Department of Energy, Labor & Economic Growth
Stanley "Skip" Pruss
Director
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Department of Energy, Labor & Economic Growth |
| Construction Safety and Health Division | |
The masonry industry has experienced significant changes in materials, designs, and standards in the past 50 years. In particular, before the mid 1990s most designs were incorporating unreinforced masonry walls. The height limit for unreinforced masonry is typically less than 20 feet. A majority of the designs today are incorporating reinforced masonry and it is not uncommon to have masonry walls vertically spanning 30 to 40 feet. In fact, there is a reinforced masonry wall in a Michigan high school vertically spanning 72 feet. Tall and thinner reinforced masonry walls that are not properly braced are more susceptible to blowing down during construction than the shorter and thicker unreinforced masonry walls of the past. Most of the tall walls of today fall outside the intent of MIOSHA Construction Safety Standard Part 2 - Masonry Wall Bracing. Improper bracing of tall masonry walls could cause a catastrophic failure, such as the wall collapse at the Flushing High School addition project in August of 1998, which killed four tradesmen and seriously injured two others. A wall collapse is not only a serious hazard affecting masonry industry employees, but affects the safety of other construction workers in the immediate vicinity. Engineering Guidelines for Bracing Tall Masonry Walls:The Mason Contractors Association of America (MCAA) established a council to develop a wall bracing standard. The Council published the Standard Practice for Bracing Masonry Walls Under Construction in 1999 and it was revised in 2001 by MCAA. In 2003 the Masonry Wallbracing Design Handbook was also published by MCAA. The Handbook displays over 700 different wall bracing configurations based on the Standard Practice for Bracing Masonry Walls Under Construction. The Handbook serves to assist mason contractors in identifying brace locations for typical applications. The sponsors recognize that not all site conditions can be taken into account in the Handbook. After all, each jobsite is unique. A registered professional engineer should be consulted for situations not addressed in the Handbook.MIOSHA, Part 2 – Masonry Wall Bracing:Rules 206(3) and 206(4) require that masonry wall bracing systems shall be designed using “acceptable engineering practices.” The Masonry Wallbracing Design Handbook and Standard Practice for Bracing Masonry Walls Under Construction meet the “acceptable engineering practices” in these two rules. Any specific design from the Handbook that is being referenced by the mason contractor must be available for review at the jobsite along with any additional specifications.Responsibilities During Construction of Masonry WallsMason Contractor:
Controlling Contractor:
Sub-Contractor Employers and Employees:
Bracing Walls:Bracing short walls may consist of the 2 x 10 planks as defined in Part 2. However, tall walls will require additional bracing in the form of timber bracing, pipe bracing, or cable bracing as defined by the Standard Practice for Bracing Masonry Walls Under Construction. Internal reinforcing embedded in grout may be used in the wall bracing design in conjunction with the Masonry Wallbracing Design Handbook. Other designs and methods for bracing masonry walls may be used when designed in accordance with acceptable engineering practicesby a qualified person. The design and specifications shall be available at the jobsite.Collapse Area / Restricted Zone:The area on each side of a wall that is subject to the effects of a wall collapse is known as the collapse area or restricted zone. This area is measured at a horizontal distance equal to the height of the constructed wall plus 4 feet, measured at right angles to the wall and continuing for the length of the constructed wall. The area shall be clearly identified by acceptable methods. Proper signage as required in Part 2 – Masonry Wall Bracing shall be placed upon all unsupported walls. Part 2 also requires evacuation of the collapse area when wind speed exceeds 35 MPH.The Standard Practice for Bracing Masonry Walls Under Construction has two separate requirements for bracing tall walls.
Monitoring and Inspecting: The key to preventing injuries and fatalities related to masonry wall bracing is good employee training and frequent/thorough inspections of the bracing methods being utilized to identify problems. The hazards associated with masonry walls must be addressed in an Accident Prevention Program required by MIOSHA Part 1, General Rules, Rule 114. |
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