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Construction Codes Explained

February 21st, 2010

With the Advent of the International Family of Codes, we have come closer than ever to having a uniform building code throughout the United States.  The International family of Codes came about when the three model code organizations Boca, ICCBO, SBC got together and worked towards developing a single building code.

A Little History

Hammurabi recieved a copy of the code from his Law Department

Hammurabi recieved a copy of the code from his Law Department

No story about codes would be complete if we didn’t talk about Hammurabi.  King of the Babylonian Empire, Hammurabi created the first known building code in 2200 B.C..  It was a little light on technical information, no span tables or egress requirements.  It simply stated that if a builder built a crappy house and it collapsed, whatever happened to the occupants would happen to the Builder.  If the homeowner’s son lost his legs in the collapse, then the builder’s son would have to have his legs removed.

The first codes in the U.S. were the results of massive fires in some of our larger cities. Chicago created a building code in 1875 after insurers threatened to cancel insurance for properties in that city. In 1915 Building Officials Conference of America (BOCA) was founded. They published the BOCA National Building Code.  This was used primarily in the east and Midwest.  In 1922 The Pacific Coast Building Code Conference (later the International Conference of Building Officials-ICBO) adopted the Uniform Building Code.  Finally, in 1940, the Southern Building Code Congress International (SBCCI) published the Standard Building Code. These were the three model codes that were used in the U.S. Today they are known as the legacy model code organizations.  In 1972 the Council of American Building Officials is formed and they produce the One and Two Family Dwelling Code.
In 1994 the three legacy codes created the International Code Council to develop a single set of model construction codes, publishing their first, The International Plumbing Code, in 1995.
One of the first orders of business for the three codes was to reorganize their codes to a single format.   This not only enabled the writers of the new International Codes to compare requirements of each code when creating the new code, it assisted users of the legacy codes to locate requirements in the new code easier.  An example is in the mid 90’s; all three codes’ Chapter on egress was changed to chapter 10.  When the International Code was published, users could easily find subjects although most found major changes to the subject matter.

What is a Code?

Building codes are regulations, when adopted by a municipality becomes law. Previously, most municipalities or states adopted one of the four model codes with amendments specific to their locale.
The purpose of building codes is to protect health, safety and welfare of the public by providing standards in construction.  I must stress that codes are minimum standards only.  The most important goal of codes is the protection of human life.  Property protection is also a concern of the code although life-safety always overrides property protection.  An example of this is slide bolts not being allowed on exit doors.  During the many inspections I’ve done of small commercial buildings, I have found rear exit doors secured with numerous “unapproved” locking devices.  I am told (by the owner) these are necessary to secure against break-ins. The code maintains life-safety over property protection and does not allow these locks. They must be removed.

Types of Codes

There are two types of codes-specification codes and performance codes. A specification code lists exactly what can be used.  For example Section 502.7.1 of the Residential Code requires Joist bridging to be …..”solid blocking, diagonal bridging, or a continuous 1-inch-by-3-inch strip nailed…..”  A performance code states a purpose that is intended and allows the designer to select the method of accomplishing this purpose. An example would be R801.2 “…..Ceiling construction shall be capable of accommodating all loads imposed…..”  The International Codes contain both types of codes.

Changes in the Code

The ICC publishes an updated set of codes every three years.  In the margin of the text you will see the occasional dark vertical line.  This means there has been a technical change in the code from the previous edition.  A small arrow indicates where an item has been deleted.  The State of Michigan, where I reside, makes state amendments to the ICC Codes.  The code is then published as The Michigan Building (Mechanical, plumbing etc.) Code.  In addition to the dark vertical lines and arrows, they use double vertical lines to indicate state changes to the code and an asterisk to denote International Code sections that were not adopted. While explaining how these changes are made to a code merits a whole other article, it is important to note that anyone can submit a code change, and hearings open to the public are held to discuss both sides of code changes.  Final say as to adopt or deny a change is left up to the “regulators”, those who enforce the code.

IBC vs. IRC

The scope of the International Residential Code and The International Building code is clearly defined.  Section 101.2 of the IRC defines it’s scope as construction, alteration……etc. of “detached, one- and two-family dwellings and townhouses not more than three stories above grade in height with a separate means of egress…”  The one and two family part is easy.  For townhouses we must look at its definition in chapter 2.  “….each unit extends from foundation to roof and with open spaces on at least two sides”.  Now we easily understand townhouses (remember separate means of egress and no more than 3 stories).  Let’s say we have a condominium complex where one building has units in the middle that meet the townhouse parameters.  On the ends of these units we have “stacked ranches”-different units on top of each other.  Even though we are providing a 2-hr horizontal separation (required 2-hr separation for townhouses in section R317.2), we are unable to use the IRC to build this building.  It must be reviewed under the IBC (bringing fire suppression into the picture).
Maybe not!! R317.2 considers each townhouse to be a separate building.  Could you secure permits for each townhouse and review it under the IRC and secure permits for the stacked ranches using the IBC for review.  I believe you can.  This is where the design professional should solicit the opinion of the local official in the predesign stages.

Referenced Standards

An interesting note on the IRC-it is an all inclusive document.  That is it not only contains the building requirements but also mechanical, electrical and plumbing codes.  Just read the 500 plus pages of the IRC and you’ll know all the requirements for building these dwellings.  Not really.  In chapter 43 of the IRC and in Ch 35 of the IBC we have a number of pages of “Referenced Standards”.  These standards become part of the code, sometimes partially or sometimes in their entirety, depending on how they are referenced.
An example of this would be “The Wood Frame Construction Manual for One-and Two-Family Dwellings” from American Forest and Paper Association (AF&PA).  This is reference in section R301.2.1.1 as one of the 5 methods of design for high wind/hurricane prone regions.  This document now becomes part of the code for these regions.

Free Advice

First and foremost, you should know which code the jurisdiction you are working in enforces.  You should have a copy of it also.  As far as understanding it, attending educational seminars is a great start but on any project I recommend you make contact with your local authority in the planning stages.  Contrary to common belief, most inspectors do not take pleasure in making you tear down what you have built.  Don’t wait until you’ve roughed-in 12 floors of a residential loft development before making contact with your inspector.

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