Contemporary masonry cavity walls rely on the rainscreen principle to integrate multiple lines of defense against moisture:
- An air space for drainage and drying
- Flashing
- Weeps
Brick veneers are frequently called water shedding planes because they effectively “screen” or “shed” most rainwater from entering the assembly. It’s commonly accepted, however, that some water will penetrate the veneer.
One of the most effective ways to resist moisture in brick veneer claddings is to fill all mortar joints, especially head joints.
Using skilled and qualified masons that are trained in the construction of the masonry veneer is critical to performance. Specifying advanced training, like IMI’s Flashing program, is one way to ensure the level of quality on any project.
Expansion joints are the most common movement joint found in masonry assemblies with characteristics of expansion, including clay brick, calcium silicate brick, and natural stone brick.
Building designers are responsible for indicating movement joint type and location on project drawings, according to TMS 402/602 Building Code Requirements and Specifications for Masonry Structures.
Masonry movement joints can be both vertical and horizontal. BIA Tech Note 18A provides guidance on locating expansion joints in clay brick veneers for both orientations. While a rule of thumb for locating expansion joints in brick is given, each building and each façade should be examined for appropriate spacing and placement.
Contact IMI for assistance.
Vertical Expansion Joints
For brick veneer without openings, space vertical expansion joints no more than 25 feet on center. For brickwork with multiple openings, spacing may need to be reduced. Typical placement of vertical expansion joints should occur:
- At or near corners
- At offsets and setbacks
- At wall intersections
- At changes in wall height
- Where wall backing or supporting elements change
- Where support of brick veneer changes
Horizontal Expansion Joints
Horizontal expansion joints in brick veneer are located at shelf angles. Shelf angles may be necessary when there is a large differential movement between the brick veneer and backing, or if you are using a flexible backing.
Lipped Brick vs. Flashing and Weeps at Shelf Angles
- At shelf angles, lipped brick is often considered to reduce the apparent size of the sealant joint.
- While lipped brick is a way to minimize the joint size, it comes with complications to the flashing required at that location.
- First, determine if the use of a lipped brick is warranted. If not, then typical flashing and weeps are used.
- Locating the lipped brick under the steel angle and turned up is a way to allow flashing to be placed normally on top of the angle.
- Lastly, using the lipped brick on top of the angle and facing down is possible, but the flashing must be installed so that it follows the lip and extends at least to the face of the wall. Often a pre-bent metal drip edge can be used to help avoid some flashing installation problems.
In all cases, the joint should not contain mortar to inhibit any movement. Using skilled craftworkers who have been trained on proper methods in IMI’s Flashing program can avoid problems on projects.
When materials other than clay brick are used (concrete brick, calcium silicate, natural stone and cast stone), different requirements for movement joints apply.
Trained craftworkers are an important component of any project. Their knowledge of the materials and proper construction practices are critical to a successful project.
Quality Assurance
Properly installed brick units can enhance a building’s appearance for generations. IMI can help you set the standard for your project’s aesthetic, constructability, and quality assurance by facilitating:
- Sample panels
- Mockups
- Pre-installation meetings
Information on brick workmanship can be found in BIA Tech Note 7B Water Penetration Resistance – Construction and Workmanship.
Tolerances
Brick masonry is held to strict tolerances and will depend on the materials used and their application. Allowable tolerances for brick are found in ASTM C216 Specification for Facing Brick (Solid Masonry Units Made from Clay or Shale).
Brick units that are not within allowable tolerances can make it impossible for the craftworker to install the wall within allowable limits. Allowable tolerances for workmanship can be found in TMS 402/602, Section 3.3 “Site Tolerances.” You can also reference our diagram on allowable construction tolerances.
Modularity
Modularity is important in project designs and can directly impact cost and time on projects. Most masonry construction is laid out to an 8” module to avoid cutting of units and to allow brick bonding to occur. Cutting units can add cost and installing small units or larger than acceptable mortar joints can detract from a design. More information on modular design can be found in BIA Tech Note #10 Dimensioning and Estimating Brick Masonry.
BIM plug-ins are available that help incorporate modularity into your design.
If you want to achieve aesthetics and structure with a thinner wall, structural clay brick is a good choice. Buildings that use a single wythe of masonry as their loadbearing structure, like fire stations, are good choices for structural clay brick.
- Clay brick not only provides structure but an attractive finish inside and out.
- Reinforced masonry walls with steel rebar embedded in grout within the brick is used effectively for bearing walls and shear walls.
- Clay brick is stronger than concrete and concrete masonry and is ideal for loadbearing applications that require higher strengths or thinner walls.
- Depending on the building’s configuration and function, structural masonry can be used alone or integrated with a steel or reinforced concrete frame.
- Often, building features already planned for masonry, like brick veneer exterior walls or concrete masonry service cores, can easily be adapted to use reinforced clay brick.
Since masonry is built on-site using standard units, projects can proceed quickly from design
to reality. There’s no lead time required for the production, review, and approval of shop drawings. As a
hand-crafted system, masonry can adapt easily to late-stage design changes. Efficiently-designed structural masonry goes up fast.
