Code and Roof Design
Code and Roof Design
Division E - General Information
Roof Design: From Code to specifciations
This is the third part of a multi-part series on the Building Code and roofing:
- Part 1: Understanding the BC Building Code
- Part 2: The Building Code and wind
- Part 3: Design Responsibility: from Code to Specification
You can find these articles in both the printed and digital editions of Roofing BC, the trade magazine published by the RCABC. You can also watch the video presentation, “Blown Away: Code Requirements for Membrane Roofs”, that addresses several articles in this series.
The content on this page has been adapted from the original published article in Roofing BC (Fall 2021).
Introduction
In the second article of this series on the British Columbia Building Code, we examined why wind matters, located Code requirements for membrane roofs and discovered that roof design is as much about structural design as it is about the building enclosure. In this third article, we address the fundamental question of design responsibility.
Who's in charge here?
Looking back at the previous article, we know that Part 5 in Division B contains new language (in 2018) about roof design that provides two pathways by which a roof system design can conform to the Code. What exactly does it all mean for the design process? More importantly, who is responsible for the design?
The question of responsibility has not been adequately answered in past years. Some designers provide detailed specifications that include Specified Wind Load values, but examples are rare. Many hold that the roof design can be assigned to the roofing contractor. Assigned or Delegated Design to constructors is a common practice1. But is the assignment of structural design permissible under the Code?
When we refer to the Design Authority (a term used in the Roofing Practices Manual), we mean anyone who takes responsibility for the design of a roof system. The term designer used in the Code imparts the same meaning. Regardless of new construction or replacement work2, the Design Authority could be any of the following:
- Architect
- Engineer
- Roofing Consultant
- Roof Manufacturer / Supplier
- Roofing Contractor
- Building Owner
So, what makes any one of these people potentially responsible for the design? The answer to that question, as we will discover, is in the Code.
Article 5.2.2.2. in Division B refers directly to Article 4.1.7.1., Specified Wind Load. Recalling that the term Specified Wind Load is mentioned in Sentence (2) of Article 5.2.2.2., we see in Part 5 a deliberate connection between the two Parts: the roof must successfully separate the outside environment from the interior conditioned space (Part 5 – Environmental Separation), and to do that it has to remain where it is built (Part 4 – Structural Design). Or, to put it another way, the roof must maintain a water-tight state (Part 5) by capably resisting the upward forces exerted by wind (Part 4). Designing the roof, then, begins with the overall structural design of the building (Part 4).
Keeping in mind this keystone relationship between Parts 4 and 5 of Division B, we turn to Division C to understand who takes ownership of a design that is both “structural” and “building enclosure” in nature.
The Building Code: Division C, Administrative Provisions
Division C of the Code contains the administrative requirements. While Division C is relatively small and lacks the “how to” appeal of Division B, it’s nevertheless packed full of critical language about responsibility for design. So, take a deep breath. We’re diving deep.
In the Code, the term “designer” is defined as “the person responsible for the design” (Division A, Article 1.4.1.2. Defined Terms). Part 2, Article 2.2.1.2. Structural Design, states that “for design work carried out in accordance with Part 4 of Division B, the designer shall be a registered professional skilled in the work concerned (See Note A-2.2.1.2.(1).).”3 Notice that this sentence pertains to the work of Division B, Part 4 Structural Design. The Notes referenced in this Code Article state that “[it is] the assumption that structural design will be carried out by a registered professional who is qualified to perform such design. Sentence 2.2.1.2.(1) is not intended to imply that a registered professional may not also be required in the application of requirements in other Parts of the British Columbia Building Code.”4
Article 2.2.1.2. and the corresponding Notes do not state whether the registered professional must be the “coordinating registered professional” or even a registered professional who is part of the design team for the building. We will circle back to this issue later in this article.
The term “registered professional” is also a defined term (Division A, Article 1.4.1.2. Defined Terms):
- “Registered professional means
- a person who is registered or licensed to practise as an architect under the Architects Act, or
- a person who is registered or licensed to practise as a professional engineer under the Engineers and Geoscientists Act.”
- “Registered professional means
In the Notes to Division C, Part 2, Note A-2.2.7. Professional Design and Review states the following (red text is by the writer for emphasis):
It is typical that the registered professional responsible for the design is also responsible for the field review. There are instances where this is not the case and having a different registered professional doing the field reviews is unavoidable. Schedule C-B requires that the registered professional who provides the field review provide assurance that the building as finally constructed is in substantial conformance with the Code. In the event that another registered professional is to provide field review, the field reviewer takes on the responsibility to confirm that the construction substantially complies with the plans and supporting documents that were submitted for the building permit. The responsibility for code compliance of the design remains with the original registered professional who undertook the design. In this event, the Schedule C-B must be modified by the field reviewer by crossing out and initialing Clause (b)(i) and providing the effective transition date.
Then, Note A-2.2.7.2. (1)(a) Coordinating Registered Professional) states the following (again, red text is by the writer for emphasis):
The coordinating registered professional is responsible to ascertain that all Code related aspects which are relevant to the project are clearly identified by each of the registered professionals in the collection of Schedules B. If a registered professional of record has crossed out any item on their Schedule B, the coordinating registered professional must confirm this item is not applicable to the project or resolve the issue with the registered professional of record.
Back to Section 2.2. of Division C, we read the following in Article 2.2.2.1. General Information Required (blue text is in keeping with the original wording in the Code):
1) Sufficient information shall be provided to show that the proposed work will conform to this Code and whether or not it may affect adjacent property.
2) Plans shall be drawn to scale and shall indicate
- a) the nature and extent of the work or proposed occupancy in sufficient detail to establish that, when completed, the work and the proposed occupancy will conform to this Code,
- b) the applicable edition of the Code,
- c) whether the building is designed under Part 3 or Part 9,
- d) the major occupancy classifications of the building,
- e) the building area and building height,
- f) the number of streets the building faces,
- g) the accessible entrances, work areas and washrooms,
- h) the accessible facilities particular to the occupancies, and
- i) the energy compliance path to which the building conforms, and, where a building conforms to Subsection 9.36.6. or 10.2.3. of Division B, the Step to which it conforms.
3) When proposed work is changed during construction, information on the changes shall comply with the requirements of this Section for proposed work.
This is followed later by Subsection 2.2.4. Structural and Foundation Drawings and Calculations (which, according to Article 2.2.4.1., applies “only to buildings covered in Part 4 of Division B”). Article 2.2.4.3. Information Required on Structural Drawings, concerning structural drawings and specifications, states (red text is for emphasis):
(Under construction...come back soon)
© RCABC 2024
No reproduction of this material, in whole or in part, is lawful without the expressed permission of the RCABC Guarantee Corp.