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New codes offer clarity
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A version of this document is published in / Une version de ce document se trouve dans : On-Site Heavy Construction News, March 2005, pp. 45-46
New National Construction Codes Offer More Clarity and Flexibility
Submitted to On Site Heavy Construction News
By Jim Gallagher and John Burrows
This is the second in a series of articles intended to inform readers about important changes to the national model building codes, which will be released later this year.
In the January/February issue of On Site, we introduced you to a new concept in building regulation. That new concept, referred to as objective-based codes, will make its debut in the 2005 versions of the National Building Code, the National Fire Code and the National Plumbing Code. “Objective-based” means all provisions in a particular code will be tied directly to the code objectives. In the case of the National Building Code, these
objectives are safety, health, accessibility, and fire and structural protection of buildings. The new objective-based format will help you a) understand the reason why a particular provision must be met and b) provide information that will help you evaluate alternative solutions should you wish to propose one.
Many of you have wondered if the change to objective-based codes will affect your everyday work. The answer is, only if you want it to, and only in positive ways. This article explains further what the new codes will be like and how they will be used. Getting used to some new terms and definitions will be part of the learning exercise. These include four key terms: “objectives,” “functional statements,” “acceptable solutions,” and “alternative solutions.”
The three national codes have always permitted what were called “alternative solutions” or “equivalencies.” This means you could devise a different solution from what the code prescribed, as long as you could prove to a building official that it would work just as well. The objective-based codes continue that tradition but carry it much further, actually providing explanatory information that will help you and building code officials develop, review and approve alternative solutions. This will apply in situations where your client wants an innovative solution that is, say, less expensive, or uses the latest technology.
The Look and Feel of the New Codes
The objective-based format will appeal to forward-thinking designers and contractors and their clients who are seeking opportunities for innovative solutions, while retaining the present code provisions for those who wish to stick to the tried and true method. For many users, the existing provisions will continue to serve them well and they won’t have need for the additional explanatory information that the objective-based codes will provide.
The objective-based National Building Code, for example, will have three parts called divisions.
“Objectives” stating what needs to be achieved in terms of safety, health, accessibility, and fire and structural protection.
“Functional statements” that further describe the functions a building must perform. Limitations on the application of certain objectives and functional statements (not all objectives and functional statements apply to all buildings).
Now that the objectives and functional statements have been established for the 2005 codes, they will not change frequently. Thus, it is expected that Division A will not necessarily require updating as each new edition of the codes is published, normally on a five-year cycle.
Division A also states how compliance with the code is achieved by:
a) Complying with the applicable “acceptable solutions” in Division B, or
b) Using alternative solutions that will achieve at least the minimum level of performance required by Division B in the areas defined by the objectives and functional statements relevant to the applicable acceptable solutions.
Division B will contain the familiar technical provisions, similar to the past but updated
to reflect research findings and technology advances since the last edition of code was published in 1995. These provisions will now be referred to as “acceptable solutions.” In addition, each provision in Division B will make reference to the Division A objectives and functional statements that it is deemed to satisfy. Division B will be updated on a regular basis as part of the ongoing code development and review processes over the five-year cycle.
Division C will contain the administrative provisions currently found in Parts 1 and 2 of
the current edition of the National Building Code. Placing this information in a separate division facilitates its replacement by administrative provisions specific to a province or territory.
As designers, contractors and builders, many of you will elect to simply follow the
provisions (acceptable solutions) in Division B, but you will now have the means to better understand why a provision appears in the code. Others among you may wish to explore an alternative solution that could be better or more economical; if so, the objective-based format gives you a better understanding of what it is the building code requires your design to achieve. Further details on the objective-based codes are available at
http://www.nationalcodes.ca.
Jim Gallagher is Manager of Publications at the Institute for Research in Construction, National Research Council of Canada. John Burrows is an Ottawa-based consultant and technical writer.
___________________________________________ Example from the National Building Code
Here is an example to illustrate how the objective-based 2005 National Building Code (NBC) would be used. The example involves the use of High Strength Steel Tendons,
from Part 4 of the NBC. You would find the acceptable solution stated in Division B as follows:
4.2.3.9. High Strength Steel Tendons
1) Where high strength steel is used for tendons in anchor systems used for the permanent support of a foundation or in the erection of temporary support of soil or rock adjacent to an excavation, it shall conform with the requirements of CSA A23.1, “Concrete Materials and Methods of Concrete Construction.”
You could meet the NBC provision in this case simply by implementing this acceptable solution. However, if you wanted to better understand the reasoning behind the
acceptable solution or understand the conditions under which you could propose an alternative solution, you refer to a table in Division B that links the acceptable solution to the relevant objectives and functional statements appearing in Division A. For the steel tendon example, the objectives that apply are as follows (note, these are direct quotes):
OS2 Structural Safety
An objective of this Code is to limit the probability that, as a result of the design or construction of the building, a person in or adjacent to the building will be exposed to an unacceptable risk of injury due to structural failure. The risks of injury due to structural failure addressed in this Code are those caused by:
OS2.5 instability of the building or part thereof OS2.6 collapse of the excavation
OP2 Structural Sufficiency of the Building
An objective of this Code is to limit the probability that, as a result of its design or construction, the building or part thereof will be exposed to an unacceptable risk of damage or loss of use due to structural failure or lack of structural serviceability. The risks of damage and of loss of use due to structural failure or lack of
serviceability addressed in this Code are those caused by: OP2.5 instability of the building or part thereof
OP2.6 instability or movement of the supporting medium
OP4 Protection of Adjacent Buildings from Structural Damage
An objective of this Code is to limit the probability that, as a result of the design, construction or demolition of the building, adjacent buildings will be exposed to an unacceptable risk of structural damage. The risks of structural damage to adjacent
buildings addressed in this Code are those caused by:
OP4.1 settlement of the medium supporting adjacent buildings OP4.4 collapse of the excavation
The relevant Functional Statements in Division A that apply to the steel tendon example are as follows (direct quotes):
The objectives of this Code are achieved by measures, such as those described in the acceptable solutions in Division B, that are intended to allow the building or its elements to perform the following functions:
F20 To support and withstand expected loads and forces.
