Brick sizes and formats: what to check before you draw
Standard UK dimensions, why 65mm and 73mm both exist, and when you need a special.
The UK standard brick is 215 × 102.5 × 65mm.
Almost everything about a brick elevation follows from that, and from the 10mm joint that goes with it.
Add the joint and you get a working module of 225mm horizontally and 75mm vertically. Four courses to 300mm. That module is why brick dimensions turn up in window heights, floor-to-floors and pier widths on drawings that never mention brickwork at all — and why a late change of format can quietly break a whole elevation.
Brick plus joint.
Designing to the module means courses land where you want them: at cill level, at heads, at the top of a parapet. Designing against it means cut bricks, awkward closers, and a bricklayer making decisions the drawing should have made.
The vertical module is the one that catches people out. Four courses of standard brick and joint come to exactly 300mm, so any dimension that is a multiple of 300 will course cleanly. Anything else needs a decision about where the discrepancy goes.
Set out the elevation to 225 and 75 before the details get drawn, not after.
| Dimension | Brick | With 10mm joint |
|---|---|---|
| Length | 215mm | 225mm |
| Width | 102.5mm | 112.5mm |
| Height | 65mm | 75mm |
| Four courses | — | 300mm |
Where the format varies.
Most of what you will be shown is 65mm, but not all of it. The variations are worth knowing because they do not course together, and mixing them is a detailing problem rather than an aesthetic one.
65mm — the standard
The UK default and by a wide margin the largest part of any supplier's range. Courses at 75mm.
73mm — the metric imperial
Used to match older imperial brickwork on extensions and restoration. Courses at 83mm, so it will not run into standard work.
50mm and under
Thinner formats, often in longer lengths, used where a finer horizontal emphasis is wanted.
Long formats
Lengths of 440mm and beyond, usually with a reduced height. A distinctly contemporary reading and a different setting-out entirely.
66 and 68mm
Small deviations from a handful of manufacturers. Close enough to look interchangeable on paper, far enough to cause trouble on site.
Specials
Purpose-made shapes — plinths, squints, bullnose, cills. Long lead times, so identify them at design stage.
Three things worth checking early.
Does it actually course?
If you are matching or abutting existing brickwork, measure the existing course height over a metre and divide. Assuming 75mm because it looks standard is how extensions end up with a stepped joint.
What are the specials?
Every projecting detail, reveal and coping implies a special. They are made to order and priced separately, so a design that needs forty of them should know that before tender.
And confirm the pack quantity before you calculate. It varies by manufacturer — commonly between 400 and 620 per pack — which matters for both delivery planning and the wastage allowance.