Dead Load Calculator
Adds up the permanent weight of a floor, wall or roof build-up and gives it in the units engineers and codes use. It tells you what the construction weighs; it does not tell you what will hold it up.
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The formula
dead load = Σ layer weights (kg/m²) kN/m² = kg/m² × 9.81 ÷ 1,000 total = dead load × area
Dead load is addition. Each layer of a build-up has a published self-weight per square metre, and the dead load is their sum. Engineers work in kN/m², which is the same weight expressed as a force — multiply by gravity.
What to watch out for
The spread between build-ups is the useful part:
- Timber floor with carpet: about 60 kg/m², or 0.6 kN/m².
- The same floor with 20 mm stone tile on a 50 mm screed: about 220 kg/m² — nearly four times the weight, on joists that were sized for carpet.
- 150 mm concrete slab: 360 kg/m² before anything goes on it.
That is why "can I put a stone floor on this" is a structural question and not a flooring one. The floor finish alone can exceed the live load the floor was designed for.
What this page leaves out, on purpose: live load (from the code), the capacity of the members (from their size, span and grade), and the combination of the two with safety factors. Those are the structural check, they are excluded from this site, and the dead load figure here is the input you take to whoever does them.
Frequently Asked Questions
What is dead load?
The permanent weight of the building itself — structure, finishes, services and fixed fittings. It is distinguished from live load, which is everything that can move or change: people, furniture, snow, stored goods.
How much does a timber floor weigh per square metre?
Around 50 kg/m² for joists, 22 mm chipboard and a plasterboard ceiling, about 0.5 kN/m². Add 5 for carpet, 30 for ceramic tile, or 110 for a 50 mm screed.
How do I convert kg/m² to kN/m²?
Multiply by 9.81 and divide by 1,000 — 100 kg/m² is 0.98 kN/m². To psf, multiply kg/m² by 0.2048, so 100 kg/m² is about 20.5 psf.
Can this tell me if my floor can take a new finish?
No. It tells you how much the new finish adds. Whether the joists can carry that plus the live load depends on their size, span, spacing and grade, which needs a structural engineer or the relevant span tables. The dead load figure is what you bring to that check.