ASTM C270 Mortar Types
- Type M (1:0.25:3): 2,500 PSI - foundations, retaining walls, below grade
- Type S (1:0.5:4.5): 1,800 PSI - exterior walls, structural masonry
- Type N (1:1:6): 750 PSI - above-grade general purpose, most common
- Type O (1:2:9): 350 PSI - interior non-load-bearing partitions