Roofing system materials, installation methods, and wind resistance design.
2
hours
0.2
CEUs
Building Construction
1.7.1
This course covers material relevant to the following ICC certification exams:
Roofing system materials, installation methods, and wind resistance design.
Format
On-Demand Online
Delivery
Self-Paced
Access
24/7 After Enrollment
Certification
Certificate of Completion
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Contact our support teamUnderstand roofing material types and weather resistance properties
IBC Chapter 15 governs roof assemblies and rooftop structures, establishing minimum performance criteria for every roof covering installed on a building within the jurisdiction. The starting point for any roof-related plan review or inspection is determining the roof covering classification. Per ASTM E108 (or UL 790), roof coverings are tested and classified as Class A, Class B, or Class C based on their resistance to fire exposure from sources outside the building. Class A coverings are effective against severe fire exposure, Class B against moderate exposure, and Class C against light exposure. IBC Section 1505.1 requires a minimum Class C rating for all roof coverings unless the building is located in a region where the fire code official has determined that a higher class is necessary due to wildland-urban interface conditions or local fire history.
Asphalt shingles remain the most common steep-slope roof covering in residential and light commercial construction. Shingles must comply with ASTM D3462 (fiberglass-reinforced) or ASTM D7158 for wind resistance classification. Under ASTM D7158, shingles receive a Class D (90 mph), Class G (120 mph), or Class H (150 mph) wind speed rating. The design professional must select a shingle class that meets or exceeds the basic design wind speed mapped in ASCE 7, Figure 26.5-1, adjusted for the building's exposure category and risk category. Fastening patterns are critical: standard application calls for four nails per shingle strip, but IBC Section 1507.2.7 requires six nails per strip in areas where the basic wind speed equals or exceeds 110 mph, or on slopes exceeding 60 degrees (approximately 21:12 pitch).
Built-up roofing (BUR) systems use multiple plies of reinforcing felt or fabric alternated with bitumen (asphalt or coal tar) to form a continuous waterproof membrane. Modified bitumen roofing uses factory-fabricated sheets with polymer-modified asphalt (APP or SBS modifiers) applied in one or two plies by torch, hot mopping, cold adhesive, or self-adhesion. Both systems must comply with IBC Section 1507.11 (BUR) and Section 1507.12 (modified bitumen), and must meet the applicable fire classification under ASTM E108.
An inspector arrives at a new residential subdivision where shingle installation is underway during a period of sustained high winds. The approved plans specify ASTM D7158 Class H shingles for a location with 130 mph basic design wind speed. The inspector observes that the roofing crew is using four nails per shingle rather than the required six. The shingle wrappers on site confirm the product meets Class H, but the fastening pattern does not comply with IBC 1507.2.7. The inspector issues a correction notice requiring the already-installed courses to be removed and reinstalled with six-nail fastening. This scenario illustrates why field verification of fastening patterns matters as much as material selection: the best shingle product fails if attachment is insufficient for the design wind speed.
Frequent field errors include using the wrong nail length (nails must penetrate the deck at least 3/4 inch or through the thickness of the sheathing), placing fasteners too high on the shingle (above the adhesive strip), and failing to offset shingle joints by the minimum 4 inches required between courses. Another common mistake is omitting the required starter strip along eaves and rakes. Correction begins with verifying the approved product data sheet, confirming the applicable wind speed zone, and cross-referencing the fastening schedule against IBC Section 1507.2.
Code Reference: IBC Sections 1505, 1507.2 and ASTM D3462/D7158 - Roof covering fire classification and asphalt shingle material and wind resistance standards.
Apply roofing installation techniques and fastening requirements
Single-ply membrane roofing dominates the low-slope commercial market. The three primary types are thermoplastic polyolefin (TPO), ethylene propylene diene monomer (EPDM), and polyvinyl chloride (PVC). Each membrane type has distinct seaming methods: TPO and PVC are heat-welded using hot-air equipment, while EPDM is typically joined with adhesive or tape. IBC Section 1507.13 governs thermoset (EPDM) single-ply roofing, and Section 1507.12 covers thermoplastic (TPO, PVC) systems. All single-ply membranes must be attached to resist the design wind uplift pressures calculated per ASCE 7, Chapter 30. Attachment methods include mechanically fastened (screws and plates through the membrane into the deck), fully adhered (membrane bonded to insulation or substrate), and ballasted (held in place by aggregate or pavers, limited to areas with basic wind speeds of 110 mph or less).
Metal roof panels are governed by IBC Section 1507.4. Structural standing-seam metal roofing provides both the weather barrier and structural deck function, while architectural metal panels are applied over solid sheathing. Metal roofing must meet the wind resistance requirements of UL 580 or the manufacturer's tested assembly data. Fastener type, spacing, and clip design are critical: concealed-fastener standing-seam panels use sliding clips that allow thermal movement while maintaining uplift resistance, whereas exposed-fastener panels rely on screw pullout and pull-through capacity.
Underlayment is the secondary weather barrier beneath the primary roof covering. IBC Section 1507.1 establishes general underlayment requirements, and Section 1507.1.1 specifically addresses ice barrier requirements. In areas where the average daily temperature in January is 25 degrees F or less (per the code's climatic data), an ice barrier must extend from the eave edge to a point at least 24 inches inside the exterior wall line of the building. The ice barrier must be a self-adhering polymer-modified bitumen sheet complying with ASTM D1970. This provision targets ice dam protection, which prevents meltwater backup under shingles from entering the building envelope.
Flashing is required at all roof-to-wall intersections, valleys, roof penetrations, changes in roof slope, and where the roof meets vertical surfaces. IBC Section 1503.2 requires flashing to be corrosion-resistant metal or an approved alternative. Step flashing at sidewalls must extend at least 4 inches onto the roof surface and at least 4 inches up the vertical wall, with each piece overlapping the next by at least 2 inches.
A commercial building in a northern climate zone is receiving a new TPO membrane roof over rigid insulation. During inspection, the inspector verifies that the membrane manufacturer's wind uplift rating matches or exceeds the calculated ASCE 7 corner, perimeter, and field zone pressures shown on the approved plans. The corner zones require mechanically fastened attachment at 12-inch spacing, while the field area uses 24-inch spacing. The inspector discovers that the installer has used uniform 24-inch spacing across the entire roof, including the corners. This creates a non-compliant condition at the corners and perimeter, where wind uplift pressures are significantly higher. The correction requires additional mechanical fasteners in the enhanced zones before the membrane cover sheet is installed.
Common errors with single-ply installation include incomplete heat welds (tested by probing seam edges), improper flashing termination at parapet walls, and failure to vary fastener density across wind zones. For metal roofing, frequent mistakes include over-torquing exposed fasteners (crushing neoprene washers and creating leak points) and omitting thermal expansion provisions on long panel runs. Underlayment errors include installing ice barrier only at the eave drip edge rather than extending it 24 inches past the interior wall line. Each error is corrected by referencing the specific IBC section and the manufacturer's installation instructions, which are enforceable when the product is part of a tested assembly.
Code Reference: IBC Sections 1507.4, 1507.12, 1507.13, 1507.1.1, and 1503.2 - Single-ply, metal roofing, underlayment, ice barrier, and flashing provisions.
Understand wind resistance design and ratings for roofing systems
Wind uplift is the dominant structural force acting on roof coverings. ASCE 7, Chapter 30, divides every roof into three pressure zones: interior field (Zone 1), perimeter (Zone 2), and corner (Zone 3). Corner zones experience the highest negative pressures due to vortex effects and are typically two to three times the field zone pressure. The roof covering attachment system must resist these calculated pressures with an adequate factor of safety. Factory Mutual (FM) Global ratings, UL 580 classifications, and SPRI wind design standards are the primary third-party frameworks for demonstrating roof assembly wind resistance. An FM 1-60 rating, for example, means the assembly withstands 60 pounds per square foot of uplift pressure. The design professional must calculate the required uplift resistance for each zone and specify an assembly rated to meet or exceed that value.
Roof drainage is addressed in IBC Section 1502 and must be designed to prevent ponding, which adds dead load and accelerates membrane deterioration. Primary roof drains must be sized per the International Plumbing Code, and overflow drainage (scuppers or secondary drains) must be provided per IBC Section 1502.2 to prevent structural overload if primary drains are blocked. The overflow system must be set 2 inches above the primary drain inlet.
Reroofing is governed by IBC Section 1511. When a new roof covering is applied over an existing covering, the total number of roof covering layers is limited to two for asphalt shingles and certain other materials. Before reroofing, the existing roof must be inspected for structural adequacy to support the additional weight. IBC Section 1511.3 requires complete removal of existing coverings when the existing roof has two or more applications, when the existing covering is wood shakes or slate, or when the existing deck is structurally inadequate. For recovering (overlay), the existing surface must be in a condition that allows proper attachment of the new covering. Reroofing also triggers compliance with current code requirements for underlayment and ice barriers, even when the underlying structure is not otherwise being modified.
A building owner submits a permit application to install a second layer of asphalt shingles over an existing single layer on a 20-year-old residence. The plan reviewer checks IBC Section 1511 and confirms that one recover is permitted over a single existing layer of asphalt shingles. However, the reviewer also notes that the jurisdiction has adopted the current code cycle, which requires ice barrier underlayment in this climate zone. Since the ice barrier cannot be installed without removing the existing shingles at the eaves, the reviewer requires tear-off along the eaves to a minimum of 24 inches past the exterior wall line so that a compliant ice barrier can be installed before the new shingle layer goes on. The remaining field area may be recovered without removal, provided the existing surface is suitable for attachment.
Common reroofing errors include failing to verify the number of existing layers before permitting a recover, not requiring structural evaluation when adding significant weight (such as converting from shingles to tile), and overlooking the requirement that current underlayment and ice barrier standards apply to reroofing projects. Wind design mistakes include using field zone uplift pressures for the entire roof rather than calculating separate corner and perimeter values. Corrections require recalculating zone pressures per ASCE 7 Chapter 30 and verifying that the specified assembly meets the highest applicable pressure in each zone.
Code Reference: IBC Sections 1502, 1511 and ASCE 7 Chapter 30 - Roof drainage, reroofing requirements, and wind uplift zone design methodology.
Roofing system compliance requires integrated understanding of material classification, installation standards, wind uplift design, and reroofing limitations. Effective plan reviewers verify that the specified roof covering classification meets the site's fire exposure requirements, that wind resistance ratings match ASCE 7 design pressures for each roof zone, and that underlayment and ice barrier provisions are addressed. Field inspectors confirm that fastening patterns, seam integrity, flashing details, and drainage systems match approved plans and manufacturer installation instructions. When reroofing projects are submitted, both the structural adequacy of the existing assembly and the applicability of current code requirements to the new covering must be evaluated. Consistent application of IBC Chapter 15 provisions, combined with knowledge of the referenced ASTM, ASCE, and FM standards, produces durable roof systems that protect buildings and occupants across their full service life.