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14.2 Elevator Systems: Traction vs. Hydraulic, Core Layout & Sizing
ARE 5.0 Project Planning & Design PPD
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1 Chapter 1: Exam Overview & Schematic Design Process
1.1 ARE 5.0 PPD Format, Scoring & Case Study Navigation 1.2 The Schematic Design Phase & Multi-Discipline Workflow 1.3 Regulatory Framework: Navigating Codes, Standards & Jurisdictions
2 Chapter 2: Site Analysis, Topography & Soil Conditions
2.1 Site Topography, Grading, Slopes & Cut/Fill Calculations 2.2 Geotechnical Reports, Soil Classification & Foundation Selection 2.3 Site Hydrology, Drainage & Stormwater Management Neighborhood Context, Historic Settings & Site Integration
3 Chapter 3: Climate, Microclimate & Solar Design
3.1 Solar Geometry, Sun Angles & Sun Path Diagrams 3.2 Microclimate Analysis, Prevailing Winds & Passive Ventilation 3.3 Passive Solar Heating & Thermal Mass Strategies
4 Chapter 4: Sustainable Principles & Energy Standards
4.1 Daylighting Metrics: Spatial Daylight Autonomy (sDA) & Annual Sun Exposure (ASE) 4.2 Building Energy Standards: ASHRAE 90.1, IECC & Energy Use Intensity (EUI) 4.3 High-Performance Frameworks: LEED v4.1, Net Zero & Embodied Carbon
5 Chapter 5: Zoning Regulations & Land Use Controls
5.1 Zoning Envelopes: Setbacks, Floor Area Ratio (FAR) & Lot Coverage 5.2 Parking Requirements, Access & Site Circulation Planning 5.3 Environmental Regulations: Wetlands, Flood Zones & Brownfields
6 Chapter 6: Building Code Fundamentals: Occupancy & Construction Types
6.1 IBC Occupancy Classifications & Group Characteristics 6.2 Mixed Occupancy Strategies: Nonseparated, Separated & Accessory 6.3 IBC Construction Types I Through V & Fire-Resistance Ratings 6.4 Allowable Building Height & Area Calculations (IBC Tables 504 & 506)
7 Chapter 7: Means of Egress & Fire Protection
7.1 Occupant Load Determination & Egress Sizing (IBC Chapter 10) 7.2 Egress Components: Common Path, Travel Distance & Exit Separation 7.3 Passive Fire Protection: Fire Walls, Barriers & Smoke Partitions 7.4 Active Fire Suppression: Sprinklers, Standpipes & Fire Alarms
8 Chapter 8: Accessibility & Universal Design
8.1 Accessible Routes, Curb Ramps & Parking Layouts (ADA / ICC A117.1) 8.2 Interior Accessibility: Doors, Maneuvering Clearances & Corridors 8.3 Accessible Plumbing Facilities: Restrooms, Grab Bars & Fixture Layouts
9 Chapter 9: Structural Systems: Wood, Steel, Concrete & Masonry
9.1 Structural Selection & Spanning Rules of Thumb 9.2 Steel Framing Systems: Beams, Girders & Open-Web Joists 9.3 Concrete Framing Systems: One-Way, Two-Way & Post-Tensioned Slabs 9.4 Wood Systems: Light-Frame, Heavy Timber & Mass Timber (CLT)
10 Chapter 10: Lateral Force Resisting Systems & Foundations
10.1 Lateral Load Paths: Wind vs. Seismic Forces 10.2 Shear Walls, Braced Frames & Moment Frames 10.3 Shallow vs. Deep Foundation Systems: Footings, Mats, Piles & Caissons
11 Chapter 11: Building Envelope: Physics, Assemblies & Moisture Control
11.1 Envelope Thermal Performance: U-Values, R-Values & Thermal Bridging 11.2 Moisture Management: Vapor Retarders, Air Barriers & Water Resistive Barriers 11.3 High-Performance Wall & Roof Assemblies: Rainscreens & Inverted Roofs 11.4 Fenestration & Glazing: U-Factor, SHGC, Condensation Resistance & VT Interior Materials, Durability & Program Performance
12 Chapter 12: Mechanical & HVAC Systems
12.1 HVAC System Types: All-Air, Air-Water, All-Water & VRF Systems 12.2 Central Plant Equipment: Chillers, Boilers, Cooling Towers & Geothermal 12.3 Ductwork Distribution, Air Handling & Plenum Space Requirements 12.4 Indoor Air Quality, Ventilation Rates & ASHRAE 62.1 Baselines
13 Chapter 13: Plumbing, Electrical & Life Safety Systems
13.1 Domestic Water Supply & Pressure Boosting Systems 13.2 Sanitary Drainage, Venting & Fixture Count Calculations 13.3 Electrical Service, Transformers, Switchgear & Backup Generators 13.4 Lighting Design, Controls & Lighting Power Density (LPD) Limits
14 Chapter 14: Specialized Building Systems & Vertical Circulation
14.1 Architectural Acoustics: STC, NRC, RT60 & Noise Criteria (NC) 14.2 Elevator Systems: Traction vs. Hydraulic, Core Layout & Sizing 14.3 Building Telecommunications, Security & Building Automation Systems (BAS)
15 Chapter 15: Systems Integration & Coordination
15.1 Floor-to-Floor Height & Plenum Coordination (Structure + MEP + Architecture) 15.2 Structural Grid Planning & Spatial Adjacencies 15.3 Building Massing, Orientation & Envelope Integration 15.4 Case Study Strategy: Synthesizing Drawings, Code Sheets & Schedules
16 Chapter 16: Project Costs, Budgeting & Life-Cycle Analysis
16.1 Schematic Estimating Techniques: Area, Volume & Parametric Costs 16.2 Project Budgets: Contingencies, Overhead, Profit & Escalation 16.3 Life-Cycle Cost Analysis (LCCA) & Value Engineering
14.2 Elevator Systems: Traction vs. Hydraulic, Core Layout & Sizing
Key Takeaways Explain This Topic AI
Elevator selection compares rise, speed, traffic, cost, power, service and architectural space.
Manufacturer dimensions and actual stretcher fit govern planning, not a generic car-capacity label.
Handling capacity, effective loading, trip time, departure interval and waiting time are distinct traffic measures.
Coordinate elevator fire/smoke provisions, while escalators and moving walks do not replace required accessible routes or exits.
Last updated: October 2026
14.2 Elevator Systems: Traction vs. Hydraulic, Core Layout & Sizing
Vertical circulation is the functional spine of multi-story architectural design. Elevator system selection and core configuration dictate building structural efficiency, floor plate leasability, egress paths, vertical shaft fire ratings, and overall spatial geometry. During the schematic design phase, architects must determine the appropriate elevator drive typology (hydraulic, geared traction, gearless traction, or machine-room-less), size hoistways, pits, and overhead clearances, establish bank groupings to optimize passenger traffic flow, and incorporate mandatory life-safety and accessibility codes (ASME A17.1 and IBC Chapter 30).
Elevator Drive Typologies & Operating Physics
Elevator systems are categorized by their mechanical lifting drive mechanisms, which establish strict physical limits on travel height, operational velocity, energy consumption, and structural machine room requirements.
1. Hydraulic Elevators
Hydraulic elevators raise a cab via an incompressible fluid (petroleum-based mineral oil or biodegradable vegetable hydraulic fluid) pumped into a steel cylinder, driving a steel piston (ram/plunger) upward. Descent is achieved entirely through gravity by opening a controlled bypass valve that returns fluid to a fluid reservoir without motor power.
Conventional Holed Hydraulic : The hydraulic cylinder extends deep into the ground beneath the hoistway pit inside a drilled well casing. The in-ground borehole depth must equal the total vertical rise of the elevator cab. While structurally stable, drilling boreholes is costly in rocky soils and carries significant environmental risk if petroleum oil leaks into underlying groundwater aquifers.
Holeless Hydraulic : Uses single-stage or multi-stage telescopic dual pistons mounted above the pit floor on opposite sides of the cab rail. Eliminates subterranean drilling, making it standard for low-rise construction, contaminated soils, or high water tables.
Roped Hydraulic : Pairs a holeless hydraulic cylinder with steel wire ropes and sheaves configured in a 2:1 mechanical ratio. The piston travels half the distance of the cab, extending vertical travel height up to approximately 75 ft 75\text{ ft} 75 ft without sub-grade drilling.
Performance Characteristics :
Travel Speed : 100 to 150 feet per minute (fpm) 100\text{ to }150\text{ feet per minute (fpm)} 100 to 150 feet per minute (fpm) (maximum 200 fpm 200\text{ fpm} 200 fpm ).
Travel Height : Practical limit of 50 to 60 ft 50\text{ to }60\text{ ft} 50 to 60 ft ( 2 to 5 stories 2\text{ to }5\text{ stories} 2 to 5 stories ).
Energy Profile : High electrical power draw on ascent ( 30 – 50 HP 30\text{–}50\text{ HP} 30 – 50 HP pump motor), generating waste heat that requires hydraulic oil coolers; zero motor power consumed on descent.
Machine Room Location : Located on the lowest level adjacent to or within 50 ft 50\text{ ft} 50 ft of the hoistway pit.
2. Geared Traction Elevators
Traction elevators suspend the cab and a counterweight from high-strength steel wire hoisting ropes or polyurethane-coated steel belts passing over a grooved drive sheave. The counterweight typically equals the empty cab weight plus 40 % to 50 % 40\%\text{ to }50\% 40% to 50% of the rated passenger live load. As a result, the electric drive motor only expends energy to lift the net weight imbalance.
Mechanical Drive : A high-speed electric motor connects to a mechanical worm-gear reduction box, which turns the drive sheave at lower rotational speed with high torque.
Performance Characteristics :
Travel Speed : 200 to 500 fpm 200\text{ to }500\text{ fpm} 200 to 500 fpm .
Travel Height : Mid-rise buildings up to 250 ft 250\text{ ft} 250 ft ( 5 to 15 stories 5\text{ to }15\text{ stories} 5 to 15 stories ).
Machine Room : Traditionally required an overhead machine room penthouse located directly above the hoistway on the building roof to house the motor, gearbox, deflector sheaves, and controller.
3. Gearless Traction Elevators
Gearless traction systems feature a slow-speed, high-torque direct-drive electric motor (typically permanent-magnet synchronous) with the traction drive sheave mounted directly on the motor shaft, completely eliminating the mechanical gearbox.
Performance : Gearless traction can serve substantial height and speed, but the selected equipment, traffic zoning and structural conditions impose real limits. It is not literally frictionless or silent; coordinate drive support, guide rails, power, heat, vibration and maintenance access.
4. Machine-Room-Less (MRL) Traction Elevators
The advent of compact, lightweight permanent-magnet synchronous motors (PMSM) revolutionized elevator planning by creating the Machine-Room-Less (MRL) elevator.
Spatial Integration : The compact gearless drive motor is mounted directly inside the hoistway—anchored either to the structural guide rails or to an overhead structural beam at the ceiling of the shaft. The digital controller and disconnect switch are housed in a shallow metal cabinet ( 8 to 12 inches 8\text{ to }12\text{ inches} 8 to 12 inches deep) integrated into the wall adjacent to the top landing entrance frame.
Architectural Advantages : Eliminates the bulky rooftop penthouse, reducing structural dead weight, eliminating penetrations through roof weatherproofing membranes, and preserving building height under restrictive municipal zoning envelopes.
Performance Characteristics :
Travel Speed : 150 to 500 fpm 150\text{ to }500\text{ fpm} 150 to 500 fpm .
Travel Height : Up to 250 to 300 ft 250\text{ to }300\text{ ft} 250 to 300 ft ( 20 to 25 stories 20\text{ to }25\text{ stories} 20 to 25 stories ).
Industry Baseline : MRL traction has rapidly become the dominant commercial standard, replacing geared traction and encroaching heavily on low-rise hydraulic markets.
Elevator Typology Comparison Matrix
System Typology Typical Speed Range Illustrative Travel Range First Cost Energy Efficiency Machine Room Needs Ideal Applications
Holeless Hydraulic 100 – 150 fpm 100\text{–}150\text{ fpm} 100 – 150 fpm 50 – 60 ft 50\text{–}60\text{ ft} 50 – 60 ft ( 2 – 5 2\text{–}5 2 – 5 stories) Lowest Low Small room at lowest floor Low-rise offices, retail, schools, apartments
Geared Traction 200 – 500 fpm 200\text{–}500\text{ fpm} 200 – 500 fpm 200 – 250 ft 200\text{–}250\text{ ft} 200 – 250 ft ( 5 – 15 5\text{–}15 5 – 15 stories) Moderate Moderate Overhead rooftop penthouse Mid-rise commercial & residential (legacy)
Gearless Traction 500 – 1 , 800 + fpm 500\text{–}1,800+\text{ fpm} 500 – 1 , 800 + fpm High rise, subject to equipment and traffic design High Highest Overhead room or mechanical floor High-rise commercial towers, hospitals, hotels
Machine-Room-Less (MRL) 150 – 500 fpm 150\text{–}500\text{ fpm} 150 – 500 fpm 250 – 300 ft 250\text{–}300\text{ ft} 250 – 300 ft ( 2 – 25 2\text{–}25 2 – 25 stories) Moderate Superior None (shallow wall cabinet at top floor) Contemporary low-to-mid rise offices & multi-family
Core Planning, Sizing & Spatial Clearances
Elevator cores represent permanent structural shear elements that cannot be easily relocated or expanded once constructed. Accurate schematic dimensioning is essential.
Passenger Cabs vs. Service / Freight Cabs
Passenger Elevators : Standard commercial capacities range from 2 , 500 lbs 2,500\text{ lbs} 2 , 500 lbs (small office/multi-family) to 3 , 500 – 4 , 000 lbs 3,500\text{–}4,000\text{ lbs} 3 , 500 – 4 , 000 lbs (corporate office/hotel). Interior cab clear heights are typically 8 ft 0 in. 8\text{ ft }0\text{ in.} 8 ft 0 in. with 7 ft 0 in. 7\text{ ft }0\text{ in.} 7 ft 0 in. door heights.
Service / Freight Elevators : Rated at 4 , 000 to 5 , 000 + lbs 4,000\text{ to }5,000+\text{ lbs} 4 , 000 to 5 , 000 + lbs , featuring taller interior cab heights ( 9 to 12 ft 9\text{ to }12\text{ ft} 9 to 12 ft ) to accommodate furniture, drywall pallets, and tall equipment. Service cars require heavy-duty floor finishes (diamond plate aluminum or heavy vinyl), protective wall pads, and separate service vestibules connected directly to the building loading dock.
Where IBC 3002.4 applies, demonstrate that at least one elevator accommodates the specified 24-by-84-inch stretcher in the required configuration. A 3,500-pound capacity label alone does not prove dimensional fit. Verify cab, door, maneuvering geometry and hoistway with the manufacturer.
Pit Depth & Overhead Clearance Dimensions
Pit Depth : The recessed structural depression at the base of the hoistway below the lowest finished landing. It accommodates mechanical car and counterweight buffers (spring buffers for speeds ≤ 200 fpm \le 200\text{ fpm} ≤ 200 fpm ; oil buffers for speeds > 200 fpm >200\text{ fpm} > 200 fpm ), safety governors, compensating rope sheaves, and structural safety clearances. Pit depths range from 4 ft 0 in. 4\text{ ft }0\text{ in.} 4 ft 0 in. for low-speed hydraulic/MRL units up to 8 to 10 ft 8\text{ to }10\text{ ft} 8 to 10 ft for high-speed traction cars.
Overhead Clearance : The vertical clear distance from the top finished landing to the lowest underside of the hoistway ceiling structure. It provides mandatory run-by safety clearance for maintenance technicians standing atop the cab roof when the counterweight is fully compressed on its buffer. Clearances range from 14 ft 0 in. 14\text{ ft }0\text{ in.} 14 ft 0 in. for low-speed units up to 20 to 25 + ft 20\text{ to }25+\text{ ft} 20 to 25 + ft for high-speed traction cars.
Elevator Lobby Sizing & Bank Configurations
Elevator lobby width and bank arrangement are program and traffic-design decisions coordinated with accessible circulation and egress. Test queue depth, opposing flows, furniture, security and wayfinding using the selected equipment. Common planning widths and four-car/eight-car groupings are not universal code minima or absolute functional limits.
Elevator lobby width and bank arrangement are program and traffic-design decisions coordinated with accessible circulation and egress. Test queue depth, opposing flows, furniture, security and wayfinding using the selected equipment. Common planning widths and four-car/eight-car groupings are not universal code minima or absolute functional limits.
Elevator lobby width and bank arrangement are program and traffic-design decisions coordinated with accessible circulation and egress. Test queue depth, opposing flows, furniture, security and wayfinding using the selected equipment. Common planning widths and four-car/eight-car groupings are not universal code minima or absolute functional limits.
Elevator Traffic Analysis & Waiting Intervals
Elevator performance in commercial buildings is governed by two fundamental traffic parameters evaluated during the morning peak arrival period (up-peak traffic):
1. Handling Capacity (HC)
Handling capacity measures the percentage of the total building population that the elevator system can transport in a 5-minute peak period :
Commercial Office Buildings : Requires an up-peak handling capacity of 12 % to 15 % 12\%\text{ to }15\% 12% to 15% of the building population.
Multi-Family Residential : Requires a 5-minute handling capacity of 5 % to 7 % 5\%\text{ to }7\% 5% to 7% .
2. Interval / Average Waiting Time (AWT)
The interval is the average elapsed time between successive elevator cars departing the main ground lobby floor during peak periods. The resulting passenger waiting time determines tenant satisfaction:
Excellent (Prime Class-A Office) : < 25 seconds <25\text{ seconds} < 25 seconds
Good (Standard Commercial Office) : 25 to 30 seconds 25\text{ to }30\text{ seconds} 25 to 30 seconds
Fair / Acceptable : 30 to 40 seconds 30\text{ to }40\text{ seconds} 30 to 40 seconds
- Residential Multi-Family : 45 to 60 seconds 45\text{ to }60\text{ seconds} 45 to 60 seconds
- Round Trip Time (RTT)
The Round Trip Time (RTT) is the average time (in seconds) required for an elevator to depart the ground lobby, accelerate, make calculated probabilistic intermediate passenger stops, discharge occupants, return express to the ground floor, and reopen its doors. The total number of elevators ( N N N ) required to serve a building zone is calculated as:
- N = R T T Target Interval N = \frac{RTT}{\text{Target Interval}} N = Target Interval RTT
- Life Safety, Firefighter's Service & Smoke Control
Under ASME A17.1 / CSA B44 and IBC Section 3003, all passenger elevators must provide dedicated two-phase emergency operations for life-safety response:
Phase I Emergency Recall
Phase I recall is designed to immediately remove elevators from public access during a fire:
Activation : Automatically initiated by smoke detectors located in elevator lobbies, hoistways, or elevator machine/control rooms, or manually by a keyed three-position switch ( RESET , OFF , ON ) at the designated primary recall landing (typically the ground lobby).
System Response : All cars in the bank immediately cancel registered car calls, close their doors, and travel non-stop to the primary recall floor. If the fire alarm was initiated by a smoke detector in the ground lobby itself, the cars automatically divert to a pre-designated alternate recall floor (typically the second floor or adjacent grade exit).
Arrival : Cars park with doors fully open to allow occupants to exit safely into the lobby. Hall call buttons and in-car passenger buttons are completely disabled.
Phase II Firefighter's In-Car Operation
Phase II operation allows emergency responders to take direct, manual tactical control of individual elevator cars:
Activation : Firefighters insert a master key into a locked control cabinet inside the cab and turn the switch to ON .
Manual Control : Hall call buttons remain disabled. The car responds only to in-car floor selections made by the firefighter. Crucially, the doors do not open automatically upon arrival at a floor; the firefighter must continuously press and hold the DOOR OPEN button. If smoke or fire is observed outside through the door gap, releasing the button immediately causes the doors to power shut, protecting the crew.
Hoistway Smoke Protection & Pressurization (IBC Section 3006)
Vertical elevator hoistways naturally act as building chimneys, accelerating the upward spread of toxic smoke and hot gases via stack effect during a fire. To prevent hoistways from contaminating upper floors, the International Building Code enforces strict smoke containment rules for buildings where elevator hoistways penetrate more than three stories:
Enclosed Elevator Lobbies (IBC 3006.2) : Fire-rated smoke barrier partitions (typically 1-hour fire-resistance rated) with self-closing, gasketed smoke doors enclosing the elevator landing doors at each floor.
Hoistway pressurization can be an allowed smoke-protection alternative when every condition is met. It does not universally remove all lobby requirements, particularly for special elevator categories. Verify pressure, door operation, smoke-control design and the applicable Section 3006/909 provisions.
Worked Example: Equipment Envelope and Traffic
Assume a top landing 94.5 feet above grade, a 115-foot zoning cap, four cars serving 1,000 people, 13 effective passengers per loaded trip and a 115-second round trip. These are supplied project inputs. Manufacturer A’s MRL arrangement needs 16.5 feet from top landing to underside of the hoistway roof and a 2-foot roof construction allowance. Its top is 94.5 + 16.5 + 2 = 113 94.5+16.5+2=113 94.5 + 16.5 + 2 = 113 feet, below the stated cap. Manufacturer B’s alternative requires an additional 16-foot overhead room in this exercise, producing 129 feet and failing the same cap. Other equipment configurations require their own dimensions rather than a universal MRL-versus-geared height rule.
Five-minute handling is 4 ( 13 ) ( 300 ) / 115 = 135.65 4(13)(300)/115=135.65 4 ( 13 ) ( 300 ) /115 = 135.65 passengers, or 13.57% of the 1,000 served. Departure interval is 115 / 4 = 28.75 115/4=28.75 115/4 = 28.75 seconds. These are preliminary up-peak checks; they are not identical to average waiting time or proof of acceptable traffic for every use. Confirm the traffic model, car loading, dispatching, accessibility, stretcher fit, pit, overhead, power, fire/smoke operation and maintenance routes before selecting the system.
Escalators and moving walks can carry substantial flows but do not replace required accessible vertical routes or exits. Coordinate their openings, landing space, protection and structural support. Use the applicable elevator and building codes and current manufacturer layouts.