Masons Revisit the Battle of Jericho

And the walls came tumblin' down... Within the building materials universe, masonry is unique. Unlike other materials, it's built on site, and affords very little tensile strength or resistance to bending loads during the early stages of its cure cycle. It is virtually impossible, therefore, to completely eliminate the possibility of a masonry wall collapsing due to wind and other forces while the wall is being laid up.

Walls made of precast concrete and other materials don't have this problem because they achieve nearly 100% of their design strength by the time they're erected and need to be braced. The key concern on construction sites is the strength of the bracing material used, and its anchorage. Where masonry walls are involved, the strength of the wall itself must also be considered.

To address these issues, a committee sponsored by the Mason Contractors Association of America (MCAA) has adopted several principles to guide the development of a new bracing standard for masonry walls. A summary of the principles follows:

• With life safety the number one concern, a safe zone will be established on either side of walls with the zone equal to the maximum wall height, plus four feet.
  
• Walls eight feet high or less do not pose a life safety threat and can therefore be built without bracing.
  
• A wind speed of 35 mph represents the threshold at which masons need to get off the scaffolding and the safe zone needs to be evacuated.
  
• Masonry strength will be considered at the wall's initial stage, defined generally as eight hours old, and the strength attained after 24 hours or when the wall is permanently connected to the structure.
  
• Bracing anchorage at the face of the walls will be able to resist tension and compression so that walls can be braced from one side.

Before issuing the standard, the committee will develop sample bracing schemes to test the practicality of the approach and to help contractors understand how it will work in practice.

The committee will distribute its draft document to industry representatives for review prior to its adoption.

This campaign is an attempt by the MCAA to be proactive in the codes and standards arena. The association seeks input from its members and others in the industry to assure that the needs of all concerned parties can be considered. For further information, contact MCAA at (630) 705-4200.