Roof building codes speak to what are roof building codes and why roof building codes.
These are specifications for manufacturing standards, minimum slopes, permitted underlayment materials and installation requirements for roofing materials.
The codes also regulate a roof’s required level of resistance to flame spread and fire penetration, tested according to standards ASTM E108 or UL 790 and rated as Class A, B or C roof coverings. Class A has the highest level of resistance to flame spread and fire penetration and class c has the lowest.
The International Building Code requires that roofs on buildings of Construction Types I, II-A, III-A, IV, or V-A meet at least Class B requirements and those on buildings of Construction Types II-B, III-B IV or V-A meet at least Class C requirements.
Roofs for single family homes and other small residential or utility buildings generally may be nonclassified, except that where portions of such roofs are located close to property lines, a minimum Class C rating is required. Property insurance policies or local building regulations such as may apply in dense urban areas or in areas prone to wildfire may also impose roof class rating requirements.
Roof class rating tests apply to whole roof assemblies, including the membrane, shingles or other covering underlayments, insulation decking and ballast, if any. Where a rated roof is required, the manufacturer of the roof covering should be consulted to determine the precise materials and construction requirements for meeting the classification.
Broadly speaking, most low slope roof membranes and non-combustible tiles such as concrete or clay as can some metal roof shingles and asphalt shingles made of glass felts. The same is true of other metal roof coverings which can meet Class B requirements. Also fire retardant wood shingles and shakes can meet Class C requirements.
Corrosion rates of metals are affected by the environment and as such are also regulated by building codes.
Exterior metals exposed to marine, salt laden air or to atmospheres laden with industrial pollutants will corrode at a faster rate than metals in less aggressive or more protected environments. The more severe the environment, the more important it is to avoid contact between dissimilar metals.
Where dissimilar metals must be combined in such environments, metal pairs with the least electrochemical potential difference, that is, as close to each other as possible in the galvanic series, are preferred.