Metal Roof Guidelines for Roof Pitch

Roof Pitch

• The pitch, or slope, of a roof is associated with how steep it is and how quickly water drains from the roof. The pitch of a roof is calculated by determining the vertical rise in inches for every 12-inch horizontal length, or run, which is a convenient standard for the roofing industry. For example, a roof with 4 rise/12 run, or 4/12, is a roof that rises vertically 4 inches for every 12 horizontal inches.

Minimum Pitch

• Minimum pitch for metal roofing varies by product and use. Most metal panel systems can be applied to pitches of 1/12 or more, according to Metal Roofing Source. Factors include roof geometry -- one roof area might drain onto another, increasing its drainage -- the material the roofing is placed on and the project's physical location. Metal shingles require a 3/12 pitch, according to RoofKey.com.

  Effective drainage is always a major factor in making a decision about roof coverings. For example, metal corrugated panels should only be placed on roofs with a minimum pitch of 2/12, to prevent roof leaks.

Flat Roofs

• Low-slope roofing material is used for roofs that are nearly flat -- those under 3/12, commonly called flat roofs. Metal interlocking panels, also known as standing-seam roofing, that run vertically along the roof surface are what typically work best for low-slope, or flat, roofs, according to the Metal Initiative. Some panels can be used on pitches as low as 1/4 /12.

Maximum Pitch

• Most metal roofing products have no maximum pitch on which they can be used, due to their interlocking panels. However, the manufacturer's specifications should be strictly followed.