Roofing Code: Chapter 15

Roofs and Roof Structures

Section 1507.3 Low-Slope Roof Coverings:

Low-slope roof covering materials and installations shall comply with Section 1507.3.1 through 1507.3.7. Roofs shall have a design slope of a minimum of one-fourth unit vertical in 12 units horizontal (¼ :12) for drainage except for coal-tar built-up roofs, which shall have a design slope of a minimum one-eighth unit vertical in 12 units horizontal (⅛ :12). The attachment of the insulation above the roof deck, the weight and distribution of ballast, the fastener type and fastening pattern, and the bitumen or adhesive application utilized in the installation of low-slope roof coverings shall meet the wind resistance requirements of Section 1505.2.

Code Interpretation:

This code implies that roof systems with a slope of ¼ inch per foot or less are considered low-slope roof systems. Roofs with slopes of ⅛ inch per foot or less require coal-tar bitumen. Roofs with slopes up to ¼ inch per foot can use the following systems:

• Built-up roofs
• Thermoset single ply
• Thermoplastic single ply
• Modified bitumen
• Spray-applied polyurethane foam
• Liquid-applied roof coatings
• Metal sheet roof coverings

Application of these systems must be in compliance with approved manufacturers’ installation instructions.

The code also implies that the selected roof materials must meet performance requirements of physical property testing, impact resistance and wind-uplift testing. The selected system must be tested by FM or ASCE for wind-uplift resistance, and the specific roof installation attachment must be completed in accordance with FM or ASCE design requirements. This includes insulation and fasteners, as well as all other roof components.

Waterproofing Code: Chapter 18

Dampproofing and Waterproofing

1807.2, Dampproofing Required:

Where hydrostatic pressure will not occur as determined by Section 1802.2.3, floors and walls for other than wood foundation systems shall be dampproofed in accordance with this section. Wood foundation systems shall be constructed in accordance with AF&PA Technical Report No. 7.

Code Interpretation:

This section implies that dampproofing is required for all below-grade floors and walls where hydrostatic pressure will not occur. ASTM defines dampproofing as the treatment of a surface or structure to block the passage of water in the absence of hydrostatic pressure. Fundamentally, it only has the ability to resist vapor migration. If soil analysis concludes that there is no hydrostatic pressure or if the water table is more than 6 inches below the lowest floor, then dampproofing may be considered.

Dampproofing is always applied at the exterior (wet) face of the wall. The most common dampproofing material for walls is a bituminous coating, either solvent-based (cutback asphalt) or emulsion, which is brushed, sprayed, roller-coated or troweled onto the substrate. Dampproofing systems may also include membranes. The general difference between waterproofing systems and dampproofing systems is that dampproofing membranes are a maximum of 10 mil thick, while waterproofing membranes exceed this thickness.

The section also implies that wood foundations shall be constructed in accordance with AF&PA Technical Report No. 7, “Basic Requirements for Permanent Wood Foundation Systems.”