— Design Loads
Minimum Uniformly Distributed Live Loads (ASCE 7)
| Occupancy / Use | Live Load |
|---|
| Residential — habitable rooms | 40 psf |
| Residential — uninhabitable attic, no storage | 10 psf |
| Residential — uninhabitable attic, with storage | 20 psf |
| Offices | 50 psf |
| Lobbies & first-floor corridors | 100 psf |
| Corridors above first floor | 80 psf |
| Assembly areas — fixed seats | 60 psf |
| Assembly areas — movable seats | 100 psf |
| Retail — first floor | 100 psf |
| Retail — upper floors | 75 psf |
| Light manufacturing | 125 psf |
| Heavy manufacturing | 250 psf |
| Libraries — reading rooms | 60 psf |
| Libraries — stack rooms | 150 psf |
| Parking garages (passenger vehicles) | 40 psf |
| Stairs and exits | 100 psf |
| Roofs, ordinary flat/pitched/curved | 20 psf |
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
| ASD (Allowable Stress) | LRFD |
|---|
| D | 1.4D |
| D + L | 1.2D + 1.6L + 0.5(Lr or S or R) |
| D + (Lr or S or R) | 1.2D + 1.6(Lr or S or R) + (L or 0.5W) |
| D + 0.75L + 0.75(Lr or S or R) | 1.2D + 1.0W + L + 0.5(Lr or S or R) |
| D + (0.6W or 0.7E) | 1.2D + 1.0E + L + 0.2S |
| D + 0.75L + 0.75(0.6W) + 0.75(Lr or S or R) | 0.9D + 1.0W |
| D + 0.75L + 0.75(0.7E) + 0.75S | 0.9D + 1.0E |
| 0.6D + 0.6W | |
| 0.6D + 0.7E | |
D = dead, L = live, Lr = roof live, S = snow, R = rain, W = wind, E = seismic. Simplified — see ASCE 7 §2.3 (LRFD) / §2.4 (ASD) for the complete combination sets, load factors, and exceptions.
Wind Exposure Categories
| Category | Description |
|---|
| B | Urban and suburban areas, wooded terrain, or other terrain with numerous closely spaced obstructions |
| C | Open terrain with scattered obstructions generally less than 30 ft, including flat open country and grasslands |
| D | Flat, unobstructed areas exposed to wind flowing over open water — includes mud flats, salt flats, and unbroken ice |
