Codes and regulations play a large role in our day-to-day business operations. They dictate what is required on projects and influence everything from material selection to application techniques. The codes and regulations are constantly changing and it appears we are headed into an environment where regulations will increase and became more stringent.
Codes and regulations play a large role in our day-to-day business operations. They dictate what is required on projects and influence everything from material selection to application techniques. The codes and regulations are constantly changing and it appears we are headed into an environment where regulations will increase and became more stringent. Chapter 15 of the International Building Code addresses Roof Assemblies and Rooftop Structures. Some of the key codes that roofing contractors should be familiar with are addressed in this article.
1503.1 General. Roof decks shall be covered with approved roof coverings secured to the building or structure in accordance with provisions of this chapter. Roof coverings shall be designed, installed and maintained in accordance with this code and the approved manufacturer’s instructions such that the roof covering shall serve to protect the building or structure.
Code interpretation: The obvious implication of this section is that structural roof decks must be covered with an approved weatherproofing material. Materials and application methods should be in accordance with the sections of the code and manufacturers’ requirements. The code provides sections for design, materials and application methods of low-slope and steep-slope roof assemblies.
1504.1 Wind resistance of roofs. Roof decks and roof coverings shall be designed for wind loads in accordance with Chapter 16 and Sections 1504.2, 1504.3, and 1504.4.
1504.3.1 Other roof systems. Roof systems with built-up, modified bitumen, fully adhered or mechanically fastened metal panel roof systems, and other types of membrane roof coverings shall also be tested in accordance with FM 4450, FM 4470, UL 580 or UL 1897.
Code interpretation: The code implies that all low-slope roof systems shall be tested for wind uplift attachment. The results of the wind uplift test provide a maximum design pressure for the roof system. A wind uplift calculation should then be performed to determine the design pressure for the specific building and determine which roof materials can be applied. Wind uplift calculations should be completed for every project.
Proper roof attachment can be determined in accordance with FM requirements or ASCE standard wind uplift calculations. The procedure to determine wind uplift pressure ratings on specific buildings during the design phase is based on a calculation that takes into account the basic wind speed in the geographical area, ground surrounding the building and the roof uplift pressure at the field of the roof. The building’s height and perimeter construction are also considered. It is the responsibility of the specifier to complete these calculations and to determine the proper wind uplift rating for the building. Only materials and systems that meet the calculated uplift pressures should be applied.
1506.2 Compatibility of materials. Roofs and roof coverings shall be of materials that are compatible with each other and with the building structure to which the materials are applied.
Code interpretation: This section implies that the materials used in roof assemblies shall be compatible with the system and the structure. Based on this code it is always a best practice to use all system components - such as the membrane, flashings, and accessories - provided by the manufacturer for the system assembly. It is also imperative that there is compatibility of metals in the assembly.
Make certain that the system assembly meets the structure’s physical components of slope and wind design pressure.
REQUIREMENTS FOR ROOF COVERINGS
1507.2 Asphalt shingles. The installation of asphalt shingles shall comply with the provisions of this section.
1507.2.1 Deck requirements. Asphalt shingles shall be fastened to solidly sheathed decks.
1507.2.2 Slope. Asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17 percent slope) or greater. For roof slopes from two units vertical in 12 units horizontal (17 percent slope) up to four units vertical in 12 units horizontal (33 percent slope), double underlayment application is required in accordance with Section 1507.2.8.
Code interpretation: This section implies that the application of asphalt shingles can only occur on roofs with slopes of 2:12 or greater. Underlayments are required on all asphalt shingle applications. If the slope of the roof is between 2:12 and 4:12 - considered a low-slope roof - then a minimum of two layers of underlayment is required. Underlayment application shall be in accordance with Section 1507.2.8.
Shingle attachment shall be completed with approved nails and not less than four fasteners for strip shingles and two fasteners for individual shingles. A minimum of six fasteners is required for shingles in high-velocity wind zones.
1507.2.3 Underlayment. Unless otherwise noted, required underlayment shall conform to ASTM D 226, Type I, ASTM D 4869, Type I, or ASTM D 6757.
1507.2.4 Self-adhering polymer modified bitumen sheet. Self-adhering polymer modified bitumen sheet shall comply with ASTM D 1970.
Code interpretation: These sections imply that underlayment used for asphalt shingle applications shall be manufactured of fiberglass felt, organic felt, modified bitumen or self-adhering modified bitumen. The underlayment shall be applied in one layer for slopes of 4:12 or more and in accordance with Section 1507.2.8 Underlayment application, which states: “Underlayment shall be applied in shingle fashion, parallel and starting from the eave and lapped 2 inches (51 mm), fastened sufficiently to hold in place. Distortions in the underlayment shall not interfere with the ability of the shingles to seal.”
Underlayment securement to the deck shall be completed in accordance with ASCE 7. Application of underlayment in high-velocity wind regions shall comply with Section 1507.2.8.1 High wind attachment, which states that corrosion-resistant fasteners must be used and fastened at the overlap at a maximum of 36 inches (914 mm) on center.
Section 1507.13 Thermoplastic single-ply roofing. The installation of thermoplastic single-ply roofing shall comply with the provisions of this section.
1507.13.1 Slope. Thermoplastic single-ply membrane roofs shall have a design slope of a minimum one-forth unit vertical in 12 units horizontal (2-percent slope) for drainage.
1507.13.2 Material standards. Thermoplastic single-ply roof coverings shall comply with ASTM D 4434, ASTM D 6754, ASTM D 6878 or CAN/CGSB 37-54.
Code interpretation: This section implies that thermoplastic roof systems shall be applied on roof substrates that have a minimum slope of two percent or 1/4 inch in 12 inches. Proper roofing industry standards require that the slope of the deck shall be sufficient to remove all standing water from the roof system within a maximum of 48 hours after a rainfall. The roof deck slope must comply with IBC requirements (1/4 inch in 12 inches). If this slope is not adequate to remove all standing water from the system, artificial means (such as tapered insulation) may be required.
The section also implies that the thermoplastic materials must meet the requirements set forth by ASTM (American) or CGSB (Canadian) standards for physical property testing. Physical property tests typically include moisture resistance, tensile, elongation, mil thickness, accelerated weathering and wind uplift testing.
Author’s note: The section provided for thermoplastic single-ply roofing is similar to all low-slope roof sections. The requirements for slope and testing are identical in all sections for built-up, modified bitumen, thermoset and SPF systems.
1508.1 General. The use of above-deck thermal insulation shall be permitted provided such insulation is covered with an approved roof covering and passes the tests of FM 4450 or UL 1256 when tested as an assembly.
Exceptions: Foam plastic roof insulation shall conform to the material and installation requirements of Chapter 26.
Where a concrete roof deck is used and the above-deck thermal insulation is covered with an approved roof covering.
Code interpretation: This section implies that insulation used in roof assemblies must be covered with an approved weatherproofing material. The section also implies that insulation used in roof assemblies is subjected to similar physical property testing and performance testing - in stand-alone conditions and system assemblies - as are all other roof system components. Knowledge of the codes could eliminate costly mistakes on projects.
Web Exclusive: Important Roofing Codes
August 1, 2009