beaufort, respectively. Normalized labor hours (from Table 10.4) are used in these tables. Costs associated with framing only are included in these tables (e.g. roof shingles are independent of framing materials and thus are not included).

Tables 11.3 and 11.4 summarize normalized labor and material costs (from Tables 10.4 and 10.7) for the different trades (and subtrades) for each of the two demonstration homes. The material costs used in these tables were taken directly from builder’s invoices. Hours per square foot for each of the trades are also tabulated in Tables 11.3 and 11.4

Tables 11.5 through 11.9 itemize the cost of each of the main framing components in the house (floors, walls, roof and stairs) using labor cost as paid by the builder and normalized labor hours as shown in Table 10.4. The tabulated costs include sheathing installation. Labor costs were taken from builder’s invoices and allocated to each framing element based on the number of hours spent. The allocation is calculated based on the number of hours spent for each activity multiplied by the total labor cost paid by builder divided by the total labor hours spent as follows:

Labor Cost = ($15,893x Hours/Activity)/380.25 for the steel house

Labor Cost = ($11,220 x Hours /Activity)/ 364.25 for the steel house

Where the 380.25 and the 364.25 are the total labor hours for the steel and wood homes respectively. These hours include framing and sheathing (floors, walls, roof) and excludes the porch framing. The porch framing hours were excluded because of the dissimilarities between the steel and wood porches and the fact that the steel porch was framed for the most part with wood. These hours are obtained from Table 10.4.

Table 11.10 estimates the cost per square foot of floor area, roof area and wall area for the different trades. Normalized builder’s costs were used.

Table 11.11 provides the total framing cost of each of the two houses. The framing cost includes material cost from Tables 11.1 and 11.2 (including fasteners) and labor cost for floors, walls, and roof from table 10.7 (without roof covering).

Table 11.12 shows the total cost of the framing and trades for each of the two demonstration homes. The cost includes materials and labor for framing, HVAC, electrical, plumbing, insulation, siding, drywall, painting, windows and doors, cabinets, trim carpentry, floor covering, and roof covering (from Tables 11.1, 11.2 and 11.10). Fasteners cost were obtained from the builder’s material invoices, which were provided and categorized by framing component.

Tool costs were not included in any of the tables. Tool costs vary based on the type of tools used. Furthermore, all framers (for wood and steel homes) had their tools with them. The builder supplied all necessary tools and did not have a separate line item for tools on his budget reports.

The steel demonstration home in Beaufort had several factors that could have impacted the total costs documented in this report. Some of these factors could have falsely showed the cost of steel framed homes to be “in the same ballpark” as wood framed homes. These factors include:

1. Engineering costs were not included for both homes. The steel house was built in accordance with the Prescriptive Method (steel framing provisions are currently in the IRC6 and the Prescriptive Method have been accepted by some jurisdictions). An approved wood house plan was used to build the wood demonstration home.

2. The builder supplied the framers with all necessary tools for both homes (tool costs were not included for both steel and wood homes).

3. The steel studs were framed at 24” (610 mm) on center while the wood studs were framed at 16” (406 mm) on center (refer to Section 14 of this report for impact of 24” (610 mm) versus 16” (406 mm) spacing). The wider stud spacing is one of the benefits that steel framing offers.

Table 11.1 – Normalized Framing Labor Hours and Material Cost of Beaufort Steel House

Framing Component Labor Hours (Hrs.) Material Cost ($) Fastener Cost ($) Total
Material Cost($)
First Floor1 31.00 $1,455.50 $160.65 $1,616.15
Second Floor1 49.50 $1,367.90 $160.00 $1,527.90
1st Story Structural Walls1 83.75 $1,746.50 $221.50 $1,968.00
2nd Story Structural Walls1 54.00 $1,590.00 $221.60 $1,811.60
1st Story Non-Structural Walls 14.75 $250.45 $46.75 $297.20
2nd Story Non-Structural Walls 26.25 $325.60 $45.50 $371.10
Ceiling Joists 28.50 $878.90 $24.10 $903.00
Rafters/Roof1 67.75 $1,623.41 $68.80 $1,692.21
Stairs 24.75 $380.00 12.50 $392.50
Totals 380.25 $9,618.26 $961.40 $10,579.66

1 Material cost includes wood sheathing for floors, walls and roofs, excluding porch framing.

Table 11.2 – Normalized Framing Labor Hours and Material Cost of Beaufort Wood House

Framing
Component
Labor Hours (Hrs.) Material Cost ($) Fastener Cost ($) Total
Material Cost($)
First Floor1 26.75 $1,031.96 $40.00 $1,071.96
Second Floor1 47.25 $1,088.30 $36.00 $1,124.30
1st Story Structural Walls1 78.25 $1,556.78 $55.00 $1,611.78
2nd Story Structural Walls1 49.50 $1,077.49 $45.00 $1,122.49
1st Story Non-Structural Walls 16.25 $159.58 $9.00 $168.58
2nd Story Non-Structural Walls 26.75 $258.22 $9.00 $267.22
Ceiling Joists 26.25 $525.68 $14 $539.68
Rafters/Roof1 68.75 $1,047.50 $31.02 $1,078.52
Stairs 24.50 $380.00 8.00 $388.00
Totals 364.25 $7,125.51 $247.02 $7,372.53

1 Material cost includes wood sheathing for floors, walls and roofs, excluding porch framing. Random Length Lumber index was $321 per 1000 board feet.

Table 11.3 – Trades Normalized Labor and Material Cost for Beaufort Steel House

Trade Builder’s
Material
Cost ($)
Labor Hours Builder’s
Labor
Cost ($)
Hours/ ft2 of House1
HVAC $6,547 55.00 (2) 0.039
Electrical $4,992 58.50 (2) 0.041
Plumbing $7,500 56.75 (2) 0.040
Insulation $2,542 51.75 (2) 0.036
Siding (include stucco) $3,587 161.50 (2) 0.113
Drywall Installation/Finish $4,547 78.00 (2) 0.055
Exterior/Interior Paint $11,309 85.75 (2) 0.060
Windows and Ext. Doors $10,209 39.25 (2) 0.027
Kitchen Cabinets & Counter top $5,641 8.25 (2) 0.006
Trim (interior and exterior) $14,008 112.00 $15,217 0.078
Floor Covering $7,516 31.75 $1,119 0.022
Roof Covering $1,921 21.50 (2) 0.015
Total $80,319 760 $18,977 0.530

For SI: 1 ft2 = 0.093 m2

1 Hours per square foot of the living area (1,428 ft2).

2 Included in material cost.

Table 11.4 – Trades Normalized Labor and Material Cost for Beaufort Wood House1

Trade Builder’s
Material
Cost ($)
Labor Hours Builder’s
Labor
Cost ($)
Hours/ ft2 of House1
HVAC $6,548 56.25 (2) 0.039
Electrical $3,153 53.50 (2) 0.037
Plumbing $4,827 55.50 (2) 0.039
Insulation $2,542 41.00 (2) 0.029
Siding (include stucco) $3,587 160.50 (2) 0.112
Drywall Installation/Finish $4,827 80.75 (2) 0.057
Exterior/Interior Paint $11,309 96.25 (2) 0.067
Windows and Ext. Doors $10,209 39.25 (2) 0.027
Kitchen Cabinets & counter top $5,641 8.00 (2) 0.006
Trim (interior and exterior) $14,008 111.50 $12,898 0.078
Floor Covering $7,516 31.75 $1,119 0.022
Roof Covering $1,921 21.50 (2) 0.015
Total $76,088 755.75 $14,017 0.528

For SI: 1 ft2 = 0.093 m2

1 Hours per square foot of the living area (1,428 ft2).

2 Includes material cost.

Table 11.5 – Total Floor Framing Cost

House Floor
Area(ft2)
Material and Fastener Cost ($) Total Hours (hours) Labor Cost ($) Material Cost per FT2 of Floor Area ($/ft2) Labor Cost per FT2 of Floor Area ($/ft2) Hours per FT2 of Floor Area (hours/ft2) Total Cost per FT2 of Floor Area ($/ft2)
Steel House 1,428 $3,144 80.50 $3,365 $2.20 $2.36 0.0564 $4.56
Wood House 1,428 $2,196 74.00 $2,279 $1.54 $1.60 0.0518 $3.14

Table 11.6 – Total Structural Walls Framing Cost

House Wall Length(ft2) Material and Fastener Cost ($) Total Hours (hours) Labor Cost ($) Material Cost per FT2 of Wall Length ($/ft2) Labor Cost per FT2 of Wall Length ($/ft2) Hours per FT2 of Wall Length (hours/ft2) Total Cost per FT2 of Wall Length ($/ft2)
Steel House 283 $3,780 137.74 $5,757 $13.36 $20.34 0.49 $33.70
Wood House 333 $2,734 127.75 $3,935 $8.21 $11.82 0.38 $20.03

Table 11.7 – Total Non-Structural Walls Framing Cost

House Wall Length(ft2) Material and Fastener Cost ($) Total Hours (hours) Labor Cost ($) Material Cost per FT2 of Wall Length ($/ft2) Labor Cost per FT2 of Wall Length ($/ft2) Hours per FT2 of Wall Length (hours/ft2) Total Cost per FT2 of Wall Length ($/ft2)
Steel House 193 $668 41.00 $1,714 $3.46 $8.88 0.21 $12.36
Wood House 141 $436 43.00 $1,325 $3.09 $9.40 0.30 $12.49

Table 11.8 – Total Roof Framing Cost

House Roof
Area(ft2)
Material and Fastener Cost ($) Total Hours (hours) Labor Cost ($) Material Cost per FT2 of Roof Area ($/ft2) Labor Cost per FT2 of Roof Area ($/ft2) Hours per FT2 of Roof Area (hours/ft2) Total Cost per FT2 of Roof Area ($/ft2)
Steel House 1,428 $2,595 96.25 $4,023 $1.82 $2.82 0.0674 $4.64
Wood House 1,428 $1,618 95.00 $2,926 $1.13 $2.05 0.0665 $3.18

Table 11.9 – Total Stairs Framing Cost

House Floor
Area(ft2)
Material and Fastener Cost ($) Total Hours (hours) Labor Cost ($) Material Cost per FT2 of Floor Area ($/ft2) Labor Cost per FT2 of Floor Area ($/ft2) Cost per FT2 of Floor Area (hours/ft2) Total Cost per FT2 of Floor Area ($/ft2)
Steel House 1,428 $392 24.75 $1,034 $0.27 $0.72 0.017 $0.99
Wood House 1,428 $388 24.50 $755 $0.27 $0.53 0.017 $0.80

For SI: 1 ft2 = 0.093 m2 1 Costs are shown per square foot of living area (1,428 ft2) 2 Included in material cost. The builder did not provide separate cost data for labor and material.

Table 11.10 – Trades Costs1

Trade STEEL HOUSE WOOD HOUSE
Labor Cost ($) Material Cost ($) Total Cost ($/ft2) Cost/ft2 of House ($/ft2) Labor Cost ($) Material Cost ($) Total Cost ($/ft2) Cost/ft2 of House ($/ft2)
HVAC (2) $6,547 $6,547 $4.58 (2) $6,548 $6,548 $4.59
Electrical (2) $4,992 $4,992 $3.50 (2) $3,153 $3,153 $2.21
Plumbing (2) $7,500 $7,500 $5.25 (2) $4,827 $4,827 $3.38
Insulation (2) $2,542 $2,542 $1.78 (2) $2,542 $2,542 $1.78
Siding and stucco (2) $3,587 $3,587 $2.51 (2) $3,587 $3,587 $2.51
Drywall Installation/Finish (2) $4,547 $4,547 $3.18 (2) $4,827 $4,827 $3.38
Exterior/Interior Paint (2) $11,309 $11,309 $7.92 (2) $11,309 $11,309 $7.92
Windows and Ext. Doors (2) $10,209 $10,209 $7.15 (2) $10,209 $10,209 $7.15
Kitchen Cabinets & Counter top (2) $5,641 $5,641 $3.95 (2) $5,641 $5,641 $3.95
Trim (interior & exterior) $15,217 $14,008 $29,225 $20.47 $12,898 $14,008 $26,906 $18.84
Floor Covering $1,119 $7,516 $8,635 $6.05 $1,119 $7,516 $8635 $6.05
Roof Covering (2) $1,921 $1,921 $1.35 (2) $1,921 $1,921 $1.35
Total $16,336 $80,319 $96,655 $67.69 $14,017 $76,088 $90,105 $63.10

Table 11.12 – Total Framing and Trades Cost 1

House Total Living Area (ft2) Material Cost ($) Builder’s Labor Cost ($) Builder’s Total Cost ($) Total Cost/ft2 of Living Area (Hr/ft2) Total Hours/ft2 of Living Area ($/ft2)
Steel House 1,428 $10,580 $15,893 $26,473 $18.54 0.266
Wood House 1,428 $7,372 $11,220 $18,592 $13.02 0.255

For SI: 1 ft2 = 0.093 m2

1 Includes framing materials, fasteners, HVAC, Electrical, Plumbing, Insulation, Siding, Drywall, Kitchen Cabinetry, Roofing and interior trim (excludes porch).

12. AIR LEAKAGE TEST COMPARISON

The blower door test was performed on the wood and steel houses in Beaufort, South Carolina on April 4, 2001. The results are summarized in Table 12.1 below:

Table 12.1 – Summary of Blower Door Tests

Measurement Steel House Wood House
Blower Door – ACH50 7.47 7.21
Estimated Natural ACH 0.35 0.34
Estimated Leakage Area-ELA (in2) 107.19 101.66

The blower door results are virtually identical for the two houses, as the difference between the two is only 3.6%. Neither of the two houses are considered very tight by today’s construction standard (when compared to a general database of building tightness measurements.) The similarity of the results may indicate that the leakage is originating from common details like the rim joists, windows, plumbing/electrical penetrations, recessed lights, and attic hatches.

13. CONCLUSION

This report provides a description of each demonstration home, a description of the framing components, list of materials, productivity and unit cost comparisons and short-term energy comparisons. Engineering costs were not included in this report as these costs typically vary depending on who provides the service. Co-heat test results are also not included in this report as the tests are not conducted yet.

Cost Comparison

The cost data indicate that the costs of certain framing components of steel-framed-homes (such as interior non-load bearing walls) are comparable with those framed with wood. However, using the builder’s costs, a steel-framed home cost is shown to be 14.2% higher than the cost of a nearly identical wood-framed home (refer to Table 11.12). The steel-framing package cost (framing labor and material) is 42.4% higher than that of a wood-framing package (refer to Table 11.11). The total framing time (labor hours) for the steel house was 4.3% higher than that for a nearly identical wood house; the framing material cost for the steel house was 43.5% higher (refer to Table 11.11). The lumber for the wood house was purchased in August 2000 when the Random Length lumber index was at $321 per 1000 board feet7 and the CME futures price index was at $300.18

It should be noted that the differences in the framing method (such as 16” (406 mm) on center for wood vs. 24” (610 mm)) on center for steel) could have a significant impact on the total cost and could potentially put the steel-framed home at a higher cost disadvantage. In fact the structural walls could cost an additional 1.6% (of the framing package) if the steel labor and material costs were adjusted for the stud spacing9. However, the wall framing spacing in the two homes is representative of the standard construction practice for each material and the inherent perception of the structural superiority of steel framing.

The cost impact on trades and sub trades, due to steel framing, does not appear to be significant. In fact, for certain trades, the difference in cost between wood and steel-framed homes was negligible, while for others the cost differential was favorable to steel. The trades cost (labor and material) for the steel house were 7.3% higher than those for the identical wood house ($96,655 for the steel house and $90,105 for the wood house from Table 11.2).

The higher cost of the steel house is attributed to three reasons:

  1. Inexperienced framing crew was used in framing the steel house. As the crew becomes familiar with steel framing the steel’s framing cost is expected to go down.
  2. The steel supplier charged a higher amount for the steel package. The cost of a similar steel package from alternative suppliers would have been approximately 25% less than what the builder had paid. If the builder shopped around and obtained a more reasonable cost for the steel package, the cost of the steel-framed house would have been lower.
  3. The first electrical contractor for the steel house was replaced with another one after he pulled the wires throughout the house. The new contractor charged the builder as if nothing was previously done. The builder ended up paying almost double the cost of an electrician. If the problem with the electrical contractor did not exist, the cost of the trades would have been similar for both houses (steel and wood)

When using the information in this report, extreme care should be taken in drawing comparisons with costs in a particular area, as local labor rates, availability of materials, and regional skill levels all influence a particular material’s final cost. The unit costs developed in this report were based on the data obtained from a small sample. This information does not include nonproductive time, builder overhead or profit. Results do not reflect a definitive study but rather indicate whether builders should consider cold-formed steel framing when searching for solutions to lumber problems and concerns. The reader should also be careful when using the cost data shown in Appendix B for a specific activity, as the data provided may not be representative of the true cost for that specific activity in another project, location, or circumstances.

Blower Door

Test Blower door (infiltration) tests concluded that both steel-framed and wood-framed homes have approximately the same leakage rate.

This report is the second of three reports that will be summarized and compiled into one comprehensive report at the end of the program. The final report will average the labor and material costs from the three sites to provide a more accurate cost comparison for steel and wood-framed homes.

Footnotes

1 The cost of engineering, building permits, blueprints, rough and final stake, water lines, sewer lines, excavation, backfill, foundations, sand and stone, damp proofing, footing drains, structural steel (I-beam and olly columns), interior concrete, interior and exterior lights, appliances, mirrors, monthly utility bills, general site cleanup, driveways, sidewalks, exterior concrete, landscaping, and interest on loan were not documented in this report./sup>

2 ASHRAE 1997.

3 Prescriptive Method for Residential Cold-Formed Steel Framing, Second Edition. U.S. Department of Housing and Urban Development (HUD), Washington, DC. September 1997.

4 It is not common practice for steel suppliers to deliver pre-cut (to length) steel members. Typically, steel studs come in lengths with 2-foot increments. The builder paid a cost premium to have the steel members cut to length. The builder’s cost is used in the cost comparison.

5 ASTM E779-99 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization. American Society for Testing and Materials, West Conshohocken PA.

6 International Residential Code for One- and Two-Family Dwellings, 2000 Edition. International Code Council. Falls Church, Virginia.

7 Random Lengths. January 7, 2000.

8 Chicago Mercantile Exchange. January 7, 2000. 9 Approximately an additional $430 ($180 in material and $250 in labor).