What are components and cladding?

Components and cladding (C&C) are building envelope elements that receive wind pressure directly but are not part of the Main Wind Force Resisting System (MWFRS). This includes windows, doors, wall panels, roof sheathing, fasteners, and all exterior building components. C&C elements transfer wind loads to the structural frame through local connections and supports.

Why are C&C wind loads higher than MWFRS loads?

Components and cladding experience higher localized wind pressures because: (1) Smaller effective wind areas result in higher pressure coefficients per ASCE 7, (2) Peak local pressure fluctuations that don't affect the entire structure simultaneously, (3) Edge and corner effects create pressure concentrations, (4) Smaller tributary areas mean less spatial averaging of pressures. C&C loads can be 2-3 times higher than MWFRS loads for the same location.

What is GCp in wind load calculations?

GCp is the combined external pressure coefficient used in components and cladding wind load calculations. It combines the gust effect factor (G) and external pressure coefficient (Cp) into a single value that varies with effective wind area. ASCE 7 provides GCp values in Chapter 30 figures for different building surfaces, zones, and effective wind areas ranging from 10 to 500 square feet.

Components and Cladding Wind Loads | C&C Pressure Calculator ASCE 7

What are Components & Cladding?

Components and cladding (C&C) are building envelope elements that receive wind loads directly but are not part of the Main Wind Force Resisting System (MWFRS).

C&C elements transfer localized wind pressures to the primary structural frame through connections, fasteners, and supports. Unlike MWFRS calculations that consider the entire building, C&C calculations focus on individual elements.

Windows and glazing systems
Doors and storefronts
Wall panels and cladding
Roof panels and sheathing
Fasteners and connections
Overhangs and canopies

Why C&C Loads are Critical

Components and cladding experience significantly higher localized wind pressures than the overall structural system. This occurs due to:

Smaller effective wind areas - Result in higher pressure coefficients per ASCE 7 methodology
Peak pressure fluctuations - Localized gusts that don't affect the entire building simultaneously
Edge and corner effects - Pressure concentrations at building discontinuities
Reduced spatial averaging - Smaller areas experience less pressure smoothing

C&C pressures can be 2-3 times higher than MWFRS pressures for the same building location.

Hurricane-Resistant C&C Applications

Critical components and cladding calculations for coastal and hurricane-prone regions

Impact Resistant

Windows & Glazing

Impact-resistant windows are the first line of defense against hurricane-force winds. Proper C&C calculations ensure glazing systems withstand extreme pressures without failure.

Window failures are the leading cause of structural damage during hurricanes

Impact-resistant laminated glass sizing
Design pressure ratings (DP 30-80)
Large missile impact testing compliance
Frame anchorage to structural openings
Positive and negative pressure resistance
Coastal zone wind-borne debris requirements

High Wind Rated

Doors & Entry Systems

Entry doors face extreme wind pressures combined with impact from flying debris. C&C calculations determine the required design pressure ratings and reinforcement details.

Door breaches create internal pressurization that can destroy roof structures

Impact-rated door assemblies
Design pressure (DP) certification requirements
Heavy-duty hinges and multi-point locking
Frame-to-wall anchoring specifications
Garage door reinforcement systems
Hurricane-rated sliding glass doors

Storm Protection

Storm Shutters & Panels

Storm shutters provide critical protection when impact-resistant windows aren't present. C&C analysis ensures shutters can withstand design wind pressures and debris impacts.

Properly installed shutters can prevent catastrophic building pressurization

Accordion shutter track and panel design
Roll-down shutter box and guide sizing
Colonial shutter hinge and fastener spacing
Plywood panel thickness and attachment
Bahama shutter arm and anchorage design
Wind load and impact testing compliance

Understanding C&C Pressure Zones

ASCE 7 divides building surfaces into distinct zones with different pressure coefficients based on distance from discontinuities

Corner Zones

Highest pressures occur at building corners where wind accelerates around edges. Typically extends distance 'a' from corners (where a = 10% of least horizontal dimension, min 3 ft).

Edge Zones

Intermediate pressures along building perimeters near roof edges and wall corners. Extends distance 'a' from discontinuities but excludes corner zones.

Field Zones

Lower pressures in interior building areas away from edges and corners. Represents the majority of building surface area with more uniform pressure distribution.

Sample C&C Calculation Process

Step 1: Determine Effective Wind Area

Calculate the effective wind area for the component. For a 4 ft × 6 ft window:

Effective Wind Area = 4 ft × 6 ft = 24 square feet

Step 2: Calculate Velocity Pressure (qh)

Apply ASCE 7 equation considering wind speed, exposure, elevation, and topography:

qh = 0.00256 × Kh × Kzt × Kd × V² = 35.2 psf (example value)

Step 3: Select GCp Coefficients

From ASCE 7 Chapter 30 figures based on zone and effective area. For wall in edge zone with 24 sf area:

GCp (positive) = +0.85
GCp (negative) = -1.15

Step 4: Calculate Design Pressures

Apply pressure equation with internal pressure coefficient:

p = qh[(GCp) - (GCpi)]
p (positive) = 35.2 × [(+0.85) - (-0.18)] = 36.3 psf
p (negative) = 35.2 × [(-1.15) - (+0.18)] = -46.8 psf

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Components & Cladding Wind Loads