Page 268 - Masonry and Concrete

Masonry Veneer

267
MASONRY VENEER

appropriate size placed at the bottom of
the joint will maintain the correct joint
width and unit spacing (Figure 7-20).
3
Place a full 8-in. mortar joint along the
top of the arch and cut adjacent units to fit
against the curve.

7.4 Drainage Cavity

Most codes require a minimum 1-in. space
between a masonry veneer and its backing
and permit the space to be solidly grouted
as the veneer is laid, or left open to form a
drainage cavity. Anchored masonry veneers
are usually designed with an open drainage
cavity. Moisture will always penetrate a
masonry veneer, even with good design,
good detailing, and good workmanship. A
certain amount of moisture penetration is
expected in most climates. The greater the
exposure to wind-driven rain, the more
FIGURE 7-17
moisture will penetrate the wall. Drainage
cavities increase the level of performance Provide temporary support during arch construction.
(from Beall, Christine, Masonry Design and Detailing,
and the longevity of the wall system by 4th edition, McGraw-Hill, New York).
removing moisture from the wall rapidly.
This allows natural wetting and drying to
occur without damage to the masonry or to
the backing wall. 3 /4" PLYWOOD
EACH SIDE
Wood stud walls behind a masonry
veneer must be covered with either a
water-repellent gypsum sheathing, a mois-
ture-resistant insulating sheathing, or a
plywood or OSB sheathing covered with 2 4s
moisture-resistant asphalt felt or poly-
olefin house wrap. Gypsum sheathing with
a moisture-resistant facing is typically
used over metal stud construction with FIGURE 7-18
additional protection against corrosion Centering for arch construction.

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