Type O Mortar is a cementitious bonding material for masonry construction providing load transfer, water tightness, and accommodation for material movement. This specification provides appropriate bond strength and flexural capacity for typical masonry applications. Proper proportioning ensures adequate workability for experienced masons while maintaining long-term durability. Installation requires proper moisture control and curing procedures. Quality control includes compressive strength testing to confirm specification compliance. Long-term performance depends on proper application and maintenance of masonry joints.