Minimum Uniformly Distributed Live Loads
| Occupancy / Use | Lo (psf) | Lo (kN/m²) |
|---|---|---|
| Residential (one- and two-family) — all areas except stairs | 40 | 1.92 |
| Residential — habitable attics and sleeping areas | 30 | 1.44 |
| Residential — uninhabitable attic, no storage | 10 | 0.48 |
| Residential — uninhabitable attic, with storage | 20 | 0.96 |
| Residential (other) — private rooms and their corridors | 40 | 1.92 |
| Residential (other) — public rooms and their corridors | 100 | 4.79 |
| Offices | 50 | 2.40 |
| Office lobbies & first-floor corridors | 100 | 4.79 |
| Office corridors above first floor | 80 | 3.83 |
| Access floors — computer use | 100 | 4.79 |
| Assembly areas — fixed seats | 60 | 2.87 |
| Assembly areas — movable seats, lobbies, platforms | 100 | 4.79 |
| Dining rooms and restaurants | 100 | 4.79 |
| Gymnasiums, dance halls and ballrooms | 100 | 4.79 |
| Hospitals — operating rooms, laboratories | 60 | 2.87 |
| Hospitals — patient rooms | 40 | 1.92 |
| Schools — classrooms | 40 | 1.92 |
| Schools — corridors above first floor | 80 | 3.83 |
| Retail — first floor | 100 | 4.79 |
| Retail — upper floors | 75 | 3.59 |
| Light manufacturing | 125 | 6.00 |
| Heavy manufacturing | 250 | 11.97 |
| Storage warehouses — light | 125 | 6.00 |
| Storage warehouses — heavy | 250 | 11.97 |
| Libraries — reading rooms | 60 | 2.87 |
| Libraries — stack rooms | 150 | 7.18 |
| Garages — passenger vehicles | 40 | 1.92 |
| Stairs and exit ways | 100 | 4.79 |
| Roofs, ordinary flat, pitched and curved | 20 | 0.96 |
Unreduced uniform live loads Lo from ASCE/SEI 7-22 Table 4.3-1 [1], the edition the 2024 IBC [2] adopts (these rows are unchanged from 7-16, which the 2021 IBC adopts). The full table also gives concentrated loads, whether live load reduction is permitted, and many more occupancies; check the edition your jurisdiction uses.
Typical Dead Load Estimates
| Material / Assembly | Approx. Weight |
|---|---|
| Normal-weight reinforced concrete | 150 pcf |
| Lightweight concrete | 90–115 pcf |
| Structural steel | 490 pcf |
| Concrete slab, per inch of thickness | ~12.5 psf/in |
| Wood floor/roof framing + sheathing | 7–10 psf |
| Asphalt shingle roofing | 2–3 psf |
| Built-up roofing (BUR) | 5–6 psf |
| Metal roof deck, uninsulated | 2–3 psf |
| Suspended acoustic ceiling | 1–2 psf |
| Mechanical/electrical allowance | 2–5 psf |
| Gypsum board, per 5/8 in layer | ~2.2 psf |
| Brick veneer, 4 in | ~40 psf |
| CMU wall, 8 in hollow | ~55 psf |
| CMU wall, 8 in grouted solid | ~85 psf |
Early-design estimates only — confirm against manufacturer data or ASCE 7 Commentary for a specific assembly.
Basic Load Combinations
| No. | Strength Design (LRFD), §2.3.1 and §2.3.6 | No. | Allowable Stress Design (ASD), §2.4.1 and §2.4.5 |
|---|---|---|---|
| 1a | 1.4D | 1a | D |
| 2a | 1.2D + 1.6L + (0.5Lr or 0.3S or 0.5R) | 2a | D + L |
| 3a | 1.2D + (1.6Lr or 1.0S or 1.6R) + (L or 0.5W) | 3a | D + (Lr or 0.7S or R) |
| 4a | 1.2D + 1.0(W or WT) + L + (0.5Lr or 0.3S or 0.5R) | 4a | D + 0.75L + 0.75(Lr or 0.7S or R) |
| 5a | 0.9D + 1.0(W or WT) | 5a | D + 0.6(W or WT) |
| 6 | 1.2D + Ev + Eh + L + 0.15S | 6a | D + 0.75L + 0.75[0.6(W or WT)] + 0.75(Lr or 0.7S or R) |
| 7 | 0.9D − Ev + Eh | 7a | 0.6D + 0.6(W or WT) |
| 8 | 1.0D + 0.7Ev + 0.7Eh | ||
| 9 | 1.0D + 0.525Ev + 0.525Eh + 0.75L + 0.1S | ||
| 10 | 0.6D − 0.7Ev + 0.7Eh |
ASCE/SEI 7-22 basic combinations [1]. D = dead, L = live, Lr = roof live, S = snow, R = rain, W = wind, WT = tornado, Eh = horizontal seismic load effect ρQE, Ev = vertical seismic load effect (0.2SDSD). 7-22 ground snow loads are strength-level, hence the snow factors of 1.0, 0.3 and 0.15 (LRFD) and 0.7 and 0.1 (ASD). The factor on L in LRFD 3a, 4a and 6 may be 0.5 where Lo ≤ 100 psf (4.78 kN/m²), except in garages and places of public assembly. Where S is a companion load (LRFD 2a, 4a and 6; ASD 4a, 6a and 9) it may be the flat or the sloped roof snow load. With WT, the roof term of LRFD 4a may be 0.5(Lr or R) and that of ASD 6a 0.75(Lr or R). Flood, ice, self-straining and overstrength (Emh) combinations, and the rules for fluid and earth-pressure loads, are in §2.3 and §2.4.
Wind Exposure Categories
| Category | Surface Roughness | Applies Where |
|---|---|---|
| B | Urban and suburban areas, wooded areas, or other terrain with many closely spaced obstructions the size of single-family homes or larger | Roughness B extends upwind more than 1,500 ft (457 m) for a mean roof height up to 30 ft (9.1 m); for taller buildings, more than 2,600 ft (792 m) or 20 times the height, whichever is greater |
| C | Open terrain with scattered obstructions generally under 30 ft (9.1 m) tall, including flat open country and grasslands | Every case where B or D does not apply |
| D | Flat, unobstructed areas and water surfaces, including smooth mud flats, salt flats and unbroken ice | Roughness D extends upwind more than 5,000 ft (1,524 m) or 20 times the height, whichever is greater; also where the roughness just upwind is B or C but the site is within 600 ft (183 m) or 20 times the height of such a D condition |
ASCE/SEI 7-22 §26.7.2 and §26.7.3 [1]. The exposure is set for each wind direction from the two 45° upwind sectors; in a transition zone, use the category giving the larger wind forces.