Most contemporary masonry walls consist of two separate wythes, comprised of one wythe of brick and one wythe of concrete masonry. However, there is an alternative masonry wall design that can produce economical and structural benefits.
Concrete masonry units are strong in compression and can be produced with strengths in excess of 3000 p.s.i. This is one of the reasons that concrete masonry units are desirable for load bearing, single wythe, concrete masonry wall design.
Also, corresponding tensile and flexural bond strengths in the mortar joints contribute to the overall structural design of the wall, and a standard mortar, like type “N” by proportion or type “S” by
physical property, will provide the structural strength required.
An 8” concrete masonry bearing wall is a popular wall type that is utilized in single-wythe masonry construction for condominium and other types of buildings in the Midwest. When designed and
constructed properly, these walls will perform as intended.
Masonry Wall Design
A single wythe concrete masonry wall must be designed with all the typical elements common for a successful multi-wythe wall. The wall must be able to resist moisture penetration or the collection of water within the wall system. Also, the single wythe wall must be capable of resisting lateral wind loads and concrete masonry shrinkage cracks.
Water penetration of the concrete masonry units and mortar must be addressed by adding water repellent to the concrete masonry units during the manufacturing process and to the mortar during the construction process.
Structural stability of the single wythe wall can be achieved by adding reinforcement in the concrete masonry cores and grouting them solid. Reinforcement bar size and spacing must be
determined by the structural engineer.
Masonry Wall Base
The bottom of the wall must be protected from water infiltration by installing through wall flashing and weeps. This is achieved by installing two wythes of 4” concrete masonry and stepping the
flashing up and into the concrete masonry backup (Figure 1).
Masonry Wall Openings
Like most typical masonry buildings, wall openings must be protected from water infiltration at the window head above the opening. At this location, the flashing should be stepped up between two – 4” concrete masonry wythes and terminated into the concrete masonry backup, as indicated in Figure 2. Also, it is more practical and inexpensive if a precast concrete lintel is provided to support the back-half of the concrete masonry above.
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