Masonry takeoff

Most of the world measures masonry with a formal standard method of measurement, the route used by quantity surveyors. In the UK, RICS NRM2 Work Section 14 states the governing principle plainly: all walling is measured on the centre line of the wall. Walls are billed in square metres with the overall thickness stated, and the thicknesses used are nominal, meaning the unit size plus its mortar joint. Measuring on the centre line is efficient because external corners balance themselves out: the small over-measure at one return is exactly cancelled by the under-measure at the other, so corners need no separate adjustment. Australia and New Zealand (ANZSMM Section 12) and the civil engineering method CESMM4 follow the same family. Germany under VOB/C DIN 18330 bills by actual member dimensions rather than nominal.

The United States and Canada have no legal standard method. Instead the contractor route, defined by Brick Industry Association Technical Note 10 and Concrete Masonry and Hardscapes Association TEK 04-02A, uses the wall area method. You measure the net face area of each wall, which is the gross elevation area less openings, and multiply it by a units per square foot rate to get the brick or block count. Thickness is carried by the unit you choose, not by the area.

The two models do not interchange. A centre line square metre figure with a stated thickness already contains both the wall body and the corner material, while a net face area figure is just a surface that then drives a count. Picking the wrong model either double counts or drops the corner and return material.

Every method keeps small voids in the wall, because the material saved by cutting around a small hole is eaten up by the labour of cutting and trimming. What differs is the size at which deductions begin, and the threshold spans a wide range by region. This is the single biggest regional fork in masonry takeoff.

Under RICS NRM2 you deduct voids larger than 0.50 m2, and there is a separate, smaller rule for flues in piers, which are not deducted at or below 0.10 m2. ANZSMM deducts only voids larger than 1.00 m2, so a 1.0 m by 0.5 m opening is explicitly kept. German VOB/C DIN 18330 is the most generous: for area billed work it over-measures, meaning it keeps, openings up to 2.50 m2, and for volume billed work it keeps recesses up to 0.50 m3. That materially inflates the billed area on facades with many windows. US practice has no codified threshold; it ignores anything under roughly 2 square feet and deducts larger openings net.

The deduction also flips by purpose, even within one region. A bid measured to a contract standard deducts exactly per the threshold. A material order leans gross, keeping small openings and adding reveal and jamb units so the pallet never falls short. A payment quantity is strict net with no ordering buffer. Reporting a material order quantity as if it were a measured for payment quantity overstates the bill.

Deducting an opening removes wall area, but the work around the opening is real and is captured separately. The standard method provides an extra-over item over walls for openings, measured by the linear metre of opening perimeter, covering sills, jambs, soffits, closing the cavity, and additional ties. US practice rolls this into a labour add on the wall rate instead. Omitting it under-prices any window-heavy facade even when the area deduction is correct.

Cutting is handled differently by region. Under NRM2 all rough and fair cutting and bonding to other work is deemed included in the walling rate and is not measured separately. US practice instead adds a cutting labour allowance and a higher unit waste band for cut-up walls. Taking a separate cutting item under a standard method bill double-pays work the rate already covers.

Damp-proof course is a separate masonry item, not absorbed into wall area. NRM2 measures damp-proof course up to 300 mm wide by the linear metre, with the width stated, and damp-proof course wider than 300 mm by the square metre. Cavity trays and flashings follow the section's split between deemed-included and separately measured items.

Cavity walls add their own items. The two leaves are each measured as walling, but forming the cavity is taken by the square metre with the cavity width stated, and the cavity insulation is taken by the square metre by type and thickness, or by the linear metre for a strip product. Wall ties bridging the cavity are counted.

The wall area rates are pure geometry: 144 square inches divided by the face area of one unit including its joint. A nominal 8 by 8 by 16 inch concrete block works out to 1.125 block per square foot. CMHA TEK 04-02A Table 1 lists 113 blocks per 100 square feet net, or 119 with a 5 percent waste allowance already included. Half-high 4 by 4 by 16 block doubles to 2.25 per square foot. Modular brick at a 3/8 inch joint is 6.75 per square foot, or 675 per 100 square feet, per BIA Technical Note 10 Table 4. Engineer modular brick is 5.63 per square foot, and closure or utility brick is about 4.5 per square foot.

Bond pattern can add units. BIA Table 6 gives exact corrections where header courses turn bricks to fill more of the same face area: common bond with headers every fifth course adds one fifth of a brick, English bond adds one half, and Flemish bond adds one third. Running bond and stack bond add nothing. Apply the bond correction before waste so the waste percentage compounds the corrected quantity, not the raw one.

Mortar yield is a function of unit size and joint thickness. BIA gives roughly 8.1 cubic feet per 1000 modular brick (5.5 cubic feet per 100 square feet) at a 3/8 inch joint, rising to 10.3 cubic feet per 1000 at a 1/2 inch joint. CMHA gives per-batch yields, where an 8-bag masonry cement mix with 1 ton of sand lays about 240 conventional blocks. Multi-leaf walls add a collar joint of about 3.13 cubic feet per 100 square feet. Hollow units laid with face-shell bedding use 25 to 35 percent less mortar, because mortar sits only on the face shells, so reduce by the void percentage. ASTM C270 is the governing mortar specification.

Grout volume swings by roughly six times depending on how much of the wall is filled, so the fill scope is the first thing to set before any coverage rate. Get the scope wrong and it becomes the largest single error in masonry material volume.

Once the fill scope and wall width are fixed, CMHA TEK 04-02A Table 3 gives the rate directly. The table assumes two-core units and bakes in 3 percent waste. For 8 inch block: solid grouted is 36.1 cubic feet per 100 square feet, which is about 2.1 cubic yards; cells grouted at 16 inches on centre is 18.1; at 24 inches is 12.1; at 32 inches is 9.1; and at 48 inches is 6.1. The full table covers 6, 8, 10, 12, and 14 inch wall widths.

Reinforcement is derived from spacing, never drawn bar by bar. Vertical bars equal the wall length divided by the spacing, plus one for the end bar; omitting that final bar under-counts every wall. Each bar runs the full storey height plus a lap splice. TMS 402 computes the splice length by formula with code minimums and caps that vary by edition. The vertical spacing typically matches the grout spacing. Horizontal joint reinforcement, the ladder or truss wire, is taken as linear feet at typically 16 inches on centre. Bond beams are a counted or linear-foot grouted course. Veneer ties are counted, at a TMS 402 maximum of one per 2.67 square feet, and cavity wall ties at a maximum grid of 36 inches horizontal by 24 inches vertical.

Each sub-item takes its own unit. Reinforcing bars are measured by weight, joint reinforcement wire by length, and ties and anchors each. Reporting bar by length, or wire by weight, breaks the bill's unit and mis-prices the item.

Special members over openings are enumerated, not absorbed into the plain wall. NRM2 measures arches by their mean girth in metres, bands by the metre with the bond stated, and isolated piers, casings, and columns by the metre. Lintels are a separate each or linear-foot item. An element counts as an isolated pier, measured linear, rather than wall, measured by area, when its plan length is no more than four times its thickness, except where the short length is caused by an opening. US practice often rolls pilasters into wall square footage with a labour add. Whichever route is used, do not also count lintel block in the plain wall unit count, or you double-pay the head of the opening.

Apply waste to the material, never to the boundary, and only after the bond and collar corrections. BIA states at least 5 percent on net brick, one of the few masonry waste figures given as an explicit clause, and 15 to 25 percent on net mortar to cover mixing, board, and cleanup losses. CMHA already bakes 5 percent into its 119-unit block figure and 3 percent into its grout table. Cut-up walls in practice carry a higher unit allowance, often in the range of 10 to 15 percent.

The reporting unit follows the regional model, and it is the same model choice expressed in the output. Standard method bills are stated in square metres with the thickness given, reinforcement by mass. The US wall area method reports per-100-square-foot tables, unit counts, and mortar and grout in cubic feet or cubic yards. Reporting a US count as if it were a standard method square metre, or the reverse, is the same model mismatch as picking the wrong boundary.

Exayard reads the drawings and applies these rules automatically, tracing each wall, cutting out the openings that cross the chosen deduction threshold, and converting the net result into the unit count, mortar, grout, and reinforcement quantities for the region in use.