Page 164 - Masonry and Concrete

Masonry Construction Techniques
163
MASONRY CONSTRUCTION TECHNIQUES

flashing should be extended beyond the face of the wall and later
trimmed flush with the face of the joint using a utility knife. The ver-
tical leg of the flashing should be turned up several inches to form a
back dam and be placed in a mortar joint in a concrete block backing
wythe or behind the sheathing in a frame wall (Figure 5-25).
Weep holes are required in masonry construction at the base course
and at all other flashing levels (such as window sills and lintels) so
that water which is collected on the flashing can be drained from the
wall as quickly and effectively as possible. Weep holes are formed by
leaving the mortar out of the head joint between bricks at a spacing of
24 in. on center, or leaving the bottom por-
tion of a concrete block head joint empty
at a spacing of 32 in. on center. To function
properly, weep holes must be unob-
structed by mortar droppings or other
debris. Blocked or missing weep holes can FOLDED
END DAM
cause saturation of the masonry just above
the flashing as moisture is dammed in the
wall for longer periods of slow evapora-
tion. Efflorescence, staining, corrosion of
steel lintels, and freeze-thaw damage can
result. To disguise the appearance of the
INSIDE
open joints, they can be fitted with lou- CORNER
vered metal or plastic grid weep vents
(Figure 5-26).
OUTSIDE
5.4.3 Installing Accessories and CORNER
Reinforcement
Metal ties, anchors, horizontal joint rein-
forcement, and steel reinforcing bars are
all placed by the mason as the work pro-
gresses. Anchors, ties, and joint reinforce-
ment must be properly spaced and placed
in the mortar to assure complete encapsu-
lation and good mortar bond. Since mortar
PREFABRICATED CORNER FLASHING
is spread only a limited distance along bed
joints to avoid excessive evaporation, long FIGURE 5-24
sections of joint reinforcement are usually Flashing corners and end dams.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.