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Understanding mortar is important… even for nonloadbearing applications

Masonry can be used for all kinds of applications that are not considered loadbearing. Using brick, block, or stone as a veneer is a great way to improve a building’s appearance, performance, and durability. Meanwhile, concrete block partition walls offer superior fire and sound resistance. However, there are some important points to consider when specifying the mortar for nonloadbearing applications.

There are often cases where a type of mortar, such as Type N or S, is specified along with some additional requirements such as a minimum strength. The intent of this article is to explain why that is not recommended and the different pathways to specify mortar in a way that ensures compliance with codes and standards.

Part of our Masonry Specification Series

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The information contained here is intended to serve as educational content for designers, specifiers, or contractors. It is not to be relied upon for formal technical advice, as masonry projects may have details and considerations that are unique to a particular project and may be beyond the scope of the content of this page.


Masonry mortar should be specified under the requirements for either proportion or property specifications in accordance with CSA A179-14: Mortar and grout for masonry.

In nearly all cases, simply specifying the type of mortar (Type S or Type N) as well as indicating that the mortar must meet the requirements  for proportion specification under CSA A179-14 is sufficient for loadbearing and nonloadbearing applications without the need for specifying a minimum strength,.

For clay brick or concrete masonry veneers, Type N mortar is typically specified. While Type S mortars are commonly specified for concrete block walls. However, more detailed recommendations for proper selection of mortars can be found in CSA A179, Annex A.

Discussion around specifying mortar for nonloadbearing masonry

Minimum mortar and grout strengths are a very common type of problematic masonry specification. Although often done with altruistic intentions, such requirements can be counterproductive for most masonry applications and may in fact lead to jobsite conflicts and larger issues in the future.

It is important to recognize that mortar and grout shall be specified according to one of two separate compliance pathways, Proportion Specification or Property Specification, but not both.

Example of potentially problematic specification:

The specification below shows an example of typical combination of requirements from both proportion and property specifications.


.1         Mortar for exterior masonry above grade:

.2         Non-Load Bearing: Type N based on proportion specifications.

.1         Minimum compressive strength of mortar to be 12 MPa.

The proportion and property specification pathways are intended to be used separately, where one or the other on its own is sufficient. Minimum compressive strength is a property, which could be in conflict with a mortar that otherwise follows the proportion specification. The minimum strength of 12 MPa is also not an appropriate benchmark for a Type N mortar.

Proportion Specification

This is by far the most common path for specifying mortars and grouts. In this case, the mortar type (Type S or N) is specified to meet the requirements for proportion specified mortars in Table 3 or Table 4 of CSA A179-14. CSA A179-14 provides installers with a prescriptive mix design to follow for either mortar type depending on the materials used (Portland cement, masonry cement or mortar cement). The standard has requirements for the gradation curves of sand and outlines how mortars are to be mixed. Field testing of proportion specified mortars may include tests for the sand/cementitious material ratio or compressive strength of mortar cubes. For a proportion specified mortar there is no minimum value of compressive strength which must be met. Rather, field testing is done against a benchmark value, typically established at the start of construction, to ensure consistency in mortar mixes throughout a project.

For mortars prepared at the job site when conventional materials and conventional procedures are expected, Proportion Specification may be specified (CSA A179-14, proportions of the ingredients comply with Table 3 or Table 4, as applicable) and no minimum value of compressive strength needs to be specified.

Property Specification

A lesser used compliance pathway is property specification for mortars and grouts. This compliance path is open for new materials or mixes that may otherwise fall outside the proportion specification. An example of this might be ready-mixed mortars that are batched and mixed off site and use additives to extend their useful life. These types of mortars require testing to ensure that they meet a baseline of performance equal to at least that provided by proportion specified mortars. This requires multiple tests, one of which is based on the type of mortar and whether it is a jobsite prepared or laboratory prepared mortar. Table 6 of CSA A179 provides minimum compressive strength values of mortar cubes at 7 and 28 days. So, for a Type S mortar prepared at the jobsite, the required minimum compressive strength values would be 5 MPa and 8.5 MPa for the 7 d and 28 d test respectively.

For mortars manufactured off-site in a batching plant (like ready-mixed mortars), Property Specification should be specified, and a minimum compressive strength value may be specified but not lesser than strength requirements in Table 6 of CSA A179-14. It should be noted that certain pre-packaged, pre-bagged or silo products of dry materials simply contain the components of a proportion specified mortar, in compliance with Table 3 or Table 4 of CSA A179 and should be treated as such. However, other dry-mixed property specified mortar products contain admixtures and/or other components and must meet the requirements of CSA A179 through property specification.

When the designer requires on-site introduction of an admixture or other materials to improve the performance of the mortar, then Property Specification should be followed. In such cases,  the designer should work with the masonry contractor to develop a mortar mix that meets the required properties.  A ratio of aggregate to cementitious material in the mortar may be established (monitoring batching, mixing, and handling procedures) or a minimum compressive strength value may be specified but not lesser than strength requirements in Table 6 of CSA A179-14. Monitoring of properties (i.e., compressive strength of mortar cubes) is often used in lieu of monitoring batching, mixing, and handling.

Applicable Standards

In this case, as with most projects involving new construction, the specification needs to reference the mortar and grout standard, CSA A179.

Finally, it is important that the most recent editions of relevant CSA standards are referenced. In the case of uncertainty, one can find out the relevant edition of the standard in the list of referenced documents accompanying the building code in effect for your specific area. For the current edition of the national model code, National Building Code of Canada 2015, the relevant editions of the CSA standards are circa 2014.

Part of our Masonry Specification Series

Offering recommendations accompanied with background explanatory material to explain how these recommendations were formed. Click here to see the full series.

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