Minimum slopes for metal roof panels shall comply with the following:
- The minimum slope for lapped, nonsoldered-seam metal roofs without applied lap sealant shall be three units vertical in 12 units horizontal (25-percent slope).
- The minimum slope for lapped, nonsoldered-seam metal roofs with applied lap sealant shall be one-half unit vertical in 12 units horizontal (4-percent slope). Lap sealants shall be applied in accordance with the approved manufacturer's installation instructions.
- The minimum slope for standing-seam roof systems shall be one-quarter unit vertical in 12 units horizontal (2-percent slope).
Metal-sheet roof covering systems that incorporate supporting structural members shall be designed in accordance with the California Building Code. Metal-sheet roof coverings installed over structural decking shall comply with Table R905.10.3(1). The materials used for metal-sheet roof coverings shall be naturally corrosion resistant or provided with corrosion resistance in accordance with the standards and minimum thicknesses shown in Table R905.10.3(2).
METAL ROOF COVERING STANDARDS
|ROOF COVERING TYPE||STANDARD APPLICATION RATE/THICKNESS|
|Galvanized steel||ASTM A653 G90 Zinc coated|
|Stainless steel||ASTM A240, 300 Series alloys|
|Lead-coated copper||ASTM B101|
|Cold-rolled copper||ASTM B370 minimum 16 oz/sq ft and 12 oz/sq ft high-yield copper for metal-sheet roof-covering systems; 12 oz/sq ft for preformed metal shingle systems.|
|Hard lead||2 lb/sq ft|
|Soft lead||3 lb/sq ft|
|Aluminum||ASTM B209, 0.024 minimum thickness for roll-formed panels and 0.019-inch minimum thickness for pressformed shingles.|
|Terne (tin) and terne-coated stainless||Terne coating of 40 lb per double base box, field painted where applicable in accordance with manufacturer's installation instructions.|
|Zinc||0.027 inch minimum thickness: 99.995% electrolytic high-grade zinc with alloy additives of copper (0.08 - 0.20%), titanium (0.07% - 0.12%) and aluminum (0.015%).|
For SI: 1 ounce per square foot = 0.305 kg/m2,
MINIMUM CORROSION RESISTANCE
|55% aluminum-zinc alloy coated steel||ASTM A792 AZ 50|
|5% aluminum alloy-coated steel||ASTM A875 GF60|
|Aluminum-coated steel||ASTM A463 T2 65|
|Galvanized steel||ASTM A653 G-90|
|Prepainted steel||ASTM A755a|
- Paint systems in accordance with ASTM A755 shall be applied over steel products with corrosion-resistant coatings complying with ASTM A792, ASTM A875, ASTM A463, or ASTM A653.
Metal roof panels shall be secured to the supports in accordance with this chapter and the manufacturer's installation instructions. In the absence of manufacturer's installation instructions, the following fasteners shall be used:
- Galvanized fasteners shall be used for steel roofs.
- Copper, brass, bronze, copper alloy and 300-series stainless steel fasteners shall be used for copper roofs.
- Stainless steel fasteners are acceptable for metal roofs.