Truss Industry Standard of Care: Part 5

Editor’s Note: The purpose of this article series is to identify truss-related structural issues sometimes missed due to the day-in and day-out demands of truss design/production and the fragmented building design review and approval process. This series will explore issues in the building market that are not normally focused upon, and provide recommended best-practice guidance. As with the previous articles (November and December 2014, March and April 2015), the objective is to raise awareness of these issues and, ultimately, improve overall quality of truss roof and floor system construction.

Production builders and developers began to encourage building material supply (BMS) companies to deliver a “dried-in” framing package in the late 1990s. This presented an opportunity for a BMS to sell manufactured and/or inventoried products and the labor to install them. Many BMSs began to offer “installed sales” as an avenue to capture large-volume customers and increase company revenue. Although the term “BMS” may be synonymous with any organization or company that provides installed sales, in the context of this article, “BMS” is used to reflect the primary audience associated with the wood truss industry offering this service. Additionally, many BMSs have a truss and/or wall panel division or resell truss and wall components that become part of the installed-sale framing package.

It is judicious for BMSs that coordinate building framing and install building components to be knowledgeable of applicable code sections, industry standards and manufacturer instructions. With respect to wood trusses, the 2012 International Building Code (IBC) contains numerous sections that pertain to metal plate connected wood truss installation. Six sections address the primary standard of care issues that may be unfamiliar to many BMSs. Section 2304.9.6 and 2304.9.7 address load path and framing requirements. 

Section 2308.10.1 speaks to wind uplift and truss connections.

Section 2303.4, 2306.1, and 2308.10.10 (including associated commentary) reference ANSI/TPI 1 The National Design Standard For Metal Plate Connected Wood Truss Construction (ANSI/TPI 1-2007) making it part of the building code.

Many BMSs may be familiar with TPI 1 in terms of truss fabrication requirements but unfamiliar with the content of this standard as it pertains to standard responsibilities in the design and application of trusses. 

First, Chapter 2 in TPI 1 contains language applicable to a BMS providing a framing package that includes wood trusses. Specifically, Section 2.3.4 delineates contractor responsibilities with respect to truss installation. 

The definition of a contractor as described in TPI 1 states in part, “The term contractor shall include those subcontractors who have a direct Contract with the Contractor to construct all or a portion of the construction” [emphasis added]. In essence, a BMS accepts responsibility to meet building code, industry standards, and manufacturer information when installing trusses. A BMS offering this service is encouraged to read Chapter 2 of TPI 1 to fully appreciate the building code/law and scope of work responsibilities their organization is undertaking by adding installed truss sales to their business.

The key concept behind the standard responsibilities document, first created by the Wood Truss Council of America (the predecessor to SBCA) in 1995, is to have precise definitions with respect to scope of work. This precision encourages everyone in the construction market to know the responsibility they are taking and then to get paid fairly for it and its associated risk. As a corollary, it is also important to not allow one’s scope of work to creep (i.e., increase), while also coming with the expectation that you will do the additional work for free. This is how the industry has often reduced the value of responsibilities performed and increased its risk that it also is not getting compensated for properly.

Second, a BMS that offers and provides installed wood truss sales has a unique opportunity to ensure proper truss bracing, connections and load paths are present. Here is a quick snapshot of some responsibilities a BMS accepts with respect to a truss package when providing this service.

1. The BMS is responsible to satisfy all truss installation requirements located on the truss placement diagram, each truss design drawing, TPI 1, BCSI and the construction documents. This includes, but may not be limited to:

a) Implementing and/or adhering to all relevant truss installation notes located on each truss design drawing and the construction documents. Examples include truss-to-truss connections, minimum bearing width, strongbacking installation and gable end wall bracing.

b) Proper installation of truss lateral restraint and diagonal bracing as detailed on each truss design drawing, contained within the construction documents or BCSI prescriptive methods.

c) Installing truss-to-wall connectors to resist calculated truss uplift reactions as required in IBC Section 2308.10.1. Knowledge of wall framing and/or wall panel materials affords the BMS (and truss supplier) to recognize insufficient tie-down connectors. When a reaction exceeds a prefabricated metal connector specified, the BMS has the responsibility to contact and resolve the issue with the building designer.

d) Perform a truss pre-installation check and post-installation check to identify dislodged or missing truss connectors, broken members, or any other damage that may impair truss structural integrity.

e) Obtain an adequate truss repair, when appropriate, and make the repair in accordance with written instructions.

2. Ensure a gravity and uplift load path (IBC Section 2304.9.6) is continuous from the roof to the foundation. This is critical at girder truss reaction points where truss tie-downs align and/or are traced to hold-downs at the foundation. Additionally, blocking and connectors must be installed, as required, to transfer load from one level to the next. Truss and/or engineered wood products personnel employed by a BMS should have the training and expertise to recognize significant loads that must have a load path from the roof to foundation. 
3. Ensure adequate connections are made to the structure to resist the maximum horizontal reactions due to lateral loads applied to the trusses. 
4. Ensure columns are framed to provide full end bearing (IBC Section 2304.9.7). This also includes proper blocking within floor truss cavities as detailed in standard truss installation details available from SBCA.

A BMS has a unique opportunity to enhance building construction quality. The BMS and the people they employ have the knowledge, expertise, means, and methods to effectively communicate and facilitate proper truss installation. This relationship affords a BMS providing installed sales a proficiency not readily available to other contractors, which helps to ensure truss installation meets published standards and relevant building code sections. Additionally, their relationship with suppliers and/or “in-house” building component manufacturing facilities provides them the distinctive advantage of knowledge and expertise to ensure products sold are installed to meet related industry standards and manufacturer installation instructions. This includes all the work needed to achieve better than average building performance.