We all know that the 2009 IRC has gone from around 3 pages of windbracing to 28 pages.
After doing a lot of research and tons of reading here are some of my thoughts. Please comment or discuss any of the items I have posted.
Most significant was the development of wind bracing tables based on engineering principles.
Separate tables for wind and seismic bracing were developed.
The IRC was reorganized to consolidate all of the bracing provisions for wood-frame construction into the Chapter 6 bracing section.
New bracing methods were added to increase the choices available to the builder and to reflect ongoing product research .
Prescriptive Construction.....Typically uses braced wall panels without hold downs to prevent walls from racking.
Engineered Design.....Typically uses shear walls with wood structural panels and pre-engineered hold downs (other than anchor bolts) to prevent walls from racking and overturning.
Prescriptive vs. Engineered
Prescriptive
Limitations
3 Stories Max
Wind < 110 (100 in hurricane prone regions)
SDC A-D2
Many others (see IRC Chapter 3)
Engineered
Applications
Any size/shape within IBC limits
Wind – No Limit
Seismic – No Limit
Governed by engineer’s calculations
Bracing methods were defined by abbreviations instead of method numbers. For example, wood structural panel bracing, formerly referred to as Method 3, became Method WSP. Gypsum board bracing became Method GB, let-in bracing became Method LIB, structural fiberboard sheathing became Method SFB, etc.
The number of narrow wall bracing alternates grew from two to five.
Method SFB (structural fiberboard sheathing) was recognized as a continuous sheathing method for use in areas of low wind and earthquake loads.
R106.1.1 Information on Construction Documents
New to the 2009 IRC is a provision that requires wall bracing information to be included on construction documents. The purpose of this provision is to place the responsibility for detailing the wall bracing on the building designer rather than the building official or builder.
If not designed by an engineer, builders will be required to submit a “Braced Wall Line” plan, identifying the locations of the braced wall lines and the construction method to be used.
When designed by an engineer, the plans must include framing (wall, floor and ceiling joists, and roof rafters), as well as, wall bracing method.
R403.1.6 requires exterior walls, and now requires interior braced wall panels, to be bolted to the foundation. Bolts must now be installed on the interior walls at the locations identified as braced wall panels. There must be an interior grade beam under the interior braced wall line to hold the bolts.
IRC Section R602.10.1.4 and Figure R602.10.1.4(2) clarify that the distance from the outside walls to the edge of the first braced wall panel, when added together, cannot exceed 12.5’.
This will allow some doors/windows to be at the exterior edge of the braced wall line.
But for design wind speeds up to and including 100 mph, builders can rely on methods written right into the IRC.
Comments!!!
After doing a lot of research and tons of reading here are some of my thoughts. Please comment or discuss any of the items I have posted.
Most significant was the development of wind bracing tables based on engineering principles.
Separate tables for wind and seismic bracing were developed.
The IRC was reorganized to consolidate all of the bracing provisions for wood-frame construction into the Chapter 6 bracing section.
New bracing methods were added to increase the choices available to the builder and to reflect ongoing product research .
Prescriptive Construction.....Typically uses braced wall panels without hold downs to prevent walls from racking.
Engineered Design.....Typically uses shear walls with wood structural panels and pre-engineered hold downs (other than anchor bolts) to prevent walls from racking and overturning.
Prescriptive vs. Engineered
Prescriptive
Limitations
3 Stories Max
Wind < 110 (100 in hurricane prone regions)
SDC A-D2
Many others (see IRC Chapter 3)
Engineered
Applications
Any size/shape within IBC limits
Wind – No Limit
Seismic – No Limit
Governed by engineer’s calculations
Bracing methods were defined by abbreviations instead of method numbers. For example, wood structural panel bracing, formerly referred to as Method 3, became Method WSP. Gypsum board bracing became Method GB, let-in bracing became Method LIB, structural fiberboard sheathing became Method SFB, etc.
The number of narrow wall bracing alternates grew from two to five.
Method SFB (structural fiberboard sheathing) was recognized as a continuous sheathing method for use in areas of low wind and earthquake loads.
R106.1.1 Information on Construction Documents
New to the 2009 IRC is a provision that requires wall bracing information to be included on construction documents. The purpose of this provision is to place the responsibility for detailing the wall bracing on the building designer rather than the building official or builder.
If not designed by an engineer, builders will be required to submit a “Braced Wall Line” plan, identifying the locations of the braced wall lines and the construction method to be used.
When designed by an engineer, the plans must include framing (wall, floor and ceiling joists, and roof rafters), as well as, wall bracing method.
R403.1.6 requires exterior walls, and now requires interior braced wall panels, to be bolted to the foundation. Bolts must now be installed on the interior walls at the locations identified as braced wall panels. There must be an interior grade beam under the interior braced wall line to hold the bolts.
IRC Section R602.10.1.4 and Figure R602.10.1.4(2) clarify that the distance from the outside walls to the edge of the first braced wall panel, when added together, cannot exceed 12.5’.
This will allow some doors/windows to be at the exterior edge of the braced wall line.
But for design wind speeds up to and including 100 mph, builders can rely on methods written right into the IRC.
Comments!!!
