Angle Masonry Anchors
Most masonry anchors are designed to be welded to columns or beams that run straight up and down. Occasionally, we get requests for Pro Angle Masonry Charleston to be set at an angle. It works, but it does have some consequences.tLintels and shelf angles must be sized by an engineer to meet the strength requirements of the steel design codes and to be stiff enough to minimize masonry cracks. It can only be done by carefully reviewing shop drawings at the submittal stage.
Steel lintel angles, also known as angle irons, support the weight of exterior brick veneer over openings in masonry walls like doors and windows. They can be made from various metals but are usually primed and painted to resist corrosion and follow building codes for load-bearing materials. They’re designed to meet the lintel design loads specified by the designer and a minimum of deflection and allowable bending stresses.
When used in a concrete and masonry structural system, they are secured by anchor bolts to the concrete or masonry. Properly designing and detailing shelf angles to support a brick veneer requires careful consideration. It’s important to select an angle with a plate “blade” that allows insulation to pass behind it, reducing the thermal bridge and improving the U value of the wall assembly.
Short masonry lintels supported by wide flange steel angles are easier to install and require less structural engineering than prefabricated lintels. However, they still need to be sized to resist lateral forces. These are typically a result of the wind loading the wall and can be mitigated by using a higher strength angle or providing means and methods for bracing the lintel.
The most commonly used lintel is the single-angle lintel, which can be produced in lengths of up to 20 feet. Depending on the project specifications, it’s available in various thicknesses and is constructed from carbon or high-strength, low-alloy steel. It’s installed with a minimum end bearing and bedded in mortar. It’s also installed with a minimum of 2 inches of clearance from the underlying structure and should have at least two-thirds of the veneer with thickness bearing on it.
It’s important to limit the use of steel lintels where possible. They produce a great deal of embodied energy during production and generate emissions in their transportation to the job site. It is one area where focusing on prefabricated and recycled materials can help reduce upfront costs operating (i.e., energy) costs and the overall embodied energy of a new building.
Steel shelf angles are used to support masonry walls; like lintels, they must be designed and detailed properly. They must also be properly sized and secured to the concrete or masonry structural system with anchors. The key difference is that while lintels resist shear, shelf angles are primarily sized to withstand bending.
As a result, it is important to recognize significant pitfalls associated with using shelf angles in masonry veneer wall construction. These pitfalls include spalling, cracking, and staining of the masonry veneer; shear failure of anchors or slab edges; yielding and slipping of shelf angles; corrosion of the steel angle due to improper design and construction; and leakage of wind-driven rain through the masonry wall and into the structure.
The most significant implication of using shelf angles in constructing a masonry veneer wall is that they create linear thermal bridges in the building envelope. These energy implications are huge, especially in meeting the high-performance requirements of NYC’s residential green standards and the state’s energy code.
Another issue is the upfront material costs and embodied energy associated with producing and transporting steel angle. Limiting the use of these components will help reduce these upfront and operating costs and offset the significant carbon emissions related to their production.
Lastly, the standard design detail of introducing relieving angles into a brick-framed wall breaks the continuity of the exterior insulation. It interrupts the insulation on each floor at every window lintel and creates a significant thermal bridge that impacts the overall R-value of the wall assembly. The designers and project managers must ensure the relieving angles are correctly sized to prevent excessive deflection and rotation. They should be anchored to the masonry or concrete with an appropriate diameter anchor bolt and properly spaced to avoid shear or buckling. They should also be adequately shimmed to allow for expansion and contraction of the masonry wythes above them. Masonry above the shelf angles should be lipped with a gap or air space to qualify for this expansion, and mortar instead of sealant should be used at the lipped joints (sealant will tend to crack and fall off in the face of brick expansion).
Relieving angles (shelf angles) support brick veneer and masonry ties on multi-story buildings. They must be installed along the wall height at certain intervals to keep the masonry from falling off the building. In addition, they are used to create a gap between the walls that allow for movement due to building expansion or contraction. These specialized structural steel components are often required by code with wood and concrete stud walls but can be used with brick or steel framing. In some cases, they are necessary to provide lateral stability to the structure and prevent water infiltration.
When properly detailed, these steel elements can provide structural integrity to a masonry cavity wall system and reduce the risk of cracking due to differential movement between the inner and outer leaf of the wall construction. However, when improperly installed, they can contribute to various issues on a project.
These problems are common in high-rise buildings, where the different elevations can experience substantial movement at the brick veneer, backup walls, and structural elements. This movement can cause the steel relief angle to separate from the masonry walls, significantly damaging the cladding system and causing moisture intrusion in the building envelope.
The most common cause of this issue is improper detailing. The project’s architectural drawings typically show the shelf angles angles’ placement. Still, they must specify a gap beneath the metal required to accommodate building movement. If the crack is not provided, the bricks that are being installed can exert pressure against the relief angle, causing it to separate from the brick masonry.
Another common issue is installing a thru-wall flashing at each relief angle. This detail is critical for proper drainage and prevents water infiltration from the cavity wall to the exterior façade. Fortunately, many of these deficiencies can be controlled with appropriate submittal review during the bid phase and by insisting on including mockups for critical transition details.
Metal brackets are hardware to hold up walls and beams, mount shelves, support pipes, and tubing, brace structures, and keep wires and cables secure. They are available in various sizes, shapes, and styles to accommodate different structural designs. Many other materials can be used to make metal brackets, including aluminum, brass, bronze, and steel. Depending on the application, different metals can offer unique qualities to help the structure withstand loads and conditions.
Several methods can be used to create metal brackets, such as casting, extrusion, and machining. Casting involves pouring molten metal into a mold, which can produce complex and intricate shapes that may not be possible using other manufacturing methods. Extrusion consists of forcing a piece of metal called a billet through a die to form the body. This method can make metal brackets in various shapes, lengths, and thicknesses.
Most metal brackets are made from sheet metal, which can be formed into various shapes and sizes using a machine called a brake. Bending is another common process used to create metal brackets. It is a technique that allows manufacturers to produce L-shaped brackets, for example, and it can be used to create angles up to 120 degrees. Manufacturers can also use a machine to weld brackets together or create threaded holes for fasteners.
Standard masonry support bracket systems can be adapted to suit special masonry details, including the support of soffit brickwork and atypical coursing positions. Designs can also be supplied curved on plan to accommodate radiused masonry.
Stainless steel packing shims can be used between the system and the frame to compensate for structural variations. Alternatively, a serrated slot in the bracket can be fixed to the edge of the concrete slab to give vertical adjustment. Lateral adjustment is achieved by using a combination of shims and slots. This type of system can be supplied from stock or fabricated on-site to suit the requirements of specific buildings.