Brick Calculator — bricks, mortar and the bed joint

Brick count is exact arithmetic off the nominal face module and the mortar is not, and the bed joint that closes the coursing is not the 3/8″ printed against the size — this shows all three, and where the industry’s own estimating table contradicts itself.

Sizes, coursing and quantities: Brick Industry Association, Technical Notes 10, Dimensioning and Estimating Brick Masonry, February 2009 — Table 1 (modular sizes, specified dimensions and vertical coursing), Table 2 (non-modular sizes), Table 4 (published brick and mortar quantities), Table 5 (collar joints: 3.13 ft³ per 100 sq ft at a 3/8″ joint, 4.17 at 1/2″), Table 6 (bond correction factors), and the waste guidance: “at least 5 percent” on brick, “add 15 to 25 percent” on mortar. gobrick.com.

The bed joint. BIA Table 1 footnote 3 says the 3/8″ and 1/2″ figures are “common joint sizes used with length and width dimensions” and that “actual bed joint thicknesses vary based on vertical coursing and actual brick height.” For modular brick the vertical module does the deciding: three courses equal 8″, so the bed joint is (8 − 3 × 2-1/4) ÷ 3 = 5/12″, about 10.6 mm. CMHA (formerly NCMA) TEK 05-12, Modular Layout of Concrete Masonry, states the same 5/12″ bed joint and calls it within allowable mortar joint tolerances. It is not 7/16″: that is the nearest sixteenth, and it grows the wall by 1/16″ every three courses. TMS 602, Specification for Masonry Structures, allows ±1/8″ on a bed joint, which is why a 5/12″ target and a 3/8″ call-out both pass inspection — and why only the coursing tells you which one you actually got.

6.75, not 6.86. The nominal face is 8″ × 2-2/3″ = 21.33 in², so 144 ÷ 21.33 = 6.75 brick per square foot. That is exactly what BIA Table 4 prints as 675 per 100 sq ft. The 6.86 that circulates — including in one manufacturer’s own consumer brochure, whose technical sheet says 6.75 — is 144 ÷ (8 × 2-5/8): the 3/8″ bed joint again. On 1,000 sq ft of wall that is a 107-brick spread.

Tolerance: ASTM C216, Standard Specification for Facing Brick, Table 3, Column A. Type FBS may vary from the specified dimension by ±3/32″ up to 3″, ±1/8″ over 3 to 4″, ±3/16″ over 4 to 6″, ±1/4″ over 6 to 8″, ±5/16″ over 8 to 12″ and ±3/8″ over 12 to 16″. Type FBX is tighter. C216 Note 12 points at ASTM E835/E835M for the list of modular sizes and warns that brick names denoting sizes are regional.

Metric sizes: metric modular 190 × 90 × 57 mm coursing three to 200 mm is from Brampton Brick’s metric modular coursing chart; UK standard format 215 × 102.5 × 65 mm with a 10 mm joint (a 225 × 75 mm module, four courses to 300 mm) is the Brick Development Association format. Neither appears in BIA Table 4, so their quantities here are derived from the geometry above and nothing else. TN 10 warns on its first page that brick for metric projects runs on a 100 mm module and that its own inch-to-millimetre equivalents should not be carried across to metric modular work.

What is not in the table: masons often quote eight bags of masonry cement per 1000 modular brick. BIA prints that rule and in the next sentence calls it a very rough estimate containing an unspecified amount of waste, so it is not used here. Nor are ties, flashing, weeps, lintels, sills, reinforcement or cleanouts. Mortar quantities assume full bed joints on solid units, coring up to 25 percent; hollow units laid with face-shell bedding use roughly 25 to 35 percent less.