When to use this Guide
- Use this Design Guide if:
- The roof is an Unblocked Diaphragm
- If the roof is a Blocked Diaphragm and the building is a single-family, two family or townhouse, refer to the Roof Ridge Design Guide for Blocked Roof Diaphragms meeting the requirements of the International Residential Code® (IRC®).
- If the roof is a Blocked Diaphragm but the building does not meet the requirements of the IRC, refer to the Roof Ridge Design Guide for Blocked Roof Diaphragms designed per the requirements of the International Building Code® (IBC®).
- If in doubt, check with the local building code official or a registered design professional to verify the type of roof diaphragm and building for your specific project
What is an Unblocked Diaphragm?
- An Unblocked Diaphragm is one in which the wood structural panels (i.e., plywood or Oriented Strand Board (OSB) roof sheathing) are only required to be attached to the framing members (i.e., rafters or trusses) and the edges of the panels between the framing members are NOT required to be supported by and attached to blocking (e.g., 2x_ lumber)
- Most wood framed roof systems in the U.S. are constructed with Unblocked Diaphragms
- If in doubt, check with the local building code official or a registered design professional to verify the type of roof diaphragm used for your specific project
- If the roof diaphragm is Unblocked, follow the steps in this design guide
Why use Shear-X?
- Shear-X brackets are designed to transfer in-plane shear forces at the ridge line of roof diaphragms
- The brackets enhance the diaphragm action in unblocked diaphragms
Roof Ridge Installation
- The brackets can be bent to accommodate any roof pitch from flat to 12:12
- The design values for the Shear-X brackets have been developed by an ISO/IEC 17065 Accredited Product Certification Body based on testing by an ISO/IEC 17025 Approved Agency
- Each Shear-X 16” and 24” bracket is capable of transferring up to 1240 lbs and 1320 lbs, respectively, of in-plane shear load across the ridge line of unblocked roof diaphragms
- Installing the Shear-X brackets in these applications greatly enhances the interaction between the diaphragm sections on opposite sides of the ridge
- The roof diaphragm must be sheathed with plywood or OSB wood structural panels installed per the requirements of the building code and the construction documents for the project
- Roof framing (e.g., rafters and trusses) must be minimum 2x4 SPF No. 2
- Use the following table to determine the number of Shear-X brackets to install along each ridge line of a roof with an unblocked diaphragm
- Install Shear-X brackets at each end of the ridgeline and at a maximum spacing of 20-ft on-center
- Attach brackets as described in Shear-X Roof Ridge Installation Guide for Unblocked Diaphragms