Page 131 - Masonry and Concrete

Understanding Masonry
130 CHAPTER FOUR

conspicuous visually. If the appearance of an open joint weep is objec-
tionable, the openings can be fitted with a variety of ventilating
screens or covers.

4.8 Weather-Resistant Masonry

One of the most important functions of any exterior building wall is
resistance to weather and moisture. Moisture can penetrate masonry
walls no matter who builds them or what materials they consist of.
Brick, concrete block, stone, and mortar are porous and they absorb
moisture easily, but they also dry out easily. Some masonry walls
allow more water penetration than others, depending on the design,
the detailing, materials, and workmanship. Most masonry walls are
built with a drainage space between the facing and backing which is
fitted with flashing and weep holes to facilitate rapid drying and to
prevent the migration of moisture into the interior of the building.
To prevent excessive moisture penetration or prolonged saturation,
it is important to limit the amount of water that can enter a wall and to
prevent the accumulation of water within the wall. There are several
specific steps which should be taken to assure good weather resistance
of masonry walls.

■ Limit moisture penetration

■ provide full mortar joints
■ control cracking
■ apply protective coating on porous materials

■ Prevent moisture accumulation
■ install flashing to collect moisture

■ install weep holes to drain moisture

4.8.1 Limit Moisture Penetration
In certain climates high winds and frequent rains combine to create
high-risk exposures where water can often penetrate buildings even
though the materials and workmanship are good. In masonry con-
struction, penetration of this wind-driven rain can be minimized by

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