BCAB #1775 - Use of Letters of Assurance for Part 9 Roof Trusses
December 17, 2015
Code Edition: 2012
Code Division: B and C
Code Reference: Part 4 and Part 9
Re: Use of Letters of Assurance for Part 9 Roof Trusses, Article 220.127.116.11. (Division C), Article 18.104.22.168.
The project is a single family residential building that falls under Part 9 of the BC Building Code. The building has a manufactured truss roof system designed to Article 22.214.171.124. Some of the trusses installed were missing metal connector plates and repaired with a detail different from the original design; the result being wood connecting members substituted the missing metal connector plates. The original trusses and the repair were designed by the same registered professional. The sealed truss drawings, including those for the repaired trusses, indicate the design complies with CSA O-86-09 and TPIC 2011.
Reason for Appeal
The Local Authority is requesting the BC Building Code’s Letters of Assurance be provided for the manufactured roof truss system.
There is a disagreement on whether the Letters of Assurance are can be required for the complete roof truss system, or for those trusses that have been repaired.
The appellant contends that the roof trusses are designed within the parameters of Article 126.96.36.199. of the BC Building Code and that Letters of Assurance are not required. The appellant considers his position is supported by the Guide to the Letters of Assurance, published by the Building and Safety Standards Branch, which states: “Factory-built roof trusses that are designed under Article 188.8.131.52 in Part 9 of Division B of the BCBC 2006 do not require Letters of Assurance from the truss designer.”
Local Authority's Position
The building official maintains that trusses, whether designed to Part 4 or Part 9 of the code, are Part 4 components and are subject to the code’s Letters of Assurance. Due to missing truss connector plates at the time of installation, Letters of Assurance are being requested to confirm that the trusses have been constructed in accordance with the engineer’s design. The building official does not consider it to be his role to verify compliance with the professional design.
Appeal Board Decision #1775
It is the determination of the Board that the BC Building Code’s Letters of Assurance are not applicable to this manufactured roof truss system.
This ruling does not preclude the local authority, under other applicable enabling legislation, to require documentation by a registered professional for design and/or field review, but the Building Code’s Letters of Assurance cannot be used for that purpose.
Reason for Decision
As the trusses, including those which have been repaired, comply with the Part 9 application limits of Section 9.4 Structural Requirements, and that analysis using good engineering practice can demonstrate their compliance with Sentence 184.108.40.206.(1), they need not be designed in accordance to Part 4 of the BC Building Code. The requirement of Sentence 220.127.116.11.(2) that truss joint connections be designed in conformance with the requirements of CSA O86 “Engineering Design in Wood,” which includes provisions for both wood and metal pate connections, has been complied with. A registered professional has indicated on sealed drawings that these requirements have been met. Further, the requirement for a registered professional to be involved in the design, which is not normally required for Part 9 structural components, has been complied with as referenced in A-23.14.11.(2) and Article 18.104.22.168. Structural Design (Division C).
Article 22.214.171.124. (Division C) indicates the Letters of Assurance are applicable to structural components that are not within the scope of Part 9. By meeting the criteria required in Article 126.96.36.199. and Article 188.8.131.52, the Board considers these truss are within the scope of Part 9.
The “Guide to the Letters of Assurance in the BC Building Code” states: “Factory-built roof trusses that are designed under Article 184.108.40.206 in Part 9 of Division B of the BCBC 2006 do not require Letters of Assurance from the truss designer.” The Board considers the intent of this statement is inclusive of the truss joint connections requirement to be designed to Subsection 4.3.1.
Other legislation, such as the Community Charter, may enable the local authority to require the involvement and documentation by a registered professional. However, the BC Building Code’s Letters of Assurance cannot be used for that purpose, which is supported by Article 220.127.116.11. (Division C) of the BC Building Code and the “Building and Other Structures Bylaws Regulation” of the Community Charter.
Lyle Kuhnert, Chair, Building Code Appeal Board