Dead Load Calculator
A dead load calculator gives an assembly's self-weight in psf: about 3 psf for a shingle roof, 10 psf for a wood floor, and 12.5 psf per inch of concrete slab.
Typical dead loads at a glance
A dead load calculator gives the permanent self-weight of a building assembly in pounds per square foot (psf). Pick the assembly and the tool returns a typical planning figure. An asphalt shingle roof is about 3 psf. A wood-frame floor of joists and subfloor is about 10 psf. A concrete slab is 12.5 psf per inch of thickness, from concrete’s weight of about 150 lb per cubic foot.
There is no single dead load formula. Total dead load = the sum of each layer’s weight in psf × the area it covers.
What dead load includes
Dead load is everything that is built in and stays put:
- Structural framing: rafters, joists, trusses, studs
- Sheathing and subfloor
- Roofing, underlayment, and insulation
- Ceiling and wall finishes, such as drywall
- Floor finishes, tile, and mortar beds
- Fixed equipment that is permanently attached
Live load is different. It covers people, furniture, and storage, which the building code sets as a minimum design figure rather than a measured weight.
Worked examples
Example 1: Roof over a garage, asphalt shingles and metal alternative
- Shingle roof: 3 psf
- Metal roof: 1.5 psf
- On 600 sq ft of roof: shingles weigh 3 × 600 = 1,800 lb; metal weighs 1.5 × 600 = 900 lb
Example 2: Second-floor bedroom, 12 × 15 ft, wood floor over a drywall ceiling
- Wood-frame floor: 10 psf
- Drywall ceiling below: 2 psf
- Combined dead load: 10 + 2 = 12 psf
- Total weight: 12 × 180 sq ft = 2,160 lb
Example 3: Concrete slab, 4 inches thick
- 4 × 12.5 = 50 psf
- Over a 10 × 10 ft area: 50 × 100 = 5,000 lb
Planning values used by the calculator
| Option | Assembly | Dead load |
|---|---|---|
| 1 | Asphalt shingle roof | 3 psf |
| 2 | Wood-frame floor (joists + subfloor) | 10 psf |
| 3 | Concrete slab | 12.5 psf per inch |
| 4 | Drywall ceiling | 2 psf |
| 5 | Metal roofing | 1.5 psf |
Approximate weights of common layers
| Material | Approx. weight |
|---|---|
| Normal-weight concrete | 150 lb/ft³ (12.5 psf per inch) |
| ½ in gypsum drywall | about 2 psf |
| ⅝ in gypsum drywall | about 2.5 psf |
| ¾ in plywood subfloor | about 2.2 psf |
| Water (ponding, tanks) | 62.4 lb/ft³ (5.2 psf per inch) |
Product data sheets and the design standard your engineer uses are the final source. These figures come from typical material densities.
How to build up an assembly’s dead load
- List every layer from top to bottom: finish, underlayment, sheathing, framing, insulation, ceiling.
- Find each layer’s psf from the table, a product sheet, or density × thickness.
- Add them. That total is the assembly’s dead load.
- Add allowances for mechanical, plumbing, and lighting if your designer uses them.
- Multiply by tributary area to get the load on a beam, joist, or footing.
Common mistakes
- Forgetting the slab multiplier. Option 3 is per inch. A 5-inch slab is 62.5 psf, not 12.5.
- Leaving out the ceiling below a floor. It hangs from the same joists.
- Missing heavy finishes. Tile on a mortar bed, stone counters, and a cast-iron tub weigh far more than carpet.
- Re-roofing over old shingles. A second layer adds its full weight to the rafters.
Related calculators
Add live load with the floor load calculator and roof snow with the snow load calculator. Then size members with the beam span calculator, or weigh a slab directly with the concrete weight calculator.
These are commonly cited planning figures for typical assemblies, not a substitute for summing your actual specified materials. A licensed structural engineer should calculate dead load from the real assembly for anything load-bearing.
Frequently asked questions
What is dead load?
Dead load is the permanent weight of the building itself: framing, sheathing, roofing, drywall, flooring, and fixed equipment. Live load is the weight that comes and goes, such as people, furniture, and stored goods. Snow and wind are separate environmental loads.
How do I total the dead load for a floor?
Add the weight of each layer in pounds per square foot. A wood-frame floor at 10 psf with a 2 psf drywall ceiling underneath is 12 psf. Multiply by the floor area: 12 psf over a 12 × 15 ft room is 12 × 180 = 2,160 lb.
Why does concrete slab dead load depend on thickness?
Normal-weight concrete weighs about 150 lb per cubic foot. A one-inch layer is 1/12 of a foot thick, so each square foot weighs 150 ÷ 12 = 12.5 lb. A 4-inch slab is 4 × 12.5 = 50 psf and a 6-inch slab is 75 psf.
Why is this a lookup instead of a formula?
Dead load is the sum of real material weights, which vary by product. The calculator returns commonly used planning values for five typical assemblies. For a final design, the engineer adds the actual specified materials layer by layer.
How do I use dead load once I have it?
Combine it with the live load and any snow or wind load the code requires, then size beams, joists, and footings to that total. A residential living area floor is commonly designed for 40 psf live load, so a 12 psf dead load gives 52 psf total before any load factors.
Estimates only. Verify quantities with your supplier before purchasing.