What is a point load?
A point load (concentrated load) is a load that acts on a small area and is therefore treated as a single point in calculations. It is expressed in kilonewtons (kN). For comparison, a line load is expressed in kN/m and a uniformly distributed load in kN/m².
Examples
- A column or post standing on a beam or floor
- A prop during building work
- The feet of a full bath, a heavy cabinet, safe or piano
- An aquarium: water weighs 1 kg per litre, so a 300-litre tank with glass and stand puts well over 300 kg on a small area
- A wood-burning stove or a heavy bookcase
- A mobile access platform or scaffold bearing on a floor or paving
Why a point load counts for more
Take a simply supported beam. The same total load F gives:
| Loading | Maximum bending moment | Midspan deflection |
|---|---|---|
| Uniformly distributed | F × L / 8 | 5 F L³ / 384 EI |
| Point load at midspan | F × L / 4 | F L³ / 48 EI |
A point load at midspan therefore produces twice the bending moment and just over one and a half times the deflection of the same load spread evenly. It can also cause local damage: crushing of timber or insulation, or punching shear in a concrete slab.
That is why Eurocode 1 (EN 1991-1-1) specifies a concentrated load alongside the uniformly distributed imposed load, to be checked separately in the most unfavourable position.
Tips for dealing with a point load
- Place heavy items close to a support, such as a load-bearing wall or beam bearing, not in the middle of a span.
- Spread the load with a stiff board or a spreader beam running across several joists.
- Prop temporarily during alterations and stand props on load-spreading pads.
- Use high-compressive-strength insulation under floors and roof build-ups where concentrated loads occur.
- Get it checked when in doubt: a large aquarium, heavy stove, hot tub or a new column on an existing timber floor are classic cases for a structural engineer.
Related terms
- Load in construction
- Beam
- Span
- Deflection
- Propping
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