19 Dec Choosing the right Mortar for your Brickwork
Mortar is the element that bonds bricks or other masonry units together and provides structural capacity to the wall or other structure.
There are four main different types of mortar mix: N, O, S, and M.
Each type is mixed with a different ratio of cement, lime, and sand to produce specific characteristics such as bonding properties, flexibility, and compressible strength. The best mortar mix type for any project depends on the application and the various design specifications.
Type N Mortar Mix
This is usually recommended on exterior and above grade walls that are exposed to severe weather and high heat. Type N mortar mix has a medium compressive strength and it is composed of 1 part Portland cement, 1 part lime, and 6 parts sand. Type N is the mortar most often used by homeowners and is the best choice for general application.
Type O Mortar Mix
Type O mortar mix has relatively low compressive strength, at only about 350 psi. It is used primarily interior, above-grade, non-load–bearing walls. Type O can be used as an alternative to Type N for some interior applications, but its exterior use is limited due to its low structural capacity. It is not recommended in areas subjected to high winds. However, type O mortar mix is ideal for repointing and similar repair work on existing structures, due to its consistency and ease of application.
Type S Mortar Mix
Offering a high compressive strength of over 1,800 psi and a high-tensile bond strength, type S mortar is suitable for many projects at or below grade. It performs extremely well to withstand soil pressure and wind and seismic loads. Type S is the common choice for many below-grade applications, such as masonry foundations, manholes, retaining walls, and sewers, as well as at-grade projects like brick and walkways.
Type M Mortar Mix
Type M mortar mix has the highest amount of Portland cement and is recommended for heavy loads and below-grade applications, including foundations, retaining walls and driveways. While type M mortar provides at least 2,500 psi of compressive strength, it offers relatively poor adhesion and sealing properties, making it unsuitable for many exposed applications. Type M is preferred for use with natural stone because it offers similar strength to that of stone.