Specifying Mortar for Non-Loadbearing Masonry

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 page 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.

This page is part of a larger series of specification examples meant to highlight cases where vague or poorly written specifications have lead to issues on masonry projects across Canada.

Disclaimer

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.

If there are any questions or concerns regarding masonry design or construction, CMDC offers technical assistance to our supporting members, as well as the design community.

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How the specification typically appears:

X.Y Mortar for brick veneer cladding to be Type N as per CSA A179.

X.Y.a Minimum compressive strength of mortar to be 12 MPa.

Items to consider when 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 are counter intuitive 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

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 the 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.

Property Specification

A lesser used compliance pathway is the 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 a minimum mortar cube compressive strength based on the type of mortar and whether it is a jobsite prepared or laboratory prepared mortar.

In this case, as with most project involving new construction, the specification need only 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 you 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.

Suggested changes to the specification:

X.Y      Mortar for brick veneer to be type N, mixed to Proportion Specification of CSA A179-14.

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