What is the ASCE 7 simplified wind load procedure?

ASCE 7 Chapter 27 provides a simplified method for low-rise buildings (h ≤ 60 ft). It uses the velocity pressure equation qh = 0.00256 × Kh × Kzt × Kd × V² × I to compute design pressures for walls and roof zones.

What is Exposure Category B, C, or D?

Exposure B is suburban terrain with obstructions (houses, trees). Exposure C is open terrain with scattered obstructions. Exposure D is coastal terrain within one mile of water. Higher exposure categories produce greater wind pressures.

What wind speed should I use?

Use the design wind speed from ASCE 7-16 Figure 26.5-1A/1B/1C for your location and occupancy category. Common U.S. values range from 85 mph in the central U.S. to 140+ mph along Gulf and Atlantic coasts.

Wind Load Calculator

ASCE 7 simplified procedure — compute velocity pressure, design wind pressures by zone, and total base shear for low-rise buildings

Building Parameters

Basic Wind Speed V (mph)

Exposure Category

Mean Roof Height h (ft) ≤ 60 ft for simplified method

Building Length (ft)

Building Width (ft)

Roof Slope

Occupancy / Risk Category

Design Wind Pressure (windward wall) 0.0 psf

Kh — Exposure coeff.

Kzt 1.00 Topographic

Kd 0.85 Directionality

I — Importance

Velocity Pressure q_h — psf

Zone	Pressure (psf)	Area (ft²)	Force (kips)
Windward Wall	—	—	—
Leeward Wall	—	—	—
Side Wall	—	—	—
Roof (windward)	—	—	—

Total Base Shear — kips

Wind Pressure Zone Diagram

WIND

Windward
— psf

Leeward
— psf

Roof
— psf

— ft wide

— ft

Force Breakdown

Zone	p (psf)	GCp / GCpi	Net Coeff.	Area (ft²)	Force (kips)

Pressures shown are net design wind pressures combining external (GCp) and internal pressure coefficients (±GCpi = 0.18 for enclosed buildings per ASCE 7-16 §26.13). Roof pressure shown is the controlling upward case.

Basic Wind Speed V (ASCE 7-16)

Design wind speed is determined from ASCE 7-16 Figures 26.5-1A (Risk Cat I), 26.5-1B (Risk Cat II), and 26.5-1C (Risk Cat III/IV). Values below are typical for common U.S. regions for Risk Category II:

Region	Typical V (mph)	Notes
Midwest / Great Plains	85–95	Low-hazard, flat terrain
Pacific Northwest / Mountain West	85–100	Varies by elevation
Mid-Atlantic / New England	100–110	Coastal influence increases toward shore
Southeast (inland)	100–115	Higher near Gulf / Atlantic coast
Gulf Coast (TX, LA, MS, AL)	120–140	Hurricane zone
Florida (Atlantic coast)	120–150	Miami-Dade: up to 170 mph
Hawaii	130–160	Higher on windward exposures
Puerto Rico	145–175	Eastern tip highest

Always use official ASCE 7-16 wind speed maps or local building department records for code-compliant design. Never interpolate between regions.

Exposure Category Definitions (ASCE 7-16 §26.7)

Suburban / Urban

Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Applies for ≥ 1500 ft upwind.

Examples: residential neighborhoods, dense suburban areas, forested regions

Open Terrain

Open terrain with scattered obstructions having heights generally less than 30 ft. Applies for flat, open country, grasslands, and shorelines in hurricane-prone regions.

Examples: farmland, open fields, airports, parking lots, golf courses

Coastal / Water

Flat, unobstructed areas and water surfaces outside hurricane-prone regions. Applies within 1 mile of open water for Exposure D upwind fetch.

Examples: shorelines, lakefronts, rivers, tidal flats

Velocity Pressure Exposure Coefficient K_h (ASCE 7-16 Table 26.10-1)

Height (ft)	Exposure B	Exposure C	Exposure D
0–15	0.57	0.85	1.03
20	0.62	0.90	1.08
25	0.66	0.94	1.12
30	0.70	0.98	1.16
40	0.76	1.04	1.22
50	0.81	1.09	1.27
60	0.85	1.13	1.31

External Pressure Coefficients GCp (ASCE 7-16 §27.3)

Surface	L/B Ratio	GCp (windward)	GCp (leeward)
Windward wall	All	+0.8	—
Leeward wall	0–1	—	−0.5
Leeward wall	2	—	−0.3
Leeward wall	≥ 4	—	−0.2
Side walls	All	−0.7
Roof (flat, 0–5°)	All	−0.9 to −0.18
Roof (low slope, 6–20°)	All	−0.5 / +0.2	−0.6
Roof (medium, 21–35°)	All	+0.2	−0.6
Roof (steep, >35°)	All	+0.8	−0.6

Importance Factor I_w (ASCE 7-16 Table 1.5-2)

Risk Category	I_w	Typical Occupancy
I	0.87	Storage, agriculture, minor facilities
II	1.00	Residential, commercial, office
III	1.15	Assembly (>300), schools, jails
IV	1.15	Hospitals, emergency facilities, power plants

Key Equations (ASCE 7-16)

Velocity Pressure q_h = 0.00256 · K_h · K_zt · K_d · V² · I V in mph → q_h in psf (ASCE 7-16 Eq. 26.10-1)

Design Wind Pressure p = q_h · G · C_p − q_i · (GC_pi) G = 0.85 (rigid buildings), GC_pi = ±0.18 enclosed

Base Shear V_wind = (p_WW − p_LW) · A_wall Combined windward push + leeward suction

Wind Force per Zone F = p · A / 1000 F in kips, p in psf, A in ft²

Common Design Pressures by Region

Region	V (mph)	Exposure	h (ft)	Windward (psf)	Base Shear*
Kansas City, MO	90	C	20	14.0	Low
Charlotte, NC	100	B	20	12.9	Moderate
Atlanta, GA	100	B	20	12.9	Moderate
Houston, TX	130	C	20	32.7	High
Miami, FL	175	D	20	76.2	Very High
New Orleans, LA	140	D	20	49.0	High
Seattle, WA	85	B	20	10.2	Low
Honolulu, HI	130	C	20	32.7	High

*Qualitative comparison only. Always calculate using project-specific wind speed maps and site conditions.

How to Use This Calculator

Select basic wind speed from the dropdown using ASCE 7-16 Figure 26.5-1 for your location and Risk Category, or enter a custom value.

Choose exposure category based on your site's terrain for at least 1500 ft upwind: B (suburban), C (open), or D (coastal).

Enter building dimensions — height (mean roof height, max 60 ft for simplified), length, and width.

Select roof slope and occupancy category. The importance factor is automatically applied.

Read results — velocity pressure qh, design pressures for all zones, and total base shear. Switch to Pressure Map for a visual diagram.

Glossary

K_h — Velocity pressure exposure coefficient at mean roof height. Increases with height and exposure openness.

K_zt — Topographic factor. Equals 1.0 for flat terrain; increases for hills/ridges (ASCE 7-16 §26.8).

K_d — Wind directionality factor. 0.85 for buildings (ASCE 7-16 Table 26.6-1).

G — Gust effect factor. 0.85 for rigid buildings (natural frequency ≥ 1 Hz).

GC_p — External pressure coefficient. Depends on surface (wall, roof), L/B ratio, and roof slope.

GC_pi — Internal pressure coefficient. ±0.18 for enclosed buildings, ±0.55 for partially enclosed.

q_h — Velocity pressure at mean roof height (psf). The fundamental pressure reference for all zones.

Base Shear — Total horizontal wind force on the building. Sum of windward wall push and leeward wall suction forces.

Frequently Asked Questions

Is this calculator valid for code submissions?

This calculator uses the ASCE 7-16 simplified procedure (Chapter 27) for educational and preliminary design purposes. For permit applications, consult a licensed structural engineer who will apply the full ASCE 7 Directional or Envelope procedure as required by your jurisdiction.

Why is the height limit 60 ft?

The ASCE 7 simplified procedure (Part 1 of Chapter 27) applies to low-rise buildings with mean roof height h ≤ 60 ft and h/L ≤ 1. Taller buildings require the full directional procedure with height-varying pressures and more complex aerodynamic considerations.

What is topographic factor Kzt and when does it change?

K_zt accounts for wind speed-up over hills, ridges, and escarpments. It equals 1.0 for flat terrain (the default). If your building is near a hilltop or escarpment, K_zt can increase to 1.5 or more — use ASCE 7-16 §26.8 and Figure 26.8-1 to calculate the actual value.

Should I use the wind load or seismic base shear for design?

Use whichever base shear is larger (governing load combination). In hurricane-prone coastal zones, wind typically controls. In seismically active regions like California and the Pacific Northwest, seismic loads often govern. Always check both and apply IBC load combinations per ASCE 7-16 §2.3 (LRFD) or §2.4 (ASD).

What GCpi value is used for internal pressure?

This calculator uses GC_pi = ±0.18 for enclosed buildings per ASCE 7-16 §26.13.2. The sign is chosen to maximize the net pressure for each surface (additive for windward, subtractive for leeward/roof). Partially enclosed or open buildings have higher internal pressure coefficients (±0.55) and require additional analysis.

How do I determine the correct exposure category?

Stand at your building site and look upwind in the direction of the prevailing storm wind. Assess the surface roughness for at least 1500 ft (Exposure B) or 1 mile (Exposure D). When the terrain falls between categories, use the more severe category. When in doubt, use Exposure C — it's the "default" for many AHJs.