ASTM C270 Mortar Types

Category: science

The standard engineering specification governing the structural classification of field-mixed masonry mortars.

ASTM C270 categorizes mortar into four primary structural designations based on compressive strength: Type M (high-strength/subterranean), Type S (high lateral bond/seismic), Type N (general exterior/above-grade), and Type O (low-strength/restoration), derived from the phrase "MASON WORK."

Common Examples

• The structural blueprint explicitly mandates an ASTM C270 Type S mortar to accommodate high lateral wind loads.
• Do not use high-strength Type M mortar for historic restoration jobs; it will crack the soft, vintage brick units during thermal shifts.