What's the Difference Between Type N and Type S Mortar?

Mortar isn't glue, it's a cushioning layer that has to flex slightly as brick and stone expand and contract with temperature swings, while still holding everything together. Type N, with its higher lime content, is softer and more flexible than the brick or stone around it, which lets it absorb that movement without cracking. That's why it's the standard choice for most house brick, chimneys above the roofline, and stone veneer. It's also generally easier to work with on repointing jobs, since it stays workable a bit longer before it starts to set.

Type S has more Portland cement and less lime, which makes it harder and stronger in compression, but also stiffer and less forgiving of movement. It's the right call for structural work: foundation walls, retaining walls, and anything below grade that has to resist soil pressure and moisture. The tradeoff is that Type S mortar can actually damage older, softer brick if it's used somewhere Type N belongs, because a mortar joint that's harder than the brick forces the brick itself to crack under stress instead of the joint flexing.

Chelo's Brick & Stone picks mortar type based on what the structure needs and, for repair work, what's already there. A retaining wall footing gets a different mix than the repointing on an older chimney, and matching that correctly is part of doing the job right the first time.

• Type N: general-purpose, more flexible, standard for above-grade brick and stone
• Type S: higher strength, used for structural and below-grade work
• More lime means softer, more flexible mortar
• More Portland cement means harder, stronger, less forgiving mortar