Determining when masonry wall bracing is needed

By Matt Morley, Kraemer Brothers

Almost all contractors are aware that some masonry walls need temporarily bracing, but the applicable OSHA standards are brief and don’t provide prescriptive requirements.  Specifically, 1926.706(b) states, “All masonry walls over eight feet in height shall be adequately braced to prevent overturning and to prevent collapse unless the wall is adequately supported so that it will not overturn or collapse.”  The standard itself doesn’t give practical information on how to prevent overturn or collapse, but simply communicates OSHA’s expectation that contractors have the aptitude to prevent masonry walls from overturning. This is known as a performance-based standard. Hypothetically, if a masonry wall were to fall over due to normally expected forces, this wall would not be considered adequately braced or supported and therefore not compliant with 1926.706(b).

“IT IS THE RESPONSIBILITY OF THE EMPLOYER TO ASSURE THAT WALLS NOT ADEQUATELY SUPPORTED TO WITHSTAND ALL NORMALLY EXPECTED FORCES, WHICH WOULD INCLUDE PREVAILING WIND PRESSURE LOADS, BUILDING GEOMETRY, AND WALL LOCATION, ARE BRACED.”

Does this mean that all masonry walls greater than 8’ in height require bracing? Not necessarily.  OSHA’s letter of interpretation further explaining the requirements of 706(b), dated June 25, 1996 states, “It is the responsibility of the employer to assure that walls not adequately supported to withstand all normally expected forces, which would include prevailing wind pressure loads, building geometry, and wall location, are braced. If the employer determines the wall is capable of withstanding the forces applied during construction, then the wall would be considered to be adequately supported and would not require bracing. The employer must be prepared to substantiate this determination.” In other words, not all masonry walls are the same. Masonry walls can vary in height, width, size of CMU, CMU density, frequency of reinforcing rebar and grout, type of mortar used, and for this reason may be intrinsically more resistant to overturn due to the nature of their specific construction. There may be some varieties of walls 8’ in height where bracing is warranted. On the other hand, Kraemer Brothers’ masonry bracing plan allows some walls to free-stand, without bracing, up to 23’-4” above grade.  Just as the letter of interpretation states, if a contractor is confident a given wall over 8’ can adequately withstand the expected forces and chooses not to brace it, they must be prepared to substantiate this determination.

For a masonry contractor, or a general contractor responsible for oversight of masonry operations, a masonry bracing plan is a must. The plan is used as the basis or methodology in decision making to determine if a given wall is adequate to withstand normally expected forces, or if additional bracing is needed to prevent collapse. Many contractors choose to engage a professional engineer who is qualified to calculate wind loads on a given wall to determine whether bracing is needed, or if the wall itself is adequate. A site-specific masonry bracing plan is then generated, which is followed throughout construction and kept on-site in the event the contractor or OSHA would need to reference it.

Another resource that can be used in making masonry wall bracing determinations is the Mason Contractors of America (MCAA) Standard Practice for Bracing Masonry Walls Under Construction 2012.  This standard was developed by a committee of professional engineers, masonry contractors, and industry experts to simply provide contractors with a framework to make their own bracing determinations, along with bracing plans for various types of walls. For contractors who prefer not to engage a P.E. on each project with 8’ masonry walls, this is an excellent resource. Internally, Kraemer Brothers leans on MCAA’s standard for a majority of our wall bracing determinations and plans, with the exception of very large or complex projects.

Keep in mind that the intention of both 1926.706(b) and MCAA’s Standard Practice for Bracing Masonry Walls is to ensure the safety of employees working around masonry walls, and not the wall itself.  For example, MCAA’s bracing standard for walls with 24 hours of cure is designed to a wind speed of 35 mph.  When winds increase above that threshold, there is potential for collapse and employees within the restricted zone must evacuate.  Masonry wall bracing systems are generally designed to buy the contractor time to get out of harm’s way before an incident occurs, ultimately preventing injury or death. They are not a guarantee the wall will never collapse, no matter the wind forces applied to wall.