What Are the Rules for Putting on a Metal Roof?

Rules

• Though metal roof rules from local, state and some federal building authorities may differ slightly, they all primarily come from the International Residential Code developed by the International Code Council. This non-profit organization was founded in 1994 to “provide safe, sustainable and affordable construction through the development of codes and standards used in the design, build and compliance process.” It streamlined the rules and regulations from three separate codes. Its accomplishments also include the International Fire Code and the International Building Code.

Shingles

• Metal shingles have the texture and color of natural slate or wooden shakes, but with the durability of metal. They must go onto a solid or closely fitted roof deck, unless originally designed for spaced sheathing. The slope of the deck must rise at least 3 inches for every 12 inches of horizontal run, which is equal to a 25 percent slope. The necessary roof underlayment must comply with the American Society for Testing and Materials standards, and must be installed according to manufacturer’s instructions. The flashing on the roof valleys must extend at least 8 inches each way from the centerline, and have a splash diverter rib over 0.75 inches that is formed as part of the flashing.

Panel Basics

• Though more common in commercial, industrial and farm buildings, metal roof panels add a modern touch to private homes. They can go on solid or spaced sheathing, except when specifically designed for spaced supports. Roofs with lapped, non-soldered leaps and no applied lap sealant must have a minimum slope of 3:12, and the same roofs with applied lap sealants need a minimum slope of 0.5:12 (4 percent). Roofing systems with standing seams need a minimum slope of 0.25:12 (2 percent), which is very nearly flat.

Panel Options

• Metal roof panels must also meet ASTM standards, which vary depending on the material types, such as galvanized or stainless steel, lead-coated or cold-rolled copper, hard or soft lead, aluminum, tin or zinc. The panels must be attached according to manufacturer’s instructions. Steel roofs need galvanized fasteners. Copper roofs must have fasteners made from copper, brass, bronze, copper alloy or 300-series stainless steel. All metal roofs can use stainless steel fasteners. Underlayment must be installed according to manufacturer’s instructions.