Truss Industry Standard of Care Issues: Part 1
Truss Industry Standard of Care Issues: Part 1
Metal plate connected wood trusses are manufactured specialty structural components designed using proprietary software by technicians and engineers who specialize in the design of these products. As with any specialty product, good communication and coordination between the truss designer/manufacturer, the truss buyer (general contractor, builder, framer, etc.) and building designer are paramount to ensure trusses are designed, installed and used correctly.
Misunderstandings and breakdowns in communication and coordination are inevitable, in part due to construction traditions, the building code, and business concepts and models beyond the control of the truss manufacturer and truss industry. ANSI/TPI 1 states very clearly that the truss manufacturer is responsible for the following key scopes of work (Note: ANSI/TPI 1 has been adopted into the building code and is, therefore, the law. All references to ANSI/TPI 1-2007 can be viewed here.):
2. “The Truss Manufacturer shall communicate the Truss design criteria and requirements to the Truss Design Engineer.”
3. “Where required by the Construction Documents or Contract, the Truss Manufacturer shall prepare the Truss Placement Diagram that identifies the assumed location for each individually designated Truss and references the corresponding Truss Design Drawing.”
4. “Where required by the Construction Documents or Contract, Legal Requirements or the Building Official, the Truss Manufacturer shall provide the appropriate Truss Submittal Package to one or more of the following: Building Official; Registered Design Professional for the Building and/or Contractor for review and/or approval per Section 18.104.22.168,” which says:
a. “The Contractor, after reviewing and/or approving the Truss Submittal Package, shall forward the Truss Submittal Package for review by the Registered Design Professional for the Building.”
5. “The Truss Manufacturer shall be permitted to rely on the accuracy and completeness of information furnished in the Construction Documents or otherwise furnished in writing by the Registered Design Professional for the Building and/or Contractor.”
The building code then complicates matters by writing the concept of deferred submittals into law as follows.
For the purposes of this section, deferred submittals are defined as those portions of the design that are not submitted at the time of the application and that are to be submitted to the building official within a specified period.
Deferral of any submittal items shall have the prior approval of the building official. The registered design professional in responsible charge shall list the deferred submittals on the construction documents for review by the building official.
Documents for deferred submittal items shall be submitted to the registered design professional in responsible charge who shall review them and forward them to the building official with a notation indicating that the deferred submittal documents have been reviewed and found to be in general conformance to the design of the building. The deferred submittal items shall not be installed until the deferred submittal documents have been approved by the building official.
This allows trusses to be designed and reviewed by the registered design professional “in responsible charge,” noting such review has been performed and submitted to the building official within a specified time after building permit application.
This process seems backward, and contributes to the fragmentation and/or scope of work silos that we see in the construction market.
Building design originates at the top of the structure, where gravity loads are applied and then, in combination with other loads, accumulate into load paths to the ground, so that the foundation supporting the structure can be designed. Accurate resistance of the load path “works best” when the building engineering and installation detailing processes take all the various structural components into account and integrate them into the design of the overall structural framework prior to designing the foundation. This leads to a more optimal design of the roof, walls, floors and foundation from the onset of the project.
Additionally, the contract to obtain trusses is also generally deferred. Therefore, a critical building component may remain undetermined after construction documents are completed and construction of the foundation and the walls has begun.
In the 2010 Florida Building Code, the definition for a Registered Design Professional in Responsible Charge follows:
This definition contemplates and resolves the issue of deferred or phased submittal documents. It states directly that the role of a registered design professional and/or a building designer is to coordinate and review certain aspects of the project for compatibility with the design of the building or structure. This includes the coordination and review of submittal documents prepared by others, deferred submittal documents and phased submittal documents. This is because only the building designer has an overall understanding of the design concepts and anticipated load paths for which design is needed.
A key issue that is often misunderstood is that a Truss Designer designs and Component Manufacturer (CM) produces a single truss* to resist loads defined in the Building Designer’s** plans and specifications. The CM does not gather information to create and design a truss system.
This environment does not yield great building engineering solutions or create value for great engineering because the process is fragmented on purpose, the motivation of which is to generally drive down costs. This fragmentation causes silos of work that most of the time do not interact or, when they do, the interaction is very inefficient. The result is often professional and business expectation mismatches (i.e., I thought the truss manufacturer was doing the truss roof system design), errors in truss application with respect to expected load path, unanticipated load paths, and resulting framing issues with the potential for construction defects that later appear in unexpected ways.
Key truss industry considerations that can lead to misunderstandings, misperceptions and potential litigation include:
1. Typically, professional architecture/engineering laws and residential building codes do not require a registered design professional to undertake a complete building design. In exempt areas of the law, the building designer, per ANSI/TPI 1, is then the home owner, builder, contractor or framer.
2. CMs have to be extremely careful not to represent themselves as the building designer or the engineering company for the project. The latter can easily be a violation of professional engineering law.
3. Because there are not clearly defined roles and responsibilities in residential construction, the CM is often viewed as selling truss solutions that are thought to be providing an engineered truss “system.” This is due to the fact that CMs provide a key set of “engineered” components for the structural framework, including headers, beams, I-joists, trusses, etc. It must be remembered CMs only provide single element structural resistance components. They are really just like sliding glass and/or garage door components, which provide resistance to specifically defined design loads.
4. When building design professionals are involved in a project, they usually undertake the design up front and then the truss layout and truss design are done by others. This is a challenge because the walls, headers, beams and foundation are then set by the load path in the design. This may not be the ideal situation for designing an optimal truss layout or individual truss design.
a. Given the contracts involved in the construction process and the code-allowed deferred submission process, it is rare that upfront truss design-oriented relationships are forged with architects or engineers that would enable a more streamlined process where component design can be accomplished in concert with their building design concepts.
b. This is a serious deficiency in the code. The law and the code devalue the collaborative benefits of building design/truss design and the intellectual property of the CM.
5. There is no doubt the fragmented nature of the engineered truss market helps to create a “commodity” sales mindset. This again devalues a CM’s intellectual property and technical creativity.
6. Truss design software is a very valuable tool. As with any software, it can become very easy for users, engineers and technicians alike, to view the software results as “always right” and wonder why field and serviceability issues occur. The CM’s IP then is in understanding the software and using it creatively and robustly in the context of the take-off and subsequent component manufacturing operations. Using the software is like using a very powerful calculator and not “the answer” to all engineering problems.
7. ANSI/TPI 1 states:
The CM generally provides a significant number of 8½" x 11" sheets of paper, and the law expects the Contractor or the Contractor’s personnel to review and approve the information these documents contain. To the extent the CM can help the contractor with implementation, it provides the opportunity to develop a strong working relationship. Obviously, the CM should get paid for any IP utilized.
8. Many times, the foregoing challenges cause many in the industry to remain perplexed why some construction professionals have a negative perception of light-frame and residential construction practice.
In short, the fragmentation and commodity attitudes that exist in the marketplace need to change in order to solve the problems caused by some of these legally-based construction practices.
Where it is in the truss industry’s control to do so, it must begin the process of ensuring truss design and installation information is conveyed to the contractor and building designer in a clear and concise manner. Obviously, the best way to do this is to eliminate the fragmented silo process encouraged by deferred submittals and contracts. However, this is a paradigm shift that will not change in the short-term, given current traditions and challenges related to exempt structures.
This article initiates a series that will identify truss-related structural items sometimes missed due to the day-in and day-out demands of truss design and production and the fragmented building design review and approval process. Each article is intended to hone in on items that may be issues in the building market that are not heavily focused upon, provide recommended solutions the truss industry can control, and encourage other options to improve the flow of critical information. The objective is to improve overall quality of truss roof and floor system construction. The next article will focus on resolving and effectively communicating truss design drawing warning notes for truss-to-truss connections.
*The Truss Design Engineer shall be responsible for the single Truss component design depicted on the Truss Design Drawing.
**Owner of the Building or the Person that Contracts with the Owner for the design of the Framing Structural System and/or who is responsible for the preparation of the Construction Documents. When mandated by the Legal Requirements, the Building Designer shall be a Registered Design Professional.
key definitions from ANSI/TPI 1:
- Building Designer: Owner of the Building or the Person that Contracts with the Owner for the design of the Framing Structural System and/or who is responsible for the preparation of the Construction Documents. When mandated by the Legal Requirements, the Building Designer shall be a Registered Design Professional.
- Contractor: Owner of a Building, or the Person who Contracts with the Owner, who constructs the Building in accordance with the Construction Documents and the Truss Submittal Package. The term “Contractor” shall include those subcontractors who have a direct Contract with the Contractor to construct all or a portion of the construction.
- Owner: Person having a legal or equitable interest in the property upon which a Building is to be constructed, and: (1) either prepares, or retains the Building Designer or Registered Design Professional to prepare the Construction Documents; and (2) either constructs, or retains the Contractor to construct the Building.
- Registered Design Professional: Architect or engineer, who is licensed to practice their respective design profession as defined by the Legal Requirements of the Jurisdiction in which the Building is to be constructed.
- Truss Design Engineer: Person who is licensed to practice engineering as defined by the Legal Requirements of the Jurisdiction in which the Building is to be constructed and who supervises the preparation of the Truss Design Drawings.
- Truss Designer: Person responsible for the preparation of the Truss Design Drawings.
- Truss Manufacturer: Person engaged in the fabrication of Trusses.
- Truss Submittal Package: Package consisting of each individual Truss Design Drawing, and, as applicable, the Truss Placement Diagram, the Cover/Truss Index Sheet, Lateral Restraint and Diagonal Bracing details designed in accordance with generally accepted engineering practice, applicable BCSI-defined Lateral Restraint and Diagonal Bracing details, and any other structural details germane to the Trusses.