Conveying Systems: Elevator Types, Height Limitations, Shaft Sizing, Machine Room Requirements, and Escalators

Covers the selection, integration, and coordination of vertical conveying systems including hydraulic and traction elevators, machine-room-less configurations, escalators, and platform lifts. Addresses shaft sizing, pit depth, overhead clearance, machine room placement, fire service access elevator requirements, accessibility scoping under ABA/ADA, and traffic analysis methodology for determining elevator quantity, speed, and grouping.

ARE · Project Development & Documentation

Overview

Every multi-story building needs a strategy for moving people and materials vertically. On the PDD exam, you need to know how to select the right conveying system for a given project, size shafts and machine rooms, and coordinate these systems with structural, fire protection, and accessibility requirements.

Conveying systems fall into several categories: traction elevators (geared and gearless), hydraulic elevators, machine-room-less (MRL) elevators, escalators, and platform lifts. Each has distinct height limitations, speed ranges, and spatial requirements that directly affect building planning.

The architectural impact is significant. Elevator shafts create vertical penetrations that run the full height of a building, consume floor area on every level, and require fire-rated enclosures. Machine rooms need structural support for heavy equipment and adequate ventilation. Escalators demand large floor openings and specific rise-to-run geometry.

You also need to understand how accessibility standards (ABA/ADA) scope elevator requirements for multi-story buildings, how fire service access elevators function in high-rises, and how traffic analysis determines the number and grouping of elevators. These decisions happen during design development and carry straight through into construction documentation. Understanding these requirements before you start designing floor plans and core layouts prevents costly retrofits when the elevator consultant identifies conflicts with shaft dimensions, pit depths, or machine room locations during DD.

Essential

Elevator Types and Their Applications Three primary elevator drive systems serve different building types, and the choice between them shapes shaft dimensions, structural loads, and building layout. Traction Elevators use steel ropes (or belts) running over a sheave driven by an electric motor. They come in two configurations: - Geared traction: A gear reducer connects the motor to the sheave. Speeds typically range from 100 to 350 fpm (feet per minute). Suitable for mid-rise buildings up to roughly 250 feet of travel. The gear reducer allows a smaller, less expensive motor but limits top speed. - Gearless traction: The motor connects directly to the sheave with no gear reducer, allowing speeds from 500 to 2,000+ fpm. Required for high-rise applications. More expensive but far more efficient at heights above 250 feet.

Professional

Selecting the Right Elevator Type for a Mid-Rise Medical Office Building Consider an architect designing a 6-story, 120,000 SF medical office building with a floor-to-floor height of 13 feet. Total rise is approximately 65 feet. The building serves a mix of ambulatory patients, staff, and visitors, with some wheelchair and stretcher traffic. Hydraulic elevators cannot serve this height economically. A holed hydraulic elevator maxes out around 50-60 feet, and stretcher-size cars at that height push against both the travel limit and speed constraints (100-150 fpm creates unacceptable wait times for 6 floors). The design team selects geared traction elevators at 200 fpm, which comfortably handle a 65-foot rise. The traffic analysis determines three elevators are needed: two grouped for passenger service and one service elevator for stretcher and material transport. The machine room goes on the roof, directly above the shaft group.

TLDR

Traction elevators: Geared (100-350 fpm, up to ~250 ft) and gearless (500-2,000+ fpm, no practical height limit). Both use counterweights and require overhead machine rooms unless MRL.
Hydraulic elevators: Limited to ~50-60 ft travel (holed) or ~20-25 ft (holeless). Slower, cheaper, machine room at lowest level. Low-rise only.
MRL elevators: Compact gearless machines inside the hoistway. No separate machine room needed. Mid-rise applications up to ~250 ft.
Shaft sizing factors: Car capacity, door type (center-opening = wider), counterweight position, pit depth (4-5 ft minimum for traction), overhead clearance (14-18 ft for traction).
Fire service access elevators: Required when occupied floors exceed 120 ft above fire department access. Pressurized shaft, fire-rated doors, dual power, protected lobby with stair access.
Escalators: 30-degree standard incline, 90-120 fpm, large floor openings with fire protection. Never count as accessible routes.
ABA F206.2.3: Accessible route required to every story/mezzanine unless specific exceptions apply (two-story with 5 or fewer occupants on one floor, etc.).
Platform lifts: Permitted only in specific situations (performance areas, judicial spaces, incidental spaces with 5 or fewer, existing site constraints).
Traffic analysis: Evaluate peak periods, average interval (25-35 sec target for offices), and handling capacity. Separate traffic streams in hospitals and courthouses.
ASME A17.1: Governing safety code for all elevators and escalators.

ELI5

Think of a tall building as a vertical neighborhood. People live and work on different floors, but unlike a flat neighborhood, they can't just walk sideways to get around. They need ways to go up and down. That is what conveying systems do. Elevators are like vertical taxis. Some are pulled up by cables and a motor at the top of the building. Those are called traction elevators, and they work great for tall buildings. Think of a pulley system with a heavy counterweight on the other side to help balance the load. The motor does not have to lift the full weight of the car and passengers; it only handles the difference between the car and the counterweight. Other elevators get pushed up from below by a hydraulic piston, like a car on a mechanic's lift at an auto shop.

AREProject Development & Documentation

Conveying Systems: Elevator Types, Height Limitations, Shaft Sizing, Machine Room Requirements, and Escalators

2 min read209 words

Moving People Through Buildings: Conveying Systems on the ARE

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