Final answer:
The best mortar type for high lateral strength is Type S, which is ideal for below-grade applications that require substantial pressure or strength, such as foundations and retaining walls.
Step-by-step explanation:
The mortar type best-suited for situations requiring high lateral strength is Type S mortar. This type of mortar is designed for use at or below grade where substantial pressure or lateral strength is required. For example, Type S mortar is suitable for foundations, retaining walls, and similar structures. It has a high tensile bond strength and is less likely to crack, ensuring the durability and stability of the structure.
Type M mortar, although it has superior compressive strength, is not necessarily best suited for high lateral strength demands. On the other hand, Type N and Type O mortars are used for above-grade, non-load-bearing walls and interior applications, respectively, and do not provide the same level of lateral strength as Type S.