A clear walkthrough of C&C pressures: the corner / edge / interior zone system, effective wind area, GCp, and how C&C differs from MWFRS for windows, doors, and cladding.
Components and cladding (C&C) are building-envelope elements that receive wind directly but are not part of the Main Wind Force Resisting System (MWFRS).
Each element transfers localized wind pressure to the primary frame through its connections, fasteners, and supports. C&C analysis sizes individual elements, not the whole building.
Components and cladding feel much higher localized pressures than the overall structural system. Four effects drive this:
Both come from ASCE 7-22, but they answer different questions about the same building.
| Question | Components & Cladding | MWFRS |
|---|---|---|
| What it sizes | Individual envelope elements | The whole structural system |
| Area it acts on | Small effective wind areas | Whole wall / roof surfaces |
| Spatial averaging | Little — peak local gusts | More — building-wide load |
| Typical pressure | 2–3× higher at corners | Lower, building-wide |
| Designs | Windows, doors, cladding, fasteners | Frames, lateral system |
| ASCE 7-22 chapter | Chapter 30 | Chapters 27 & 28 |
ASCE 7-22 divides each surface into zones with different pressure coefficients, based on distance from discontinuities.
Highest pressures, where wind accelerates around edges. Extends distance 'a' from corners, where a = 10% of the least horizontal dimension, minimum 3 ft.
Intermediate pressures along perimeters near roof edges and wall corners. Extends distance 'a' from discontinuities, but excludes the corner zones.
Lower pressures in interior areas away from edges and corners. Covers most of the surface area, with more uniform pressure distribution.
Walls and roofs each carry their own zone layout — so the same window is designed for more pressure in a corner zone than in the field.
A four-step walkthrough for one element — here, a 4 ft × 6 ft window — per ASCE 7-22 Chapter 30.
Find the effective wind area of the component. For a 4 ft × 6 ft window:
Effective wind area = 4 ft × 6 ft = 24 sq ft
Apply the ASCE 7-22 equation for wind speed, exposure, elevation, and topography:
qh = 0.00256 × Kh × Kzt × Kd × V²
= 35.2 psf (example value)
From ASCE 7-22 Chapter 30 figures, by zone and effective area. For a wall edge zone at 24 sq ft:
GCp (positive) = +0.85
GCp (negative) = −1.15
Apply the pressure equation with the internal pressure coefficient (GCpi = ±0.18, enclosed):
p = qh[(GCp) − (GCpi)]
p (pos) = 35.2 × [(+0.85) − (−0.18)] = 36.3 psf
p (neg) = 35.2 × [(−1.15) − (+0.18)] = −46.8 psf
Where C&C design pressures decide whether an envelope element holds in a windstorm.
Glazing systems must resist the peak C&C pressure at their zone without failure.
Entry doors face high C&C pressures plus impact from flying debris.
Wall and roof panels, sheathing, and shutters all transfer C&C pressure through their fasteners.
Need the numbers fast? Windows, Doors & Shutters calculator · Full calculator overview
C&C are building-envelope elements that receive wind loads directly but are not part of the Main Wind Force Resisting System (MWFRS).
They include windows, doors, wall panels, roof panels and sheathing, fasteners, and overhangs.
Each element transfers localized wind pressure to the primary frame through its connections.
MWFRS analysis sizes the whole structural system for the building-wide wind load.
C&C analysis sizes individual envelope elements for the peak local pressure they see.
Because C&C acts on small areas with less spatial averaging, C&C pressures can be 2 to 3 times higher than MWFRS pressures at the same location.
ASCE 7-22 divides each surface into corner, edge, and interior (field) zones.
Corners carry the highest pressures, edges are intermediate, and the interior field carries the lowest.
Walls and roofs each have their own zone layout, so a corner-zone window is designed for more pressure than the same window in the field.
The width of the corner and edge zones is set by the edge-strip dimension 'a'.
It equals 10% of the least horizontal building dimension, with a minimum of 3 ft.
Corner and edge zones extend distance 'a' inward from discontinuities; everything beyond is the interior field.
Effective wind area is the area used to select the GCp coefficient for a component.
A 4 ft by 6 ft window has an effective wind area of 24 square feet.
Smaller effective areas yield higher GCp values, because small elements feel peak gusts that larger areas average out.
Design pressure is p = qh[(GCp) − (GCpi)].
Compute velocity pressure qh = 0.00256 × Kh × Kzt × Kd × V², then select GCp from ASCE 7-22 Chapter 30 by zone and effective area.
Finally apply the internal pressure coefficient GCpi (±0.18 for an enclosed building).
Components and cladding experience higher localized pressures than the overall system.
This is driven by smaller effective wind areas, peak gust fluctuations, edge and corner concentrations, and reduced spatial averaging.
A breached opening can also pressurize the interior, raising loads on the rest of the building.
ASCE 7-22 Chapter 30 governs components and cladding.
It provides the GCp figures by surface, zone, and effective wind area, plus the velocity-pressure and design-pressure equations.
Our calculator implements Chapter 30 with the correct figure for each component.
Run zone detection, GCp selection, and design pressures automatically, then export a permit-ready Engineering Report. PE sign and seal is available in all 50 states.