Code Changes: A review of major revisions in the 2010 National Model Construction Codes

by Elaina Adams | December 1, 2011 9:40 am

By John Burrows, P.Eng.
The 2010 editions of the National Model Construction Codes—the National Building Code of Canada (NBC), the National Fire Code of Canada (NFC), and the National Plumbing Code of Canada (NPC)—were released last November. Published by the National Research Council Institute for Research in Construction (NRC-IRC), the new codes contain about 800 technical changes.

The revisions are the result of a five-year collaboration between the Canadian Commission on Building and Fire Codes (CCBFC), the provinces and territories, the construction industry, and the public. This article focuses primarily on the most significant changes. (More detailed information about these code changes—and many more not mentioned in this article—can be found in presentations that are available at www.nationalcodes.ca/eng/presentations/2010_codes_presentations.shtml[1]. Emergency changes were also published for the NBC in June. NRC also released a new edition of the National Energy Code of Canada for Buildings 2011).

Structural safety
The 2010 edition of NBC has changed requirements in Part 4, “Structural Design,” for live loads due to use and occupancy. A new load combination table has been added for cranes to ensure design adequacy when acting in concert with other loads.

The minimum live loads for arenas, grandstands, and stadiums having fixed seats with backs were reduced to reflect the fact this seating arrangement discourages overcrowding and overloading that can result where there is moveable seating or bleachers. The same principle was applied to churches, lecture halls, and theatres that have fixed seats with backs. Guard-loading has been revised for open viewing stands, where spectators are not restricted by fixed seating from crowding a guard. More weight-specific loads were introduced for live and concentrated loads for garages.

For wind design, Part 4 now requires very tall buildings be designed using experimental methods (e.g. wind tunnel testing). Buildings 60 m (197 ft) or higher require dynamic analysis.

Safety issues for Part 9, “Housing and Small Buildings,” structures began to arise with the trend of ‘open-concept construction,’ such as the practice of building on narrow lots and use of big windows, particularly in areas where exposure to wind and earthquakes is high. This type of construction meant there could be inadequate strength to resist the lateral loads from windstorms or seismic activity.

To address this problem, new requirements for bracing and lateral load resistance were added to Part 9 based on three levels of risk:

• low to moderate;
• high; and
• extreme.

Buildings in the first category have resistance to wind and earthquake loads by virtue of traditional wood-frame construction composed of exterior sheathing, panel-type cladding, or gypsum board finish.

Buildings in the high exposure category require additional features to provide required resistance to lateral loads. Of all the locations identified in NBC Appendix C, six fall into this category for wind and 45 for earthquakes. For wind, areas in Newfoundland, Alberta, and the Northwest Territories are impacted. Of the locations affected by seismic risk, most are located in the coastal region of British Columbia, but three are in the Lower St. Lawrence region of Québec.

For these areas, prescriptive requirements have been added to Part 9 so builders can incorporate adequate lateral load resistance without the need for further structural engineering design. These include constructing walls using ‘braced wall panels’ in ‘braced wall bands’ that are continuous horizontally and vertically throughout the building.

The panels and bands extend from the top of the supporting foundation, slab, or sub-floor to the roof framing above.
The requirements specify the number and type of walls needed and the spacing and materials that can be used. There is also the option of obtaining an engineered design based on Part 4.

Buildings in the extreme exposure category must be engineered according to Part 4, or to the Canadian Wood Council’s (CWC’s) Engineering Guide for Wood Frame Construction. Of all the locations identified in NBC Appendix C, only one location—in Nunavut—falls into this category for wind; there are three locations for earthquake exposure, all in Québec’s Upper St. Lawrence region.

Fire safety
New buildings falling under NBC Parts 3, “Fire Protection, Occupant Safety, and Accessibility,” and 9 now require exit signs to be in pictogram form, green on white. The requirement follows International Organization for Standardization (ISO) standards:

• colour specifications: ISO 3864-1, Graphical Symbols: Safety Colours and Safety Signs–Part 1: Design principles for safety signs and safety markings; and
• dimensions: ISO 7010, Graphical Symbols: Safety Colours and Safety Signs: Safety signs used in workplaces and public areas.

Unlike the old format, using red lettering that read “Exit/Sortie” on a white background, the new signage is not dependent on literacy; it is an easily discerned ‘running man’ image and directional arrows. This change—Underwriters Laboratories of Canada (CAN/ULC) S572-10, Photoluminescent and Self-luminous Exit Signs and Path Marking Systems—reflects the international trend for exit signs and is more universally recognized.

Measures have been introduced in Parts 3 and 9 to improve fire safety in residential occupancies. In addition to the requirements for interconnected smoke alarms on each storey of a residential occupancy, interconnected smoke alarms must now be installed in each bedroom. These smoke alarms must be equipped with a battery backup in addition to being hardwired.

NBC has added definitions and clarifications to Parts 3 and 9 to improve the understanding of fire stops and fire blocks and the importance of sealing pipe and duct penetrations through fire separations. Cables placed within plenum spaces will require either an FT4 or FT6 rating depending on whether the building is made of combustible or noncombustible construction, respectively. (The higher FT rating relates to a lower flame spread and smoke development classification.) New requirements have been introduced for the protection of conductors serving life safety systems, including:

• fire alarms;
• emergency lighting;
• smoke control;
• elevators; and
• fire pumps.

A number of fires that impacted multiple homes and buildings led to new requirements in Parts 3 and 9 to prevent the spread of flames from one building to another. These changes clarify fire department response time assumptions and under certain conditions limit the:

• number and size of unprotected openings;
• cladding type that can be used; and
• degree to which soffits may overhang buildings.

Another safety issue is openable windows in high-rise residential buildings, as they can pose a potential falling hazard, especially for children. This has led to new code requirements in Part 3 intended to limit the likelihood of falls. One safety option is a guard 1070 mm (42 in.) high, on the front of windows. The other is a limiter that restricts the opening of a window to no more than 100 mm (4 in.).

Air quality
In addition to structural and life safety concerns, the new edition of the National Building Code of Canada also has updated requirements for indoor air quality (IAQ).

Ventilation
The 2010 NBC includes some changes to Part 6, “Heating, Ventilating, and Air-conditioning” that affect the design and operation of building ventilation systems. In previous editions of the code, it was not specifically indicated what constituted acceptable air for building ventilation purposes in terms of the concentration of particles and gases. Rather, it was simply assumed the air being vented into the indoor building environment was good enough. However, it was evident that, in some areas, outdoor air is not necessarily suitable for building ventilation.

For this reason, the new NBC has set maximum levels in air used for building ventilation purposes for particulate matter, ground-level ozone, and carbon monoxide. These are based on the National Ambient Air Quality Objective (NAAQO) benchmark levels published under Section 8, Part 1, of the Canadian Environmental Protection Act (CEPA). The goal of the limits is to reduce the probability that, as a result of the operation of a ventilation system, a person in a building will be exposed to an unacceptable risk of illness due to poor IAQ.

In locales where there are provincial or territorial requirements for air quality, the design of ventilation systems should be based on them. In the absence of such requirements, the limits prescribed by NBC apply. The change to Part 6 requires that, in areas where the outdoor air quality does not meet the acceptable NAAQO levels, building ventilation systems be provided with devices to clean the outdoor air before it is distributed to indoor occupied spaces.

Soil gas 
Protection from soil gas ingress has always been required in all buildings. This protection is achieved by the mandating of a continuous air/soil gas barrier at soil/foundation interfaces. The new Health Canada guideline of 200 Bq/m³ for maximum allowable radon concentration led to further changes on specific protection from radon—one of the soil gases. Under Parts 5, “Environmental Separation,” and 6, engineers must now consider radon protection in their designs.

Air barrier requirements have been consolidated and prescriptive measures have been added to Part 9, including measures for providing a rough-in for an active radon removal system. This way, if radon becomes a problem, an economic way of removing it will be available.

The responsibility of testing for radon is left to the building owner. The Health Canada guideline recommends if test results indicate an annual average concentration exceeding 200 Bq/m³, then the completion of the subfloor depressurization system may be necessary to reduce the radon concentration. This would involve uncapping the rough-in pipe and connecting it to a ventilation system exhausting to the outside.

Standards
The National Model Construction Codes reference many Canadian or North American standards. One important change to the 2010 NBC is the reference in Parts 5 and 9 to a new harmonized North American Fenestration Standard for Windows, Doors, and Skylights (NAFS), along with Canadian Standards Association (CSA) A440S1-09, Canadian Supplement to AAMA/WDMA/CSA 101/I.S.2/A440.

There is now a new procedure for specifying windows, doors, and skylights, as the previous rating system has been replaced with actual design load and pressure ratings. Performance grades for windows, doors, and skylights will now need to be selected according to the Canadian Supplement to ensure products suit the conditions and geographic location for which they are intended.

A number of new ASTM standards for sealants used in building envelope construction are now referenced in Parts 5 and 9. Reflecting changes in technology, materials, and design, they replace several standards that were considerably out of date.

Climatic and seismic data
Climatic data for wind, rain, degree days, and temperature were updated using recent data from Environment Canada. (Snow load data will be updated in the 2015 code.) A better way of calculating seismic data has been used. For short-period (i.e. low-rise) structures, the seismic design loads have generally been decreased. For long-period (i.e. high-rise) structures, they have generally increased.

Secondary suites
Requirements for secondary suites (i.e. accessory apartments or in-law suites) located in houses have been introduced into Part 9. In this context, ‘houses’ include both freehold row houses and semi-detached (i.e. two dwelling units side-by-side), but excludes condominiums, duplexes (i.e. two dwelling units on top of each other), and other multi-family buildings.

Before 2010, secondary suites were addressed using the same provisions as for duplexes or multi-unit residential buildings. These provisions often imposed additional requirements in terms of fire and sound protection, egress, and exiting, when compared to requirements for single-family dwellings. The new requirements are intended to accommodate the construction of secondary suites at a reasonable cost without compromising occupant health
and safety.

NFC and NPC changes
The National Fire Code now requires buildings or facilities be protected from fires originating from demolition or construction sites. Protective measures might be active (e.g. sprinklers, water curtains, or fire watch) or passive (e.g. keeping the storage of combustible materials away from buildings). Requirements for fire safety plans and fire department access to sites have also been improved.

NFC has added requirements for the commissioning and decommissioning of standpipe systems, as well as restrictions on placement of bitumen kettles on rooftops. Roofing operations that include ‘hot works’—activities such as open flames or anything producing heat or sparks—must meet these new regulations.

Other key NFC changes deal with leak detection, monitoring and handling of certain dangerous goods, and the protection of storage tanks, sumps, and piping systems containing flammable and combustible liquids. Limits to quantities of flammable and combustible liquids stored within buildings have been updated.

To draw a clear line between the roles of NFC and NBC, building design requirements in the former were moved to the latter (except for spill control measures). Appropriate cross-referencing between the two codes was added.

The National Plumbing Code has updated pipe sizing requirements to accommodate the current standard practice of using water-conserving appliances and fixtures in buildings and facilities. Appendix material has been added to clarify hydraulic loading and the effect of water quality on plumbing design.

Non-potable water systems are gaining popularity due to water-conserving practices. Consequently, guidance has been introduced to indicate how these need to be designed and identified.

Conclusion
These codes are published by NRC as models for provincial and territorial building and fire regulations. However, as mentioned, they must be adopted by an AHJ to come into effect. Therefore, code-users should check with their local authority to determine what codes and regulations are in effect.

Printed versions of all three codes are available in both binder and soft-cover formats. Electronic versions come as downloadable PDF documents, replacing the CD-ROM versions. Online subscriptions are also offered.

The new codes can be purchased from NRC-IRC through the virtual store: www.nrc.gc.ca/virtualstore[2].

John Burrows, P.Eng., is an Ottawa-based consultant and technical writer. With an engineering background, he has been writing for the National Research Council Institute for Research in Construction (NRC-IRC) for the past 11 years.

Source URL: https://www.constructioncanada.net/code-changes-a-review-of-major-revisions-in-the-2010-national-model-construction-codes/

---