How to Lay Brick to a Line

Job: build a course-by-course brick wall — garden wall, planter, screen wall, pier, veneer — plumb, level, straight, with joints that shed rain for fifty years.

Time: a weekend for a first small wall. Setting the corners and the line eats the first hours; the field between them goes fast once the line is up. A working mason lays several hundred brick a day — you will not, and the wall does not care that you didn't.

Difficulty: genuinely skilled work, with one great equalizer. A taut mason's line makes the wall *between* the corners straight for you. The corners themselves — the leads — are where the skill lives, and where a beginner should spend the patience.

Everything else — and most of it this catalog does not sell, said plainly: the mason's line itself and its line blocks or line pins; a story pole (gauge rod); a 2‑ft and a 4‑ft spirit level; a brick hammer and a brick set / bolster chisel for cutting closures (or a wet masonry saw); a mortar board or mud pan; a mixing bucket and a hoe or drill paddle; mortar (Type N for most above-grade work, Type S where the wall carries load or meets the weather hard), sand, and cement — or a bag of pre-mixed mortar; a stiff brush; a bucket of clean water and a sponge; gloves and a respirator. This line sells the trowels and the jointer. It does not sell the line, the blocks, the level, the hammer, or the story pole — and you cannot lay a straight wall without them. Buy them before you start.

Before you start: set the line (this is most of a good wall)

The header promised the line is the equalizer. Here is how you earn it — the setup is slow, deliberate, and worth every minute, because a wall that starts crooked never recovers.

Plan the course dry — "dry bond" it. Before any mortar, stand the whole first course along the wall's chalk line, corner to corner, with a pencil's width of gap between bricks for the head joints. Now you can see where the joints land and whether you will end on an ugly sliver. Adjust the spacing, or plan a cut, *now*. A wall that finishes on a 1" closure brick was designed wrong at this step — not laid wrong three courses later.

Start on a foundation that is flat, clean, and damp. Brick beds on a sound, level footing or foundation, swept clean and lightly dampened so it doesn't rob the mortar of water. The first course goes down in a full mortar bed — the entire footprint, not the two face-shell ribbons that concrete block uses — so the wall begins on complete bearing. Snap your chalk line and lay that first course to it exactly; everything above trusts it.

Build the leads first — the corners are the whole job. Do not try to run a long course off the ground. Build up each end of the wall four to six courses high as a lead (a racked-back corner), laying each brick individually and checking three things on every one: plumb (level held vertical against the face), level (across the top of the course), and gauge (course height against the story pole, below). Rack the lead back a half-brick per course so the stepped bond is visible and the line has a clean corner to hook. The leads carry the wall's accuracy; the field between them only has to follow the line.

Gauge every course to a story pole. A story pole (gauge rod) is a straight stick marked with your course heights — one brick plus one bed joint per mark. Standard modular brick runs three courses to 8" with a 3/8" bed joint; hold the pole against each lead course and make the mortar joint thick or thin to hit the mark. Let the bed joints wander and the two leads will disagree by an inch at head height, the courses won't meet at the corner, and no line will save you.

Stretch the line, and treat it as sacred. Hook a line block over the outside top corner of each lead (or set a line pin in the bed joint) and pull a mason's line taut between them, level with the top outside edge of the course you are about to lay. On runs over about 20 feet, support the middle with a trig (line stretcher) set on a gauged brick so the line can't sag or belly in the wind. The line is a guide you kiss, never crowd: set each brick so its top face sits about 1/16" back from the line with daylight just showing between — push bricks tight against the line and every mason's instinct to "crowd" a hair compounds into a wall bowed out of true.

Mix the mortar — and mind the two hazards while you do. Mortar wants to be plastic: it clings to the trowel held briefly on edge and doesn't run, roughly the body of soft ice cream. Mix small, workable batches with the margin trowels (18050 / 18060) — water in the pail first, powder cut down into it and folded up from the bottom, the square corner dragged around the pail's base so nothing cakes dry (the 18060's extra half inch turns a batch faster; the 18050 chases the tight pail corner cleaner). Two boundaries are load-bearing and neither is boilerplate:

Silica. Dry mortar mix, cement, and sand carry respirable crystalline silica, and the instant of pouring powder is the instant it goes airborne. Pour low (bag mouth at the water's surface, not shoulder height), mix wet, stay upwind, and wear a respirator for repeated batches. The same warning covers cutting brick — a brick set and hammer, and above all a dry saw, throw silica dust; wet-cut or chop-and-dust-control, and mask up. Silicosis is dose-driven and incurable; OSHA's construction limit is 50 µg/m³ over a shift (29 CFR 1926.1153).

Caustic / lime burns. Wet mortar is strongly alkaline — pH 12 to 13, driven by its lime and cement — and it burns skin caustically without any pain to warn you; a national survey found cement burns in 35% of apprentice masons (eLCOSH, Poison Control, NPCA). Gloves on before the first board is loaded, and never kneel bare-skinned in fresh mortar. A bricklayer's hands meet wet mortar more times a day than any other trade's.

Laying the course to the line

Throw and furrow the bed. Cut a slice of mortar off the board and pick it up with a rolling sweep of the wrist. On the London 18095 the rounded heel sheds nothing rearward, so the load gathers forward toward the tip in about one brick's portion — the pattern hands you the amount a bed wants instead of the amount a blade can carry. Throw it: a wrist-flick that strings the mortar down the course as a rope the width of one brick, two or three bricks ahead of yourself. Then furrow lightly — draw the tip down the center of the bed just enough to let the brick seat and squeeze mortar toward both edges. *Light.* A deep furrow leaves a hollow channel under the finished course — a void that drinks water. (Prefer a heavier blade or already own the Philadelphia 18090 from block work? It lays brick too — you simply meter one brick's worth with your wrist that the London meters with its heel.

Butter the head joint — on the brick, not the wall. Pick up the next brick in your free hand and swipe a full wedge of mortar onto the end (the head) that will butt against the brick already laid — press it on thick enough to stand, so it squeezes when you shove. This is the stroke the London's narrow tip exists for: it lays a square, full butter on a brick end in one pass and cleans the arris with its point. A skimpy or hollow head joint is the single most common leak path in an amateur wall; butter it full and let it squeeze.

Lay to the line, then tap down — plumb, level, gauge. Set the buttered brick onto the bed and shove it in one motion toward its neighbor until the head joint squeezes tight and the brick sits to the line — top edge level with the line, face a hair back from it, daylight just showing. Shove once and commit; sliding a brick around after it's down tears the young bond and starves the joint. Tap it down to the line and level with the handle end of the trowel or the brick hammer — never the steel blade edge, which chips a fired face. The line keeps the field straight and level for you; still spot-check plumb at the leads with the level every few bricks, because the corners are the only place the wall can go out.

Cut off the squeeze-out — mortar is money. A properly full joint squeezes a ridge of mortar out both faces. Slice it off clean with the trowel held flat against the wall, one pass per face, and flip it straight back onto the board to be reused — a day's squeeze-out scraped to the ground is a wheelbarrow of mortar thrown away. Do not smear it into the joint face; that comes later, with the right tool, at the right time.

Fill the field, then raise the line. Lay the whole course between the leads to the line, working brick to brick. When the course is full, move the line blocks up one gauge mark on each lead and lay the next course. Every few courses, build the leads up again ahead of the field so the line always has somewhere to hook. This rhythm — leads ahead, line up, field to the line — is the whole trade, repeated until the wall is done.

After: strike the joints, then clean the wall

Strike the joints concave at thumbprint-hard. The joints you laid are still loose, open-textured, and shrinking. Jointing fixes that: run the 18170 jointer's 3/8" end (the modular-brick width) along each joint once the mortar is thumbprint-hard — stiff enough to hold a clean thumbprint without wet paste lifting onto your thumb. Strike the short vertical head joints first, then run the long horizontal bed joints through them so the horizontal lines — the ones raking light reads on a finished wall — come out continuous. The half-round doesn't carve a groove; it compresses the joint's surface and leaves a concave curve, and that profile is weather doctrine, not decoration: the Brick Industry Association ranks tooled concave joints best for shedding water, while flush and raked joints leave ledges that let it in (BIA TN 7B). The window slides with the weather and moves along the wall in laying order — tool the morning's first joints while the fresh end waits.

Dress the fins dry, then clean the faces — patiently. Tooling raises thin ridges of mortar (fins) at the joint edges. Leave them. When they have dried crumbly — an hour or three on — knock them off with a stiff brush stroked diagonally across the joints. Brushing or wiping fins *wet* is the classic beginner's mistake: it drags cement paste across the brick and builds a gray haze no rinse fully forgives. Sponge or brush the faces clean only after the fins are dressed. Heavy final cleaning with muriatic acid is sometimes done on new brickwork, but it is a real hazard with its own procedure (dilution, pre-wetting, neutralizing, eye and skin protection) and is beyond this guide — if the wall needs it, treat it as a separate, researched job, not an afterthought.

What goes wrong (and the fix)

"The wall's bellying out / it's not plumb." You crowded the line, or your leads went out.

"My joints are fat here and starved there / courses don't line up." You stopped gauging. Every lead course must hit the story-pole mark; make the bed joint thick or thin to land on gauge, and the courses will meet at the corners and at every window and door.

"The faces are smeared gray." You wiped fins or squeeze-out while it was wet. Cut squeeze-out off flat and dry-brush fins only after they crumble. Cement haze is far easier to never make than to wash off.

"Mortar slides off the brick / won't stick." Mortar too wet, or the brick is bone-dry and sucking the water out of the joint before it can grab. Stiffen the batch a touch, and on a hot day lightly dampen very absorbent brick before laying (damp, not wet — a wet brick floats). Retemper a stiffening board only within the mortar's first working hours, never after it has begun to set for good.

"The line sags in the middle of a long run." Set a trig on a gauged brick at mid-span to carry it, and re-tension. A sagging line lays a sagging course.

The history footnote (because these pages should be worth reading)

The two brick trowels you can choose between here are the last survivors of a crowded nineteenth-century field. American catalogs once listed a dozen regional patterns; the trade thinned them to two, both named for cities, and both still on this shelf — the wide, square-heeled Philadelphia and the narrow, round-heeled London. Philadelphia's name is no accident: William Rose opened a smithy near the city in 1798, spent his early decades forging cavalry sabers, and in 1864 turned to edge tools and the brick trowel that became the American form. The mason's line is older than either and has never changed, because the problem hasn't: a taut string is still the only thing that makes a long wall straight, and a bricklayer in Rome kissed one exactly the way you will.

Every linked PDP lists this guide under its applications — the graph runs both directions.