US Standards Series · Part 3 of 9

Load Determination per ASCE 7-22

ASCE 7-22 Chapter-by-chapter guide to establishing design loads: dead loads, live loads with reduction, snow, wind. Includes a ready-to-use rule-of-thumb table for preliminary sizing in both US Customary and SI units.

Dead Loads — Chapter 3
Live Loads — Chapter 4
Live Load Reduction
Snow Loads — Chapter 7
Wind Loads — Chapter 26–27
Rule-of-Thumb Table

1. Dead Loads — ASCE 7-22 Chapter 3

Dead loads are the permanent weights of the structure and its fixed elements. ASCE 7-22 Chapter 3 provides minimum requirements; actual dead loads must be computed from the actual materials and construction used.

Common Dead Load Values

Element	US (psf)	SI (kN/m²)	Notes
Normal-weight concrete (per in depth)	12.5	0.60	145 pcf / 22.8 kN/m³
Structural steel framing (estimate)	8–15	0.38–0.72	Beam weight; varies with span/spacing
Metal deck (1½ in, 20 ga)	2.5	0.12	Without concrete fill
Normal concrete slab (4.5 in / 115 mm)	56	2.68	4.5 in × 12.5 psf/in
Mechanical / electrical / plumbing	5–8	0.24–0.38	Allow for ducts, sprinklers
Ceiling + light fixtures	3–5	0.14–0.24	Acoustic tile + grid + lights
Floor finish (tile, carpet)	1–5	0.05–0.24	Tile: ~5 psf, carpet: ~1 psf
Partitions (ASCE 7 §4.3.2 minimum)	15	0.72	Treat as live load min. per ASCE 7
Roofing (built-up)	5–10	0.24–0.48	Metal: 3–5 psf; BUR: 8–10 psf

Partition loads (ASCE 7-22 §4.3.2): Where partitions are anticipated, a live load of at least 15 psf (0.72 kN/m²) must be included. This provision treats moveable partitions as live load, not dead load.

2. Live Loads — ASCE 7-22 Chapter 4 (Table 4.3-1)

Live loads represent the expected occupancy loads. ASCE 7-22 Table 4.3-1 specifies minimum uniformly distributed live loads (Lo) by occupancy. These are nominal loads before any permitted reduction.

Occupancy / Use	Lo (psf)	Lo (kN/m²)	Notes
Residential: bedrooms, living areas	40	1.92	Private apartments, dwellings
Residential: public rooms, corridors	100	4.79	Hotels, apartments
Office: typical floor	50	2.39	Reducible (AT ≥ 400 ft²)
Office: lobbies, first floor	100	4.79	Not reducible
Retail: ground floor	100	4.79	Not reducible
Retail: upper floors	75	3.59	Reducible
Assembly: fixed seats	60	2.87	Churches, theaters
Assembly: moveable seats	100	4.79	Not reducible
Schools: classrooms	40	1.92	Reducible
Schools: corridors above 1st floor	80	3.83
Storage: light	125	5.99	Not reducible
Storage: heavy	250	11.97	Not reducible
Parking: passenger vehicles	40	1.92	Reducible with AT limit
Roof: ordinary flat / low slope	20	0.96	Min. roof live load Lr; governs if > snow
Stairs and exits	100	4.79	Not reducible

3. Live Load Reduction — ASCE 7-22 §4.7

For members with large tributary areas, the full nominal live load is unlikely to act simultaneously everywhere. ASCE 7-22 §4.7 permits reducing the design live load L as follows:

ASCE 7-22 Eq. 4.7-1 — Reduced live load

USL = Lo × (0.25 + 15/√(KLL × AT))Lo and L in psf; AT in ft²

SIL = Lo × (0.25 + 4.57/√(KLL × AT))Lo and L in kN/m²; AT in m²

Live Load Element Factor KLL

Element	KLL
Interior columns	4
Interior beams without cantilever slabs	2
Edge beams without cantilever slabs	2
Edge columns with cantilever slabs	3
Corner columns with cantilever slabs	2
Two-way slabs	1

Reduction Limits — §4.7.3

L shall not be reduced below 0.50 Lo for members supporting one floor
L shall not be reduced below 0.40 Lo for columns or members supporting two or more floors
No reduction for Lo ≥ 100 psf (4.79 kN/m²) or for assembly occupancies
Reduction requires KLL × AT ≥ 400 ft² (37.2 m²)

Example — Interior office column, 5 floors: Lo = 50 psf, AT = 20 ft × 20 ft = 400 ft², KLL = 4. KLL×AT = 1,600 ft². L = 50×(0.25 + 15/√1600) = 50×(0.25 + 0.375) = 31.25 psf. But limit ≥ 0.40×50 = 20 psf. → Use L = 31.25 psf per floor.

4. Snow Loads — ASCE 7-22 Chapter 7

Snow loads depend on the geographic location (ground snow load Pg from ASCE 7 Figure 7.2-1), roof geometry, and thermal conditions.

ASCE 7-22 §7.3 — Flat roof snow load

US & SIpf = 0.7 × Ce × Ct × Is × pgsame units as pg (psf or kN/m²)

Key Snow Load Factors

Factor	Description	Typical Range
Ce (Exposure)	Terrain category and exposure	0.7 (fully exposed) – 1.3 (sheltered)
Ct (Thermal)	Heat loss through roof	1.0 (heated) – 1.3 (cold, unheated)
Is (Importance)	Risk Category I–IV factor	0.80 (RC I) – 1.20 (RC IV)
pg	Ground snow load from Fig. 7.2-1	0–100+ psf (0–4.8+ kN/m²) by region

ASCE 7-22 §7.4 — Sloped roof snow load

US & SIps = Cs × pf

Cs = roof slope factor (≤ 1.0); Cs = 1.0 for slope ≤ 15°; decreases to 0 at 70° for warm roofs.

Minimum roof live load vs snow: ASCE 7 §4.5 specifies a minimum roof live load Lr (12–20 psf / 0.58–0.96 kN/m²) that acts when snow is absent. Use max(Lr, S) in load combinations — they are not additive.

5. Wind Loads — ASCE 7-22 Chapters 26–27

Wind loads require a full procedure per ASCE 7-22. The simplified approach for low-rise buildings (Method 1) and the directional method for all buildings (Method 2) are most common.

ASCE 7-22 §27.3.1 — Design wind pressure on MWFRS

US & SIp = qz × G × Cp − qi × G × Cpipsf or kN/m²

ASCE 7-22 §26.10.1 — Velocity pressure

USqz = 0.00256 × Kz × Kzt × Ke × V²V in mph; qz in psf

SIqz = 0.613 × Kz × Kzt × Ke × V²V in m/s; qz in Pa (N/m²)

Key Wind Parameters

Parameter	Description	Source
V (mph or m/s)	Basic wind speed for Risk Category	ASCE 7-22 Figs. 26.5-1A through C
Kz	Velocity pressure exposure coefficient	ASCE 7-22 Table 26.10-1
Kzt	Topographic factor (hills, ridges)	§26.8; = 1.0 for flat terrain
Ke	Ground elevation factor	§26.9; = 1.0 if not determined
G	Gust factor	0.85 (rigid) or dynamic analysis
Cp	External pressure coefficient	ASCE 7-22 Fig. 27.3-1
Cpi	Internal pressure coefficient	ASCE 7-22 Table 26.13-1

Typical Design Wind Speeds (Risk Category II)

Region	V (mph)	V (m/s)
Interior US (low wind)	95–115	43–51
Gulf Coast (Tx, La)	130–150	58–67
Florida Atlantic coast	150–180+	67–80+
Pacific Coast (Calif.)	85–110	38–49
Pacific Northwest	90–100	40–45

5a. Wind Exposure Categories — ASCE 7-22 §26.7

The exposure category defines how rough or smooth the surrounding terrain is, directly affecting the Kz coefficient and thus the velocity pressure at any height.

Category	Terrain Description	Typical Applications
B	Urban and suburban areas, wooded areas, or terrain with closely spaced obstructions the size of single-family dwellings or larger, over a distance ≥ 1,500 ft (460 m) or 10× building height	Downtown low-rise, suburban residential
C	Open terrain with scattered obstructions having heights generally < 30 ft (9.1 m); flat open country and grasslands	Rural, farmland, airports
D	Flat, unobstructed areas and water surfaces; mudflats, salt flats, unbroken ice; fetch distance ≥ 5,000 ft (1,500 m) or 10× building height	Coastal shorelines, open bays, large lakes

5b. Velocity Pressure Exposure Coefficient Kz — ASCE 7-22 Table 26.10-1

Kz reflects how wind speed increases with height over each terrain type. Exposure C (open flat) produces the highest values; Exposure B (urban/suburban) the lowest. Minimum heights apply: use the 0–15 ft value for any height below the listed minimum.

Height z	Exp. B	Exp. C	Exp. D	Height z (m)
0–15 ft	0.57*	0.85	1.03	0–4.6 m
20 ft	0.62	0.90	1.08	6.1 m
25 ft	0.66	0.94	1.12	7.6 m
30 ft	0.70	0.98	1.16	9.1 m
40 ft	0.74	1.04	1.22	12.2 m
50 ft	0.79	1.09	1.27	15.2 m
60 ft	0.83	1.13	1.31	18.3 m
80 ft	0.90	1.21	1.38	24.4 m
100 ft	0.95	1.26	1.43	30.5 m

*Exposure B minimum height (zmin) = 30 ft — use Kz = 0.70 for all heights ≤ 30 ft in Exp. B. Exp. C: zmin = 15 ft. Exp. D: zmin = 7 ft.

5c. External Pressure Coefficients Cp — ASCE 7-22 Fig. 27.3-1

Used with the MWFRS directional procedure (Part 1, Method 2). Positive Cp = pressure toward surface; negative = suction away from surface.

Surface	Cp	Applied with	Notes
Windward wall	+0.8	qz at each height	All L/B ratios
Leeward wall, L/B ≤ 1	−0.5	qh (at mean roof height)	L = dimension parallel to wind; B = perpendicular to wind
Leeward wall, L/B = 2	−0.3
Leeward wall, L/B ≥ 4	−0.2
Side walls	−0.7	qh	All L/B ratios
Flat roof — windward	−0.9 and −0.18	qh	Apply both values; use governing case per element
Flat roof — leeward	−0.7 to −0.5	qh	Depends on h/L ratio; −0.7 at h/L ≤ 0.25

5d. Internal Pressure Coefficient GCpi — ASCE 7-22 Table 26.13-1

Enclosure Classification	GCpi	Use
Enclosed buildings	±0.18	Apply both + and −; use sign that creates critical combined load with external Cp
Partially enclosed buildings	±0.55	Dominant opening on one wall; drives critical C&C roof/wall cladding loads
Open buildings	0.00	No enclosed volume; GCpi = 0

Enclosure classification matters: A building is "partially enclosed" when: (a) total area of openings in a windward wall exceeds the sum of openings in all other walls and roof by more than 10%, AND (b) that windward opening area exceeds 4 ft² (0.37 m²) or 1% of the windward wall area. The jump from ±0.18 to ±0.55 can significantly increase cladding design loads.

5e. Worked Example: Design Wind Pressure

Given: V = 115 mph (51.4 m/s), Exposure B, mean roof height h = 40 ft (12.2 m), Risk Category II, enclosed rectangular building, L/B = 1, flat terrain (Kzt = 1.0), sea level (Ke = 1.0), rigid building (G = 0.85).

Step 1 — Velocity pressure at h = 40 ft

USqz = 0.00256 × 0.74 × 1.0 × 1.0 × 115² = 25.1 psf

SIqz = 0.613 × 0.74 × 1.0 × 1.0 × 51.4² = 1,199 Pa = 1.20 kPa

Kz = 0.74 from Table 26.10-1 at 40 ft, Exp. B. Use qh = qz = 25.1 psf at mean roof height.

Step 2 — Design pressure on windward wall (Cp = +0.8)

USp = qz × G × Cp − qi × GCpi = 25.1 × 0.85 × 0.8 − 25.1 × (±0.18)

= 17.1 − (±4.5) → max 21.6 psf (suction internal) / min 12.6 psf

SIp = 1.20 × 0.85 × 0.8 − 1.20 × (±0.18) → max 1.03 kPa / min 0.60 kPa

Step 3 — Design pressure on leeward wall (L/B = 1 → Cp = −0.5)

USp = qh × G × Cp − qi × GCpi = 25.1 × 0.85 × (−0.5) − 25.1 × (∓0.18)

= −10.7 − (∓4.5) → max suction −15.2 psf / min suction −6.2 psf

SI→ max suction −0.73 kPa

Step 4 — Total lateral wind pressure across building (MWFRS)

USp_total = p_windward − p_leeward = 21.6 − (−6.2) = 27.8 psf

SIp_total = 1.03 − (−0.30) = 1.33 kPa

This is the combined lateral pressure used to design the MWFRS (frames, shear walls, bracing).

6. Rule-of-Thumb Loads for Preliminary Design

These typical combined dead + live loads are used in early-stage member sizing. Confirm with actual material takeoffs before final design.

Office Building — Typical Floor

Dead (SDL)30–40 psf (1.44–1.92 kN/m²)

Live (office)50 psf (2.39 kN/m²)

Total unfactored80–90 psf (3.8–4.3 kN/m²)

Residential Building — Typical Floor

Dead (SDL)25–35 psf (1.20–1.68 kN/m²)

Live (residential)40 psf (1.92 kN/m²)

Total unfactored65–75 psf (3.1–3.6 kN/m²)

Retail — Ground Floor

Dead (SDL)35–50 psf (1.68–2.39 kN/m²)

Live (retail)100 psf (4.79 kN/m²)

Total unfactored135–150 psf (6.5–7.2 kN/m²)

Roof (Flat, Heated, Snow ≤ 20 psf)

Roofing SDL15–25 psf (0.72–1.20 kN/m²)

Roof live / snow20–30 psf (0.96–1.44 kN/m²)

Total unfactored35–55 psf (1.7–2.6 kN/m²)

Quick Factored Load Estimate (LRFD)

Governing gravity combination 1.2D + 1.6L

US & SIwu = 1.2 × wD + 1.6 × wL

Office example: wu = 1.2×35 + 1.6×50 = 42 + 80 = 122 psf (5.84 kN/m²)

Load Combinations in Detail →

Preliminary design only. Loads shown are from ASCE 7-22 and typical practice. Always verify with a licensed structural engineer, site-specific geotechnical data, and the governing local code edition and wind/snow maps.

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Load Determination per ASCE 7-22

Contents

1. Dead Loads — ASCE 7-22 Chapter 3

Common Dead Load Values

2. Live Loads — ASCE 7-22 Chapter 4 (Table 4.3-1)

3. Live Load Reduction — ASCE 7-22 §4.7

Live Load Element Factor KLL

Reduction Limits — §4.7.3

4. Snow Loads — ASCE 7-22 Chapter 7

Key Snow Load Factors

5. Wind Loads — ASCE 7-22 Chapters 26–27

Key Wind Parameters

Typical Design Wind Speeds (Risk Category II)

5a. Wind Exposure Categories — ASCE 7-22 §26.7

5b. Velocity Pressure Exposure Coefficient Kz — ASCE 7-22 Table 26.10-1

5c. External Pressure Coefficients Cp — ASCE 7-22 Fig. 27.3-1

5d. Internal Pressure Coefficient GCpi — ASCE 7-22 Table 26.13-1

5e. Worked Example: Design Wind Pressure

6. Rule-of-Thumb Loads for Preliminary Design

Quick Factored Load Estimate (LRFD)

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