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New building code offers unified standards

IBC will provide uniform minimum building standards

by Mark S. Graham

A new model building code, the International Building Code (IBC), recently has been published by the International Codes Council (ICC). This new model building code is intended to eventually replace the existing model building codes—Standard Building Code, The BOCA [Building Officials and Code Administrators International Inc.] National Building Code and Uniform Building Code—and provide one model building code that applies throughout the United States and possibly internationally.


ICC was established in 1994 as a nonprofit organization dedicated to developing and maintaining a single set of comprehensive, coordinated national building codes. ICC's founders are the three major U.S. model building code groups: BOCA, International Conference of Building Officials and Southern Building Code Congress International Inc.

From 1995 through 1999, ICC developed and began to publish a series of new national model codes, including the following:

  • International Plumbing Code (IPC)

  • International Private Sewage Disposal Code

  • International Mechanical Code

  • International Fuel Gas Code

  • International Zoning Code

  • International Property Maintenance Code

  • International Energy Conservation Code

In 1997, the Council of American Building Officials (CABO) was incorporated into ICC. CABO previously had published its own codes, including the CABO One- and Two-Family Dwelling Code and CABO Model Energy Code. In 1998, ICC updated the CABO One- and Two-Family Dwelling Code and titled it International One- and Two-Family Dwelling Code.

In addition to publishing IBC, ICC plans to publish the International Residential Code (IRC), International Fire Code and ICC Electrical Code. IRC is intended to replace the International One- and Two-Family Dwelling Code. ICC's 11 model codes, commonly referred to as "I-codes," provide a comprehensive, coordinated set of model building codes for adoption by code jurisdictions throughout the United States.


NRCA and several other roofing industry organizations participated in IBC's development. IBC consists of 35 chapters. A majority of roofing-related code requirements are provided in Chapter 15, "Roof Assemblies and Rooftop Structures." However, some roofing-related requirements are provided in the code's other chapters. For example, requirements for attic ventilation are outlined in Chapter 12, "Interior Environment." Minimum requirements for thermal insulation for roof systems are provided in Chapter 13, "Energy Efficiency," and wind-load requirements are offered in Chapter 16, "Structural Design Requirements." Below-grade dampproofing and waterproofing requirements can be found in Chapter 18, "Soils and Foundations."

Roofing requirements

Chapter 15 governs overall roof assembly and rooftop structure design, materials, construction and quality. The chapter is divided into 10 sections. (See Figure 1 for a list of the sections' titles.)

Section 1502 provides terms and definitions specific to Chapter 15. In addition, Chapter 2, "Definitions," lists terms and definitions that apply throughout the code.

Section 1503's requirements apply to all roof assemblies, including flashings, parapet copings, and drainage system and attic ventilation design. For example, this section indicates roof drains, gutters and downspouts are required to be sized according to IPC.

Wind resistance

Section 1504 provides specific performance requirements for all roof assemblies, including requirements for physical properties, as well as impact and wind resistances. All roof assemblies are required to be designed to resist wind loads that are explained in Chapter 16. Asphalt shingle roof assemblies are exempt from this requirement; they must be attached to roof decks according to the prescriptive fastening requirements provided in Section 1507.2.

IBC requires roofs' resistances to wind loads be tested according to FM 4450, "Approval Standard for Class 1 Insulated Steel Deck Roofs"; FM 4470, "Approval Standard for Class 1 Roof Coverings"; UL 580, "Tests for Wind Uplift Resistance of Roof Assemblies"; or UL 1897, "Uplift Tests for Roof Covering Systems," for built-up, polymer-modified bitumen, fully adhered and mechanically attached single-ply, metal panel and other membrane roof systems.

Ballasted single-ply roof systems' wind resistances are required to be designed according to ANSI/RMA/SPRI RP-4, "Wind Design Guide For Ballasted Single-Ply Roofing Systems."

Fire resistance

Section 1505 details fire-resistance classification requirements for roof assemblies. Generally, all roof assemblies are required to have fire-resistance classifications. Specific classification requirements primarily are based on type of building construction, as prescribed in Chapter 6, "Types of Construction." Fire-resistance classifications typically are determined by testing according to ASTM E 180, "Standard Test Methods for Fire Tests of Roof Coverings," or ANSI/UL 790, "Tests for Fire Resistance of Roof Covering Materials."

Brick, masonry, slate, clay or concrete tile, exposed concrete deck, ferrous or copper shingle, and panel roof coverings are considered to have Class A fire-resistance classifications without being tested. Similarly, metal sheet or shingle roof systems are considered to have Class B fire-resistance classifications without testing.


General roof system requirements, such as component compatibility, physical characteristics and specifications, are addressed in Section 1506. This section also outlines product identification requirements for roofing materials' labeling. According to IBC, roofing materials' packaging must bear manufacturers' and approved testing agency's (e.g., Factory Mutual [FM], Underwriters Laboratories [UL] Inc.) labels identifying the materials' fire-resistance classifications.

For example, such labeling should include a product's name and manufacturer; American Society for Testing and Materials (ASTM) or other material standard designation; and approved testing agency approval.

Materials standards

Section 1507 provides requirements for the following roof systems: asphalt shingle; clay and concrete tile; metal panel and shingle; slate; wood shingle and shake; spray polyurethane foam; liquid-applied; built-up; polymer-modified bitumen; and thermoplastic and thermoset single-ply membranes.

For each roof system addressed, specific minimum requirements are provided for deck, slope, materials and application. Generally, roofing materials are required to comply with consensus-based materials standards. Figure 2 provides a list of the specific materials standards referenced in IBC.

Other requirements

Section 1508 provides general requirements for insulation used in roof assemblies. Wood fiberboard insulation must comply with requirements in Chapter 23, "Wood." Foam plastic roof insulation is required to comply with requirements in Chapter 26, "Plastic."

Section 1509 details requirements for structures that sometimes are built on roofs. Specific requirements are provided for penthouses, tanks, cooling towers, towers, spires, domes and cupolas.


Section 1510 details IBC's requirements for reroofing applications. Reroofing situations need to be treated the same as new construction applications, with one notable exception—reroofing applications are not required to meet minimum design slope requirements for new construction (e.g., ¼ inch per foot [1.2 degrees]) provided roofs have positive drainage. The code's definition of positive drainage is similar to the definition in The NRCA Roofing and Waterproofing Manual, Fourth Edition: a drainage condition in which consideration has been made for all loading deflections of a roof deck and additional slope has been provided to ensure a roof will drain within 48 hours of precipitation.

Roof system removal and replacement, instead of re-cover applications, are required if an existing roof system is wet or has been re-covered. IBC does not permit re-covering of existing wood shake; slate; or clay, cement or cement-asbestos tile roof systems.

Code adoption

Now that IBC is published, individual code jurisdictions (e.g., state, county, municipal governments) can adopt it as the basis for their building codes.

NRCA is aware of several code jurisdictions that either are considering or already have begun the process of adopting IBC. These include Illinois, New York, North Dakota, Pennsylvania, Rhode Island, Wisconsin and Chicago. Additional code jurisdictions likely will adopt and enforce IBC by the end of the year. At press time, the extent to which the code will be adopted internationally was unclear.

Closing thoughts

Although IBC is the most stringent of the current model building codes, roofing professionals likely will find its adoption to be beneficial because, unlike other codes, IBC features a relatively easy-to-follow format, as well as technical accuracy.

However, these advantages will not be seen for several years. Once IBC is accepted universally, a single set of model building codes that provides the technical basis for code adoption and enforcement throughout the United States will benefit the entire construction industry.

Mark S. Graham is NRCA's associate executive director of technical services.

Copyright 2004 National Roofing Contractors Association