Masonry coursing calculator

Why a dimension has to land

Brick and block come in fixed sizes and go up in fixed increments. A wall that is not a whole number of units long ends in a cut unit, and a sill that is not a whole number of courses up sits on a sliver. The mason will make either work, and the drawing will look like someone did not know. The habit that prevents it is to let the module set the dimension rather than the dimension set the module: lay the plan out in units and joints, and the overall comes out of that.

This calculator is for the moment of laying out. Pick the masonry first, read the rule of thumb for it, then type the dimension you are about to draw. Green means it lands on a whole unit; yellow means it lands on a half unit, which running bond allows and stack bond does not; red means it misses, by how much, with the nearest dimensions that land either side and the count of courses or units for each. Vertical and horizontal wear their own colours throughout, so the direction of the dimension is never in doubt.

Modular and non-modular, nominal and actual

A modular brick is 3 5/8" × 2 1/4" × 7 5/8" as made. With a 3/8" joint on top and on one end it fills a nominal 4" × 2 2/3" × 8", and three courses stack to 8". That 8" is the story pole: the mason marks it on a rod and lays to the marks, and the joints absorb the arithmetic. Three specified bricks plus three 3/8" joints come to 7 7/8", not 8", and the extra eighth lives in slightly fuller joints. The drawing dimensions to the story pole, which is why the tool drives modular units by the nominal module and shows the specified-plus-joint arithmetic beside it as the actual.

Non-modular brick has no module. A standard 8" brick with a 3/8" joint is 8 3/8" per brick along the wall and 2 5/8" per course, and nothing in that lands on a clean foot. King and queen sizes vary by producer and should be confirmed before a dimension depends on them. Concrete block is modular and its arithmetic closes: 7 5/8" plus 3/8" is exactly 8", and a 15 5/8" block plus its joint is exactly 16".

The rule of thumb

For an 8" module, which is modular brick vertically and concrete block both ways, a dimension lands when even feet end in 0" or 8" and odd feet end in 4". That is the whole rule, and it covers 2'-8", 3'-4", 4'-0", 4'-8", 5'-4", 6'-0" and so on. A 4" module, closure and utility brick, half-high block, lands every 0", 4" and 8". A 16" module, five courses of engineer brick, repeats every four feet: 0" at a multiple of four feet, 4" one foot past it, 8" two feet past, and nothing in the third foot.

The rule moves by a joint when the dimension does not run centreline to centreline. Brick to brick, a wall or a pier, the endings drop by 3/8": 7 5/8", 3 5/8", 11 5/8". Joint to joint, an opening, they rise by 3/8". The tool rewrites the rule for whatever you have picked, so you do not have to carry the shift in your head.

Horizontal: what the dimension runs between

A horizontal masonry dimension is N modules plus or minus a joint depending on what is at its ends. Masonry at both ends, a wall from corner to corner or a pier between openings, is N units and N less one joints: twelve modular bricks make 7'-11 5/8", not 8'-0". A joint at both ends, an opening from jamb to jamb, is N units and N plus one joints: six bricks make a 4'-0 3/8" opening. Centreline to centreline, or the module on its own, is N units exactly.

Running bond lands on the half module as well, because a closer is a normal thing to lay, so a stretcher wall lands every 4" rather than every 8". Stack bond does not; the tool treats it as whole units. A header or soldier course lands on one brick width per unit, 4" nominal, and a rowlock on one brick height, 2 2/3" nominal.

Vertical: top of course or top of brick

A vertical dimension to the top of a course includes the bed joint above the last brick, which is how a story pole reads and how a sill or a lintel bears. A dimension to the top of a brick, a cap with nothing above it, is one joint less. The tool offers both, and the rule of thumb follows.

Soldier courses are the common trap. A soldier course of modular brick is one brick length tall, 8" nominal, which is three stretcher courses exactly; a rowlock sill is one brick width tall, 4"; a sailor is 8" like a soldier. Pick the orientation and the tool uses the right dimension of the unit.

Concrete block

Block coursing is the simplest case because the arithmetic closes: 8" courses, 16" units, 8" half units, and the brick-to-brick and joint-to-joint rules apply unchanged. A 10'-8" wall height is sixteen courses; a 20'-0" wall length brick to brick wants fifteen blocks at 19'-11 5/8", or an opening at 20'-0 3/8". Half-high block courses at 4". The block's width, 4" to 12" nominal, does not change its coursing.

A worked layout

A garage in modular brick, running bond, with a 9'-0" door. The wall is drawn 24'-0" long corner to corner: brick to brick, that is 36.05 bricks, so it misses; 36 bricks land at 23'-11 5/8" and the drawing changes by 3/8". The door opening drawn 9'-0" jamb to jamb misses; 27 half modules land at 9'-0 3/8". The eave height drawn 9'-4" to the top of a course lands on 42 courses, fourteen 8" modules, and stays. Three dimensions checked in the time it takes to read this paragraph, which is the point.

Coursing charts

The three charts architects reach for most, generated from the same module as the tool so they cannot disagree with it. Nominal is the story-pole dimension the drawing carries; actual is the specified unit plus a 3/8" joint, course by course. Module boundaries are highlighted. Print the page and they come out as tables.