ASCE 7-22 Wind Load Calculation: Step-by-Step Worked Example

by

Wind load calculations trip up more PEs than almost any other code-driven exercise. ASCE 7-22 has tightened the wording in several places versus ASCE 7-16, but the underlying mechanics are the same: pick a procedure, build up a velocity pressure, scale it with directionality and gust factors, and apply external/internal pressure coefficients to every surface you care about. This walkthrough takes a single low-rise enclosed building and grinds the numbers from start to finish.

Worked example — the building

  • Location: Dallas, TX (Risk Category II)
  • Plan: 60 ft × 40 ft, mean roof height h = 20 ft
  • Gable roof, 4:12 slope (theta ≈ 18.4°)
  • Enclosed building, Exposure C (open terrain)
  • Basic wind speed V = 105 mph (ASCE 7-22 Hazard Tool, Risk Cat II)

Step 1 — Choose a procedure

ASCE 7-22 offers Directional (Ch. 27), Envelope (Ch. 28), and Simplified procedures. For h ≤ 60 ft enclosed/low-rise buildings the Directional Procedure (Part 1 of Ch. 27) is the most flexible and is what most plan reviewers expect. We’ll use it.

Step 2 — Velocity pressure qz

qz = 0.00256 · Kz · Kzt · Kd · Ke · V² (lb/ft²)

For h = 20 ft, Exposure C, Table 26.10-1 gives Kz = 0.90. Flat site so Kzt = 1.0. Buildings: Kd = 0.85. Ground elevation factor Ke = 1.0 (sea level conservatism).

qh = 0.00256(0.90)(1.0)(0.85)(1.0)(105)² = 21.6 psf

Step 3 — Gust effect factor G

The building is rigid (n1 > 1 Hz for a single-story shed). ASCE 7-22 26.11.1 permits G = 0.85. No flexible-structure correction needed.

Step 4 — External pressure coefficients

From Figure 27.3-1 for L/B = 60/40 = 1.5 and theta = 18.4°:

  • Windward wall: Cp = +0.8
  • Leeward wall: Cp = −0.5 (interpolated for L/B = 1.5)
  • Side walls: Cp = −0.7
  • Windward roof (theta ≈ 18°): Cp = −0.5 or +0.0 (use the controlling case for the member)
  • Leeward roof: Cp = −0.5

Step 5 — Internal pressure coefficient

Enclosed building → (GCpi) = ±0.18 per Table 26.13-1.

Step 6 — Net design pressures p

p = q · G · Cp − qi · (GCpi)

For an enclosed building, qi = qh = 21.6 psf. Windward wall (q evaluated at height z, but for h = 20 ft we use qh for the entire wall on this simple geometry):

  • Windward wall, positive internal: p = 21.6(0.85)(0.8) − 21.6(+0.18) = 14.7 − 3.9 = +10.8 psf
  • Windward wall, negative internal: p = 14.7 − (−3.9) = +18.6 psf (controls inward)
  • Leeward wall: p = 21.6(0.85)(−0.5) − 21.6(±0.18) = −9.2 ∓ 3.9 → −13.1 psf (suction controls)
  • Side walls: p = 21.6(0.85)(−0.7) − 21.6(±0.18) → −16.8 psf peak

Common mistakes to avoid

  1. Mixing ASD and LRFD pressures. ASCE 7-22 wind pressures are strength-level. Apply the 0.6W factor when checking against ASD allowables.
  2. Forgetting Kd on individual members. Kd = 0.85 only applies when wind is combined with other loads (Section 26.6); pure wind-only checks use 1.0.
  3. Using MWFRS coefficients for cladding. Cladding and components (C&C) use Chapter 30 with much higher localized coefficients near edges and corners.
  4. Sea-level Ke at altitude. If you’re designing in Denver or Albuquerque, Ke < 1.0 is a legitimate reduction worth taking.

Speed up the math

If you’re running wind on more than one or two buildings a year, automate the velocity pressure and coefficient lookups. Our free engineering toolset includes a beam calculator for distributing those pressures into framing, a column buckling calculator for sizing the vertical members that resist the resulting axial + bending, and a base plate calculator for the connection at the bottom of the column. Chain them and you can iterate a low-rise wind design in an afternoon.

Closing

ASCE 7-22 wind isn’t hard once you internalize the “velocity pressure × gust × coefficient” structure. The traps are in the bookkeeping: which q applies where, when Kd is allowed, MWFRS vs C&C, and strength vs allowable. Walk every project through the same checklist and the calculation collapses into about 30 minutes of work.