Gutters & Downspouts

Gutters and downspouts for distributing rainwater should be the correct size, durable, attractive and well-suited to buildings on which they are used. Because specifications depend on gutter type and special considerations, such as roof construction, you should consult with a company specializing in gutter design and installation for product advice.

General guidelines for selecting and installing gutters include:
  • Select gutters at least 5 inches wide.
  • Select gutters made from galvanized steel (29 gauge minimum) or aluminum (0.025 inch minimum).
  • To enhance flow, slop sectional gutters 1/16 inch per 1 foot of gutter; slope seamless gutters 1/16 inch per 10 feet.
  • Use expansion joints at connections for straight runs exceeding 40 feet.
  • Keep the front of the gutter ½ inch lower than the back.
  • Provide gutter hangers at least every 3 feet; every 1 foot in areas of heavy snow load.
  • Select elbows with 45, 60, 75 or 90 degree angles, as needed.
General guidelines for selecting and installing downspouts include:
  • Space downspouts from 20 to 50 feet apart.
  • Provide 1-square-inch of downspout area for every 100 square feet of roof area. A 2-inch-by-3-inch downspout will accommodate 600 to 700 square feet; a 3-inch-by-4-inch downspout will accommodate up to 1,200 square feet.
  • Do not exceed 45-degree angle bends.
  • Select downspout configuration (square, round or corrugated round) depending on your needs.
  • Use 4-inch diameter pipes to convey water to storage containers or filters.