BS 7533-102:2025
Last reviewed: 9 September 2026
What it covers
BS 7533-102:2025 is the current UK code of practice for installing modular paving - both block paving (previously BS EN 1338) and paving flags/slabs (previously BS EN 1339) - under one part, since it came into effect in March 2025. It replaced the older, now-withdrawn BS 7533-3 (which covered blocks) and BS 7533-4 (which covered flags) as two separate documents.
For bedding method, it describes a full mortar bed - mortar spread evenly under the whole slab, not just at the corners and centre - as the specification-compliant method for laying flags. A full bed avoids the voids that "dabs" (blobs of mortar at a few points) leave underneath a slab, which is what lets a slab rock and eventually crack under load, especially with modern thinner, more consistent slabs.
What it does not cover
The standard describes full bedding as the specification-compliant method; it does not document mortar dabs as an approved alternative. Dabs are a widely-used shortcut on smaller DIY jobs precisely because they're faster, not because the standard endorses them - a distinction worth being clear about rather than presenting a common shortcut as if it were an equally valid documented method.
Which of our calculators rely on it
- Paving Slab Calculator - bedding volume and mortar quantities are calculated for a full bed, matching the standard's specification-compliant method, not a dabs allowance.
- Patio Calculator - inherits the same full-bed bedding assumption for its own bedding mortar line.