BUILDING CODES FOR ROOFS
- By Larry Glass
- January 1st, 2003
Just about every building built in a populated area is required to meet certain standards laid out by a building code. While there are local building codes and state building codes, most of the building codes in the United States are patterned on one of four national building codes. Building codes are complex and can be confusing to those not in the construction industry. This article is intended to help make a little more sense of how building codes developed and what building codes say about low-sloped commercial roofing systems.
The first building code is attributed to the Babylonian emperor Hammurabi in 1800 BC. Most contractors today would not appreciate the severity of this code, which said that if a building collapsed and killed the son of the building owner, the contractor's son should be put to death! Throughout history most major civilizations adopted rules to protect the safety of building occupants.
In the United States, in the early 1900s, insurance companies encouraged the development of building codes to reduce property loss payouts due to inadequate construction standards. Not-for-profit associations were formed to develop construction standards. These standards were then adopted by municipalities and states as legally binding building codes.
Currently in the United States there are four not-for-profit code associations. The Building Officials and Code Administrators International, Inc. (BOCA) was established in 1915 and became the basis for many building codes in the northeast U.S. The International Conference of Building Officials (ICBO) was established in 1927 and provided the basis for many building codes in the Midwest and western United States. The Southern Building Code Congress International (SBCCI) was established in 1940 and, as the name indicates, became the basis for many building codes in the southern part of the U.S.
As time moved on, all of these building codes were revised and updated. When a building code is adopted by a governmental body, they cite a specific edition of the code that they are adopting. So when dealing with questions about a particular code, it is important to know which version is being cited (1994 UBC or 1997 UBC).
All of these codes were similar in language and organization, but there were differences between them. Designers, builders and owners who were national in scope had to know the differences between the codes when they operated in different parts of the country. In the late 1990s a movement began to consolidate these three building codes into one common code that would be applicable throughout the United States. In 2000, all three model code bodies agreed to adopt the International Building Code so that all of these organizations had the same "book."
To date, 40 states have adopted one or more parts of the International Building Code. It is estimated that within three years the International Building Code will be adopted by virtually every municipality in the nation. In the meantime, various states follow whatever code is on the books.
Today, building codes serve to protect the public and standardize building practices. The 2000 edition of the International Building Code states that its purpose isto establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress, facilities, stability, sanitation, adequate light and ventilation, energy conservation, and safety to life and property from fire and other standards attributed to the built environment.
The design professional, architect or engineer on a project has the ultimate responsibility to ensure that the building he or she designs meets the applicable codes. Many of the requirements of the codes require complex engineering calculations and are different for every building. "Do you meet the code?" is not necessarily a question that a nonprofessional can answer.
All of the codes discussed thus far are "performance based" codes. This means that the code requires the materials and finished building to meet certain performance criteria. For roofing systems, this criteria includes properties such as fire resistance, wind resistance, corrosion resistance, weatherability, etc. Building inspectors are the government’s agents in determining whether the building is "to code." Commercial buildings require a certificate of occupancy issued by the local building department before people can use the building. The design engineer determines what performance criteria are needed based on a lot of factors such as use/occupancy, location and/or structural requirements.
Most of the model code editions written after 1996 also include roofing product material requirements. Where certain types of roofing materials had industrywide standards, such as those adopted by the American Society for Testing and Materials (ASTM), they were included in the code. These later edition codes contain ASTM standards for built-up roofs, SBS modified bitumen, EPDM and PVC. They do not contain material standard references for APP modified bitumen and TPO.
Since there are no material standards listed in most of the codes for APP and TPO, does this mean that these materials cannot be legally used? Fortunately this is not the case. While the codes try to regulate the quality of materials used in building through material standards, they also recognize that alternate materials may be developed that will perform as good as, if not better than, those listed in the standards. To this end, most of the codes have provisions to use alternate materials.
The International Building Code (2000) allows for these alternate roofing materials in paragraph 1506.3 — "In the absence of applicable standards or where materials are of questionable suitability, testing by an approved testing agency shall be required by the building official to determine the character, quality and limitations of the materials."
If we know what the performance requirements of the roofing system is and we have UL/FM fire and wind uplift resistance tests to verify this performance, these materials may be used.
One commonly asked question for all of the codes is, "Do I have to use a thermal barrier on the deck if I use polyisocyanurate roof insulation?" The answer is a qualified "no" in most cases. All of the codes treat foamed plastic used in a roofing system differently from foamed plastic used in other parts of the building. Most foam plastics used in a building must be separated from the interior of the building by a thermal barrier. All of the codes allow the use of foam plastic roof insulation without a thermal barrier provided that the roof assembly passes FM 4450 or UL 1256.
Here is how the International Building Code handles it in paragraph 2603.4.1.5, "A thermal barrier is not required for foam plastic insulation that is a part of a Class A, B or C roof-covering assembly, provided the assembly with the foam plastic insulation satisfactorily passes FM 4450 or UL 1256."
FM 4450 is the series of tests required to get FM approval and appear in the FM Approval Guide. Any construction listed in the FM Guide has passed FM 4450. Passing UL 1256 results in a Roof Deck Construction listing.
While building codes can be convoluted and complex, the things you need to know about roofing are pretty straight forward and can make answering the question, "Do you meet the code?" a lot easier.