Masonry
Laying Brick and Block
Every masonry wall is one course repeated: get the unit, its bed, its perpend and its bond right, and the rest is multiplication.
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The Unit, Measured Cold
A brick is a module before it is a lump of fired clay. The number in the specification is nominal — it already contains the joint. A modular clay unit in North America is called 8 by 2-2/3 by 4 inches because the unit plus a 3/8-inch joint adds up that way, three courses to eight inches vertically, while the thing in your hand measures nearer 7-5/8 by 2-1/4 by 3-5/8. Metric standard format behaves identically: a 215 by 102.5 by 65 mm brick plus a 10 mm joint gives a 225 by 75 mm module, four courses to 300 mm. Every setting-out decision downstream comes from that arithmetic, and it collapses the moment the bed drifts a couple of millimetres a course.
Dimensional variation lives in the unit as much as in your trowel hand. ASTM C216 Standard Specification for Facing Brick (Solid Masonry Units Made from Clay or Shale) and ASTM C62 Standard Specification for Building Brick (Solid Masonry Units Made from Clay or Shale) sort clay units by permissible variation and by chippage; BS EN 771-1 Specification for Masonry Units — Clay Masonry Units does the same work through declared tolerance categories, and concrete units answer to ASTM C90 Standard Specification for Loadbearing Concrete Masonry Units. On the deck that means two packs from different firings can differ enough in size and shade to read as a stripe across a gable. Draw from three or four packs simultaneously, all day, every day, and never let a bricklayer work a pallet out before opening the next.
Suction decides whether bond forms at all. A dry, thirsty clay unit pulls water out of the bed before the cement has anything left to hydrate with, and the result is a joint that looks perfect and has almost no tensile bond across it. ASTM C67 Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile gives the initial rate of absorption test; the threshold above which units get wetted before laying is set by the project specification and by regional guidance, so read the spec rather than guessing from the last job. Wetting means docking — surface damp, no free water, the sheen gone off before the unit meets mortar. A saturated brick swims on the bed, bleeds fines down the face, and takes the whole lead out of plumb by the time you have laid six.
The Bed It Sits On
Mortar is neither glue nor concrete. Its job is to bed an irregular unit, seal the plane, and let the wall move a little without cracking the units. ASTM C270 Standard Specification for Mortar for Unit Masonry sets out Types M, S, N and O and permits specification either by proportion or by property — never both at once, because the two routes contradict one another on site and the supplier will pick whichever suits him. Reaching for a stronger mortar than the design calls for is the routine error: a hard mortar in a soft brick wall drives cracking through the units and into the face, and a spalled face cannot be repointed back.
Sand grading does more visible work than the cement does. ASTM C144 Standard Specification for Aggregate for Masonry Mortar covers it, and a poorly graded sand makes a harsh, unworkable mix that the gang fixes by adding water, then fixes again by adding cement, and the joint colour walks across the elevation from bay to bay. Batch by measured volume — gauge boxes, not shovel counts — and hold the same sand stockpile and the same water target from the first lift to the last.
Board life governs the pace of the day. Mortar is commonly required to be placed within roughly two and a half hours of initial mixing, with the exact window and the retempering rules coming from the governing specification; past that it is spoil, whatever it still looks like. Spread only the bed you can lay into before it stiffens — three or four units ahead in warm weather, more in cool — and furrow lightly if at all, because a deep furrow leaves a channel down the middle of the bed that fills with water and does its damage the first time the wall freezes.
The Perpend Nobody Sees
Head joints fail far more often than bed joints because gravity is working against you rather than for you. The unit gets buttered standing on end, pushed up tight, and the mortar has to hold its shape while the next one arrives. Full perpends are what the specification asks for, and slushing mortar down into the gap afterwards does not produce one — it produces a plug at the face with a void sitting behind it, which is worse than an honest open joint because nobody can see it.
Voids in perpends are a water path, an air path and a sound path at once. In a drained cavity they hand rain straight onto the back of the outer leaf and load the tray with more water than the weeps were sized for; in single-leaf work they explain why a nominally solid elevation wets through in a driving storm on one exposure only. Field testing to ASTM C1601 Standard Test Method for Field Determination of Water Penetration of Masonry Wall Surfaces very often traces leakage to head joints and to the interface between joint and unit rather than to the units themselves.
Tooling is compaction, not decoration. A concave iron run when the mortar is thumbprint hard presses the surface tight against the arris and closes the shrinkage gap that opens as the joint stiffens; too early and you smear laitance across the face, too late and you burnish a joint that has already begun to set, which then cracks along its edge. Raked and recessed profiles cut the effective cover over the bed and are a poor choice on an exposed elevation no matter how well they photographed on the sample panel.
Bond: What the Lap Actually Does
Lap is structure, not pattern. Half bond puts each perpend over the middle of the unit below, so a point load spreads sideways through the courses instead of running down a continuous vertical seam. Longer units take third bond for the same reason. Stack bond has no lap whatsoever, which is why the code treats it as a separate case and calls for continuous horizontal joint reinforcement — ASTM A951/A951M Standard Specification for Steel Wire for Masonry Joint Reinforcement covers the wire, with the requirement itself coming from TMS 402/602 Building Code Requirements and Specification for Masonry Structures or the local equivalent.
Set the course out dry before anything is bedded. Run the first course along the footing or the damp-proof course with the perpend gaps gauged, corner to corner and past every reveal, then shift the whole run if that kills a sliver cut at a window jamb. A wall that arrives at an opening needing a thirty-millimetre slip of brick will display that slip for the life of the building, and it will be the first joint on the elevation to leak.
Traditional bonds change the count as much as the appearance. English and Flemish bond bring headers through the wall and demand closers at every quoin; a veneer imitating them uses snapped headers, which doubles the units cut and lifts breakage sharply. Decide bond before the take-off rather than after, because header courses, closers and returns are the whole difference between a comfortable waste allowance and running short on the last elevation with the scaffold already struck.
One Course, Multiplied
Corners come first and everything else obeys them. Build the leads racked back, plumbed on both faces, gauged off a storey rod that already carries the damp-proof course, sill, head, lintel bearing and eaves marks — then fill between them to the line. A lead built one course out of gauge multiplies that error into every unit between it and the next corner, and the fix is demolition rather than adjustment.
Line and pins hold the plane, provided the line itself is not sagging. Use a tingle plate at midspan on a long run, keep the line just clear of the face so units are laid to it rather than pressed against it, and check the middle of the run with a level instead of trusting the string. Plumb, level and alignment tolerances are tabulated in the governing specification — quarter-inch-in-ten-feet territory in the American documents — and a wall that genuinely meets them still reads straight in raking evening light, which is the test that matters to the client.
Quantities fall out of the same module the gauge came from. Face size plus joint thickness gives the units in a square metre or square foot; joint thickness and unit depth govern how much mortar a thousand units will drink. Cutting waste is pure geometry — openings, returns, rakes, and any bond that snaps headers — with breakage from handling and site cutting sitting on top of it. Take off elevation by elevation rather than as one lump, because that is how material actually gets ordered and how a shortfall on the last gable gets caught while there is still time to order in.
Work the unit count, joint allowance and mortar volume for each elevation from the face dimensions and joint thickness you have just set on the gauge rod.
The standard allowance most suppliers and estimating guides assume for ordinary work.
Estimated brick needed
1,106 bricks
- Wall area
- 156 sq ft
- Coverage rate (from your dimensions)
- 6.44 bricks/sq ft
- Base brick count (no waste)
- 1006 bricks
- Mortar mix needed
- 17 80 lb bags
For the dimensions entered, expect a result of 1106 bricks. Of the working steps, base brick count (no waste) dominates at 1006 bricks. Set for United States. The market selector changes the units and the trade terminology; any standard behind the formula is cited under sources.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
The Hollow Unit's Arithmetic
Concrete block rewrites the rules of the bed. Standard practice beds the face shells only, so mortar sits on two narrow strips and the cells run continuous top to bottom — except at the starting course and wherever grout has to be contained, where the webs get bedded as well. Nominal 8 by 8 by 16 inch and 440 by 215 mm units both carry the joint inside the module exactly as brick does, and a block wall that wanders off gauge will fight every bond beam, every bearing and every opening head above it.
Cells only earn their keep if they line up. Reinforced cells have to stack cleanly from the dowel out of the footing to the top of the pour, and a course laid a half-unit out of bond puts a web precisely where the bar wants to be. Cleanouts at the base of grouted cells let you clear debris and dropped mortar before grouting begins; TMS 402/602 Building Code Requirements and Specification for Masonry Structures governs when they are required, along with pour and lift heights and the consolidation regime, and those limits vary with the grout space and the grout type rather than being one number you can memorise.
Grout is neither mortar nor a lean concrete. ASTM C476 Standard Specification for Grout for Masonry covers it, and it is deliberately fluid because it must flow into a narrow cell and fully around a bar — the units absorb the surplus water afterwards, which is why a high slump here is correct rather than sloppy. Consolidate each lift with a vibrator and reconsolidate after initial water loss, otherwise you leave voids exactly where the bar needs cover. Dam the cell beneath a bond beam with a grout stop or wire mesh so the pour does not run away down the wall, and count every knock-out and lintel block on the drawing, because bond beam volume is what a plain cell count always misses.
Count the block, then the cells that actually take grout — reinforced cells, bond beams and any solid-grouted zones — before the ready-mix order goes in.
Waste is set to 5% by hand. Pick a tier above to replace it, or keep your own figure.
CMU blocks needed
185 blocks
Grout volume assumes uniform void geometry across all cells — face-shell-bedded (ungrouted) cells and webs reduce the actual grout consumption if only some cells are filled.
- Wall area
- 156 sq ft
- Coverage rate (from your dimensions)
- 1.13 blocks/sq ft
- Grout volume needed
- 351 gal
For the dimensions entered, expect a cmu blocks needed of 185. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States. The market selector changes the units and the trade terminology; any standard behind the formula is cited under sources.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Water, Ties and the Right to Move
A cavity wall works by draining, not by resisting. Flashing at the base of the cavity and at every interruption — sills, heads, shelf angles — collects water and discharges it through weeps whose spacing and form come from the governing building code rather than from habit carried off the last job. Mortar droppings on that flashing dam it, and a dammed tray means a wet inner leaf. Bevel the bed away from the cavity, run a cavity batten or a mortar collection device, and clear the tray before the scaffold lift rises past it, because afterwards it is inaccessible.
Ties carry the leaves together and carry water apart, and they do neither if they are installed carelessly. Full embedment into both beds, the correct fall to the outer leaf where the tie type calls for it, no mortar bridging along the wire, and spacing and type per code — BS EN 845-1 Specification for Ancillary Components for Masonry covers the components in the European system, TMS 402/602 in the American. Ties pushed in after the bed has stiffened, bent up over a course, or resting on a dry joint are worth nothing structurally and are entirely invisible once the wall is closed.
Clay and concrete move in opposite directions, which is the single most useful fact to carry onto a long elevation. Fired clay takes up moisture after it leaves the kiln and grows, permanently and slowly; concrete block cures and shrinks. Clay brickwork therefore takes expansion joints and concrete masonry takes control joints, the two are not interchangeable, and their positions — at offsets, at changes of height, near corners, at large openings — belong on the setting-out before the first course goes down. Nothing done at day thirty inserts a joint that was needed on day one.
What the Wall Remembers
Weather bounds the working day at both ends. Cold-weather provisions in the governing specification take effect below a stated ambient temperature and require heated materials, protection, and in the harder cases heated enclosures; hot-weather provisions address the opposite failure, where the bed stiffens before the unit lands and no bond ever develops. Cover the top of unfinished work at every break, not merely overnight — rain entering open cells and unfilled cavities is the origin of most efflorescence that later gets blamed on the sand.
Cleaning down belongs to the build, not to goodwill at handover. Leave droppings until they are hard enough to come away with a trowel and stiff brush instead of smearing, prewet the wall thoroughly so cleaner cannot soak into dry units, follow the unit manufacturer's own cleaning guidance for that product, and rinse properly afterwards. Acid applied to an unwetted wall burns the face, strips cement from the joint surface and can draw metallic staining out of the units themselves — damage no amount of repointing corrects.
Everything about masonry stays legible afterwards, which is the trade's peculiar exposure. A joint tooled too early reads as a grey smear at ten years; a lead built out of gauge reads as a converging line under the eaves; a hollow perpend reads as a damp patch on the inside face of a wall two rooms away from where the water entered. One course laid properly — units blended, bed full and workable, perpend solid, lap honest — is the entire wall, because a wall has never been anything else.
Taking Off One Course at a Time
Fix the module first — unit face size plus joint thickness — then let every quantity on the job fall out of it, elevation by elevation rather than as a single lump sum.
- Unit count per elevation, with cutting waste separated out — Openings, returns, rakes and snapped headers are geometry you can count; handling breakage is an allowance on top and belongs in its own line.
- Mortar volume against the specified joint thickness — Joint thickness and unit depth drive it. If the gang is laying a fatter joint than specified, both the mortar figure and the gauge are already wrong.
- Grouted cells, bond beams and lintel blocks counted separately — A plain cell count misses bond beam and knock-out volume every time; list them off the reinforcement drawing rather than the block schedule.
- Ties, joint reinforcement and movement joint positions marked before the first course — Spacing and type come from the governing code. Positions marked on the setting-out cost nothing; positions discovered at first floor cost a rebuild.
- Unit suction checked against the specification before wetting policy is set — High-suction clay laid dry gives a joint with no tensile bond. Test result and spec threshold decide whether units are docked, not the weather that morning.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.
Drawn from
- ASTM C216 Standard Specification for Facing Brick (Solid Masonry Units Made from Clay or Shale)
- ASTM C62 Standard Specification for Building Brick (Solid Masonry Units Made from Clay or Shale)
- ASTM C90 Standard Specification for Loadbearing Concrete Masonry Units
- ASTM C67 Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile
- ASTM C270 Standard Specification for Mortar for Unit Masonry
- ASTM C144 Standard Specification for Aggregate for Masonry Mortar
- ASTM C476 Standard Specification for Grout for Masonry
- ASTM C1601 Standard Test Method for Field Determination of Water Penetration of Masonry Wall Surfaces
- ASTM A951/A951M Standard Specification for Steel Wire for Masonry Joint Reinforcement
- TMS 402/602 Building Code Requirements and Specification for Masonry Structures
- BS EN 771-1 Specification for Masonry Units — Clay Masonry Units
- BS EN 845-1 Specification for Ancillary Components for Masonry
Guidance, not a specification. Local codes, the engineer of record and the product manufacturer’s instructions govern where they differ from anything written here.