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Advertising supplement provided by Portland Cement Association

by Jennifer Grover Prokopy

Choose Your Mortar

The four mortar types—M, S, N and O—are designed to perform optimally in a variety of construction situations. As a general rule, Type N mortar is used for above-grade exterior walls under normal loads, and for interior load-bearing and nonload-bearing walls. Type S is recommended for exterior work at or below grade, specifically on foundation walls, retaining walls, manholes, sewers, pavements, walks and patios. Types S and M are recommended for masonry under heavy loads (such as seismic loads) or exposed to severe saturated freezing. Type O is applicable for some repointing applications. Building codes may contain restrictions on mortar types for different applications.

Use governing standards—ASTM C270 or CSA Standard A179—to specify the mortar that will best fit your application. Indiscriminate use of high-strength mortar (Type M) should be avoided; lower-strength mortar such as Type N will bring its own advantages in many cases. As a rule of thumb, use Type N unless there is a structural, mortar-unit compatibility or other reason to consider the use of a higher- or lower-strength mortar.

Developing a Quality Assurance Program for Masonry Mortar

A comprehensive quality assurance (QA) program prescribes policies and requirements that ensure a project’s success for the architect, building team, and owner. While most project contracts clearly spell out strategies for QA, strategies for specific narrowscope components such as masonry mortar are often ill-defined or excluded. In situations where a large number of organizations and products are involved in a single project, the importance of individual components like mortar can be overlooked—with detrimental results—if a QA program is not spelled out explicitly.

When developing a QA program for masonry mortar, expectations of the owner (both explicit and implicit), as well as general project parameters, including the structure’s function, environment, budget constraints and life-cycle considerations, must be taken into account. The establishment of general quality objectives at the outset of project development is the foundation for sound QA for the overall project and individual components.

Preconstruction Planning

Effective building teams count on a good flow of communication. Architects and other specifiers should play an active role in the planning process. Preconstruction planning should include a full review of all plans by the mason contractor, who will submit any changes or corrections in writing to the appropriate member of the building team. Later in the process will come submittals and mockups, which confirm the correct choice of materials and the capability of the mason to produce the desired quality and aesthetics. Finally, scheduling should take into account all components of each phase of construction, and any schedule changes should be communicated throughout the project.