Masonry veneer or cladding is a thin brick or stone layer that provides the look of solid masonry without adding the weight and cost. It can be installed either in an anchored or attached arrangement.
A properly designed masonry veneer wall consists of components that act together to provide structural integrity combined with proper drainage and drying. These include a proper sized cavity, a weep system and an insulated backing such as foam or batts between studs.
The History of Veneer
Masonry veneer is a common exterior finish for homes. It grew in popularity as demand for housing boomed during the postwar expansion of the 1950s and 1960s. It was a cost-effective alternative to solid brick that allowed builders to construct homes more quickly than traditional brick construction.
A masonry veneer wall is different from a full brick structure because the structural framing of a masonry veneer wall performs all of the load-bearing work. This type of system is commonly referred to as an anchored brick wall, and it relies on brick ties and angle brackets to anchor the cladding to the frame. This construction method is preferred by many local building codes over the alternate, and less preferred, system called an adhered brick wall.
An anchored brick wall is a good choice when there are high wind speeds or if the design of the building calls for an extra level of protection against seismic forces. Brick cladding is also an excellent insulator, and the cavity that is left between the structural framing and the brick wall helps to further increase energy efficiency.
Deflection of the structural backing should be considered when an anchored brick veneer is used, since this can impact the crack width in the cladding. For this reason, many building codes require a deflection limit for the backing. Masonry designers should use TMS 402/602-16, Building Code Requirements and Specification for Masonry Structures, to establish the appropriate deflection limits for anchored brick veneer systems.
Types of Veneer
Masonry veneer is made from thin brick or other types of stone fragments that provide the appearance of substantial masonry without the weight. It can be attached to the framework of a building in two different ways: anchored or glued. The anchored arrangement uses brick ties to transfer out-of-plane loads from the structure of the building to the veneer wall.
These walls are also less expensive to build than traditional masonry. Their relatively low weight means they can be installed after the walls and roof are in place, saving time and money. They are also resistant to corrosion and fire. Because of their high R-value, brick veneer walls provide greater insulation value than vinyl, fiber cement and wood siding.
Adhered veneer walls are attached to a backer board, which can be either plywood or dense foam. This board is typically positioned over a sheathing component that is placed on top of steel or wood framing. An air cavity is maintained behind the sheathing, which is used for drainage and drying.
These walls can be designed to use a variety of backup systems, including masonry blocks and traditional timber frame or concrete stud framing in the United States and Australia and reinforced concrete masonry infilled frames in Europe. The design of a brick cavity wall must be such that its articulation joints support structural motions resulting from temperature, humidity, movement of the frame and deformation of the foundation.
Installation
Masonry veneer requires special construction techniques. Most importantly, it requires the use of quality materials, proper design and detailing and a high level of care during installation. These requirements are well documented in industry and building codes throughout the country.
Generally, masonry veneer is installed over non-combustible concrete or masonry backing with corrosion resistant metal lath in accordance with ASTM C 847 and anchored to framing members using a minimum of 6” on center vertically and 16” on center horizontally. The metal lath should be fastened using galvanized or stainless steel lag screws or nails and penetrating at least 3/4″ into the framing member. Lath should be overlapped at outside corners 1” and at inside corners 4″ and wrapped around the frame member to a point a minimum of 4” up the wall.
For masonry veneer over stud walls, the first wall sheathing layer should be installed by the carpenters who frame the structure. The carpenters should install a water resistant barrier on the sheathing to keep it dry until the masons arrive to adhere the veneer over it.
Brick veneer has a higher R-value than vinyl, fiber cement and wood siding which can help reduce energy costs. It also slows down heat transfer which can decrease thermal migration into the building envelope. For this reason, it is important to anchor brick to the backing and to install articulation joints that allow for movement of the masonry veneer.
Maintenance
Few materials in nature are as hardy or long-lasting as brick, which makes it an excellent choice for building homes. But just like any other material, it requires care and maintenance to keep it looking its best. The most common types of problems include loose, deteriorating or cracked mortar joints and moisture intrusion. Fortunately, these are relatively simple issues to address.
Loose bricks can easily be replaced with a fast-setting repair mortar and color-matched stain, while repointing, or the process of cutting out damaged or weakened mortar joints, is an important step in maintaining any type of masonry veneer, including stone. When repointing, it’s important to match the existing mortar in texture and color so that no one can tell where new meets old.
Masonry veneer must be anchored to the structural backing to prevent deflection and ensure proper support. Conventional adhered veneer utilizes bonding material to secure the masonry units to the substrate; however, alternative systems that use metal panels or portland cement plaster backing placed against sheathing and attached to stud framing members are also available.
Regardless of the type of installation, it’s critical that all manufacturers’ instructions are followed to the letter. In particular, a breathable sealer must be used to avoid blocking the pores of the manufactured stone, which could lead to moisture build-up and damage the veneer.