Bricks · twelve countries · four old English rules

Two Headers and a Joint

A British brick is 215 by 102.5 by 65 millimetres. Lay two of them side by side with a 10 mm joint between and they come to 215, the length of one. The German brick does the same with 240 and 115, the Russian with 250 and 120, the Danish with 228, 108 and a 12 mm joint, the American with 7⅝ and 3⅝ inches and a ⅜ inch joint. The length is set by the width and the joint, because a wall is bonded; the height is set by nothing of the kind, and runs from 50 to 113 mm. Below, lay a wall with any brick you like and see where it breaks.

A sum on the tape measure

A brick shows a wall one of two faces. Laid lengthwise it is a stretcher, showing its length; laid across the wall it is a header, showing its width, with its length running back into the wall's thickness. A wall is strong when no vertical joint (a perpend) sits directly above another, so the courses are made to overlap, and English bond does it by laying a course of stretchers, then a course of headers, then stretchers again.

For that to work without cutting bricks, two headers and the joint between them have to fill the same space as one stretcher. The Brick Industry Association in the United States puts it as one of the relationships its modular sizes are built on:

“two brick widths plus one mortar joint equal one brick length”

Brick Industry Association, Technical Note 10, Dimensioning and Estimating Brick Masonry (2009)

L = 2W + j

The British brick meets it to the millimetre: 2 × 102.5 + 10 = 215. So does the principal brick of every country we found a source for, as the next picture shows; not every brick in every catalogue, and the exceptions are on the picture too. For the formats that obey it, the width and the joint are the real choices, and the length follows from them.

Every standard, one line

Each dot is a brick: its width across, its length up. The gold line is L = 2W + 10. The shaded band is every length a bricklayer can bond without cutting if each joint may be anything from 6 to 15 mm, the range NHBC Standards allow for bed and perpend joints in the UK. The grey dashed line is L = 2W, a brick exactly two widths long with no room for a joint. Pale dots are the old English rules, grey ones ancient bricks, the blue one an American brick three widths long, and the open orange rings are other formats listed in the same Russian and Dutch sources. The open red rings are sizes printed without a source that could bear them out. Click any dot to lay a wall with it.

Seventeen principal formats from twelve countries. Fourteen of them come with a joint named in the sources read, and in thirteen of those, length minus two widths is exactly that joint: 10 mm in Britain, Germany, Russia, China, the Netherlands, India (the modular brick) and Australia, 12 mm in Denmark, ⅜ inch (9.5 mm) in the United States. The sources for Sweden's brick, Japan's and India's non-modular one name no joint, and all three leave exactly 10. The one that misses is South Africa's, 222 by 106, which leaves 10 mm while its brick association recommends 12, a miss of 2 mm that any joint absorbs.

The same catalogues hold bricks that do not fit. Russia's GOST 530 also lists a brick 250 by 85 (two widths are 80 mm short of a length) and one of 288 by 138 (12 mm over, against a 10 mm vertical joint). The Dutch brick association lists old regional formats beside the Waal: the Limburg and Groningen bricks are 240 by 120, exactly two widths long, the Moef is 215 by 100, leaving 15, and the Brabant 180 by 88, leaving 4. These are the open orange rings. The sum is a design rule some bricks were made to, not a law every brick obeys.

The blue dot is the exception that proves the arithmetic rather than the rule. America's Norman brick is 11⅝ by 3⅝ inches, three widths and two joints long (3 × 3⅝ + 2 × ⅜ = 11⅝), and bonds at thirds rather than halves. It sits on its own line, L = 3W + 2j.

What goes wrong when it doesn't

Here is a wall four metres long, eight courses high, running away from a corner at the left. In English bond the header courses turn the corner with the end of the other wall's stretcher, then a queen closer (a brick split along its length), and that sets every header's perpend a quarter of a brick away from the stretcher perpends below. If two headers and a joint do not quite equal a stretcher, the difference piles up, once per stretcher, until a header's perpend lands on a stretcher's: a straight joint, drawn in white. The dots underneath are the laps, how far each perpend is from the nearest one in the course below; the red strip is closer than one joint.

Try a British brick 5 mm too long. With every joint at 10 mm, the first straight joint arrives about 2.3 m from the corner. Tick the box and it is gone: opening the header courses' perpends to 12.5 mm takes up the difference. Taking up differences is half of what a joint is for, because bricks vary: a British brick declared at 215 mm may average anywhere from 211 to 219 mm under tolerance class T2, and the joints absorb it. So the rule is not a knife edge. It is a target, and the band on the plane is how far off it a mason can still hit.

Stretcher bond has no header courses at all, and you might expect it not to care. It cares at every corner. The course that turns the corner shows the end of the other wall's brick, one width, before its first stretcher; so its perpends sit L − W from the ones below, and half bond wants that to be half a stretcher and its joint, (L + j) / 2. Solve it and it is the same sum again.

And China's brick as English Wikipedia prints it, 240 by 155 by 53, cannot be laid in English bond at all: two headers and a joint come to 320 mm against a stretcher of 240, and the header perpends would need to be 30 mm less than nothing. The first straight joint is 0.24 m from the corner.

The one dimension left free

Nothing in the bond cares how tall a brick is. Germany's brick industry makes the same 240 by 115 in three standard heights, 52, 71 and 113 mm (Dünnformat, Normalformat and 2DF); Russia's standard has 250 by 120 at 65 and 88; the Netherlands has 210 by 100 at 50 (Waalformaat) and 65 (Waaldikformaat). Across the principal formats on this page the heights run from 50 to 113 mm, a factor of more than two, while length minus two widths stays between 9.5 and 12.

What the height answers to instead is the storey. Each country picks it so that some round number of courses, brick plus bed joint, comes out to a round height: in Britain 65 + 10 = 75 mm, four courses to 300 mm; in the United States 3C = 8 in., three courses to eight inches; in Denmark a 12 to 13 mm bed joint gives 66-67 mm a course, so three come to about 200 mm; in Australia 7 Courses to 600mm. Germany's bed joint is set by the format: about 10.5 mm for Dünnformat, so sixteen courses a metre, and about 12.3 mm for Normalformat, so twelve. In Britain the height is tied to the length as well: three courses make one brick length (3 × 65 + 2 × 10 = 215), so a row of bricks stood on end lines up with three courses laid flat. Most formats do not bother. Three Dutch Waal courses make 170 mm against a 210 mm brick.

Four English rules and an encyclopedia

England made several rules about the size of bricks before 1800. Four of them were read for this page, and each can be put to the same sum. In 1571 the ordinances of the Tylers and Bricklayers of London asked whether each brick for sale was

“of the length of nine inches, and in breadth four inches and one quarter, and two inches and one quarter in thickneſs”

Ordinances of the Tylers and Bricklayers, confirmed 14 July 1571 (EEBO-TCP transcription)

Nine less two widths of 4¼ leaves half an inch, 12.7 mm, for the joint. The proclamation of Charles I in 1625, for London, fixed in length nyne ynches, in bredth fower inches one quarter and half a quarter of an ynch, 4⅜, which leaves a quarter inch, 6.35 mm. The Act 12 Geo. I c. 35, which Dowell dates to 1725, for London and fifteen miles round, went back to nine by 4¼, half an inch again; and the Act of 1777 (17 Geo. III c. 42), for bricks made for sale in any part of England, set minimums of 8½ by 4 inches, half an inch once more. Four rules over two centuries, and every one leaves a joint.

The 1911 Encyclopaedia Britannica, which English Wikipedia still cites for this, says something else:

“in that year the sizes were regulated by statute, and the present standard size was adopted, viz. 9 ✕ 4 1/2 ✕ 3 in.”

Encyclopaedia Britannica, 11th ed. (1911), vol. 4, “Brick”

“That year” is 1625. But the 1625 rule was a proclamation, not a statute: Dowell writes that the dimensions of bricks were first set by statute at a much later date, viz., in 1725, and that bricks had before then been regulated by order of Charles I. And the proclamation's width was 4⅜ inches, not 4½, and its thickness 2¼, not 3. Put Britannica's brick on the plane and it is the only one of these five English sizes with no room for a joint: two widths of 4½ are exactly nine.

The one time the Treasury changed the brick

Britain taxed bricks by the thousand from 1784 to 1850, and a tax on the count is a reason to make each one bigger. It worked. Stephen Dowell's History of Taxation (1888) says an additional shilling per thousand, imposed in 1797, soon led to the enlargement of the size of bricks. In 1801, he goes on, bricks over 10 inches long, 5 wide and 3 thick were charged an extra 5s. per thousand. The often-repeated limit of 150 cubic inches is real but later: Dowell dates it to 1839, when the duty was reimposed for bricks not exceeding 150 cubic inches per brick, a volume test that let makers vary the shape.

Older than the joint

The ancient proportion is simpler and leaves nothing over. Brick sizes in the Indus valley are usually described by a ratio of 4:2:1, length to width to height, which Khan and Lemmen, following Possehl, call the “Indus proportion”; the dominant size is given as 7 by 14 by 28 cm. Hnaihen's study of Mesopotamian brick gives the rule of thumb that its length is twice its width, and among his Uruk-period bricks from Eridu is one of 26 by 13 by 7 cm. A brick exactly two widths long sits on the dashed line: laid as a header course over a stretcher course with the same joint throughout, it drifts. How those walls were bonded, and how thick their mud joints were, the sources read for this page do not say (to count bricks in a wall Hnaihen adds two centimetres of clay to each brick's height), so the grey dots are here as a contrast, not as a judgement.

A row with no source

English Wikipedia's article on the brick has a table of house-brick sizes by country. Its row for China reads 240 × 155 × 53 mm. That brick sits 80 mm below the gold line on the plane and 70 below even the dashed line of no joint at all; no brick in any source read for this page sits lower. China's standard for fired common brick, GB/T 5101, gives 长240mm、宽115mm、高53mm: length 240, width 115, height 53. With 115 the brick meets the rule exactly, like Germany's, which has the same length and width. The row was added on 19 April 2021 with the 155 already in it and no citation, and it still read 155 when this page was written (29 September 2026). The sum found it before any source did, which is the only reason it is here: a relation that sixteen other principal formats obey is a proofreader.

Measure one

Any brick, any unit. The page places it on the plane and says what joint it was made for.

What this page does not show

It does not explain the width. The usual explanation is that a brick must be gripped in one hand while the other holds the trowel, so its width is about a hand's span; it is repeated widely and we found no measurement behind it, so it is left as a story. (The average British brick, for what it is worth, is taken by the Brick Development Association to weigh 2.13 kg.) Most of the modern sizes come from industry associations and manufacturers who quote their standards, not from the standards themselves (BS EN 771-1, DIN 105, AS/NZS 4455 and SANS 227 are paywalled); Russia's, Japan's and India's were read in the standards' own text. Australia's size and joint rest on manufacturers' documents only. The English rules are read from transcriptions and scans (the 1625 proclamation through Dowell's quotation of it), not from manuscripts. The wall assumes every brick is exactly its stated size and every joint exactly its setting, and it does not model Flemish bond or any bond but the two drawn. Of the ancient sizes, only the ratio is well sourced; the Harappan centimetres are Kak's, citing Kenoyer, whose own book was not read.

Sources

1. Brick Industry Association, Technical Note 10: Dimensioning and Estimating Brick Masonry (February 2009), Tables 1 and 2. gobrick.com.
2. Brick Development Association, Designing to brickwork dimensions (technical guide, 2023): work size, co-ordinating size and tolerances. brick.org.uk. Average mass from the BDA environmental product declaration as reproduced by Wienerberger UK (2024). Date of the metric brick: Metrication UK.
3. NHBC Standards 2025, chapter 6.1 (joint thickness 6 to 15 mm). Copy at newbuildinspections.com.
4. Germany: formats from BauNetz Wissen; perpend 10 mm and bed 12 mm from Ziegel-Zentrum, Baupraxis 10; bed joints by format from the KS-Original lexicon.
5. Russia: GOST 530-2012, Table 2 (stroyinf.ru); SP 70.13330.2012, 9.2.4 (copy).
6. China: GB/T 5101 nominal size as quoted by Sohu and a drafting body, Xi'an Wall Materials Institute; joint from GB 50203-2011, 5.3.2 (jianbiaoku).
7. Denmark: Mur & Tag; joint, Randers Tegl; coursing, Tegelmäster, Murverksmått. Sweden: Randers Tegl (same page). Netherlands: KNB, formaten; joints, Wienerberger NL.
8. Japan: JIS R 1250:2011, Table 4 (full text). India: IS 1077:1992 (Public.Resource.Org) and IS 2212:1991 (Public.Resource.Org). Australia: Midland Brick coursing chart (copy); joint from The Brickery, Brick Specification Technical Manual (2020). South Africa: Clay Brick Association, Contractors' Handbook.
9. The Ordinances of the Tylers and Bricklayers, EEBO-TCP A72820 (transcription). Stephen Dowell, A History of Taxation and Taxes in England, vol. IV (1888), pp. 377 to 384 (Internet Archive). Statutes at Large: 12 Geo. I c. 35 (vol. 5) and 17 Geo. III c. 42 (vol. 13), Internet Archive.
10. Encyclopaedia Britannica, 11th ed., “Brick” (Wikisource). English Wikipedia, “Brick”, the table of face brick sizes, revision of 19 April 2021 and the current version.
11. A. Khan and C. Lemmen, “Bricks and urbanism in the Indus Valley rise and decline” (arXiv:1303.1426). S. Kak, arXiv:0903.3252, citing J. M. Kenoyer (1998). K. Hasson Hnaihen, “The Appearance of Bricks in Ancient Mesopotamia”, Athens Journal of History 6 (2020), doi:10.30958/ajhis.6-1-4.