-110 psf
-85 psf
-65 psf
-85 psf
-70 psf
-50 psf
-45 psf
-70 psf
-95 psf
-75 psf
-75 psf
-95 psf
-95 psf
-75 psf
-75 psf
-95 psf
Tower Height Factor
1.0x
Home / Florida / Broward / Scissor Stair Wind Design
Broward County Stair Enclosures

Scissor Stair Enclosure Wind Load Design

Stair towers and scissor stair enclosures in Broward County face unique wind engineering challenges. With design wind speeds of 170-180 MPH, every face of the enclosure experiences different pressure loads. Doors, walls, and roof connections must all be designed for their specific exposure. Get the calculations right before construction begins.

Calculate Stair Tower Loads Compare Enclosure Types

ASCE 7-22 Components and Cladding

Stair enclosures are designed as C&C elements under ASCE 7-22. Each wall face and the roof use different pressure coefficients based on their orientation to wind. Corner zones experience significantly higher loads than field areas - often 50-80% greater pressures that require reinforced connections and upgraded door assemblies.

0 MPH Broward Design Wind Speed
4 Faces Different Pressure Zones
0 PSF Max Corner Suction
2-Hour Fire Rating Typical

Stair Enclosure Types and Wind Considerations

Each enclosure configuration presents unique wind load challenges in Broward County

Scissor Stairs

Two interlocking stair flights within a single shaft, providing dual egress paths. Common in mid-rise residential and mixed-use buildings where floor area is limited.

Typical Height
60-120 ft
Door Count
2 per floor
Wall Pressure
+65/-95 psf
Fire Rating
2-hour min
  • Higher aspect ratio increases wind loads
  • Multiple door openings weaken wall sections
  • Interior pressurization affects door operation
  • Compact footprint limits structural options
Conventional Stair Tower

Single stair flight per shaft with landing at each level. Used in commercial buildings, parking structures, and high-rise construction where separate egress routes are required.

Typical Height
40-200+ ft
Door Count
1 per floor
Wall Pressure
+55/-85 psf
Fire Rating
2-hour min
  • Larger footprint allows structural flexibility
  • Fewer door penetrations per level
  • Often exposed on multiple building faces
  • Roof penthouse may add complexity
Exterior Stair Tower

Fully exposed stair enclosure attached to building exterior. Maximum wind exposure on all faces with direct impact from wind-borne debris in hurricane conditions.

Exposure
All 4 faces
Door Count
1-2 per floor
Wall Pressure
+70/-110 psf
Impact Zone
Large missile
  • Highest wind load requirements
  • All glazing requires impact rating
  • Connection to main building is critical
  • Debris protection on all faces required
Rooftop Stair Penthouse

Stair enclosure extending above main roof level. Acts as an obstruction creating unique aerodynamic effects and highest velocity pressures at building top.

Height Above Roof
10-15 ft
Exposure Factor
1.15-1.25
Wall Pressure
+75/-120 psf
Roof Uplift
-140 psf max
  • Maximum velocity pressure exposure
  • Roof corners are highest load zones
  • Door must resist penthouse pressures
  • Parapet effects influence loads

Wind Pressure Distribution on Stair Towers

Understanding how pressure varies across each face of the enclosure

Zone 5
-110 psf
Zone 4
-85 psf
Zone 4
-65 psf
Zone 5
-95 psf

Corner Zones (Zone 5)

Within 3-6 ft of corners, highest suction loads

-95 to -110
psf

Edge Zones (Zone 4)

Along edges between corners and field

-70 to -85
psf

Field Zone (Zone 4)

Central wall area, lowest pressures

-55 to -65
psf

Windward Face (Positive Pressure)

Direct wind impact pushes inward on walls and doors

+45 to +70
psf

Stair Tower Door Rating Requirements

Door specifications for Broward County stair enclosures at 170-180 MPH

Door Location Design Pressure Impact Rating Fire Rating Notes
Ground Floor Entry DP +55/-70 Large Missile Required 90 min Highest traffic, must allow egress during storms
Mid-Level Floors (2-6) DP +60/-80 Large Missile Required 90 min Standard requirements, verify corner proximity
Upper Floors (7+) DP +70/-95 Large Missile Required 90 min Increased velocity pressure with height
Roof Access Door DP +75/-110 Large Missile Required 90 min Maximum exposure, weathersealing critical
Interior Corridor Door DP +20/-25 Not Required 90 min Protected location, fire rating primary concern
Exterior Tower Door DP +70/-110 Large Missile Required 90 min Full exterior exposure, hurricane hardware

HVHZ Product Approval Requirements

All doors in Broward County's High Velocity Hurricane Zone must carry Miami-Dade NOA approval with large missile impact certification. The NOA document must show a Maximum Design Pressure (MDP) that meets or exceeds your calculated requirements. Standard Florida Product Approval is not sufficient for HVHZ locations - verify the NOA number before purchase.

Stair Enclosure Wind Design Process

From initial analysis to permit approval in Broward County

1

Determine Enclosure Classification

Identify if your stair tower is fully enclosed, partially enclosed, or exterior-exposed. This classification affects internal pressure coefficients and overall wind load calculations per ASCE 7-22 Section 26.12.

2

Calculate Each Face Separately

Wind pressures vary by face orientation. Calculate windward (+), leeward (-), and side wall (-) pressures independently. Corner zones on each face require separate zone calculations with higher GCp values.

3

Map Door Locations to Pressure Zones

Each door's required design pressure depends on which wall face it penetrates and whether it falls in a corner, edge, or field zone. A door near a corner may require ratings 50% higher than one in the field.

4

Specify Wall Assembly and Connections

CMU walls need reinforcement schedules matching wind loads. Steel stud walls require structural backup. All wall-to-floor and wall-to-roof connections must transfer calculated forces to the structure.

5

Submit with PE Certification

Broward County requires wind load calculations sealed by a Florida PE for stair enclosures. Include door schedules with NOA numbers, wall assembly details, and connection specifications in the permit package.

Stair Enclosure Wind Design FAQs

Common questions about scissor stairs and stair tower wind requirements

What are the wind load requirements for scissor stair enclosures in Broward County?
Scissor stair enclosures in Broward County must be designed for wind speeds of 170-180 MPH depending on location within the county. The enclosure walls typically require design pressures of +45 to +85 psf positive and -55 to -110 psf negative, varying by height and exposure. Stair tower doors must meet the same wind load requirements as the wall sections they penetrate, plus impact resistance in HVHZ areas. All calculations follow ASCE 7-22 Components and Cladding provisions.
Do scissor stair tower doors need impact ratings in Broward County?
In Broward County's High Velocity Hurricane Zone (HVHZ) areas, stair tower doors must have Miami-Dade NOA approval with large missile impact ratings. For non-HVHZ areas of Broward, doors need Florida Product Approval with small missile impact certification. All doors must meet the calculated design pressure for their specific location on the tower. The NOA's Maximum Design Pressure must equal or exceed your calculated DP requirements.
How do wind pressures differ on each face of a stair tower?
Wind pressures vary significantly across stair tower faces depending on wind direction. The windward face experiences positive pressure (pushing inward) typically +40 to +70 psf. Side walls experience negative pressure (suction outward) of -50 to -90 psf. The leeward face sees lower negative pressures around -30 to -50 psf. Most critically, corner zones on all faces experience amplified pressures, often 1.5-2x higher than field areas, requiring upgraded components and connections.
What is the difference between scissor stairs and conventional stair towers?
Scissor stairs consist of two interlocking stair flights within a single shaft, allowing two separate paths of egress in the same footprint as a conventional single stair. Conventional stair towers have a single stair path per shaft. For wind design, scissor stairs create a more compact but taller enclosure with a higher height-to-width aspect ratio, often resulting in increased wind loads. They also have multiple door openings at each level, creating more penetrations that must be designed for wind and fire ratings.
What wall assembly ratings are required for stair tower enclosures?
Stair tower wall assemblies must satisfy both fire and wind requirements simultaneously. Fire ratings typically require 2-hour construction for stairs serving 4 or more stories per Florida Building Code. Wind requirements demand wall systems rated for the calculated design pressures - commonly +60/-80 psf in Broward County locations. CMU walls with appropriate reinforcement are common, but curtain wall systems with proper structural backup are also used for towers requiring glazing for daylighting.
How do I calculate wind loads for a stair tower roof?
Stair tower roofs are designed as Components and Cladding (C&C) under ASCE 7-22 Chapter 30. For flat or low-slope roofs typical of stair towers, calculate using Zone 1 (field), Zone 2 (edge within the a-dimension), and Zone 3 (corner) pressure coefficients from Figure 30.3-2A. In Broward County at 170 MPH design wind speed with Exposure C, expect uplift pressures of -80 to -150 psf in corner zones. The roof structure and its connections to the tower walls must resist these forces with appropriate safety factors.

Get Accurate Stair Tower Wind Calculations

Every face, every door, every zone - calculate the exact design pressures your stair enclosure needs for Broward County approval.

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