Masonry Magazine November 2005 Page. 19
Revisions to the International Building Code (IBC)
The 2005 MSJC Code and Specification was adopted by reference into the 2006 IBC and International Residential Code (IRC). There were three modifications made to the MSJC in its adoption-lap splice requirements, AAC masonry and veneer seismic detailing.
* Masonry lap splices
The lap splice design requirements for masonry were revised to be more consistent with historical lap splice design requirements of the Uniform Building Code. The required length of lap is limited to 72 bar diameters for strength design. For allowable stress design, the length of lap is 48 bar diameters, with a 50% increase in lap length for highly stressed regions. These required lap splice lengths are, in general, less than required by the 2005 MSJC and the 2003 IBC and are more simplistic to calculate. Lap splice lengths are expected to be reviewed in more detail in future standards and code hearings.
* Aerated autoclaved concrete (AAC)
AAC masonry as a construction material was first introduced with the publication of the 2005 MSJC. While the MSJC contains design and detailing requirements for AAC masonry for all seismic design categories (SDC), the IBC arbitrarily limited its use as a loadbearing shear wall assembly to SDC A only in commercial applications.
* Veneer seismic detailing
Based upon an analytical study funded in part by MACS, the 2005 MSJC veneer detailing provisions were revised to remove the required use of bed joint reinforcement in seismic design category SDC D. In its adoption of the MSJC, the IBC reintroduced that same requirement and further required that the wire be mechanically attached to the backup ties in SDC D and higher.
* Gravel ballasted roofing systems
During hurricanes and other high wind events, one significant source of damage comes from flying debris - sometimes this includes flying gravel blown off of gravel ballasted roofing systems. A change that would have reduced the required size of gravel ballast was denied, recognizing that large stone and tile is a far more effective and safe ballast system in regions of the country subjected to high winds. This change opens a potential revitalized market for the use of masonry products as roof ballast materials in high-wind regions.
* Proprietary precast concrete basement systems
The ICC rejected the proposed inclusion of a proprietary precast basement wall system that does not require a concrete foundation footer. The structural engineering community noted the potential structural problems with this system along with the incorrect nature in which a proprietary system is being proposed for the code.
Revisions to the International Energy Conservation Code (IECC)
* Air barrier requirements
Citing its technical and logistical inadequacies, the ICC membership rejected the required use of a continuous air barrier system for commercial construction. The proponents of this code change have argued that requiring the use of a continuous air barrier system would increase energy efficiency in the built environment, but have not supplied substantiating evidence to support this claim. A similar requirement is currently under debate within the ASHRAE 90.1 standard.
Revisions to the International Residential Code (IRC)
* Residential inspection
A proposal specifically targeting increased inspection requirements for masonry in residential construction was defeated. While all residential construction requires some inspection, if accepted, this change would have placed additional inspection requirements on masonry compared to other construction materials.
* High-wind design
Historically, residential building codes have required that housing be designed by engineered or pre-engineered methods when the design wind speed reaches 110 mph or greater. Under the new revision, this wind trigger would be reduced to 100 mph in hurricane prone regions of the country, increasing the safety of new housing and the economy of constructing with masonry materials.
* Residential separation
As the density of housing developments continues to increase and, correspondingly, the separation between houses decreases, protecting the exterior walls of adjacent houses from fire becomes more critical. Based in part upon research conducted by the National Institute of Standards and Technology