16.3 Sizing Structural, Mechanical, Electrical & Plumbing Components

Architect Registration Examination ARE 5.0

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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

16.3 Sizing Structural, Mechanical, Electrical & Plumbing Components

Key Takeaways Explain This Topic AI

Preliminary structural depth is estimated as a fraction of span, and for steel a useful shortcut is a depth in inches of roughly half the span in feet.

Duct cross-sectional area equals airflow divided by velocity, which converts an engineering quantity directly into a plenum dimension.

Typical office planning figures are roughly one ton of cooling per 300 to 400 square feet and roughly 400 cfm of supply air per ton.

NEC Article 110.26 requires working clearance at electrical equipment of not less than 36 inches deep, 30 inches wide, and 6 feet 6 inches high.

Plumbing fixture counts follow from occupancy classification to occupant load to the code fixture table, so an occupant load error corrupts every downstream count.

Last updated: September 2026

PDD objectives 1.2 and 1.3 ask you to determine the size of mechanical, electrical, plumbing, and structural systems and components. You are not performing engineering; you are reserving the right amount of space and confirming that the engineer's sizes fit the architecture. If a formula is required on the exam, NCARB supplies it in the item — what you must bring is the method and the planning rules of thumb.

Structural Depth Rules of Thumb

Preliminary member depth is expressed as a fraction of span. These are planning approximations for reserving space, not design values.

• Member Approximate depth
• Steel beam or girder span / 20 to span / 15
• Open-web steel joist span / 20 to span / 24
• Steel truss span / 10 to span / 12
• Wood joist or rafter span / 20
• Glulam beam span / 16 to span / 20
• Concrete one-way slab span / 24 to span / 28
• Concrete beam span / 12 to span / 15
• Concrete flat plate span / 30 to span / 33
• Post-tensioned slab span / 40 to span / 45

A useful shortcut for steel: beam depth in inches is roughly half the span in feet. A 40-foot span suggests a member on the order of 20 inches deep. That single approximation is enough to test whether a floor sandwich fits.

Depth is not the only sizing question. Preliminary column size grows with tributary area and the number of floors above; preliminary footing size is the supported load divided by the allowable soil bearing pressure from the geotechnical report.

Mechanical Sizing

Quantity Planning rule of thumb

Cooling load Roughly 1 ton (12,000 Btu/h) per 300–400 sq ft for typical office; far denser for data, kitchen, and laboratory spaces

• Supply airflow Roughly 400 cfm per ton of cooling
• Office supply air Roughly 1 cfm per square foot
• Duct main velocity Roughly 1,500–2,500 feet per minute for medium-velocity commercial mains
• Duct cross-sectional area Airflow divided by velocity: A (sq ft) = cfm ÷ fpm
• Mechanical room area Roughly 3% to 6% of gross floor area for an all-air system
• Ceiling plenum depth Roughly 18 to 36 inches for an all-air system with ducted mains

The duct area relationship is the one to internalize, because it converts an engineering quantity into an architectural dimension. A 10,000 cfm main at 2,000 fpm requires 5 square feet of cross section — a 30-inch by 24-inch duct before insulation and hangers. That duct will not fit in a 16-inch plenum, and discovering it at design development is the failure this objective is written to prevent.

Outdoor air quantities come from ASHRAE Standard 62.1 , which combines a per-person rate with a per-area rate, so occupancy density drives ventilation independently of floor area.

Electrical Sizing

• Quantity Planning rule of thumb
• Total connected load, office Roughly 5 to 10 watts per square foot
• Lighting power density Roughly 0.6 to 0.9 W/sq ft under current energy codes, by space type
• Electrical room One main service room plus a distribution closet per floor, stacked

Working clearance at equipment Not less than 36 inches deep, 30 inches wide, and 6 feet 6 inches high under NEC Article 110.26

Transformer Requires ventilation, clearance, and structural support; often located at grade or in a vault

Architecturally, the sizing question is not the ampacity — it is the volume and clearance the equipment demands, and the riser path connecting the service entrance to every floor.

Plumbing Sizing

Two calculations recur.

Fixture counts come from the plumbing code table of minimum required fixtures, applied to the occupant load derived from the building code. The sequence is fixed: occupancy classification → occupant load → fixture table → required water closets, lavatories, drinking fountains, and service sinks, typically divided evenly between the sexes unless the occupancy justifies otherwise. Get the occupant load wrong and every downstream fixture count is wrong.

Supply and drainage sizing is driven by fixture units: each fixture type carries a water supply fixture unit value and a drainage fixture unit value, the values are totaled, and the pipe size is read from the code table. Hot water heater capacity is sized from peak demand, not from total fixture count.

Static pressure changes by roughly 0.433 psi per foot of elevation, which is why a tall building needs pressure zones and why the architect must reserve space for pressure-reducing stations or intermediate mechanical floors.

Special Systems

Preliminary elevator quantity is driven by population, handling capacity, and interval; preliminary sprinkler design is driven by the hazard classification, which sets the design density and remote-area size under NFPA 13; and preliminary generator sizing is driven by the connected emergency and standby loads under NEC Articles 700 through 702.

Exam Tip: These items are almost always testing whether the engineered quantity fits the architecture . Convert every sizing answer into a dimension — duct depth, shaft footprint, equipment room area, structural depth — and then check it against the plenum, the shaft, the room, and the floor-to-floor height that the design actually provides.