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2005 National Construction Codes : increasing clarity and flexibility for design
Gallagher, J. F.; Thériault, M.
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N a t i o n a l R e s e a r c h C o u n c i l C a n a d a
2 0 0 5 N at iona l Const ruc t ion
Code s : inc re a sing cla rit y a nd
flex ibilit y for de sign
N R C C - 4 8 3 7 8
G a l l a g h e r , J . ; T h é r i a u l t , M .
A version of this document is published in / Une version de ce document se trouve dans :
Construction Canada, v. 48, no. 1, Jan. 2006, pp. 58-60, 62, 64
2005 National Construction Codes Published More Clarity and More Flexibility for Design
Submitted to Construction Canada By Jim Gallagher and Martin Thériault
The recent publication of the 2005 National Building Code by the National Research Council signals a new era in construction in Canada. First published in 1941, the highly regarded instrument of regulation has been retooled and reorganized into what is called an objective-based format.
The National Fire Code and the National Plumbing Code have undergone the same metamorphosis as a result of a ten-year review that began after the publication of the 1995 editions. Industry leaders and provincial/territorial representatives, in collaboration with the NRC Institute for Research in Construction, laboured long and hard to analyze every provision in all three of the 1995 codes. The careful scrutiny revealed that through the years the codes had occasionally gone off course, to embrace tangential albeit
important issues beyond the original scope.
Once they got the focus of the codes back on course, the review team moved on to the next task, one of adding significant new information to the documents to help users understand what must be done to satisfy code provisions. This new information, at the heart of the objective-based format, makes the codes clearer, enables easier application to existing buildings and removes barriers to innovation by assisting designers in proposing “alternative solutions” to code requirements if they wish to do so. The third step in the review and overhaul was to convert the codes to the objective-based form and seek public review.
“Objective-based” means all provisions in a particular code will be tied directly to the code’s objectives. The objective-based format will help designers understand the reason why a particular provision must be met and provide information that will assist them to evaluate alternative solutions.
Veteran code users know that past editions of the national codes have always permitted alternative solutions, previously known as “equivalencies.” Designers could devise a solution that was different from what the code prescribed, as long as they could prove to a building official that it would work just as well. The new objective-based codes continue that tradition but make the process clearer by providing the aforesaid
explanatory information that will help designers develop alternative solutions. This same information will help building code officials to review and approve the alternative
solutions. When something new is proposed, there are always risks involved, so the new codes will help reduce those risks by providing users with a better means to demonstrate whether an innovative solution will provide a level of performance at least equivalent to that achieved by the prescribed acceptable solution.
This new design flexibility offered by the 2005 codes is only for those who wish to use it. For the many users who wish to stick to the tried and true approach – those who wish to simply “meet code” and nothing more because that is what their clients expect – the new codes will require little change or adjustment. For their day-to-day work these users will find the same prescriptive code provisions they found in the 1995 editions, except that those provisions are now called “acceptable solutions.”
The new codes will also be easier to apply to renovation and more responsive to innovation. In renovation projects, the costs of bringing an existing building up to modern standards are often prohibitive. Because the new codes clearly identify the key concerns addressed by code provisions, other approaches to achieving the same levels of performance can be proposed. Similarly, the expanded information provided will
facilitate the evaluation of new products and systems to determine if they are as good as those already specified in the Codes.
A New Organizational Structure
Because of the code review and overhaul that took place, the 2005 editions have a new organizational layout that differs from the 1995 editions. Each new code comprises three divisions: A, B and C. Divisions A and B are of greater interest for users.
Division B is for those wishing to stick to the tried and true, containing the acceptable
solutions referred to above, updated with the many technical changes that reflect research findings and technology advances since 1995. Technical changes – changes in code requirements – are part of every new code and this time over 1300 have been
incorporated in the three documents.
For designers who wish to work with their clients to develop alternative solutions, both Divisions A and B apply. In such a scenario, the design team would first consider the code requirements (acceptable solutions) in Division B, then turn to Division A to find explanatory information to help assess whether an alternative solution they are
considering will offer equivalent performance. This new information includes
“Objectives” and “Functional Statements.” Objectives state conditions what needs to be achieved, which, for the National Building Code are safety, health, accessibility of occupants, and fire and structural protection of buildings. Functional statements further describe the functions a building must perform.
All of the provisions in Division B are linked to at least one objective and one functional statement in Division A to help designers and regulatory authorities better understand the reason why a particular provision must be met and to help them evaluate alternative solutions. There are limitations on the application of certain objectives and functional statements (not all objectives and functional statements apply to all buildings).
Division C contains administrative provisions, which have all been consolidated into this
one place from various places in the 1995 codes. Division C also contains general provisions for the review and documentation of alternative solutions.
Highlights of NBC Technical Changes
The following is a review of some of the key changes in the NBC of interest to readers of Construction Canada.
Part 3: Fire Protection, Occupant Safety and Accessibility
Noncombustible materials: Changes have been made to allow the use of materials of
limited combustibility based on specific criteria. This change was made because the previous noncombustibility requirement excluded materials that pose a low risk but have other desirable properties. This change will allow various products, such as washable interior finishes, to be used in buildings in which they were not previously permitted.
Firewalls: The requirement for masonry or concrete to be used for the construction of
two-hour firewalls has been changed from a prescriptive requirement to a more performance-based requirement. This change was made in response to provincial and builder requests and to facilitate construction under adverse climatic conditions.
Mezzanines: A number of changes have been made regarding mezzanines including the
calculation of building area, fire-resistance rating and exit travel distance. These changes will facilitate plan review and design, and reduce the difficulties users were having with the previous requirements.
Nonmetallic raceways: This change will allow larger-sized non-metallic conduits within
a fire compartment (without penetrating a fire separation). In some cases, there will be a cost benefit in permitting a wider choice of code-complying materials.
Part 4: Structural Design
Live loads: Snow load is no longer considered to be a live load. This will allow a more
rational treatment of the load combinations because the full design snow load will not have to be taken into account in combination with the full design live load derived from the use and occupancy.
Importance categories: A table of importance categories and environmental loads based
on building use and occupancy has been established to determine the degree of functionality required in the event of a natural catastrophe or emergency situation.
Earthquake design: The earthquake acceleration values have been adjusted to provide a
more geographically accurate calculation of the earthquake effects on structures. Eight categories of structural irregularities have been defined to better categorize buildings for earthquake design. Dynamic analysis has been established as the default analysis method for earthquake design. (The use of the equivalent static force procedure is allowed if certain criteria are met.) Requirements have been added for the interconnection of deep foundation units and spread footings, the magnitude of the tying force, and the transfer of earthquake loads between the superstructure and substructure.
Part 5: Environmental Separation
Air leakage and vapour diffusion: Information has been added to clarify the treatment
of air leakage, vapour diffusion, precipitation ingress, and ingress of moisture from the ground. The requirements for controlling air leakage and vapour diffusion have been amended to present the basic requirements in more performance-based terms and to recognize the role of venting to achieve the intents of the requirements.
Heat transfer and ice damming: Changes to the heat transfer control requirements
acknowledge that providing means to dissipate heat can be as important in some
instances such as providing means to control heat transfer (e.g., in reducing the likelihood of ice damming).
Part 6: Heating, Ventilating and Air Conditioning
Ventilation: Wording has been revised to clarify the types of spaces that do not require
ventilation. In addition, revisions have been made to permit natural ventilation where climatic conditions make it feasible and where suitable substantiating information is provided to the authority having jurisdiction.
Carbon monoxide alarms: Carbon monoxide alarms are to be required in buildings that
contain a residential occupancy and a fuel-burning appliance or a storage garage. Part 9: Housing and Small Buildings
Application of Part 4 versus Part 9 structural requirements: Changes have been made
to clarify when Part 9 applies, when Part 9 loads can be used for design under Part 4, and when the design must be done under Part 4.
Simplified snow load calculation: A change has been made to extend the simplified
approach to structures made of any material (previously it applied only to wood-frame construction) where the structure has a high degree of redundancy created by the closely spaced, repetitive members of frame construction, where the total roof area does not exceed that for Part 9 buildings (regardless of firewalls), and where there are no obstructions on the roof that would contribute to significant snow accumulation.
Support of decks: Several changes clarify the requirements for foundations and lateral
bracing for decks, and identify exceptions and alternative solutions to existing requirements.
Insulated concrete form (ICF) walls: Detailed prescriptive requirements for engineered
insulated concrete form walls for small houses have been added and apply to both foundations and above-ground walls. Other changes will permit higher masonry foundation walls for a given thickness if the masonry incorporates reinforcing.
Keeping the rain out: A new climatic indicator, the moisture index, has been added to
identify high moisture load regions. The indicator is a single number that reflects both the amount of rainfall that a location receives and the duration of drying periods. Two planes of protection are required to provide protection from precipitation – the first is the cladding and the second is the sheathing membrane and flashing, with or without a
drained and vented air space. All residential buildings will be required to be constructed with two planes of protection (no face-sealed cladding). In high moisture load regions, the two planes of protection will need to be separated by a capillary break.
These and all technical changes in the new codes reflect issues and concerns expressed in the industry. This is because code development is overseen by the Canadian Commission on Building and Fire Codes, an NRC-appointed committee of approximately 40
volunteers from across Canada including consumer representatives, architects, engineers, building officials, fire officials, plumbing officials, material suppliers and builders. The technical work for the Commission is carried out by standing committees in collaboration with advisors from NRC. Typically, a standing committee can identify an issue and request that research be undertaken to investigate the possible need for, or support for, a code change. Alternately, NRC researchers themselves may propose a code change as a result of their work.
NRC is presenting a series of seminars in which technical advisors review the most significant technical changes in all three new codes. The seminars began in December 2005 and will continue until April 2006.
At the moment, only the print versions of the codes are available. CD-ROM versions will be available in a few months. These enable users to navigate back and forth easily between the various parts of the codes and access the key information they need to know to develop alternative solutions. One of the main features of the CD-ROM versions is that most code provisions will be linked to intent statements (detailed statements on the specific intent of the provisions) and application statements (detailed statements on what the provisions apply to). The intent and application statements will also be available separately in CD-ROMs entitled “User’s Guides,” which complement the printed versions of the codes.
Further details on the 2005 National Construction Codes and the NRC seminars are available at www.nationalcodes.ca. The codes are available for purchase at
www.nrc.gc.ca/virtualstore
Jim Gallagher is Manager of Publication Services at the NRC Institute for Research in Construction (IRC). Martin Thériault is the communications officer with the Canadian Codes Centre of IRC.
