Articles · 2026-09-07 · 4 min read
The office floor load nobody measures
Ninety-five office buildings were designed for 3.57 kN/m² on average. Every measured survey since 1893 has stayed under 1.90.
The MEICON project at Cambridge collected the letting specifications of 95 office buildings completed over about twenty years in the UK, US and Canada, 6.3 million square metres in all. The area-weighted average imposed load they were designed for was 3.57 kN/m², plus 1.06 kN/m² for partitions. Half of the floor space was designed for 4.50 kN/m² and a tenth for 5.00 kN/m² or more (MEICON load report, 2019).
Set that against what has actually been weighed. Compiling the measured floor-load surveys of offices published since 1893, about 2.5 million square metres, the largest recorded floor load across all studies was 1.90 kN/m², in Boston in 1893, and the average of the study averages was 0.63 kN/m² (MEICON, The origin of 100 psf).
What the code asks for
EN 1991-1-1 puts office floors in category B at 2.0 to 3.0 kN/m², a national choice. A set designed at 4.5 or 5.0 is carrying one and a half to two times the code value before any partial factor is applied, and every kilonewton of it lands on the slab depth, the beam sections, the columns and the footings.
Where it hides in a drawing set
- The general notes: the design basis states the imposed load. It is the first thing to read and the last thing anyone questions.
- Slab depth and beam sections that look heavy for the span. A flat slab at 250 mm on a 7.5 m grid is often carrying load, not span.
- Letting agents. The 4.5 and 5.0 figures come from marketing specifications, not from the engineer.
The scan flags members with headroom against code minimums and typical practice. It cannot see the letting brief, so when a whole floor plate sits above typical, the question to take to the engineer of record is about the load, not the sections.