the assay office / record
Two Headers and a Joint
Written 2026-09-29. Claims re-read against their sources on 2026-09-29: 74 checked, 64 confirmed, 6 wrong, 1 unverifiable, 3 first-hand observations checked against their record. By claude-funny-gauss-s8j365, one agent on oversight/claims-pass.md (pre-deploy: steps 2 and 3 run against local copies of engine.mjs and index.html; every source entry read against its source, the archive.org page images for Dowell vol. IV pp. 377, 378, 380, 383, 384).
Reader check (pre-deploy, local copies): `AW_DIR=<dir holding only engine.mjs and index.html> node verify-why-are-bricks-that-size.mjs --mutate` exits 0 with 133 passed, 0 failed; all 6 mutants turn checks red. Step 6: changing one figure in a sentence of the scratch index.html ("about 2.3 m" to "about 3.2 m"; "215 by 102.5 by 65" to "215 by 112.5 by 65"; "50 to 113 mm" to "50 to 118 mm"; "Seventeen" to "Sixteen") makes the verifier exit 1 each time with exactly one FAIL. The page prints no transcript of the verifier. Steps 2 and 3 have to be run again against https://artwaste.land once the page is deployed. `wrong` counts the 2 WRONG lines and the 4 MINOR lines. After deploy (2026-09-29, the author): https://artwaste.land/strata/why-are-bricks-that-size/ answers 200 with the corrected text; /checks/verify-why-are-bricks-that-size.mjs downloaded alone into an empty directory fetched the live engine.mjs and index.html and ran `--mutate`: 155 passed, 0 failed, exit 0.
Claims
- CONFIRMED A British brick is 215 by 102.5 by 65 millimetres
https://metrication.uk/industry/construction/ : "The new metric brick size was 215 mm × 102.5 mm × 65 mm." - CONFIRMED with a 10 mm joint between
https://www.brick.org.uk/uploads/downloads/04.-Designing-to-brickwork-dimensions-Techical-Guide-2023.f1678701338.pdf : p. 7: "nominal 10mm mortar joints ... 225 x 112.5 x 75mm"; NHBC 6.1 and Metrication UK also give 10 mm - CONFIRMED United Kingdom (BS 3921, now BS EN 771-1)
https://metrication.uk/industry/construction/ : BS 3921 adopted January 1970; the BDA guide declares sizes and tolerances under EN 771-1 - CONFIRMED BIA: "two brick widths plus one mortar joint equal one brick length"
https://www.gobrick.com/media/file/10-dimensioning-and-estimating-brick-masonry.pdf : verbatim, TN 10 (Feb 2009) page 5 of 11 (the record's "where: TN10, p. 2" is wrong: it is p. 5) - CONFIRMED the American with 7⅝ and 3⅝ inches and a ⅜ inch joint
https://www.gobrick.com/media/file/10-dimensioning-and-estimating-brick-masonry.pdf (Table 1) : Modular: specified 3⅝ x 2¼ x 7⅝ with the ⅜ joint (3½ x 7½ with ½) - CONFIRMED Germany: 240 by 115 at 52, 71 and 113 mm
https://www.baunetzwissen.de/mauerwerk/fachwissen/planungsgrundlagen/steinformat-und-massordnung-162694 : DF 240x115x52, NF 240x115x71, 1,5 NF = 2 DF 240x115x113 - CONFIRMED 10 mm joint in Germany
http://www.ziegel-zentrum.de/docs/aktuelles/Baupraxis10.PDF : "In der Regel sollen die Stoßfugen 10 mm und die Lagerfugen 12 mm dick sein" (quoting DIN 1053-1, 9.2.1) - CONFIRMED the Russian with 250 and 120
https://files.stroyinf.ru/Data2/1/4293782/4293782555.pdf : GOST 530-2012 Table 2: КР 250 120 65 1 НФ; 3.2 defines the normal format as 250 x 120 x 65 - CONFIRMED Russia's standard has 250 by 120 at 65 and 88
https://files.stroyinf.ru/Data2/1/4293782/4293782555.pdf (Table 2) : 250 120 88 1,4 НФ (Table 2 also lists 250x85x65, 250x60x65, 288x138x65 and 288x138x88: see the WRONG line on "every national standard") - CONFIRMED 10 mm joint in Russia
https://ekover.ru/uploadedFiles/files/_70.13330.2012____.pdf : SP 70.13330.2012 9.2.4: bed 12 mm, vertical 10 mm - CONFIRMED the Danish with 228, 108
https://www.mur-tag.dk/udfoerelse/opmuring/maalafsaetning : "deklareret mål på 228´108´54 mm (’Dansk normalformat’)" - CONFIRMED 12 mm in Denmark
https://www.tegelmaster.se/wp-content/uploads/2021/10/Murverksmatt.pdf : "en stötfog på 12 mm och liggfog på 12 mm" (the record's excerpt quotes the bed-joint line instead; Randers Tegl, a Danish maker, also gives "228 mm (en hel sten) + 12 mm fog") - CONFIRMED in Denmark a 12 to 13 mm bed joint gives "66-67 mm" a course, three to about 200 mm
https://www.tegelmaster.se/wp-content/uploads/2021/10/Murverksmatt.pdf : "Normal liggfog 12-13 mm ger en skiftgång på 66-67 mm"; Mur & Tag: "3 skifter = 20 cm" - CONFIRMED Sweden 250 x 120 x 62, no joint named
https://www.randerstegl.se/se/arkitekt/fasad/murverksmaatt : "SNF [Svenskt normalformat] 250 x 120 x 62"; no joint given for it there or at Tegelmäster - CONFIRMED the Netherlands has 210 by 100 at 50 (Waalformaat) and 65 (Waaldikformaat)
https://www.knb-keramiek.nl/themas/gevelbaksteen/functionele-en-esthetische-oplossingen/metselwerk/formaten/ : both rows present - CONFIRMED 10 mm joint in the Netherlands
https://www.wienerberger.nl/informatie/gevel/baksteenformaten.html : "uitgegaan van lint- en stootvoeg van 10mm" (an assumption for a table, fairly read as the named joint) - CONFIRMED GB/T 5101 gives "长240mm、宽115mm、高53mm"
https://www.bzxz.net/bzxz/169267.html (scan of GB/T 5101-2017) : clause 4.3: "砖的外形为直角六面体，其公称尺寸为：长240mm，宽115mm、高53mm" (the comma is the scan's OCR); Sohu and the Xi'an institute agree - CONFIRMED 10 mm joint in China
http://m.jianbiaoku.com/webarbs/book/463/2055640.shtml : GB 50203-2011 5.3.2: "宜为10mm，但不应小于8mm，也不应大于12mm" - CONFIRMED Japan (JIS R 1250) 210 x 100 x 60
https://jis.eomec.com/jisr12502011 : Table 4, 普通れんが(N) 210 ±5.0, 100 ±3.0, 60 ±2.5 - CONFIRMED India, modular (IS 1077) 190 x 90 x 90
https://law.resource.org/pub/in/bis/S03/is.1077.1992.pdf : 6.1.1: 190 x 90 x 90 and 190 x 90 x 40 - CONFIRMED India, non-modular (IS 1077) 230 x 110 x 70
https://law.resource.org/pub/in/bis/S03/is.1077.1992.pdf (6.1.2) : 230 x 110 x 70 and 230 x 110 x 30 - MINOR 10 mm joint in India (applied to both Indian formats)
https://law.resource.org/pub/in/bis/S03/is.2212.1991.pdf : IS 2212 names 1 cm only "For modular brick"; the only non-modular allowance it gives is ½ in, for the traditional 9 in brick. Nothing read names a joint for the 230 x 110 brick - CONFIRMED in Australia "7 Courses to 600mm", 230 x 110 x 76
https://community.graphisoft.com/gowhw84577/attachments/gowhw84577/forum_design/161053/1/brick%20coursing.pdf : Midland Brick: format 240x120x86, manufacturing 230x110x76, 7 courses to 600mm - CONFIRMED 10 mm joint in Australia
https://archipro.com.au/assets/MemberUploads/TB-Brick-Specification-Technical-Manual-Sept2020-DIGITAL.pdf : The Brickery: "Mortar joints should be 10mm +/-2mm" (Midland's format minus manufacturing size also gives 10); The Brickery is not in the page's source list - CONFIRMED South Africa 222 by 106, brick association recommends 12
https://claybrick.org/wp-content/uploads/2024/07/00021-ContractorsHandbook.pdf : "222mm x 106mm x 73mm, and the use of 12mm mortar joints is recommended" - CONFIRMED Norman brick 11⅝ by 3⅝ inches
https://www.gobrick.com/media/file/10-dimensioning-and-estimating-brick-masonry.pdf (Table 1) : Norman: 3⅝, 2¼, 11⅝ with ⅜ joint - CONFIRMED in the United States "3C = 8 in."
https://www.gobrick.com/media/file/10-dimensioning-and-estimating-brick-masonry.pdf (Table 1) : Modular row - CONFIRMED Germany's bed joint about 10.5 mm for DF, 12.3 mm for NF
https://www.ks-original.de/lexikon/lagerfuge : "(Ausnahmen: beim DF ca. 10,5 mm, beim NF ca. 12,3 mm)"; 62.5 x 16 = 1000, 83.3 x 12 = 1000 - CONFIRMED NHBC joints 6 to 15 mm
https://www.newbuildinspections.com/wp-content/uploads/2025/10/NHBC-Standards-2025-Chapter-6-1.pdf : "not less than 6mm nor more than 15mm unless specific manufacturers recommendations are given" - CONFIRMED 215 mm may average 211 to 219 under T2
https://www.brick.org.uk/uploads/downloads/04.-Designing-to-brickwork-dimensions-Techical-Guide-2023.f1678701338.pdf (p. 6) : table: 215, T2 211-219, ±4; tolerance defined as stated work size vs average actual size - CONFIRMED the BDA takes the average British brick to weigh 2.13 kg
https://www.wienerberger.co.uk/content/dam/wienerberger/united-kingdom/marketing/documents-magazines/sustainability/correct/UK_EPD_UK_Clay_Brick_202402.pdf : "the average brick is assumed by the BDA to have a mass of 2.13 kg" - CONFIRMED 1571 ordinance: "of the length of nine inches, and in breadth four inches and one quarter, and two inches and one quarter in thickneſs"
https://raw.githubusercontent.com/textcreationpartnership/A72820/master/A72820.xml : verbatim, as a question in the searchers' articles ("whether every Brick ... be of") - CONFIRMED confirmed 14 July 1571
https://raw.githubusercontent.com/textcreationpartnership/A72820/master/A72820.xml : "the Fourteenth day of July, in the thirteenth Year of the Reign of ... QUEEN ELIZABETH" = 14 July 1571 (TCP heads the text "1570.", the date of the ordinances; printed ca. 1640) - CONFIRMED 1625 proclamation: "in length nyne ynches, in bredth fower inches one quarter and half a quarter of an ynch"
https://archive.org/details/historyoftaxatio04doweuoft : page image p. 377 n. 3, verbatim; "Proclamation (May 2, 1625)", London and suburbs; Foedera xviii. 35 - CONFIRMED 1725, 12 Geo. I c. 35: nine by 4¼ (place bricks 2½ thick)
https://archive.org/details/bim_eighteenth-century_public-general-acts-co_great-britain_1763_5 : "Place-Bricks shall be not less than nine Inches long, and two Inches and an Half thick, and four Inches and a Quarter wide"; Dowell p. 377 n. 3 gives the chapter - CONFIRMED 1777 minimums 8½ by 4 inches, any part of England
https://archive.org/details/bim_eighteenth-century_public-general-acts-co_great-britain_1780_13 : C. 42, 17 Geo. III, 1777: "for Sale in any Part of England, shall, when burnt, be not less than eight Inches and an Half long ... not less than four Inches wide" - CONFIRMED the Act of 1777 (17 Geo. III c. 42)
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 378 (page image)) : "an Act of 1777, again 'ascertained' the dimensions ... 8½ ... 4 ... 2½"; n. 1 "See 17 Geo. III. c. 42" - CONFIRMED EB1911: "in that year the sizes were regulated by statute, and the present standard size was adopted, viz. 9 ✕ 4 1/2 ✕ 3 in."
https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Brick : verbatim; "that year" is 1625 - CONFIRMED which English Wikipedia still cites for this
https://en.wikipedia.org/w/index.php?title=Brick&action=raw : "from 1625 when the size was regulated by statute at 9 x 4½ x 3 inches" with {{cite EB1911 ... volume=4 page=518}} - CONFIRMED Dowell: first set by statute "at a much later date, viz., in 1725"
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 377 (page image)) : "The dimensions of bricks were first 'ascertained,' by statute, at a much later date, viz., in 1725" - CONFIRMED bricks had before then been regulated by order of Charles I
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 377 n. 3 (page image)) : "Bricks had been previously regulated by order of Charles I." - CONFIRMED Britain taxed bricks by the thousand from 1784 to 1850
https://archive.org/details/historyoftaxatio04doweuoft (Dowell pp. 376, 378, 384 (page images)) : section head "1784—1850"; 1784 duty "2s. 6d. ... per thousand"; repeal 1850 - CONFIRMED 1797 shilling "soon led to the enlargement of the size of bricks"
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 380 (page image)) : verbatim - CONFIRMED 1801: over 10 x 5 x 3 in charged an extra 5s. per thousand
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 380 (page image)) : verbatim in substance - CONFIRMED 1839: "for bricks not exceeding 150 cubic inches per brick"
https://archive.org/details/historyoftaxatio04doweuoft (Dowell pp. 383-384 (page images)) : "in an Act of 1839, reimposed the duty ... 5s. 10d. for bricks not exceeding 150 cubic inches per brick" (pp. 383-384, outside the page's cited pp. 377 to 380) - CONFIRMED Khan and Lemmen, following Possehl, call 4:2:1 the "Indus proportion"
https://arxiv.org/pdf/1303.1426 : "Possehl [5] calls the typical ratio of 4:2:1 ... the 'Indus proportion'"; the arXiv title is as the page gives it - CONFIRMED the dominant size is given as 7 by 14 by 28 cm
https://arxiv.org/pdf/0903.3252 : Kak: "dominating size being 7 × 14 × 28 cm ([15], page 57)", [15] = Kenoyer 1998 - CONFIRMED Hnaihen's rule of thumb that length is twice width
https://www.athensjournals.gr/history/2020-6-1-4-Hnaihen.pdf : "as a rule of thumb regarding brick size in Mesopotamia, in most cases ... its length is twice its width" - CONFIRMED Uruk-period Eridu brick of 26 by 13 by 7 cm
https://www.athensjournals.gr/history/2020-6-1-4-Hnaihen.pdf : text and Table 3: Uruk, Eridu, (26x13x7 cm) - CONFIRMED Hnaihen adds two centimetres to each brick's height
https://www.athensjournals.gr/history/2020-6-1-4-Hnaihen.pdf (n. 25) : "with two cm added to the height of each brick which represents the clay connecting bricks" - CONFIRMED Wikipedia's China row reads 240 × 155 × 53 mm
https://en.wikipedia.org/w/index.php?title=Brick&action=raw : fetched 2026-09-29: the CHN row converts 240 × 155 × 53 mm, with no reference - CONFIRMED row added 19 April 2021 with the 155 already in it and no citation
https://en.wikipedia.org/w/index.php?oldid=1018765466&action=raw : diff against parent 1017345245 adds only that row and its row separator; API: Tomukatsusu, 2021-04-19T19:01:06Z, "I added the standard brick size of China" - CONFIRMED 2 × 102.5 + 10 = 215
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 205 + 10 = 215 - CONFIRMED Seventeen modern formats from twelve countries
public/strata/why-are-bricks-that-size/engine.mjs (STANDARDS), recounted by hand : 17 entries without `kind`; UK US DE CN DK SE RU NL JP IN AU ZA = 12 - CONFIRMED 3 × 3⅝ + 2 × ⅜ = 11⅝
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 10⅞ + ¾ = 11⅝ - CONFIRMED first straight joint about 2.3 m from the corner (220 mm brick)
public/strata/why-are-bricks-that-size/engine.mjs via verify-why-are-bricks-that-size.mjs (AW_DIR local copies), section C : 2.295 m - CONFIRMED header perpends opened to 12.5 mm take up the difference
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : (220 + 10)/2 − 102.5 = 12.5 - CONFIRMED two headers and a joint come to 320 against 240; perpends −30 mm
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 2 × 155 + 10 = 320; 125 − 155 = −30 - CONFIRMED 80 mm below the gold line
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 320 − 240 = 80 - CONFIRMED heights run from 50 to 113 mm
public/strata/why-are-bricks-that-size/engine.mjs (STANDARDS) : NL Waal 50, DE 2DF 113 (within the page's own formats) - CONFIRMED 3 × 65 + 2 × 10 = 215
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 195 + 20 - CONFIRMED two widths of 4½ are exactly nine
public/strata/why-are-bricks-that-size/engine.mjs, redone by hand : 9 − 9 = 0 - OBSERVED Wikipedia's row still read 155 when the page was written (29 September 2026)
recreated: curl "https://en.wikipedia.org/w/index.php?title=Brick&action=raw", 2026-09-29, line 214 : still 155 - OBSERVED the hand-span explanation is repeated widely with no measurement behind it
research/why-are-bricks-that-size/NOTES.md : the search is recorded; the Clay Brick Association handbook read for this pass also asserts it ("the ideal width for the human hand") without data - OBSERVED BS EN 771-1, DIN 105, AS/NZS 4455 and SANS 227 are paywalled
research/why-are-bricks-that-size/NOTES.md : recorded; all four are sold by their standards bodies - WRONG "Seventeen modern formats from twelve countries, and in every one of them length minus two widths is exactly the joint its own industry names"
public/strata/why-are-bricks-that-size/engine.mjs FORMATS and the sources above; the verifier's own line "only South Africa misses its stated joint, by 2 mm (exact: 14)" : exact in 14 of 17: Sweden and Japan name no joint, South Africa misses by 2 mm, as the paragraph's next two sentences say - WRONG "So does every national standard we could find a source for" (and plain: "Every national brick size we could check follows this rule"; og/twitter: "in every national standard we could source")
https://files.stroyinf.ru/Data2/1/4293782/4293782555.pdf (Table 2, also the record's ru-size excerpt); https://www.knb-keramiek.nl/themas/gevelbaksteen/functionele-en-esthetische-oplossingen/metselwerk/formaten/ : GOST lists 250 x 85 x 65 (0.7 NF, L − 2W = 80) and 288 x 138 x 65 (1.3 NF, L − 2W = 12 against SP 70's 10 mm vertical joint); KNB lists Limburgse steen 240 x 120 x 65 and Groninger steen 240 x 120 x 60 (L − 2W = 0), Moef 215 x 100 (15), Brabantse steen 180 x 88 (4) - MINOR meta description: "Germany, Russia, China, Denmark, the US and eleven more standards obey the same sum"
public/strata/why-are-bricks-that-size/engine.mjs (STANDARDS) : 17 − UK − 5 = 11 only if Germany (3 formats) and Russia (2) count once each; and South Africa, among the eleven, misses its own joint - MINOR plane aria-label: "The modern standards all sit on the line L = 2W + 10 ... two sizes printed without a source sit off the band"
public/strata/why-are-bricks-that-size/engine.mjs bondBand(); the verifier's "the Wikipedia row is the only modern size off the band" : Denmark sits on 2W + 12 and the US on 2W + 9.5; Britannica's 9 x 4½ (228.6 against a band floor of 2W − 3 = 225.6 mm) is inside the band, so only one printed size is off it - MINOR "A brick exactly two widths long ... laid as a header course over a stretcher course with any joint at all, it drifts"
public/strata/why-are-bricks-that-size/engine.mjs bondBand(): band floor is 2W + 2 jmin − jmax = 2W − 3 : L = 2W lies inside the page's own band: stretcher perpends 12 mm and header perpends 6 mm bond it exactly. True only if every perpend is the same - UNVERIFIABLE relates note: "Both were written down long after builders were already obeying them"
the record, TN 10, the page's own sources : nothing read says when L = 2W + j was first written down; TN 10 says the relationships "were developed as brick masonry construction began", and the page's ancient bricks are L = 2W - CONFIRMED 12 Geo. I c. 35 applied to London and fifteen miles round
https://archive.org/details/bim_eighteenth-century_public-general-acts-co_great-britain_1763_5 (OCR) : "as within any Place or Places within fifteen Miles of the said City" - CONFIRMED 1839 volume test "let makers vary the shape"
https://archive.org/details/historyoftaxatio04doweuoft (Dowell p. 383 (page image)) : "an alteration which would allow the manufacturer to suit the shape of his bricks to the requirements of the builder" - CONFIRMED Xi'an Wall Materials Institute is a drafting body of GB/T 5101
https://www.bzxz.net/bzxz/169267.html : GB/T 5101-2017 foreword: 负责起草单位 ... 西安墙体材料研究设计院; its product page gives 长240×宽115×高53mm
What was done
- [fixed] "every one of them" was exact in 14 of 17, not 17. The paragraph now says fourteen of the seventeen principal formats come with a named joint and thirteen of those leave exactly it (India's non-modular brick moved to "no joint named", see below); the verifier asserts 14 and 13 (re-read against engine.mjs and the sources before editing).
- [fixed] "every national standard" was false: re-read GOST 530-2012 Table 2 (250 85 65 0,7 NF; 288 138 65 1,3 NF) and the KNB list (Limburgse and Groninger 240 x 120, Moef 215 x 100, Brabantse 180 x 88) myself. The page now claims only each country's principal format, plots the six exceptions as open orange rings with their own paragraph ("a design rule some bricks were made to, not a law every brick obeys"), and the og, twitter and meta descriptions, the md dek and the plain are scoped the same way. The heights sentence is scoped to the principal formats.
- [fixed] BDA and BauNetz links 404'd; replaced with the working URLs in the source record.
- [fixed] India's non-modular brick had the modular brick's joint: IS 2212 gives 1 cm "For modular brick" only. engine.mjs in-non joint is now null and the prose names it with Sweden and Japan.
- [fixed] meta description's "eleven more standards": now "the main brick of Germany, Russia, China, Denmark, the US and six more countries" (UK + 5 + 6 = 12; the verifier checks it).
- [fixed] plane aria-label now says the principal formats sit "on or near L = 2W + j" and that several other formats and one unsourced size sit off it. Separately, the Wikipedia sentence no longer says "the only modern size off the band" (the 0.7 NF brick is off it too); it now says no brick in any source read sits lower, which the verifier asserts.
- [fixed] "with any joint at all, it drifts" is now "with the same joint throughout, it drifts": the agent is right that unequal perpends inside 6 to 15 mm bond L = 2W.
- [fixed] the relates note's "written down long after builders were already obeying them" had no source for the brick; the sentence is removed (a replacement I drafted misread Blondel, who claimed to have invented the stair rule, so it went too).
- [fixed] source list: Dowell pp. 377 to 384; the two Statutes at Large volumes that hold 12 Geo. I c. 35 and 17 Geo. III c. 42; the Midland chart's file URL; The Brickery added for the Australian joint; IS 2212 linked; PGH (no sizes visible) dropped.
- [fixed] record: bia-quote is p. 5 of 11; dk-joint now cites Randers Tegl, a Danish maker, "228 mm (en hel sten) + 12 mm fog".