Archived – Public review on proposed changes to the National Model Construction Codes – Fall 2014

• National Building Code (NBC)
  • Part 3
  • Part 4
  • Part 9
• National Fire Code (NFC)
• National Energy Code for Buildings (NECB)

National Building Code of Canada (NBC)

Division B

Part 3

Self-service storage buildings (1 storey with external access)

The proposed change introduces requirements for self-service storage buildings that are one storey in height with no basement or mezzanine and only external access to storage units, as many jurisdictions currently have no building code requirements specific to self-service storage buildings. These requirements provide specific relaxations in terms of fire protection, such as spatial separations and egress, and represent the first step towards introducing requirements for multi-storey self-service storage buildings.

Building on sloped sites

The proposed changes resolve confusion regarding the definition of grade and its application to buildings located on sloping sites. They expand the building height from three to four stories and permit the consideration of assembly, business and personal services, as well as mercantile major occupancies, when dealing with four-storey Part 3 buildings and non-residential major occupancies in Part 9.

Soffit protection

The proposed change clarifies and relaxes roof soffit protection when facing a street, lane or a public thoroughfare. It provides for harmonization with similar provisions for spatial separation in Part 9.

Handrail graspability

In response to many comments raised during the 2013 public review, this proposed change deletes the notion of "graspable portion" of handrails for Part 3 public stairs.

Part 4

Changes to ground snow load values

Due to newly available data, the proposal is to change the ground snow load values for different areas of Canada. About 84% of the locations listed in Table C-2 of Appendix C of the NBC remain unchanged. The greatest increases in ground snow load values are for locations in the Yukon, Northwest Territories and Nunavut.

Updated seismic model

A major overhaul of the seismic model for Canada has resulted in changes relating to seismicity. These changes are based on improved ground motion data from large earthquakes in the last decade, as well as an improved understanding of the relationship between earthquake occurrence and the geological structure of the earth's crust. The new seismic model for Canada incorporates these advancements and is the first major update in 20 years. It provides better risk coverage against seismic events.

The proposed changes fall into three categories: location-specific changes as listed in Table C-2 of Appendix C of the NBC; site-specific changes such as revised foundation factors and equations; and structure-specific changes such as revised higher mode factors. These changes are interrelated. Consequently, design seismic loads will change in some areas, and a different trigger zone may apply. Some jurisdictions may end up falling under a different zone after the trigger value is calculated. This may result in either an increase or a decrease in the requirements, and an increase or decrease of about 1% in the building's construction cost.

The seismicity changes also impact Part 9 buildings and housing, as the prescriptive solutions in Part 9 use the spectral hazard values as triggers for construction requirements. For example, an increase in the spectral hazard for short period buildings may trigger more stringent construction requirements for elements such as braced wall bands, roof sheathing nailing, masonry and ICF wall construction, and the attachment of HVAC equipment. The areas affected by increased values include locations in British Columbia, Northwest Territories, Yukon, Quebec and New Brunswick. In addition, some locations in British Columbia and Yukon's Destruction Bay that currently fall outside the Part 9 prescriptive solutions will require that housing and small buildings be designed according to Part 4.

Part 9

Spatial separation of houses

A 10-minute response time was introduced into Part 9 of the 2010 NBC as a trigger for more stringent spatial separation requirements for houses. Some jurisdictions have reported difficulties with its measurement and application.

The proposed change deletes the 10-minute response time for spatial separation of houses and restores the wording used in the 2005 NBC with some additional changes. It does, however, maintain the two levels of requirements – a less stringent one where a fire department is organized, and a more stringent one where a fire department does not exist or is not organized, trained and equipped. Sprinklered houses will continue to be exempted from the more stringent requirements.

Run dimension in dwelling units

This proposed change increases the run dimension in stairs serving single dwelling units to a minimum of 255 mm (10 inches). It is based on an assessment of technical literature and statistics indicating that the current NBC residential step dimension requirement provides a less than acceptable performance level. A review of studies and reports indicated that steps with a larger run dimension provided better foot placement and greater margins of stability, resulting in a reduction of fall incidents for all fall scenarios and all age groups.

Fire-resistance and sound transmission class ratings

This proposed change introduces a new exterior wall assembly, EW2, using glass fibre insulation fill, as its use in assemblies has demonstrated an acceptable fire performance when constructed in a similar way to assemblies using mineral fibre. The proposed assembly would be deemed to comply with fire-resistance ratings of 45 minutes and 1 hour and would be consistent with the existing fire-rated assembly EW1 that is still limited to mineral fibre insulation.

Low permeance materials

Currently, a material's water vapour permeance triggers the requirement to insulate assemblies on the exterior; however, this creates an unlevel playing field for the rigid foam board industry. Based on the results of an NRC modeling project that examined the risk potential for moisture condensation within various wall assembly configurations and key climate areas, the proposed change would allow installation of more products on the exterior without the need for additional insulation.

CSA A23.1 concrete strength

This proposed change creates a qualified reference to the 2014 edition of CSA A23.1 by explicitly writing the existing strength and water cement ratio requirements into the body of the code. The revision to the 2014 edition of the CSA A23.1 standard calls for higher strength and lower cement-water ratios for concrete used in foundations, footings and interior floor slabs of houses and small buildings. However, based on the evidence provided, the committee was not convinced that the current minimum requirements were inadequate.

National Fire Code of Canada (NFC)

Division B

Dangerous goods – Laboratories

In response to comments received during the fall 2013 public review, further clarification was required to determine the maximum quantities of dangerous goods permitted in laboratories. This proposed change was needed to clarify that the maximum quantities permitted in laboratories does not include those in piping systems supplied from a source external to the laboratory.

Repair and refurbishment of storage tanks

The proposed change for repair and refurbishments of storage tanks introduces new standards when reusing storage tanks and removes the reference to withdrawn certification programs.

National Energy Code of Canada for Buildings (NECB)

Division B

Demand control ventilation

This proposed change adds demand control ventilation system requirements for enclosed semi-heated or conditioned spaces for intermittently used fuel-powered vehicles or mobile equipment.

Service water pumping

This proposed change broadens the scope of NECB Part 6 to address the energy used for moving unheated service water, as the current provisions only address energy of heated service water. It would not apply to water used for firefighting.

Hot water maximum discharge rates

The NECB has requirements for maximum hot water discharge rates for supply fittings and shower heads that were carried over from the 1997 Model National Code of Canada for Buildings. This proposed change updates the maximum values to be in line with current practice and with the proposed requirements for the next edition of the National Plumbing Code.