The pitch matters for a variety of reasons, including the type of roofing material used, walkability, proportions to the building as a whole (which is sometimes a critical factor in some architectural styles such as a steep pitch in Gothic architecture and a low pitch in Classical architecture), and combinations of pitches to form distinctive roof shapes such as a gambrel roof. The basic ranges of pitch are not uniformly defined, but range from "flat", which are not perfectly flat but sloped to drain water up to 1/2:12 to 2:12 (1 in 24 to 1 in 6); "low-slope" roofing, which requires special materials and techniques to avoid leaks and ranges from 1:12 (2:12) to 4:12 (1 in 3); "conventional" from 4:12 (1 in 3) to 9:12 (3 in 4); and "steep-slope" roofing, which is above 9:12 (3 in 4) (21:12) (7 in 4) and may require extra fasteners.