The mistakes, and the fixes
1. One unit count for every wall
Concrete Masonry and Hardscapes Association (CMHA, formerly NCMA) TEK 04-02A gives the basic rule: an 8 x 16 in. nominal CMU covers 8/9 sq ft of wall, so 112.5 units per 100 sq ft, or about 119 with a 5% allowance for waste and breakage, regardless of unit width. Modular brick runs about 6.75 per sq ft (675 per 100 sq ft) with 3/8 in. joints. But corner units, bond beam units, lintel units, pilaster units, sash and jamb units and split-face or ground-face units are different products at different prices. Take off by wall type and unit, count the special units separately and subtract them from the field units.
2. Deducting openings without adding back
Openings reduce field units, but add lintels or lintel units, jamb and sash units, sills, flashing and the labor of laying around the opening. Count openings by size and type, and price the jamb and head conditions. A wall broken by many small windows is slower per square foot than a blank wall.
3. Missing or misreading grout
Solid grouting versus cells grouted at spacing changes grout volume dramatically. CMHA's tables give about 36 cubic feet of grout per 100 sq ft for an 8 in. wall grouted solid (including a small waste allowance), with partial grouting scaling down by cell spacing, plus extra for bond beams. Grout waste varies with unit density (lighter units absorb more water) and with pumping versus bucketing. The grouting pattern is usually in the structural general notes or a typical wall section, not on the elevations.
4. Missing reinforcing
Vertical bars at spacing, bars at each side of openings, at corners, at wall ends and at control joints, bond beam bars, dowels to the foundation and horizontal joint reinforcement every few courses all add up. Count vertical bars by wall length and spacing, then add the extra bars from the typical details. Joint reinforcement is linear feet of wall times courses at the specified spacing (often every second course, 16 in. on center, for 8 in. block).
5. Ignoring bond beams and lintels
Bond beams at floor lines, roof bearing and tops of walls need bond beam units, bars and horizontal grout. Lintels may be precast, steel angles (often by the steel supplier) or grouted CMU lintels. Read the lintel schedule and confirm who furnishes steel lintels; it is a frequent gap between masonry and misc. metals bids.
6. Mortar as an afterthought
CMHA calls mortar, after grout, the most commonly misestimated masonry material. Its rules of thumb for face-shell bedding: one 70 lb bag of masonry cement lays roughly 30 hollow units, with about one ton of sand per eight bags; one 94 lb bag of portland cement in a typical cement-lime mix lays roughly 62 units. Preblended mortar yields depend on the product. Use these as starting points and adjust from your own jobs.
7. Forgetting control joints and accessories
Control joints in CMU walls are commonly spaced at the lesser of 1.5 times the wall height or 25 ft, per CMHA TEK 10-2C guidance, when the specified horizontal reinforcement is present; the drawings govern. Each joint needs sash or control-joint units, backer rod and sealant. Add flashing, weeps, drip edges, ties and anchors for veneer, and expansion joints in brick veneer.
8. Underpricing scaffolding
Height, access and duration drive scaffold cost. Price scaffold by area and duration, including erection, moves, planking and dismantling, or price mast climbers by the month. OSHA's scaffold standard (29 CFR 1926 Subpart L) sets competent-person inspection and fall protection requirements that affect crew time. Masonry production drops on scaffold and drops again above the first lift.
9. Ignoring cold and hot weather
TMS 602 (the masonry construction specification) triggers cold-weather procedures when the ambient temperature or the unit temperature falls below 40°F, with heated materials, protection and, at lower temperatures, heated enclosures. Hot-weather procedures apply above 100°F, or above 90°F with wind over 8 mph. In cold climates, enclosures, heaters, fuel and lost productivity can be a large line; price them explicitly against the schedule they assume.
Worked example
An 8 in. CMU wall, 180 ft long x 16 ft high, four 6 x 7 ft openings, grouted at 32 in. on center with #5 verticals, bond beam at top, joint reinforcement every second course.
Grout volume comes from the grouted cells (76 cells x 16 ft) plus the bond beam, using CMHA's tables or the cell volume of the specified unit plus your waste history.
Takeoff checklist
| Item | Unit | Where it lives |
|---|---|---|
| Wall area by unit type | SF | Plans, elevations, wall types |
| Field and special units | EA with waste | Wall types, details |
| Grout | CF/CY by pattern | Structural notes, wall sections |
| Vertical and bond beam rebar | LF / lb | Structural notes, typical details |
| Joint reinforcement | LF | Spec, wall sections |
| Lintels | EA by size and type | Lintel schedule |
| Control and expansion joints | LF | Elevations, notes |
| Flashing, weeps, ties, anchors | LF / EA | Wall sections, spec |
| Scaffolding | Area x duration | Elevations, schedule |
| Weather protection | Duration and area | Schedule, climate |
Production adjustments
Masonry production depends on unit size and weight, wall height, corners and openings, bond pattern, unit finish and weather. Long straight walls go faster than walls broken by openings and pilasters; heavy and architectural units slow every course. Adjust production from your own records rather than one rate for all walls, and note what drove each adjustment.
A final check before pricing
Compare wall areas with elevations, count lintels and bond beams against schedules, and confirm which walls are grouted solid. Those three checks catch most masonry errors. For the math, the concrete and masonry hub links CMU and grout calculators. RenderDraw's AI takeoff proposes wall lengths, heights and openings from your plans with sources for review; test it with a free sample takeoff.
