Benefits of Specifying Complete Masonry Veneer Wall Systems – Part 4
This is part four of a seven-part series of blog entries about the benefits of specifying and building with manufacturer-tested and warrantied wall systems compared to specifying individual components. Benefits include a much faster design and specification process, proven component compatibility, faster component installation and better performance, plus the peace of mind that comes from knowing all components are proven compatible and will perform as specified. Part four provides a look through-wall flashing, mortar dropping collectors and weep vents.
Through-wall flashing is a three-part moisture management path consisting of a flashing membrane, mortar dropping collection, and weep vents. When properly specified and installed, this system captures and directs water out of the wall, no matter where or how water penetrates it.
A flashing membrane must:
- be attached to the sheathing;
- run continuously from the front of the brick ledge to at least 305 mm (12 in.) up the substrate;
- be behind the continuous insulation; and
- be fastened with a termination bar sealed at its top edge with a compatible sealant.
The membrane should also include a drainage mesh to prevent the possibility of mortar damming. Including a drip edge is highly recommended to prevent ultraviolet (UV) exposure from degrading the flashing membrane edge.
TotalFlash® from Mortar Net Solutions is a complete flashing system for masonry cavity walls that includes the membrane with a termination bar, mortar dropping collector and drip edge fastened to the membrane in the factory. It comes in 5’ long (installed length) panels that can easily be installed by one person, and Mortar Net Solutions will custom cut TotalFlash panels at no charge to fit perfectly over multiple wall openings. Learn more at www.mortarnet.com/totalflash-panel.
A mortar dropping collection device is the second component of the three-part moisture management path. Various techniques have been employed over the decades, but specially designed mesh products were introduced in 1992 by Mortar Net Solutions and have become mandatory in a well-designed wall.
These products should be:
- shaped with two levels; (For example, MortarNet™ employs a two-level trapezoidal shape that breaks up and suspends mortar droppings above the flashing. This trapezoidal shape also prevents mortar dams as the top is wider than the bottom, acting as an overhang to prevent droppings from covering the entire lower level. Learn more at www.mortarnet.com/mortarnet-with-insect-barrier.)
- placed in a single continuous row on top of the flashing membrane at the bottom of the cavity;
- able to suspend mortar droppings on two levels to prevent mortar damming; and
- made from 90 percent open-weave mesh (allowing water to flow through the mesh to the flashing membrane and the weep vents, as well as letting air circulate through the device to promote drying).
Weep vents are the third part of the complete moisture management path. They prevent the weep holes located in masonry veneer head joints—both low at the flashing level and high near the top of the cavity—from being clogged by insects or debris. Located low, they allow water to run freely off the flashing and out of the cavity. Located high and low, they allow air to move through the cavity to enable drying. WeepVent™ from Mortar Net Solutions is a weep vent insert made from mesh that is slightly compressible so it fills the head joint, replacing the mortar so the mason need not apply mortar to fill gaps between the vent insert and masonry. They are also available in colors to match mortar choices. Learn more at www.mortarnet.com/weepvent.
It is extremely important to specify weeps that do not block the flow of water off the flashing membrane. Weeps such as tubes and some rigid weeps form a barrier at the flashing level, which means water has to rise behind them in the cavity before it can run out. Rope weeps are not recommended because they provide no ventilation and can rot over time. It does not matter how good the rest of the moisture management path is—if water cannot get out through the weeps, it will not work.
Be sure to come back for part five to learn about the importance of proper sealants and for an introduction to insulation.