ESSENTIAL KNOWLEDGE

The purpose of gutter and leader (downspout) systems is to collect rainwater from the roof and direct it away from the building foundation by means of leader extensions, splash blocks, or underground drain lines.

An improperly functioning gutter and leader system can contribute to water and ice backing up against fascias and under roof shingles, can damage soffits, and can discolor or deteriorate siding materials. Faulty gutters and leaders can also lead to soil erosion adjacent to buildings and serious water and foundation displacement problems in basements and crawl spaces.

Unfortunately, gutter systems take more abuse from extreme weather conditions, particularly ice and snow, than any other component of the building envelope. They are also subject to damage from ladders and being stepped on, as well as from falling treel limbs and debris.

Gutters are often sized according to the roof area they drain.

• Five-inch-wide K-style gutters are the residential industry's standard.
• Six-inch-wide K-style gutters are used for larger roofs.
• Half-round gutters are typically sized 1 inch wider than K-style to provide the equivalent capacity.

Therefore, 6-inch half-round gutters are equivalent to 5-inch K-style. Four-inch-wide K-style and 5-inch half-round gutters (with equivalent capacity) are rarely used except for small roofs.

Wider gutters may be required for certain hard surface roofing materials, such as slate and tile, or used on steeply-pitched roofs, to prevent water from shooting over the gutter. Gutters should be positioned tight against roofing materials and the fascia.

In heavy snow areas, snow guards should be used to prevent gutter tear-off. Vertical leaders (downspouts) are used to capture and distribute rain water to storm drainage systems, or by means splash blocks, to areas away from the building's foundation walls to prevent the build up of water in the soil and possible resulting structural or basement moisture problems.

Leaders are typically rectangular and of the same material as the gutter to prevent destructive galvanic actions. Connections between gutters and leaders and leaders and storm drains require continuing maintenance to assure the drain is free of leaves and debris and the connection has not become loose. Other maintenance points include the connections of leaders to the building.

Leader diameters are sized according to the roof area they drain. A rule of thumb used in the industry is that a 2-by 3-inch leader will suffice for a 600 sq. ft. roof and a 3-by 4-inch leader for 1,200 sq. ft. The typical leader size for a 5-inch K-style gutter is 2 by 3 inches, but 3 by 4 inches is preferable because it is less likely to become clogged and is easier to clean out.

Before 1960, most gutters were made of wood or metal in a "half-round" shape. During the 1960s, roll-formed metal gutter technology was introduced that allowed metal gutters to be made lighter and less expensively. Initially available primarily in galvanized steel, roll-formed gutters are now available in copper, aluminum, galvanized, and painted steel.

Gutter profiles (above) include half-round and square, but the K-style (also called formed, Ogee, or OG) predominates because it is visually compatible with recently-built housing and adds interest to simple fascia details. Recent developments in truck-mounted roll-forming equipment have allowed gutter installers to form continuous, seamless metal gutters to fit site-measured field dimensions and individual roof profiles.