Some older masonry structures use steel angle irons to support brickwork over openings such as doors and windows. These often sag or crack over time. Charleston Masonry allows structural engineers to determine if relieving angles are necessary for their buildings. This is a step in the right direction to save cost and time.
Brick is known for its strength and longevity. Still, structural brick applications often require additional strengthening for a project to be successful. Many of these other applications involve the use of large L-angles. These L-angles are different from the typical angle iron used on most home projects and are sized to support heavy loads. They can be found in various applications, including supporting beams in building foundations and even helping keep cell phone and broadcast towers standing tall.
It is common to see concrete masonry structures with angle supports on their face, but less familiar are brick structures with these structural angles in the back. This angle supports a strong, durable backbone for these masonry structures. This helps keep the structure from buckling under the stress of a high wind load or the vibrations caused by the operation of nearby equipment.
These support angles are typically attached to the back side of the masonry wall through anchor bolts. This provides a solid connection to the concrete or masonry structure and allows for an effective transfer of forces to the adjacent walls. The connection through the angle also ensures that the mortar and brick do not break under heavy compressive loads.
Most masonry structures work in compression perpendicular to their bed joints. This is how they are tested to determine their compressive strength. However, it is more likely that a masonry wall will be subjected to a compression load at a non-perpendicular angle to the bed joints. In these cases, the mechanical properties of the masonry can vary greatly depending on the direction of the load.
This variation is called anisotropy and can cause significant strength loss. The correct design must be implemented to avoid these problems and to prevent the structural failure of the masonry construction.
It is possible to eliminate these problems with a rational veneer design and steel shelf angles. The alternative design procedures for masonry veneers in TMS 402 (Chapter 12) provide a step toward this goal by defining a minimum steel shelf angle length for each opening. This shelf angle offers vertical support to the masonry veneer while reducing thermal bridges by connecting it to the underlying structural system at discreet, evenly spaced points such as plate “blades,” allowing insulation to pass behind them.
The large L angles that are typically used to support beams and certain columns in building foundations and even towers for cell phone and broadcasting stations also offer great strength and help to keep masonry walls from crushing during windy conditions. However, if not properly designed and installed, they can be a source of serious construction problems that can compromise the performance of the overall wall system.
For example, using lipped bricks above shelf angles creates a gap between bricks that can allow moisture infiltration and expansion of the grout to crack the masonry units. Similarly, the placement of shelf angle anchors that are incompatible with the backup wall structure can create a thermal bridge between the backup wall and the masonry veneer and result in energy code compliance issues.
In addition to the concerns mentioned above, the use of steel shelf angles as a means to support masonry veneer on concrete and wood framing can result in spalling and cracking of the masonry veneer, corrosion of the shelf angle, deterioration of interior finishes, and water leaks. These failures are caused by various factors, including improper grade sizing, improper shimming, using mortar instead of concrete for filling the joints, inadequate masonry reinforcement, and the lack of adequate expansion space between the shelf angle and the backup wall structure.
Designers need to consider these and other issues when specifying brick masonry anchors. Several parties are involved in the design and installation of these anchors, which must be compatible with the structural and architectural requirements of the project. The designer of record, architect, and structural engineer should be involved in a pre-construction meeting to discuss the details and ensure that masons and laborers understand how the design works during installation.
In addition to the above concerns, additional considerations for anchoring masonry include openings in the wall and a change in bonding pattern. For example, suppose the masonry is constructed using a stack bond construction (masonry where the head joints in successive courses are offset by less than one-quarter of the unit length). In that case, MSJC requires that additional horizontal joint reinforcement be provided at 457 mm (18 in.) oc near this opening. Similarly, suppose the masonry is laid in a bonding pattern other than a running bond. In that case, this will also require additional horizontal joint reinforcement.
The design of masonry walls allows for a wide range of aesthetic effects. Inventive bond patterns, unit sizes, surface treatments, and color choices can create a feeling of strength, modernity, tradition, or even whimsy. These design features can add beauty to a building while remaining within code requirements for load-bearing masonry walls.
Concrete masonry walls interact with changing sunlight to visually present a variety of colors throughout the day, a characteristic that can be enhanced by coordinating electric lighting to accentuate the movement of light over the wall surfaces. The texture of a concrete masonry wall also adds to the aesthetic of a building, with fluted units adding an interest in the interplay of shadow and light.
While the code requirements for masonry construction are performance-based and do not directly address aesthetics, several design, construction, and inspection items can impact the masonry wall aesthetics. These include:
The selection of brick materials (including color and texture) and the color choice of mortar affect the visual appearance of masonry. Using mortar that contrasts with the color of the brick accentuates the masonry, including any imperfections in the material. Conversely, using mortar that compliments the masonry mutes any flaws in the material.
Masonry wall-lipped edge details also have a direct impact on the aesthetics of the masonry project. They can contribute to the overall quality of the installation. A poorly conceived lipped edge detail that does not provide a means for moisture or water to escape through the wall can result in spalling, cracking, and blistering of the masonry veneer. The design and installation of these elements must be carefully analyzed and detailed to ensure that the resulting appearance is as desired.
While not required by code, this guide recommends using sample panels and mock-ups to establish a project specification requirement for artistry and aesthetic standards for all masonry buildings. These pre-construction reviews help resolve conflicts in work quality, multi-trade coordination, and enclosure performance. They may also aid in the identification and resolution of problems before they result in significant costs to a construction schedule or budget.
Masonry requires proper maintenance to protect the integrity of a building. Leaving brick damaged or untreated can lead to serious structural problems and potential safety hazards. Fortunately, many ways exist to prevent masonry damage before it becomes a major problem. Masonry repair specialists can identify early warning signs, such as water infiltration through brick or stone walls, bowed bricks, and other structural issues affecting the entire structure.
The most common masonry issue is soil settlement. This happens when the ground surrounding your home begins to weaken and shift over time. This can be due to cycles of freezing and thawing or just seasonal changes in moisture that cause the soil to shrink or move. This can put a great deal of pressure on the brick and mortar in your wall, causing it to crack or cave in. A masonry expert can replace compacted bricks and install push piers to support the foundation if necessary.
Another common masonry problem is spalling, which is when the face of a brick begins to chip. This usually indicates that the shelf angle behind the brick has already started to rust. If left unattended, the shelf angle can break free and shift the weight of the brick to other parts of the wall or even the foundation. A masonry specialist can remove the corroded shelf angle and install a new one to restore the structural strength of the wall.
Masonry maintenance can also include tuckpointing, which is repairing deteriorated mortar joints. This can be a very effective way to prolong the life of your masonry and enhance its aesthetics. However, it is important to use the right type of mortar for your project. Your masonry contractor should be able to provide you with a mortar analysis and recommend the correct type of mortar for your specific application.
For the best possible results, choose a company that is skilled in both tuckpointing and masonry restoration. This will ensure that your masonry repairs are done properly and to the highest quality standards.