Type S vs Type N Mortar: Choose by the Wall, Not Just PSI

Type N is the usual starting point for normal above-grade brickwork, including most anchored brick veneer. Type S generally offers higher compressive and flexural bond strength for applications that need it. The right choice follows the wall design, exposure and masonry units—not simply the higher PSI on the bag. The Brick Industry Association recommends selecting the lowest-strength mortar that meets the project requirements. BIA mortar-selection guidance

What actually differs?

Type S and Type N are mortar classifications under ASTM C270. Both can be produced using cement and lime, masonry cement, or mortar cement. The letter alone does not identify every ingredient or performance characteristic.

The strength figures apply to laboratory-prepared mortar under the property specification. They are not wall-load ratings or acceptance limits for mortar sampled on the jobsite. ASTM C270 also provides a proportion specification, which establishes ingredient proportions instead. BIA mortar specifications and strength table

Compressive strength measures resistance to crushing. Bond concerns contact and adhesion between mortar and the masonry unit. Those are different properties: a higher crushing-strength number does not guarantee a better joint. Bond also depends on the unit surface and absorption, mortar materials, workmanship and curing. CMHA mortar guidance

When to choose Type N or Type S

Most anchored brick veneer and ordinary non-loadbearing brick walls: Start with Type N unless the project specification requires otherwise. Its workability helps establish intimate contact between mortar and brick; good contact contributes to durability and resistance to water penetration. Type S can be an acceptable alternative, but it is not an automatic upgrade. BIA selection guidance

Reinforced or loadbearing masonry: Follow the structural specification. For exterior above-grade reinforced or loadbearing brick walls, BIA recommends Type S and lists Type N as an alternate. For interior loadbearing brick walls, it recommends Type N with Type S as an alternate. Type N is not inherently “nonstructural,” and Type S is not required for every loadbearing wall. High wind or seismic demands can affect the permitted mortar type and cementitious materials. BIA application recommendations

Foundation or mortared retaining walls: Between N and S, Type S is the option to evaluate for at- or below-grade work. However, the actual specification may require Type M: BIA’s brickwork table recommends M for foundation and retaining walls, with S as an alternate. Do not substitute N because it is available, or assume that selecting S resolves the wall’s structural design. BIA below-grade recommendations For block assemblies, see our guide to concrete blockwork wall components and design.

Repointing existing masonry: Compatibility takes priority over choosing the stronger product. Type N may suit newer brickwork, but older soft brick or lime-mortar construction may need a weaker repair mortar rather than either N or S. BIA repointing recommendations National Park Service guidance calls for replacement mortar that is softer and more vapor-permeable than the masonry units, and as soft and permeable as—or softer and more permeable than—the historic mortar. Excessively strong or impermeable mortar can shift damage into the brick or stone. NPS repointing guidance

Check the product, not just the letter

Before ordering, confirm the specified mortar type and cementitious material system. Masonry cement, mortar cement and cement-lime mortar are not identical in bond performance or design treatment. A same-letter substitution may therefore still need approval. BIA material guidance

Also distinguish a complete, sanded mortar mix from a cement product that requires added sand. For example, QUIKRETE’s standard Mortar Mix is a preblended Type N product, while its standard Mason Mix is preblended Type S. Read the actual bag and data sheet, then follow that product’s mixing instructions. Do not try to “upgrade” N to S by adding an unmeasured amount of cement.