The overall square footage of a house has little to do with gutter size. The size of gutters pertains to how well they will function. How big each individual roof area is and what material the roof is made of dictate the necessary gutter and downspout size.
5" gutters with 2" x 3" downspouts are the most common size gutter in Michigan.
6" gutters and 3" x 4" downspouts are typically referred to as "commercial" gutters. They are gaining in popularity primarily because steel roofs are more prevalent, and homes are getting bigger (think "barndominiums").
6" gutters hold about 50 percent more water than 5" gutters.
Michigan averages about 30" of rainfall a year. There are some tedious calculations and formulas you can use to calculate gutter and downspout size using several factors, but our real-world experience across northern Michigan has led to create these guidelines:
By default, 5" gutters are for shingle roofs; 6" gutters are for steel roofs.
The velocity of water flowing from a steel roof often overshoots a 5" gutter. To make sure all that water is captured and not left to ruin your foundation and sidewalks, we recommend a larger gutter.
Occasionally a shingle roof will have a large roof area, or there will be several roof valleys draining together, so a 6" gutter is needed so the system performs as expected.
When one of our experienced estimators comes out to measure your home, they will leverage our combined decades of experience to make a recommendation.
Sometimes a home just has a "large" presence, so a 6" gutter with larger 3" x 4" downspouts will look more proportionate.
Upgrading to 6" gutters will cost about 30 percent more than 5" gutters. That investment includes the larger gutters and 3" x 4" downspouts. We think it’s worth it because of the water damage it prevents.
On a side note, 3" x 4" downspouts can be used on 5" gutters. This helps if you have two or more valleys draining into one section of gutter, or a section of gutter over 40' and only want one downspout. Using this combination of sizes also greatly reduces the chance of your gutters getting clogged at the downspouts if you don't have a leaf guard system installed.
If you’re getting ready to replace or install new gutters, use this guide as you walk around your home, take measurements and consider your best options. Or give us a call to schedule a free estimate and we’ll do it for you.