Masonry Magazine February 2001 Page. 26
Proper flashing installation is crucial in masonry construction to prevent moisture damage, which can lead to structural issues and unhealthy environments for building occupants, making them susceptible to illnesses like allergic reactions and headaches.
Many years ago, the industry created the concept of the "rain screen principle" for masonry buildings. This building method involves the use of a cavity wall system, where multi-wythe walls use the veneer as a rain screen to protect the rest of the building from moisture penetration (see Figure 1). This building design method assumes that moisture will penetrate the veneer and provides for its swift elimination via flashing and weeps.
This article will discuss proper installation of flashing and accessories as well as typical problem areas in cavity wall flashing.
Flashing should be installed at the base of the wall, over all openings, at every shelf angle and at parapet walls.
QUALITY MASONRY TOOLS
KING BRICK HOO
THE TYPE OF FLASHING BEING USED DETERMINES ITS PROPER INSTALLATION:
# Non-Adhesive:
Composite or sheet flashing that does not have an adhesive backing should be extended from the outer most face of the veneer through the mortar joint, across the cavity and up the substrate wall a minimum of 8 inches. Testing has shown that moisture driven by winds of 90 mph will splash about 6 inches high so bringing the flashing 8 inches up the substrate wall provides more than adequate coverage. It should be inserted into the outermost face shell bed joint of the masonry substrate (see Figure 2). If the substrate is concrete, reglets can be formed into it to receive the flashing, or a termination bar can be screwed into the wall through the flashing to hold the flashing up (see Figure 3). If a termination bar is used, the screws should have a washer. If the back-up wall is steel or wood stud, the flashing can be run behind the sheathing and screwed to the stud. Regardless of the type of substrate, a bead of mastic should be run across the top of the flashing to prevent migration of moisture into the substrate.
Figure 3
# Adhesive-Backed:
Composite flashings such as rubberized asphalt composites are usually manufactured with an adhesive backing covered with kraft release paper. So instead of having to install the flashing when the back-wall or substrate is erected, the contractor can wait until they are ready to build the veneer to install the flashing. Once the paper backing is peeled off, the flashing can be brought up the wall eight inches and literally stuck to the wall. Again, a bead of mastic should be run across the top of the flashing (as shown in Figure 4).
It should be noted that most of these adhesive-backed flashings will not adhere to a dirt or mortar specked wall, or at temperatures below 40 degrees, unless a primer has
LIFT UP TO A HIGHER LEVEL
MR-2001
PLATFORM
MATERIAL HOIST
THE RACK & PINION MATERIAL HOIST
DESIGNED WITH SAFETY & RELIABILITY IN MIND
2000 LB. LIFTING CAPACITY
70/100 FPM HOISTING SPEEDS
TOWER SPECS: 5' LENGTHS/90 LBS. EACH
70" (W) x 45" (D) x 48" (H) PLATFORM BASKET
350' MAXIMUM LIFTING HEIGHT
OVERSPEED BRAKE
FOR MORE INFORMATION CALL US AT
800.451.5053
321.733.3387 FAX: 321.733.9433
E-MAIL: SALES@HITECHHOIST.COM
WEB SITE: WWW.H-TECHHOIST.COM
3128 LAKE WASHINGTON ROAD,
SUITE 202. MELBOURNE, FL 32934
26 MASONRY FEBRUARY, 2001