Mortar Calculator

Type N (750 PSI) is the most common for above-grade, non-load-bearing walls and interior partitions. It has the best workability and is easiest to tool. Type S (1,800 PSI) is required for structural walls, below-grade foundations, retaining walls, and any exterior wall subject to wind or seismic loads. Most commercial specs default to Type S. Type M(2,500 PSI) has the highest compressive strength and is specified for below-grade masonry in contact with earth (basement walls, manholes, catch basins) and for engineered masonry requiring high axial load capacity. When in doubt, use Type S — it covers the widest range of applications.

For modular brick with a 3/8-inch joint, plan on approximately 33–35 bags of pre-mixed mortar per 1,000 bricks (1 bag covers about 30 bricks). With a 1/2-inch joint, usage increases to roughly 40 bags per 1,000 bricks. These numbers assume single-wythe running bond. Flemish bond and other patterns with more head joints will use 10–15% more mortar. Always add 10% for waste, dropped mortar, and repointing.

Yes, but only where the spec allows it and where different structural requirements apply to different parts of the wall. A common example: Type S for below-grade foundation walls transitioning to Type N for above-grade veneer on the same building. Never mix types within the same wall section or course — the different strengths and bond characteristics can cause cracking at the transition. Always document which type was used where for the project record.

Pre-mixed mortar stays workable for about 90 minutes to 2 hours after mixing, depending on temperature and humidity. In hot weather (above 90 degrees F), that window can shrink to 60 minutes. You can re-temper mortar once by adding a small amount of water and remixing, but only within the first 2.5 hours. After that, discard it — retempering past initial set weakens the bond. Mix smaller batches in hot weather to avoid waste.