18 l ROOFINGBC l WINTER 2018 TECHNICAL UPDATE I n the Summer 2018 issue of Roofing  BC, we examined the nature and power of wind, the relationship between wind and flat membrane roof surfaces, and reviewed code requirements for roof design. We also briefly described ways for the Design Authority to effectively specify wind-resistance requirements for a roof project. In this article, we take a deeper look at the role of the Specifier, and describe two pathways for writing an effective project specification. Roles and Responsibilities A good specification clearly expresses the nature, scope, general design and details of the building project, and articulates a well-rounded understanding of the responsibilities borne both by the Design Authority and by contractors who put it all together. To ensure a roof is wind-resistant, designers and contractors have different and complementary roles and responsibilities. Article 5.2.2.2. (BCBC) states that “…the wind load…shall be 100% of the specified wind load [for the roof]…”  By specified wind load, the BCBC means the negative pressure wind exerts on the roof (Div. B, 4.1.7.1 SPECIFYING A WIND-RESISTANT MEMBRANE ROOFBY JAMES KLASSEN fied to understand all these aspects of building design. In fact, the BC Building Code explicitly defines this responsibility under Div. C, 2.2.1.2 Structural Design:  For design carried out in accor- dance with Part 4 of Division B, the designer shall be a registered profes- sional skilled in the work concerned. For Projects where drawings and spec- ifications are prepared, contractors are asked to do one thing – build the struc- ture to match the design specifications. A clearly written specification also keeps a project on budget. When a speci- fication properly articulates the specified wind loads the roof design must address, and provides a clear pathway for the contractor to follow, the result is success for everyone – a project that is built on time and on budget. Code Requirements To understand how the 2018 BC Building Code works, we first need to be clear about what it is, and what it is not. The BC Building Code regulates building design and construction concerning fire protection, occu- pant safety, comfort and acces- sibility, energy efficiency and environmental separation, and seismic stability. It is not inter- ested in construction quality, Specified Wind Load).  Calculating the specified wind loads requires a structural understanding of the building in its context, and since the Design Authority is responsible for (and coordinating) the design of the building, he or she is ideally positioned to do this. This is because the calculation of specified wind loads requires an understanding of the entire building – its supporting framework, where it will be situated, its orientation relative to its surroundings, the nature of harmonics generated by the pres- ence of proximate buildings, and how the building will be occupied and used. Contractors may not be the best quali-