Mortar joins masonry units into an integral structure. Whether you choose concrete masonry or clay bricks, the mortar must create tight seals with masonry units to keep out air and water.

Mortar has to fill the joint completely.

  • On new construction, this is accomplished by spreading an adequate amount of mortar to create a bed. Vertical ends of units are “buttered,” or coated with fresh mortar before placing them against the preceding unit. These are known as “head” joints and must be completely filled and tooled for maximum weather resistance.
  • On tuckpointing projects, old mortar is removed and joints are cleaned out so they can receive new mortar, which has to be tightly packed into the space. Click here for diagram.

Mortar joints can be tooled or untooled, although the tried-and-true concave joint is the most popular and durable of all joints. (Fig. 9-7) The V-joint and weathered joint are the next most durable. (Figs. 9-8 and 9-14) The other styles have other uses. For instance, the flush joint may be used when the masonry is to receive a stucco finish. Most of the other styles are primarily for creating specific architectural appearances. Joints in milder climates and interior exposures can be finished in any style.

For more information:

Building Weather-Resistant Masonry Walls, IS220

Concrete Masonry Handbook for Architects, Engineers, Builders
, EB008