In June 2008, the Council of the Association of Professional Engineers and Geoscientists of British Columbia (APEGBC) adopted new guidelines for the structural design of homes and other small buildings. The Guidelines for Professional Structural Engineering Services for Part 9 Buildings (Guidelines) apply to structures with a maximum height of three storeys and floor space of up to 600 square metres. Such buildings are used for residential, business, or light- to medium-hazard industrial purposes.
The Guidelines fill a longstanding void in practice standards for structural design of housing and small buildings that come under Part 9 of the British Columbia Building Code (BCBC). In this article Part 4 and Part 9 refer to the corresponding sections of BCBC that deal with "structural design" and "housing and small buildings" respectively. The primary objective is to improve public safety by ensuring a consistent level of structural performance, particularly a building’s resistance to lateral loads such as strong winds or earthquakes. Simultaneously, APEGBC introduced a parallel set of recommendations for local authorities, homeowners and developers.
Both sets of guidelines address three specific practice concerns:
- the lack of resistance of some buildings to swaying caused by severe lateral loads
- the lack of design coordination for various structural components
- the weakening of a building frame due to renovations or additions.
For example, there are growing concerns that new homes are being built with non-traditional layouts, including excessive windows or doors, lengthy spans, or absence of supporting walls and columns: consequently, these homes may have a reduced resistance to wind and earthquakes.
One of the key problems addressed by the Guidelines is integration of a building’s structural components (some of which may need to be designed under Part 4 provisions) and to clarify responsibility for design integration and overall review. A building has a primary structural system that can be affected by secondary and specialty structural elements. The Structural Engineer of Record (SER) is responsible for the structural integrity of the primary structural system and for ensuring the substantial conformance of secondary and specialty elements with the primary system.
The SER works with specialty designers to determine site-specific loads and design criteria that result in an overall primary structural system that follows good engineering practice. When Part 4 structural design of components is required, then the authority having jurisdiction, typically a municipality, may also require Letters of Assurance from an engineer with the building permit application. If, as often happens, the designers of a Part 4 structural component are not involved in the overall structural design and integration of components in the building, they cannot provide such Letters. This problem becomes further pronounced when a renovation or addition is built onto an existing primary structural system.
APEGBC acknowledges that a building’s owner or contractor may not retain a Part 4 component designer for further review of an overall primary structural system. In such instances, these designers should clearly define their scope of services and exercise due diligence should they accept the role of reviewing the primary structural system. Further, those engineers designing renovations or additions should conform to the Part 9 philosophy by implementing one of several rational schemes for ensuring building safety and performance.
The Guidelines recommend that engineers document and retain records of their selection of schemes. They also establish standards for the disclosure of deficiencies observed by a structural engineer. Pursuant to their professional Code of Ethics and APEGBC Bylaw Article 14(a)(9), engineers are expected to report any observed deficiencies to owners or their representatives, whether or not the observation falls within their scope of services. If the owners fail to "respond appropriately", the engineer must inform the APEGBC and the "Authority Having Jurisdiction". If an engineer makes recommendations to mitigate risks associated with lateral load resistance that are ignored, it is recommended that the engineer document such concerns in writing. It remains unclear how far an engineer should follow up with the client’s responses or what is meant by an "appropriate response".
For professional engineers, the title, Guidelines for Professional Structural Engineering Services for Part 9 Buildings is a misnomer; in fact, engineers must substantially follow them in order to meet their standard of care and to fulfill their professional obligations. APEGBC categorically states that "failure to meet the intent of these Guidelines could be evidence of unprofessional misconduct and lead to disciplinary proceedings" and warns that professional engineers cannot blame low fees for failing to meet the Guidelines’ standards.
The Guidelines provide much needed standards for design of small buildings in British Columbia, especially given the province’s susceptibility to earthquakes. However, they unfortunately lack sufficient detail and clarity, possibly leaving engineers vulnerable to allegations of negligence or professional misconduct. It remains to be seen if the Guidelines will fairly balance the interests of engineers, the public and other stakeholders.
In September 2008, the Building and Safety Policy Branch of British Columbia issued its "Information Bulletin" and "Revised Appendix Notes" to Section 9.4 of the 2006 British Columbia Building Code. This clarifies the application of the Code’s Section 9.4—specifically for the structural design of wood-frame buildings for earthquakes and strong winds—and assists engineers in complying with the Code and in meeting the Guidelines. Further changes to structural design of Part 9 wood-frame buildings is being proposed for the next edition of the National Building Code, which is the model for the B.C. Code.
In the past, APEGBC has brought disciplinary proceedings against structural engineers for failure to adhere to other guidelines for structural design or concept review. Engineers should be aware that failure to follow these Guidelines could result in APEGBC bringing charges of unprofessional conduct against them. They should carefully review them and, when hired, fully document the scope of their design services with the owner (or its representative) and maintain detailed records.