Type S mortar is a high-strength mix, around 1800 psi, with strong bond strength, used for below-grade construction, foundations, and retaining walls that must resist soil pressure and moisture.
Type S mortar is a higher-strength mix, roughly 1800 psi, with a stronger bond between mortar and masonry unit than Type N provides. That extra bond strength matters anywhere a wall has to resist lateral pressure or where the mortar joint itself is doing structural work, not just holding units in visual alignment. It's the standard choice for below-grade construction, foundation walls, and stonework that has to resist soil pressure or sustained moisture contact.
In the foothills, Type S is what we spec for retaining walls and stone footings, because those structures take on constant soil pressure and moisture year-round and need mortar that can hold a stronger bond under that load. A retaining wall built with a mortar that's too soft for the job can develop cracked or failing joints well before the wall itself would otherwise show any sign of trouble, especially once winter freeze-thaw starts working on those cracks.
More masonry vocabulary from the glossary.
The services where this term comes up.
Chelo's Brick & Stone serves Hillsville, Galax, Wytheville, Fancy Gap, and Independence, VA. Call for a straight answer and a free on-site estimate.
