This document aims to assist designers and builders when setting out brickwork for buildings and determining the co-ordinating size in various applications. The brickwork dimension tables within this document are based on a standard size UK clay brick, combined with a nominal 10mm mortar joint. Should you wish to deviate from these dimensions the same principles will apply.
The most widely used brick size for UK clay bricks is 215 x 102.5 x 65mm which is so called metric brick size. But there are a lot of size variations out there.
When specifying brick it is important to consider the tolerance and range values declared by the manufacturer in accordance with EN771-1. Both T2, T1 and R2, R1 are derived from formula set out in EN 771-1.
The tolerance is the difference between the stated work size and the average actual size. The tolerance will be stated as T2 (generally the smallest deviation from the stated work size), T1 or Tm (deviation in mm from the stated work size declared by the manufacturer; it may be wider or closer than the other categories).
| Declared Size [mm] | T2 Lower & upper limits [mm] | T2 Tolerances [mm] | T1 Lower & upper limits [mm] | T1 Tolerances [mm] | Tm |
| 215 | 211-219 | ±4 | 209-221 | ±6 | As declared by the manufacturer |
| 102.5 | 99-105 | ±3 | 98-106 | ±4 | |
| 65 | 63-67 | ±2 | 62-68 | ±3 |
The range value covers the dimension difference within a sample, between the largest brick and the smallest. The range will be stated as R2 (generally the smallest range), R1 or Rm (range in mm declared by the manufacturer; it may be wider or closer than the other categories).
| Declared Size [mm] | R2 [mm] | R1 [mm] | Rm [mm] |
| 215 | 4 | 9 | As declared by the manufacturer |
| 102.5 | 3 | 6 | |
| 65 | 2 | 5 |
The primary concern is to ensure that the tolerance of the specified brick is compatible with the desired aesthetic effect i.e. If the design requires extremely crisp, regular brickwork, then the smaller range and tolerance (R2, T2) should be considered. Adjacent components and design details must also be co-ordinated with the specified brick tolerances.