By Herbert Slone, RA, and Art Fox
This is part one 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 one describes the components of a masonry veneer wall system and the tests a wall system must pass to provide optimal performance.
A masonry cavity wall system must successfully perform multiple functions throughout the life of the building. A proper wall is expected to manage moisture, air, and heat, contain fire, and hold up the structure itself. For a wall to perform all these functions, specifications should include all the products necessary for the components to work together.
For the contractor, building a masonry cavity wall is just as challenging as specifying it is for the architect. Contractors rely on the architect for highly precise drawings and specifications so they can produce an accurate bid. They want to be able to build with familiar, proven methods and materials that are compatible and readily available through distribution.
For these reasons, specifying a complete wall system with all the components tested and warrantied together can offer many advantages to the design professional, such as helping support risk management. The design professional’s ability to thrive depends on his or her ability to provide timely documentation for the building’s performance.
Components of a masonry veneer wall system
The structural components forming the basis of the substrate may be steel or wood studs or concrete masonry units (CMUs). On the outside is the weather-resistant component—the cladding or masonry veneer. Between those are three functional component categories that complete the wall system and make the wall perform: moisture/air, thermal, and structural management.
Moisture/air management relies on:
Thermal management involves:
Structural management depends on:
Systemization
Having all the right components in the wall is not enough. A true wall system must have passed extensive testing proving the components, as a system, meet the code-mandated performance criteria and are physically and chemically compatible. Further, the system must pass industry-standard tests, such as:
Individual product components of the system can also provide the protection of a warranty that covers them against defects. In the event there is a problem, unified and cooperative solutions are best rather than multiple companies acting separately.
Be sure to come back to this blog for part two to learn about moisture management, including a discussion of water-resistive barriers and air barriers.
Examining different types of anchors and the types of applications for which they work best.
We use anchoring and reinforcement on every project, whether in restoration or new construction. The types of anchors generally are based on the veneer we are anchoring, the weight of the veneer, the condition of the substrate and installation challenges.
The drive pin, also called the lead anchor, zinc anchor, hammer pin, Nailon anchor or Zamac Nailin anchor, is used for light-duty applications. However, it should not be a consideration for overhead attachments under any circumstances. This anchor is tamperproof once installed, and it can be used for light-duty static anchoring for strapping, securing and anchor fastening.
The drive pin is used for attaching termination bars for masonry flashing installations. This anchor is not recommended for anchoring sealed termination bars as the hammering of the drive pin creates uneven pressure. This can bow the term bar and create gaps where water can penetrate behind the flashing and contribute to leaks or water damage.
Corrugated wall ties – used as their first anchoring system – can be bent into place by hand, nailed into place easily without much thought, and have held millions of square feet of veneers across the country. In the current building environment, the 22-gauge corrugated tie is only legally used for wood frame commercial and residential brick veneer that has a maximum cavity space of 1 inch. You can complete several stories of a building with the anchors, but only on a stick-built building.
Lighter gauge corrugated ties are available from commercial suppliers, but these ties should not be considered for any exterior veneers. These are said to be marketed for interior commercial brick veneers. The corrugated ties are so flimsy and incapable of handling the exterior lateral loading of a brick veneer, this anchor should probably be avoided completely.
Thermal break anchors are important to veneer work across the country. They have a simple concept, but are complicated to design. The idea is to interrupt the transmission of cold or heat across the metal tie to the substrate of the building. Two popular double-pintle, single-post ties are available, but with completely different methods for installation.
One tie is a single-post screw that supports the double-pintle as a single anchor. The tie is installed using a 5/16-inch nut driver. This tie was first introduced to a crew with whom I worked in early-2014 in Las Vegas. The anchor, for the most part, went in well.
The second type of double-pintle, single-post anchor is an updated version of the commonly used and familiar Posi-Tie. The Posi-Tie is installed using the setting bit, and a plastic double-pintle insulating cap is snapped or clicked into place. This Posi-Tie anchor is easier and more adaptable for other uses, such as scaffolding ties and other project utility anchoring, due to the loop that is available as the base part of the anchor.
Spiral ties have been around for a while and are an option if you have a lot of veneer to anchor either temporally or permanently. The anchor is a good choice for restoration and demolition contractors. It can be installed to support an existing veneer prior to removal of veneer below the anchors, when repairing either shelf angles or loose lintels.
The anchors placed above a repair can remain in place after the work is complete as they can be nearly invisible in the final work. A setting tool that increases the production of the installer has a pilot bit with a removable cover that actually hammer drives the anchor into place. This tool allows the installer to use a single hammer drill without changing bits during the installation. The spiral tie has different configurations. The most common includes a center core surrounded by spiral flanges.
Dowel pins are used in masonry when setting coping stones, cast stone and small precast units, and when applying stone patches, among other uses. Several considerations are important: The dowel pin should be at least 304 stainless steel. A threaded rod offers increased surface area for setting resins and epoxies. This assists in the chemical bonding of the dowel pin to the substrate.
When patching mortars are used, the dowel pin should be bent to at least 45 degrees to assist in securing the patch, and patches should cover the dowel pin by a minimum of ¼ inch. Epoxies that allow for setting the pins should be matched to the substrate material for bonding. Epoxy odor should be evaluated if working in an occupied building, and ambient working temperatures should be considered when calculating setting times.
Not much time is spent thinking about anchors and reinforcing items, but they are on every project. Getting them right is extremely important. When it is up to you to choose, plan your submittals wisely.
Anchoring and reinforcement are used on every project, whether restoration or new construction. The types of anchors generally are based on the veneer being anchored, the weight of that veneer, the condition of the substrate and challenges that are present when installing the anchors.
Years ago, before the cavity wall, multi-wythe walls were successfully constructed with two to 11 courses of brick, with 11 being the most I have ever seen. While many of them still stand, a header brick used as a wythe tie isn’t recommended. This is due to thermal movement that occurs within the wall. The movement between the wythes of brick can cause some of the header brick to snap, resulting in a wythe-to-wythe tie that takes on different characteristics from when it was constructed.
Though common among older walls, these characteristics demonstrate the importance of selecting the correct wall anchoring and reinforcing for your project. What we have learned from repairing this type of wall has assisted in the development of different types of masonry reinforcing and anchoring.
Wall reinforcing wire has two basic configurations when embedded within a concrete masonry unit (CMU) wall, truss and ladder wire, which have become the standard. Wall wire typically is comprised of a three-wire system. The outer wires usually are larger than the interior wires.
Ladder wire generally is used with vertically reinforced walls. Truss wire normally is not used with walls that are vertically reinforced and grouted, unless specifically specified. Reinforcing wire is available in several commercial types. In locations where moisture is an extreme constant, such as a natatorium, stainless steel wall wire is available.
In exterior walls, hot-dipped galvanized or fusion-bonded epoxy is available. Standard mil-galvanized wall wire is available for interior walls. The use of wall wire with the hook-and-eye pintles allows the contractor who is constructing both the inner and outer masonry to use wythes to reinforce and anchor them in a simple set of steps.
The hook-and-eye design allows for proper veneer anchoring, regardless of whether the bed joints of each wythe align in the same plane. The hook-and-eye allows for differential movement between the different wythes of materials, such as the shrinkage of CMU and the expansive characteristics of brick. This ability to self-adjust stabilizes the cavity wall system for a safe installation, while controlling lateral forces on the veneer. This is an economical use of wall wire, and it hooks to properly support the wall and veneer to provide quality reinforcement for standard construction.