The last step of a masonry estimate is waste, and one rule of thumb handles it differently. This unit also covers the cold-weather threshold.
Waste allowances
BIA Technical Note 10 says to add to net quantities:
- Brick: at least 5%.
- Mortar: 15 to 25%.
The traps: swapping them (15% brick, 5% mortar), a flat 10% for both, and giving mortar only 5%, far below its 15-25% range.
Waste goes last
The Table 4 quantities exclude waste. Waste is added last, after the net quantities and any correction factors.
- Treating table figures as if they already include 5% brick waste or 15-25% mortar waste orders too little.
- Adding waste before the correction factors is the sequencing error the note warns against.
The order: net area, table rate, correction factors, then waste.
The 8-bag rule of thumb
Technical Note 10 also gives a rough rule: eight bags of masonry cement lay about 1000 modular brick. This figure already includes waste.
For 5000 modular brick: 8 × 5 = 40 bags. Nothing is added on top. Adding waste double-counts it:
- 42 bags adds 5%.
- 48 bags adds 20%.
- 50 bags adds 25%.
The table rates need waste added; the 8-bag rule does not.
Cold-weather threshold
CMHA TEK 03-01C states that when ambient temperatures fall below 40°F (4.4°C), the Specification for Masonry Structures requires consideration of special construction procedures.
- 32°F is the freezing point of water, not the threshold.
- 45°F and 50°F are higher than the 40°F the TEK gives.
Quick recap
- Waste: at least 5% brick and 15-25% mortar, added last, per BIA Technical Note 10.
- 8 bags per 1000 modular brick, waste already included.
- Cold weather: below 40°F (4.4°C), per CMHA TEK 03-01C.