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Elevator shaft sizing, pit depth, and ASME A17.1

Helonic is an AI construction drawing analysis platform for teams looking up hoistway size, pit depth, and ASME A17.1 rules. This is the reference for hoistway width and depth, pit depth, overhead clearance, and ASME A17.1 equipment that is not allowed in the shaft.

Field stories about rails, pits, and cab clearance live on elevator shaft coordination errors. Helonic flags when a hoistway on the architectural plan does not match the manufacturer layout or when MEP crosses a hoistway wall.

Elevator shafts are among the most coordination-intensive elements in any multi-story building. They involve every major discipline, architecture (shaft layout, lobbies), structural (hoistway walls, pit, machine room), mechanical (venting, fire protection), electrical (power, controls, communications), and plumbing (pit drainage). Errors in elevator coordination discovered during construction are extremely costly because shafts are constrained by structure on all sides.

Timing is Critical

Elevator manufacturer layout drawings must be incorporated into the design before structural drawings are finalized. The hoistway is one of the few building elements where the structural opening size is dictated by equipment rather than design preference, getting it wrong means expensive structural modifications.

What elevator system types show up on construction drawings?

Construction drawings typically show traction, machine-room-less, or hydraulic elevators, and the type sets shaft size, pit depth, and machine-room location.

Traction (Geared)
Speed
150-500 FPM
Max Rise
Up to 250 feet
Machine Room
Dedicated room at top of hoistway
Best For
Mid-rise buildings (4-15 stories)
Traction (Gearless)
Speed
500-2,000 FPM
Max Rise
Unlimited
Machine Room
Dedicated room at top of hoistway
Best For
High-rise buildings (15+ stories)
Machine-Room-Less (MRL)
Speed
150-500 FPM
Max Rise
Up to 250 feet
Machine Room
Controller in adjacent closet, machine in hoistway
Best For
Low to mid-rise, limited space
Hydraulic
Speed
75-200 FPM
Max Rise
Up to 70 feet (6 stories)
Machine Room
Adjacent machine room (any location)
Best For
Low-rise buildings (2-6 stories)
Holeless Hydraulic
Speed
75-150 FPM
Max Rise
Up to 50 feet (4 stories)
Machine Room
Adjacent machine room
Best For
Retrofit, no below-grade drilling

Who dictates hoistway dimensions and clearances?

Hoistway dimensions are dictated by the elevator manufacturer and must accommodate the car, counterweight, guide rails, and required clearances. Key dimensions to verify:

Inside Hoistway Width
Car width plus counterweight width plus clearances. Typically 7'-0" to 9'-6" for passenger elevators. Must match manufacturer's layout exactly.
Inside Hoistway Depth
Car depth plus front/rear clearances. Typically 6'-6" to 8'-0" for standard passenger cars. Rear-opening elevators require additional depth.
Overhead Clearance
Distance from top floor landing to underside of overhead structure. Typically 14'-18' for traction, 12'-14' for hydraulic. Per ASME A17.1 minimum requirements.
Front Wall to Guide Rail
Critical for door operator clearance. Verify dimension from hoistway face to centerline of guide rails matches manufacturer requirements.
Rough Opening at Landings
Width and height of structural opening at each landing for elevator entrance frames. Typically 4'-2" wide × 8'-2" high for standard 3'-6" doors.

What does an elevator pit need to include?

An elevator pit needs the manufacturer-required depth, waterproofing and drainage, a pit ladder when depth exceeds 35 inches, lighting, and a GFCI receptacle.

Pit Depth
Varies by elevator type and speed. Hydraulic: 4-6 feet typical. Traction: 8-14 feet typical. MRL: 5-8 feet. Always confirm with elevator manufacturer's layout drawings.
Pit Waterproofing
Pits below the water table require waterproofing membrane and drainage. A sump pit with pump is required by ASME A17.1 for all elevator pits to remove water accumulation.
Pit Ladder
Fixed steel ladder required per ASME A17.1 when pit depth exceeds 35 inches. Must be accessible from the lowest landing door.
Pit Lighting & Receptacle
Minimum one light fixture (permanently installed, not connected to elevator power) and one GFCI duplex outlet required in every pit.
Structural Loading
Pit floor must support elevator buffer impact loads. Typically 40,000-80,000 lbs for hydraulic buffers. Structural engineer must design pit slab for these loads.
Pit Drainage
Floor slope toward sump pit. Sump pump with alarm connection to building monitoring system. No drain connected to sanitary sewer (oil contamination risk).

What must you coordinate in an elevator machine room?

Machine rooms need the manufacturer location and size, structural loading, HVAC to hold 55-110°F, a dedicated disconnect in sight of the machine, and lockable rated access.

Location
Traditional traction: directly above the hoistway. Hydraulic: can be adjacent at any level within 65 feet of hydraulic jack. MRL: controller closet adjacent to top landing, machine mounted in hoistway.
Room Size
Minimum size per manufacturer requirements, typically 1.5× hoistway footprint for traction. Must accommodate equipment, electrical panels, and required working clearances.
Structural Loads
Machine room floor must support elevator machine, sheaves, and dynamic loads. Traction machine rooms: 300-500 PSF typical. Structural engineer must design for manufacturer-provided loading data.
HVAC Requirements
Machine rooms must maintain 55-110°F temperature range per ASME A17.1. Dedicated cooling often required, machine rooms generate significant heat. Ventilation must not introduce contaminants.
Electrical Service
Dedicated electrical disconnect in machine room (within sight of machine). Power requirements vary: hydraulic 25-50 HP, traction 15-75 HP, high-speed traction 100+ HP.
Access
Machine room doors must be lockable, fire-rated to match shaft rating, and accessible to authorized personnel only. Minimum 7'-0" ceiling height. No other building systems may be routed through the machine room.

What fire rating and venting rules apply to hoistways?

Hoistway enclosures need a 2-hour rating for four or more stories and 1-hour for fewer, and IBC 3004 requires venting when a hoistway connects three or more stories.

Fire Rating Requirements

  • Hoistway enclosure: 2-hour rating for 4+ stories, 1-hour for fewer (IBC 713.4)
  • Landing doors: 1.5-hour rating for 2-hour shaft, 1-hour for 1-hour shaft
  • All penetrations through rated walls require listed firestopping
  • Elevator lobby not required if building is fully sprinklered (with additional protections per IBC 3006)
  • Smoke-proof enclosure may be required for firefighter elevator

Hoistway Venting

  • Required by IBC 3004 for hoistways connecting 3+ stories
  • Minimum 3.5% of hoistway cross-section area at top
  • Vents must open automatically upon fire alarm activation
  • May be replaced by mechanical smoke exhaust system per IBC 3004.3
  • Venting prevents hoistway from acting as chimney for smoke migration

What MEP work is banned from an elevator hoistway?

Critical Rule

ASME A17.1 Section 2.1.1 prohibits any equipment or wiring not directly related to elevator operation from being installed in the hoistway. This means no HVAC ducts, plumbing pipes, electrical conduits, fire sprinkler mains, or communication cables may pass through or be installed within the elevator shaft. The only exceptions are sprinkler piping protecting the hoistway itself, elevator-related wiring, and elevator pit drainage.

No plumbing pipes of any kind may pass through the hoistway, reroute around the shaft
No HVAC ductwork permitted in the hoistway, this includes exhaust ducts from adjacent spaces
Electrical conduits serving non-elevator systems may not be routed through the shaft
Sprinkler piping within the hoistway must be specifically designed for elevator protection per NFPA 13
Smoke detectors in the elevator lobby (not in the shaft) are required for elevator recall
Sill angle support steel is permitted but must not reduce required clearances

What elevator shaft coordination issues show up most often?

The most common shaft failures are size changes after elevator selection, MEP routed through the hoistway, and overhead clearance that no longer meets ASME A17.1.

Shaft Size Changes After Elevator Selection
The architect designs a shaft based on preliminary dimensions, but the selected elevator manufacturer requires different clearances. This results in structural modifications to completed shafts.
Prevention: Get manufacturer layout drawings during design development, before structural drawings are issued for permit.
MEP Penetrations Through Hoistway Walls
Piping, conduits, or ductwork routed through the elevator shaft violates ASME A17.1 Section 2.1.1, which prohibits non-elevator equipment in hoistways.
Prevention: Flag all MEP routing near shafts during coordination. Nothing except elevator-related wiring and sprinkler piping may enter the hoistway.
Insufficient Overhead Clearance
Mechanical equipment, ductwork, or structural members in the overhead (top of shaft) reduce clearance below ASME A17.1 minimums, preventing elevator installation.
Prevention: Maintain minimum overhead clearance per manufacturer (typically 14-18 feet above top floor landing). Coordinate with structural and mechanical early.
Slab Edge Conflict with Door Frames
Structural slab edges or beams conflict with elevator entrance frame embedments. Entrance frames require specific rough openings that must align with structural openings.
Prevention: Coordinate sill angles and header beams with elevator entrance schedule. Verify rough opening dimensions at every landing.
Fire Rating Discontinuity
Hoistway fire rating is not maintained where sprinkler piping, electrical conduit, or sill angles penetrate the shaft wall.
Prevention: All penetrations through rated hoistway walls require listed firestopping. Sill angles must be coordinated with fire-rated wall construction.
Lobby Dimension Conflicts
Elevator lobby depth, door swing clearances, or stretcher elevator requirements conflict with corridor widths or adjacent rooms.
Prevention: Verify ADA lobby clearances (60" minimum depth), stretcher elevator size (IBC 3002.4), and door swing clearances with floor plan layouts.

Sources

ASME A17.1/CSA B44, Safety Code for Elevators and Escalators

IBC 2021, Chapter 30, Elevators and Conveying Systems

IBC 2021, Section 713, Shaft Enclosures

NFPA 13, Standard for Installation of Sprinkler Systems (Elevator Hoistway Protection)

ADA/ABA Guidelines, Section 407, Elevators

Keep exploring

Companion guides for shaft, life safety, and MEP coordination.

Fire Rating Guide

Shaft enclosure fire rating requirements.

Firestopping Guide

Penetration firestopping at shaft walls.

MEP-Structural Clashes

Common MEP and structural coordination conflicts.

ADA Accessibility Guide

Elevator accessibility requirements.

Clash Detection Feature

AI-powered clash detection across all disciplines.

MEP Coordination Best Practices

Strategies for effective MEP coordination on projects.

Automate elevator shaft coordination

Helonic's AI can cross-reference elevator shaft dimensions across architectural and structural drawings, flag MEP routing conflicts near hoistways, and verify fire rating continuity at every landing, catching coordination issues before they become field problems.