Steel, Aluminum, Vinyl

• Most gutters are made of galvanized steel, aluminum or vinyl. All are formed the same way, either in a semi-circle called a round gutter or in what's called K-style, with a flat back and bottom and a front that is curved upward in various angles with a lip at the top. Downspouts are either round, for round gutters, or rectangular, for K-style. The usual sizes are four-inch or five-inch, depending on the roof drainage.
  
  

Slopes and Spacing

• Gutters need to slope at least 1/4 inch for every 10 feet to drain properly. Downspouts must be installed at one end of a straight run gutter or on both ends and in the center on a longer gutter; put downspouts at least every 20 feet. Slope gutters just in one direction on short runs, like beside a porch. Slope gutters from the center, toward both ends, for longer runs. Use downspouts on both ends of a long run.
  
  

Use Downspout Elbows

• Attach downspouts to gutters with whatever technique is recommended by the manufacturer. This will vary with materials; metal downspouts are usually attached with screws, vinyl gutters may just snap into place. Put an elbow spout just below the gutter downspout opening, turned toward the house so the gutter can attach to a wall. Secure downspouts to a wall with mounting straps, which fit over the spout and either nail or screw to the wall. Stop the downspout about 18 inches off the ground and put on another elbow to turn it out, so water runs away from the house.
  
  

Install With Hangers

• Install gutters with hangers, which usually clip on or snap over the gutter sections. Start a slope one inch down from the shingle away from the downspout location. Drive a nail there and fasten one end of a chalk line to it. Move to the downspout location and mark the slope, 1/4-inch per 10 feet, and then snap a chalk line between those points as a guide for hangers, which are nailed or screwed to the fascia or facing board on the roof.
  
  

Test the Flow

• Test the gutters and downspouts by pouring a bucket of water into the high end. Look for any leaks at seams or downspout junctions and repair any loose connections. Put caulk on the inside of the gutter at a leaky seam if you can't fix it any other way. Watch where the downspout drains; if it does not move water far enough from the house foundation, add an extender to direct it farther away.