Which of the following mortar types has the highest strength?

Type M mortar is recognized for having the highest compressive strength among the various types of mortar. It typically has a compressive strength of 1,800 psi or greater and is composed of a mix that includes Portland cement, lime, and sand in specific proportions. This high strength makes Type M mortar particularly suitable for load-bearing applications, such as in structural walls and when used in conjunction with concrete masonry units.

The formulation of Type M also makes it resistant to moisture, which further enhances its performance in demanding environments. Its use is thus ideal in below-grade applications, in foundations, or wherever structural integrity is a top priority.

In comparison to other mortar types, Type S has a medium strength and is often used for exterior applications and above-grade walls. Type N is considered a general-purpose mortar that balances strength and flexibility, making it suitable for building projects of lighter nature. Type O, on the other hand, has the lowest compressive strength, making it more appropriate for non-load-bearing walls and interior work, where high strength is not a critical requirement.

Understanding the strengths and appropriate applications of these mortar types emphasizes the importance of selecting the right material based on structural needs and environmental considerations.