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Chapter 8 Metals
Structural steel members, construction methods, quantity takeoff, and cost estimation for metal systems in commercial and industrial construction.
Structural Steel Members
Types, grades, and properties of steel used in construction
Structural steel construction uses horizontal beams, trusses, and vertical columns joined together to create large open structures. The type of steel chosen depends on engineering requirements — yield strength, corrosion resistance, and application.
The most common structural steel is ASTM A36 — a carbon steel with a yield strength of 36,000 lb/sq in. It is ductile (deforms without fracturing) and can be welded or bolted. In Canada, A44 is most common.
Steel Grades & ASTM Designations
| Steel Type | ASTM | Min Yield (KSI) | Form | Best For |
|---|---|---|---|---|
| Carbon — A36 | A36 | 36 | Plates, shapes, bars, bolts | General buildings, high toughness |
| Carbon — A529 | A529 | 42 | Plates, shapes, bars | Buildings, similar construction |
| High-Strength | A440 | 42–50 | Plates, shapes, bars | Lightweight, superior corrosion |
| Hi-Str. Low-Alloy | A572 | 42–65 | Some as plates, shapes, bars | Bridges, high toughness |
| Corr.-Res. Hi-Str. | A242 | 42–50 | Plates, shapes, bars | Lightweight, weathering grades |
| Corr.-Res. Hi-Str. | A588 | 42–50 | Plates, shapes, bars | Durable, weathering grades |
| Quenched & Tempered | A514 | 90–100 | Several types as plates | Strength varies with thickness |
Beams & Girders
A beam is a horizontal structural member that carries loads over an opening. Beams spaced more than 4′-0″ OC are classified as girders — large horizontal members that support loads at isolated points along their length and are the heaviest members in a structure.
- Parallel inner and outer flange surfaces of constant thickness
- Joined with a perpendicular web
- Web provides vertical-plane strength; flanges provide horizontal-plane strength
- Noted as “W” + web depth (in) + nominal weight (lb/ft)
- Example: W24×76 = 24″ web, 76 lb/ft
- Most common for beams, columns, trusses
- Parallel outer flange surfaces but sloping inner flange surfaces (~17% slope)
- Joined with a perpendicular web
- Noted as “S” + web nominal depth + nominal weight (lb/ft)
- Example: S12×31.8 = 12″ web depth, 31.8 lb/ft
- Nominal and actual depths are equal for S-shapes
Columns
A column is a vertical structural member that supports axial compressive loads. They are the principal load-carrying vertical members. Columns are constructed using W- and S-shapes, or hollow structural shapes (HSS) such as round pipe or square tubing where loads are relatively light.
Round HSS columns are commonly used with W-shape beams to support floor loads in residential basement construction.
Joists & Purlins
A joist supports the load of a floor or ceiling and is spaced less than 4′-0″ OC. An open web joist uses steel angles as chords with steel bars extending between them at angles. A purlin spans across adjacent rafters or between beams/columns to carry intermediate loads.
Open Web Joist Designation System
Open web joists are designated using nominal depth (inches), joist series, and chord diameter (⅛″ increments).
- K series: 8″–24″ depth, 2″ increments, spans up to 60′-0″ — light commercial
- LH series (Long-Span): spans up to 96′-0″
- DLH series (Deep Long-Span): spans up to 144′-0″ without center support
- Example: 24LH07 = 24″ nominal depth, LH (long-span) series, ⅞″ chord diameter
Quick Reference: Click to Reveal Definitions
A horizontal structural member used to support loads over an opening. W- and S-shapes are most common. Classified as beams when spaced greater than 4′-0″ OC and carrying horizontal loads.
A large horizontal structural member that supports loads at isolated points along its length. Carries the loads of beams and joists. Usually the heaviest horizontal members in a structure.
A vertical structural member used to support axial compressive loads. Principal load-carrying vertical members in structural steel construction. Made from W- or S-shapes, or hollow structural shapes (HSS).
A horizontal support member spanning across adjacent rafters or between beams, columns, or joists to carry intermediate loads. Purlins carrying wall panels are also called girts. Formed using C-shapes or zees.
A beam in the perimeter of a structure that spans several columns and typically supports a floor or roof. Angles fastened to the columns or beams allow the spandrel beams to be fastened into place.
A floor made of light-gauge corrugated metal panels (decking) placed horizontally and fastened to structural members. Used for both roof decks (high strength-to-weight, reduces dead load) and floor decks (provides working platform and forms for concrete slabs).
Steel Shapes Reference
Symbols, designations, and notation systems for structural steel members
Estimators must recognize steel shape symbols on architectural and structural drawings. Different manufacturers, fabricators, and architects may use slightly different notations — always verify with the source when unfamiliar symbols are encountered.
Notation / Reading Steel Designations
W-Shape Notation
Format: W [Web Nominal Depth in inches] × [Nominal Weight in lb/ft]
Example: W24×76
- W = Wide Flange shape
- 24 = 24-inch nominal web depth
- 76 = 76 lb per linear foot
- Note: due to weight variances (lb/sq ft), actual size may differ from nominal
S-Shape Notation
Format: S [Web Nominal Depth in inches] × [Nominal Weight in lb/ft]
Example: S12×31.8
- S = Standard (I-Beam) shape
- 12 = 12-inch nominal web depth
- 31.8 = 31.8 lb per linear foot
- Unlike W-shapes, the nominal and actual depths of S-shapes are equal
Structural Tee Notation
Tees are cut from W-, S-, or M-shapes through the center of the web, forming two tees from each full member.
Example: WT6×11
- WT = Tee cut from a W-shape
- 6 = nominal depth of 6 inches (flange width listed first)
- 11 = 11 lb/lf
- ST = cut from S-shape | MT = cut from M-shape
Zee Shape Notation
Zees are noted in sequence of: depth × first flange width × second flange width × steel thickness.
Example: Z4×3×3×⁵⁄₁₆
- 4 = depth of 4 inches
- 3 = equal flange width of 3 inches (first flange)
- 3 = equal flange width of 3 inches (second flange)
- ⁵⁄₁₆ = steel thickness of ⁵⁄₁₆ inches
Hollow Structural Section (HSS) Notation
Columns may use round pipe or square/rectangular tubing when loads are relatively light.
Round Pipe — Example: 8 Sch 60
- 8 = 8-inch nominal inside diameter
- Sch 60 = Schedule 60 wall thickness
Square Tubing — Example: 3×3×¼
- 3 = 3-inch square tube column
- ¼ = ¼-inch wall thickness
Always check with the manufacturer, fabricator, or architect when unfamiliar symbols or notations appear. Errors in shape identification directly affect material costs and can lead to significant bid errors.
Structural Steel Construction Methods
Five major methods: beam-and-column, long-span, moment-resisting, framed-tube, and wall-bearing
Varying engineering requirements and job-site conditions create the need for several structural steel construction designs. A structural engineer determines all loads, then specifies the steel types, sizes, and shapes. Shop drawings are developed for individual structural components at a fabrication shop, then transported to the job site and “shaken out” (unloaded in planned manner).
Building Information Modeling (BIM) is commonly used in structural steel fabrication. BIM allows for seamless integration from design through fabrication shop to job site. Bar codes and marking systems track delivery and final placement of each member.
Beam-and-Column Construction
The most common structural steel construction method. Consists of bays of framed structural steel members repeated to create large structures.
- Foundation footings, piers, or piles support columns
- Anchor bolts and baseplates prepared before setting columns
- Columns are normally the first members erected
- Horizontal beams and girders attached; angles may form seats for beams
- Tie rods, channels, wire rope, and bracing added to plumb and secure all members
- Robotic welding increasingly used for repetitive processes (e.g., welding studs to bridge deck girders)
Long-Span Construction
Consists of fastening large horizontal steel members together and bracing them with angles, channels, and other steel members to create large girders and trusses.
- Used for structures requiring large open areas: bridges, arenas
- Utilizes a series of built-up girders and trusses
- Spans large areas with few intermediate columns or supports
- Large girders and beams span between bridge abutments, piers, and other supports
- A concrete or steel deck is supported by the large structural steel members
- Detail and shop drawings indicate the layout of angles, channels, and other members for girder/truss construction
Moment-Resisting Construction
The stability of the steel frame and its wind and seismic resistance depend on a solid connection between columns and beams.
- Top and bottom flanges of each beam are welded or bolted to columns using full-length welds or high-strength bolts
- Structures designed to act as a single unit when subjected to wind or seismic loads
- Typically used with low-rise structures
- Connection hardware: angle seats, shear plates, seat lugs attached to columns to support beams during erection
Framed-Tube Construction
Structural steel members form an exterior load-bearing wall resembling a structural steel tube.
- Columns in exterior walls spaced close together, welded to large horizontal spandrel beams spanning several columns
- Most common type used with high-rise structures
- Provides excellent resistance to lateral wind and seismic loads through the tube-like exterior frame
Wall-Bearing Construction
Horizontal steel beams and joists are supported and reinforced with masonry or reinforced concrete walls.
- Steel beams and joists span areas between masonry or reinforced concrete walls
- Masonry or concrete walls support the vertical loads; steel carries horizontal loads
- Bearing baseplates on the walls provide proper load distribution at points where structural steel members rest on walls
- Common for buildings with large open spaces: warehouses, airplane hangars, convention centers
Visual: Beam-and-Column vs. Framed-Tube
Decks, Framing & Stairways
Roof decks, floor decks, metal framing members, studs, channels, and metal stairways
Metal roof decks provide a high strength-to-weight ratio that reduces dead load. Corrugated decking is placed horizontally and fastened to structural members.
Roof deck variations include: width and height of corrugated ribs, distance between corrugations, and metal finish. Some create watertight joints; others are covered with insulation and roofing materials. Where sustainable roof structures are needed, additional weight support may be required for turf, plantings, and water.
| Profile Depth | Span Range | Width | Max Length |
|---|---|---|---|
| 1″ | 2′-6″ to 8′-0″ | 32–33 | 42′-0″ |
| 1½″ | 4′-0″ to 11′-0″ | 36 | 42′-0″ |
| 1½″ (acoustical) | 10′-0″ to 20′-0″ | 24 | 42′-0″ |
| 3″ deep deck | 9′-0″ to 13′-0″ | 24 | 40′-0″ |
| 4½″ deep deck | 20′-0″ to 30′-0″ | 24 | 30′-0″ |
A metal floor deck provides a work platform during construction as well as a form and reinforcement for concrete slabs.
Composite vs. Noncomposite Floor Decks
- Composite Floor Decks: Corrugated floor decking fastened to top of joists with self-tapping screws or welding. Topped with several inches of concrete — the concrete depth varies depending on supported loads. Thickness of concrete is indicated on erection plans, floor plans, or detail drawings.
- Noncomposite Floor Decks: Similar installation but the deck and concrete do not act compositely — the steel deck serves primarily as formwork and construction platform.
Estimators count deck panels of each type and enter numbers into a ledger sheet, spreadsheet, or estimating program. A schedule from the manufacturer may help take off the proper quantity of each panel type. Material, transportation, fastener, and labor costs must all be included in the final estimate.
Metal framing constructs a framework using light-gauge metal components — analogous to wood-platform framing. Studs are fastened with self-tapping screws or welded to top and bottom tracks.
- Vertical steel-framing members extending from bottom track to top track
- Most commonly made of 14 ga, 16 ga, 18 ga, or 20 ga steel
- Load-bearing studs: C-shapes and nailable studs
- Common channel studs: 2½″ to 6″ wide, 1″ and 1⅝″ depths
- C-shapes: 2½″ to 8″ wide, 1¼″ to 1¹³⁄₁₆″ depths
- Nailable studs: 3⅝″ and 4″ wide, 1¹³⁄₁₆″ and 1¹⁵⁄₁₆″ depths
- U- and furring channels are most common light-gauge types
- Used for framing and supporting gypsum board and other wall-finish materials
- Shown on erection plans using the [ symbol
- Channel size notation: depth first, then flange width, then steel thickness
- Ex: [1⅜×3½×97 = 1⅜″ depth, 3½″ flange, 97 mil thickness
- C-channels and zees used for purlins and girts
In some areas, lighter-gauge metal studs and joists are installed by a drywall or carpentry contractor rather than a structural steel subcontractor. This will impact labor rate calculations — the estimator must check stud spacing and placement on each job.
Metal stairway systems are installed in commercial buildings for common areas, fire escapes, or freestanding structures (e.g., spiral stairs). Materials include cast iron, steel, or aluminum.
Spiral Metal Stairs
Supported by a vertical center pipe onto which treads are fastened.
- Platform sizes and well openings correspond to stair diameter
- Stair diameters range from 42″ to 72″; platform size from 22×22 to 37×37; well opening from 44×44 to 74×74
- Center pipe OD: Cast iron 3½″–4½″; Stainless/Aluminum 3½″–5″ (varies with stair diameter)
Stairway costs include: fabrication labor, installation labor, stringer materials, tread pans, risers, handrail. Estimators should check specifications to determine if installation is part of the stairway cost in their scope of work prior to submitting a bid.
Metal stairway treads may be made of: cast iron, checker plate steel, expanded metal grating, C-channel, angles, or bar grating — depending on tread application and location. Treads may be coated with abrasive grit for traction. Metal nosing may also be used.
Structural Steel Quantity Takeoff
How estimators measure, count, and price structural steel members
Estimators rely on bids from a steel fabricator for costs regarding structural steel members. The fabrication shop determines costs for each element including material, labor, and transportation costs. Lead times for fabrication and shipping of structural steel materials may be longer than other materials.
BIM software enables users to create a structural framing schedule of all sizes and weights of structural components as a building is being designed — providing quantity information without additional calculation.
How to Take Off Each Member Type
Columns
- Column locations noted on erection plans by a grid of letters and numbers (e.g., column D2 = intersection of grid line D and 2)
- Notation “W12×53” at an intersection = W-shape, 12″ web, 53 lb/lf
- Estimators count the number of columns of each type and enter into a ledger sheet, spreadsheet, or estimating program
- Pricing for each column must include: overall height, bearing capacity, steel type, baseplate, and connections for intersecting beams/girders
- For multistory buildings, material cost variations, transportation, fasteners, and labor costs must all be included
Beams & Girders
- Beam and girder sizes noted on plan views and elevations, along grid lines
- Lengths obtained from grid spacing dimensions
- Letter and number identification system used — marked on beam/girder at fabrication shop and correspond to erection plan drawings
- A schedule of beam sizes and types may be provided in addition to drawings
- Estimators take into account material size, material type, and connection information when pricing
- Material cost variations, transportation, fasteners, and labor costs must be included in the final estimate
Joists
- Unlike columns and beams, joists are not normally identified using a grid of letters and numbers
- The spacing and direction of joists are noted on the erection plans
- Open areas indicated by dashed lines in an “X” pattern; solid diagonal lines indicate required cross-bracing
- Joist type may be noted by manufacturer ID code, standard classification format, or fabrication-shop code number
- Estimators determine the number of each joist type of a particular length and develop a joist schedule
- Information forwarded to fabrication shop: quantity, length (span), depth, top and bottom channel design, web design, and bearing/support design at each end
Framing Members (Studs & Track)
- Estimators identify stud spacing, length, and gauge from prints and specifications
- Linear feet of wall for each stud gauge are determined
- Multipliers are used to determine number of studs: 1′-0″ OC = multiplier 1; 16″ OC = 0.75; 24″ OC = 0.50
- Number of studs = (wall plate length × multiplier) + 1
- Track length = wall plate length × 2 (top and bottom)
- Totals for each length and gauge should include approximately 3% to 5% for waste
Worked Example: Metal Studs
Wall section = 12′-10½″ long, studs at 16″ OC
Step 1: Convert to decimal feet: 12′-10½″ = 12.875′
Step 2: Number of studs = (12.875 × 0.75) + 1 = 9.66 + 1 = 10.66 → rounded to 11 studs
Step 3: Track length = 12.875 × 2 = 25.75′ → rounded up to 26′ (without waste)
Labor Cost Factors — Steel Erection
- Job-site accessibility for steel delivery
- Shaking-out areas and hoisting equipment availability
- Coordination with field supervisory personnel
- Building height and need for additional lifting equipment
- Season of the year (cold weather impacts)
- Safety netting requirements
- Personal fall-protection equipment
- Perimeter protection for tradesworkers erecting structural steel
- Titles 01 35 23 and 01 35 26 of specifications — worker fall protection requirements
- Additional mobilization for robotic welding at job site
Interactive Calculators
Apply formulas from this chapter to real estimating scenarios
Practice Problems
Apply chapter concepts to realistic construction estimating scenarios
- Convert the wall length from feet-inches to decimal feet
- Apply the stud count formula: (wall length × multiplier) + 1
- Round up to the nearest whole stud
- Calculate track: wall length × 2, then add 4% waste
- Calculate total material cost: quantity × material unit cost
- Calculate total labor cost: quantity × labor unit cost
- Calculate total equipment cost: quantity × equipment unit cost
- Sum all three for the total project cost
- Calculate the roof area (L × W)
- Calculate material cost: area × material unit cost
- Calculate labor cost: area × labor unit cost
- Calculate the combined material + labor total
- Identify the series letter code and what it means
- Identify the depth from the numeric prefix
- Identify the chord diameter from the last two digits
- Explain what an “X” pattern of diagonal lines indicates on a joist plan
This is a conceptual problem — review the answer below.
Chapter Quiz
Test your understanding of structural steel members, methods, and quantity takeoff
Glossary of Terms
Key vocabulary from Chapter 8 — Metals
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