It is not difficult to find gutter installers who will custom make the gutters to the exact lengths and shapes you need. Their gutter sheet metal is in long rolls, and they form it at your house. They should also be able to sell all the other parts you need and may be willing to give you some planning advice if you have not done it before.
Even if you have a single-story house, always have a helper to handle the long pieces because they are awkward up on a ladder. Wear all the appropriate safety clothing, gloves, helmet, etc., and have a cellphone nearby. I actually wear my motorcycle helmet and a climbing vest tied off from the chimney in case I fall.
Another option is to buy pre-formed gutters at your local home center store in 10-foot lengths. The quality of the materials is as good as those used by the fabricators, but these short lengths require many joints and seams. This increases the possibility of leaks, and it takes more time to install, but they are easier to handle.
When you select the gutter profile, consider the size you need. The size of gutters is measured across the top. Your typical choices are five- or six-inch gutters. Five-inch gutters are less expensive and slightly lighter to handle, but they cannot hold as much water in a hard rain. If your area typically has heavy downpours, it would be best to select six-inch gutters.
There are quite a few different types of gutter hardware and fittings you will need—various size outlets, outside and inside miters, elbows, downspouts, end caps, and hangers. Even though it costs a little more, it is best to buy these from the gutter fabricator to be sure they perfectly fit their gutter profiles.
You have two size choices for downspouts—two inch by three inch and three inch by four inch. In typical rain amounts, the smaller downspout can handle the water flow from about 600 square feet of roof area. The larger downspout can handle about twice that much roof area. The cost is not significantly different, so if you do not mind the appearance of the larger downspouts, select them.
When the fabricator forms the long gutter sections at your home, have them made several inches longer than you actually need. The shearing operation on the fabrication equipment can sometimes leave rough or deformed ends. You will likely have to cut off several of the ends to get the end caps and miters to fit on properly.
Cutting the thin gutter material without deforming it can be a little tricky. First, support the long gutter on sawhorses. Attach two blocks to the top of each sawhorse so the gutter does not slide back and forth. Use a fine-tooth hacksaw blade to cut the front so the profile detail is not deformed. The bottom and back can be cut with tin snips because they are flat. Wear heavy gloves because the cut edges, especially from the snips, can be sharp.
