For cavity walls that will experience wind velocities exceeding 80 mph, which type of mortar is recommended?

For cavity walls that will experience wind velocities exceeding 80 mph, Type S mortar is recommended due to its superior strength and durability. Type S mortar is specifically formulated to handle high-stress environments, making it ideal for locations facing severe weather conditions, including strong wind loads.

This type of mortar has a compressive strength of at least 1,800 psi, which provides the structural integrity needed for supporting walls in windy conditions. Additionally, Type S mortar has better bonding characteristics and is more resistant to hydraulic pressure, which is particularly important in cavity wall systems where moisture management is a concern.

In contrast, Type N mortar has a lower compressive strength and is better suited for above-grade, interior walls. Type O mortar is intended for non-load-bearing applications and has even lower strength, while Type M, although strong, is typically used in applications requiring high compressive strength but is not necessarily the best choice for walls subjected to high winds due to its rigidity. Therefore, Type S mortar is preferred for its balanced performance attributes in high-wind scenarios.