Common Roof Pitches

Flat Roof

• Any roof with a pitch less than 2/12, or 2 inches of rise for every 12 inches of run, is said to be a flat roof. From a framing standpoint, these roofs are easy to build. Their serious downside is that they are prone to leaks, as they do not force any water to runoff quickly. For this reason, flat roofs are much more common in dry areas with little precipitation. To prevent moisture penetration, flat roofs are covered with a solid membrane instead of shingles or tiles.

Low Slope

• A low slope roof is one with a pitch between 2/12 and 4/12. Low slope roofs are still fairly vulnerable to moisture and are often treated much like flat roofs in construction. They are generally not covered with shingles or tiles, although they may be in low precipitation areas.

Conventional Slope

• The range for a conventional slope roof is a pitch between 4/12 and 9/12. Roofs of this pitch are quite common and are more the "average" slope to find. They strike a balance among water resistance, cost and overall durability. Shingles and tiles are common for covering roofs of this pitch, and construction and maintenance are straightforward.

Steep Slope

• A roof is considered to have a steep slope with a pitch at or greater than 9/12. These roofs add a striking visual element to construction, but they tend to be much more expensive to build, often as much as 50 percent more expensive. They require specially engineered trusses for support and present a challenge and potential safety hazard to anyone needing to walk on them for construction or maintenance. They do a fantastic job of displacing water however, and are attractive for this purpose in areas with a lot of precipitation. That effectiveness comes with a catch, however, as the eaves troughs and downspouts must be designed to accommodate the large amounts of water that these roofs will displace in short amounts of time.