13.1 Selecting Structural Systems: Steel, Concrete, Wood & Masonry

Architect Registration Examination ARE 5.0

Track your progress as you read

Finished sections get a check mark.

1 Chapter 1: ARE 5.0 Structure, Delivery & Scoring

1.1 The Six Divisions: Items, Durations, Sections & Objectives 1.2 Eligibility, PSI Delivery, Fees, Scheduling & Rescheduling 1.3 Cut Scores, Score Reports, Provisional Feedback & Retakes

2 Chapter 2: Licensure Path, Item Types & Test-Day Strategy

2.1 Education Standard, AXP Hours, Settings & Reporting Rules 2.2 The NCARB Record, Score Validity Policy & Reciprocity 2.3 Item Types, Case Studies, Exam Tools, Breaks & Pacing

3 Chapter 3: Practice Management — Firm Resources, Conduct & the Work Environment

3.1 Assessing Practice Resources: Staffing, Development & Capital Investment 3.2 Regulating the Work Environment: FLSA, Antidiscrimination Law, OSHA & ADA Title III 3.3 Ethical Standards, the NCARB Rules of Conduct & the Standard of Care 3.4 Business Structures, Firm Ownership Rules & Practice-Wide Methodologies

4 Chapter 4: Practice Management — Firm Finances & Financial Health

4.1 Utilization, Overhead, Break-Even & Net Multiplier 4.2 Liquidity, Solvency & Reading Firm Financials Strategically 4.3 Accrual vs. Cash Accounting & the Architectural Balance Sheet 4.4 The Income Statement, Net Operating Revenue & Cash Flow Management

5 Chapter 5: Practice Management — Risk, Insurance & Business Development

5.1 Risk Management & the Firm’s Insurance Portfolio 5.2 Contractual Risk Allocation, Intellectual Property & Dispute Resolution 5.3 Client Requests, Compensation Methods, Project Delivery & Project Risk

6 Chapter 6: Project Management — Team, Resources & Consultants

6.1 Assembling the Project Team: Roles, Authority & Selection Criteria 6.2 Allocating & Managing Project Resources: Hours, Rates & Leveling 6.3 Consultant Selection, Qualifications-Based Selection & Scope Boundaries 6.4 AIA C401: Flow-Through, Consultant Standard of Care, Insurance & Payment

7 Chapter 7: Project Management — Work Planning, Scheduling & Budget Control

7.1 The Project Work Plan & Phase Fee Allocation 7.2 Work Breakdown Structures, Scheduling Methods & Dependency Logic 7.3 Critical Path Calculations, Float & Schedule Compression 7.4 Project Communication: Paths, Instruments, Meetings & the Record 7.5 Monitoring the Project Budget with Earned Value Management 7.6 Scope Creep, Additional Services & Written Authorization

8 Chapter 8: Project Management — Contracts, Approvals & Quality Control

8.1 AIA B101: Initial Information, Standard of Care & Basic Services 8.2 B101: Owner Duties, Cost of the Work, Copyright, Termination & Compensation 8.3 The Owner-Contractor Agreement & A201 Contractor Responsibilities 8.4 A201: Architect Administration, Changes, Claims & Separate Contractors 8.5 Regulatory Compliance, Authorities Having Jurisdiction & Project Approvals 8.6 Documenting a Project for the Specified Delivery Method 8.7 Quality Assurance, Quality Control, Constructability & the Record

9 Chapter 9: Programming & Analysis — Site & Environmental Conditions

9.1 Climate Classification, Solar Geometry & Passive Site Opportunities 9.2 Microclimate, Wind, Topography, Grading & Site Hydrology 9.3 Environmental Due Diligence: CERCLA Liability & Phase I / Phase II Assessments 9.4 Soil Mechanics, Geotechnical Investigation & Foundation Selection 9.5 Vehicular Circulation, Access Management, Parking & Emergency Access

10 Chapter 10: Programming & Analysis — Zoning, Codes & Site Infrastructure

10.1 Pedestrian Circulation, Site Utilities & Contextual Constraints 10.2 Zoning Authority, Euclidean and Form-Based Codes & Bulk Standards 10.3 Non-Conforming Uses, Variances, Easements & Parking Feasibility 10.4 IBC Occupancy Classification, Mixed Occupancy & Incidental Uses 10.5 IBC Construction Types, Fire-Resistance Ratings & Compartmentation

11 Chapter 11: Programming & Analysis — Building Programming & Feasibility

11.1 Programming Methodology, Net vs. Gross Area & Building Efficiency 11.2 Adjacency Matrices, Bubble Diagrams, Blocking & Stacking 11.3 Evaluating an Existing Building Against a Program 11.4 Reviewing Project Budget & Schedule Feasibility Against Scope 11.5 Identifying Building & Structural System Alternatives at Programming

12 Chapter 12: Project Planning & Design — Siting, Configuration, Codes & Life Safety

12.1 Building Siting, Neighborhood Context, Zoning Application & Configuration 12.2 IBC Allowable Area: Tabular Area, Frontage & Sprinkler Increases 12.3 Building Height, Story Limits, Mixed Occupancy & Unlimited Area Buildings 12.4 Means of Egress Components & Occupant Load Calculation 12.5 Exit Count, Remoteness, Egress Capacity, Travel Distance & Dead Ends 12.6 Accessible Routes, Slopes, Protruding Objects & Ramp Design 12.7 Door Clearances, Operating Hardware & Accessible Toilet Room Geometry

13 Chapter 13: Project Planning & Design — Structural & Mechanical Systems

13.1 Selecting Structural Systems: Steel, Concrete, Wood & Masonry 13.2 Lateral Force-Resisting Systems, Wind Loads & Seismic Design 13.3 Thermal Comfort, ASHRAE Standard 55 & Psychrometrics 13.4 HVAC System Typologies, Spatial Allocation & Central Plant Equipment 13.5 Potable Water Supply, Drainage, Waste & Vent Systems 13.6 Electrical Distribution, Emergency Power, Lighting & Daylighting 13.7 Fire Suppression, Standpipes, Conveying, Security & Communications

14 Chapter 14: Project Planning & Design — Envelope, Materials & Cost

14.1 Envelope Thermodynamics, Heat Transfer & Fenestration Performance 14.2 Thermal Bridging, Continuous Insulation & Thermal Mass 14.3 Passive Solar Heating, Natural Ventilation & Daylighting Architecture 14.4 Material Selection Criteria, Fire Performance & Vapor Permeance 14.5 Life Cycle Assessment, Embodied Carbon & Material Transparency 14.6 Galvanic Compatibility, Thermal Movement & Masonry Durability 14.7 Cost Estimating by Phase & Contingency Planning 14.8 Life-Cycle Cost Analysis, Present Value & Value Engineering

15 Chapter 15: Project Development & Documentation — Roofing, Waterproofing & Wall Assemblies

15.1 Low-Slope Roofing Systems, Membranes & Drainage Geometry 15.2 Flashing, Parapets, Copings & Roof Penetration Detailing 15.3 Steep-Slope Roofing & Below-Grade Waterproofing 15.4 Enclosure Control Layers & Rain Screen Cladding Systems 15.5 Vapor Retarders, Permeance Classes & Dew Point Control

16 Chapter 16: Project Development & Documentation — Connections, Coordination & Interiors

16.1 Structural Steel Connections & Base Plate Detailing 16.2 Concrete Reinforcing, Cover & Building Movement Joints 16.3 Sizing Structural, Mechanical, Electrical & Plumbing Components 16.4 Ceiling Plenum Coordination, Clash Detection & Level of Development 16.5 Vertical Chases, Shaft Walls, Through-Penetration Firestopping & Rated Joints 16.6 Interior Partition Framing, Head-of-Wall Details & Rated Gypsum Assemblies 16.7 Sound Isolation, STC, NRC & Reverberation Time 16.8 Door and Frame Construction & Fire Door Assemblies Under NFPA 80 16.9 Hardware Functions, Fire-Protection vs. Fire-Resistance Glazing

17 Chapter 17: Project Development & Documentation — Drawings, Specifications & Estimates

17.1 The National CAD Standard, Sheet Modules & Title Blocks 17.2 Drawing Cross-Referencing, Coordination & Revision Control 17.3 Documenting Site Features: Survey, Civil, Grading, Utilities & Landscape 17.4 The Project Manual & CSI MasterFormat Divisions 17.5 Section Numbering & the CSI Three-Part SectionFormat 17.6 Specification Methods & Document Precedence 17.7 Quantity Takeoff Estimating, General Conditions, Overhead & Alternates

18 Chapter 18: Construction & Evaluation — Procurement, Bidding & Preconstruction

18.1 Procurement Methods & AIA A701 Instructions to Bidders 18.2 Addenda Mechanics & Surety Bonds 18.3 The Preconstruction Conference & Administrative Protocols 18.4 Submittal Schedules, Long-Lead Items, Permits & Special Inspections 18.5 Bid Opening, Bidder Qualification & Discrepancy Rules 18.6 Alternates, Allowances, Unit Prices & Contract Award

19 Chapter 19: Construction & Evaluation — Observation & Contract Administration

19.1 The Architect’s Site Observation Role & the Means and Methods Firewall 19.2 Rejecting Non-Conforming Work, Special Inspections & Field Reports 19.3 Submittal Workflow, Review Responsibility & Action Stamps 19.4 Delegated Design, Design-Assist & Deferred Submittals 19.5 Requests for Information & Architect’s Supplemental Instructions 19.6 Change Orders, Construction Change Directives & Instrument Comparison

20 Chapter 20: Construction & Evaluation — Payment, Closeout & Evaluation

20.1 The Schedule of Values & the Application and Certificate for Payment 20.2 Stored Materials, Retainage, Certification Duties & Withholding 20.3 Substantial Completion & the Punch List Protocol 20.4 The Certificate of Substantial Completion & Its Legal Consequences 20.5 Final Completion, Final Payment & the Closeout Package 20.6 Warranty Administration, the Eleven-Month Walk-Through & Post-Occupancy Evaluation

13.1 Selecting Structural Systems: Steel, Concrete, Wood & Masonry

Key Takeaways Explain This Topic AI

Structural steel achieves the longest economical spans and the fastest erection, but requires applied fire protection to meet rated construction types.

Cast-in-place concrete flat plate produces the shallowest floor sandwich, which minimizes floor-to-floor height in repetitive cellular buildings.

Post-tensioned concrete achieves long spans with thin slabs, but post-tensioning tendons severely restrict later penetrations.

Heavy timber and mass timber offer low embodied carbon and an exposed finish, with moisture protection during construction as the principal risk.

Reinforced masonry bearing wall systems are economical for cellular plans but impose a rigid layout that resists later reconfiguration.

Last updated: September 2026

Structural System Comparative Selection

Selecting an optimal structural system is one of the architect's most consequential schematic design decisions. The choice dictates building geometry, floor-to-floor heights, column spacing, MEP routing strategies, construction logistics, cost, and passive fire resistance. On the ARE 5.0 Project Planning & Design (PPD) division, candidates must evaluate competing structural systems based on span capabilities, structural depth, material behaviors, and architectural program requirements.

Structural Steel Framing Systems

Structural steel offers the highest strength-to-weight ratio of any common building material, making it the primary choice for long spans, high-rise construction, and irregular architectural massing.

Wide-Flange Shapes (W-Shapes): Standard hot-rolled wide-flange beams and columns (e.g., W18x35, W24x68) typically span 20 to 50+ feet with span-to-depth ratios of approximately L / 20 L/20 L /20 to L / 24 L/24 L /24 for standard floor beams and L / 28 L/28 L /28 to L / 32 L/32 L /32 for composite beams. In composite construction, steel shear studs welded through corrugated steel decking lock the cast-in-place concrete slab to the steel beam, forcing them to act as a unified T-beam that substantially increases stiffness and load capacity while reducing structural depth.

Open-Web Steel Joists (K, LH, DLH Series): Lightweight, shop-fabricated steel trusses composed of hot-rolled angles and round bars. Standard K-series joists span up to 60 feet; Longspan (LH) joists span up to 96 feet; Deep Longspan (DLH) joists span up to 100+ feet . Open webs provide continuous, unobstructed pathways for mechanical ductwork, electrical conduit, and plumbing piping. Commonly used for roof structures in big-box retail, warehouses, athletic facilities, and gymnasiums. Span-to-depth ratios typically range from L / 18 L/18 L /18 to L / 24 L/24 L /24 .

Light-Gauge Cold-Formed Steel (CFS): Cold-rolled galvanized sheet steel (C-shaped studs and tracks) used for non-load-bearing interior partitions, exterior curtain wall framing, and low-rise load-bearing structures (typically 1 to 4 stories) spanning 15 to 25 feet . CFS provides non-combustible construction (Type I/II), dimensional stability (will not warp, shrink, or twist like dimensional lumber), and resistance to rot and termites.

Passive Fireproofing for Steel: Structural steel is non-combustible but loses approximately 50% of its structural yield strength at 1,000°F (538°C) and buckles rapidly near 1,200°F. Building codes require passive fire protection to achieve 1- to 4-hour fire-resistance ratings:

Spray-Applied Fire-Resistive Materials (SFRM): Cementitious or mineral fiber wet slurries sprayed directly onto steel members; lowest initial cost, lightweight, but visually rough and typically concealed above suspended lay-in ceilings.

Gypsum Board Encasement: Multiple layers of 5/8-inch Type X gypsum board fastened around beams and columns; clean, smooth appearance suitable for enclosed partitions.

Concrete Encasement: Pouring solid concrete around steel members; extremely durable and impact-resistant, but adds massive dead weight.

Intumescent Coatings: Thin, paint-like coatings applied directly to exposed steel. Under high heat (>390°F), the chemical coating undergoes an endothermic reaction, swelling 50 times its original thickness into an insulating cellular carbonaceous char. Ideal for exposed Architecturally Exposed Structural Steel (AESS) where aesthetic elegance and code-mandated fire ratings must coexist.

Concrete Framing Typologies

Cast-in-place and precast concrete systems provide inherent 1- to 4-hour fire resistance without supplemental thermal insulation, superior acoustic separation (high Sound Transmission Class [STC] ratings exceeding STC 50), and massive thermal capacity that damps interior temperature swings.

Concrete System Typology Typical Span Range Structural Depth Ratio Key Advantages Architectural Limitations

One-Way Solid Slab Cast-in-place 10 to 20 ft L / 20 L/20 L /20 to L / 28 L/28 L /28 Simple planar formwork; excellent for heavy concentrated live loads; thin slab profile Requires closely spaced parallel concrete beams and girders, increasing overall floor ceiling depth

One-Way Joist (Pan Joist) Cast-in-place 20 to 35 ft L / 18 L/18 L /18 to L / 22 L/22 L /22 Deep narrow ribs formed by modular pans; removes dead-weight concrete from tension zone below neutral axis Ribbed ceiling requires suspended ceiling or exposed modular aesthetic; limits perpendicular MEP runs

Two-Way Flat Plate Cast-in-place 15 to 25 ft L / 30 L/30 L /30 to L / 36 L/36 L /36 Completely flat ceiling with uniform slab thickness (6–10 in); absolute minimum floor-to-floor height; simple formwork Highly susceptible to punching shear at column heads; requires embedded shear studs or steel shearheads

Two-Way Flat Slab Cast-in-place 20 to 30 ft L / 28 L/28 L /28 to L / 32 L/32 L /32 Thickened drop panels and/or flared column capitals resist high negative moments and punching shear Drop panels project 2 to 4 inches below ceiling, interrupting ceiling planes and horizontal MEP duct routing

Two-Way Waffle Slab Cast-in-place 30 to 50 ft L / 20 L/20 L /20 to L / 26 L/26 L /26 Intersecting two-way joists formed by dome pans; highly rigid; solid heads at columns resist shear; long column-free spans Expensive modular formwork; complex labor; deep ceiling profile requires careful lighting integration

Hollow-Core Planks Precast / Prestressed 25 to 40 ft L / 35 L/35 L /35 to L / 40 L/40 L /40 Rapid crane erection; extruded voids reduce dead load; prestressed strands minimize cracking; smooth underside Rigid modular grid (typically 4- or 8-foot widths); field core-drilling for plumbing penetrations strictly limited

Single / Double Tees Precast / Prestressed 30 to 100+ ft L / 25 L/25 L /25 to L / 32 L/32 L /32 Massive clear spans; deep stems resist huge bending moments; ideal for parking garages, pools, and arenas Large structural depth (24–36+ inches); challenging shipping logistics; difficult to conceal under ceilings

Critical Exam Concept — Punching Shear in Flat Plates: In a two-way flat plate, the entire gravity load transfers directly from the slab into the column over a small perimeter area ( d / 2 d/2 d /2 from the column face). Without deep beams, drop panels, or column capitals, concentrated shear stresses can cause the column to punch vertically through the slab like a hole-punch through paper, precipitating progressive structural collapse. Mitigation strategies include increasing slab thickness, increasing column cross-sectional dimensions, embedding vertical steel shear studs on rail assemblies, or fabricating internal structural steel shearheads.

Wood & Heavy Timber Framing

Light-Frame Wood Construction: Nominal 2x dimensional lumber (2x4, 2x6, 2x8) and prefabricated engineered wood I-joists. Spans typically range from 15 to 25 feet . Dominates residential and low-rise commercial construction up to 5 stories (Type V or Type III construction, frequently combined with a Type I-A concrete podium in "5-over-1" or "5-over-2" podium configurations). Economical, highly workable, but combustible and subject to moisture rot, insect attack, and long-term shrinkage.

Heavy Timber (Type IV-HT) & Glulam: Glued-laminated timber (Glulam) consists of individual 1.5-inch dimensional lumber laminations glued with water-resistant adhesives. Glulams span 40 to 80+ feet , engineered into straight beams, heavy girders, and dramatic curved arches.

Mass Timber & Cross-Laminated Timber (CLT): CLT consists of 3, 5, 7, or 9 layers of kiln-dried dimensional lumber stacked perpendicularly to adjacent layers and glued under massive hydraulic pressure. CLT panels span bi-axially, functioning as rigid two-way structural floor and roof slabs, as well as multi-story load-bearing shear walls. Mass timber offers structural strength comparable to reinforced concrete at approximately 20% of the dead weight.

Wood Charring Mechanics: Heavy timber and mass timber achieve predictable fire resistance through natural charring. When exposed to standard ASTM E119 fire conditions, wood burns from the outside in at a predictable nominal charring rate of approximately 1.5 inches per hour (0.024 in/min) . The resulting outer layer of charcoal has virtually zero oxygen permeability and a thermal conductivity only one-sixth that of virgin wood. This sacrificial char layer insulates the interior unburned wood core, which maintains room temperature, nominal yield strength, and full load-bearing capacity throughout the fire duration.

Reinforced Masonry

Reinforced Concrete Masonry Unit (CMU) construction utilizes hollow modular blocks (typically 8x8x16 inches) laid in mortar. Vertical reinforcing steel bars are placed within the hollow cells, and horizontal ladder/truss wire reinforcement is embedded in mortar bed joints. Solid grout is poured into the reinforced cells, and continuous reinforced horizontal bond beams are cast at floor and roof levels. Reinforced CMU provides superior compressive load-bearing strength, 2- to 4-hour inherent fire resistance, high impact durability, and exceptional resistance to windborne hurricane debris and seismic shear forces.