What distinguishes type O mortar from other types?

Type O mortar is specifically formulated to have low compressive strength, typically around 350 psi, which makes it suitable for non-load-bearing applications. This distinct characteristic allows it to be used primarily in specific projects like interior non-structural walls and for purposes where high strength is not a requirement.

The formulation is lighter, making it more appropriate for situations where structural support is not critical, such as in certain masonry work for tuckpointing or restoration. Unlike other types of mortar, which are designed for load-bearing capacities (like type S or type M), type O emphasizes flexibility and ease of workability, catering primarily to scenarios that do not require the strength provided by more robust mortar types.

Thus, type O's low strength specifications clearly set it apart in the context of mortar types, emphasizing its intended use in non-load-bearing scenarios.