Gravity Loads on Floor Slabs
Learn the components of slab loading, from self-weight of reinforced concrete to standard live loads for residential and commercial buildings.
The Horizontal Load Path
A floor slab is the first element to receive weight in a building. Everything—your furniture, the tiles on the floor, and even the air above it (wind loads)—exerts pressure on the slab. This pressure is measured in kN/m² (KiloNewtons per square meter).
Load Composition
Dead Load ($DL$) includes self-weight, finishes, and partitions. Live Load ($LL$) is based on usage.
Common Dead Load Values
- Self-Weight: Calculated as $\text{Thickness (m)} \times 25 \text{ kN/m}^3$. A $150$mm slab weighs $3.75$ kN/m².
- Floor Finishes: Tiles, mortar bedding, and ceiling plaster. Standard allowance is $1.0$-$1.5$ kN/m².
- Partitions: If internal walls aren't directly over beams, their weight is distributed over the slab area ($0.5$-$1.0$ kN/m²).
Occupancy Live Loads (Standard)
- Residential Rooms: $2.0$ kN/m².
- Office Space: $2.5$ - $3.0$ kN/m².
- Public Corridors / Stairs: $3.0$ - $4.0$ kN/m².
- Storage / Warehouse: $5.0$ - $10.0$ kN/m².
Frequently Asked Questions (FAQ)
Why is self-weight so high?
Reinforced concrete is extremely heavy. In a typical residential building, the weight of the slab itself (Dead Load) often makes up $50$-$60\%$ of the total load. This is why "Lightweight Concrete" or "Hollow Core" slabs are used in large-scale projects to reduce the structural demand on columns and foundations.