When replacing gutters in Des Moines, one of the first questions is: 5-inch or 6-inch? Most homes have 5-inch gutters, but 6-inch is becoming increasingly common — and for good reason. Here's how to decide.
The Difference in Capacity
A 6-inch K-style gutter handles approximately 40% more water than a 5-inch gutter. That's a significant difference — and in Iowa's increasingly intense rainfall events, that 40% matters.
Des Moines has experienced several 100-year rainfall events in the past 20 years. The rain intensity that would have been exceptional in 1980 is now occurring regularly. Gutters sized for historical rainfall are increasingly undersized for current Iowa weather patterns.
When 5-Inch Gutters Are Sufficient
- Smaller roofs (under 1,000 sq ft per gutter run)
- Low-pitch roofs that shed water slowly
- Minimal tree coverage (debris load is low)
- Homes in protected locations (less exposure to heavy rain events)
- Replacement in kind on an older home where 5-inch is standard
When to Upgrade to 6-Inch Gutters
- Larger roofs (over 1,200–1,500 sq ft per gutter run)
- Steep roof pitches that shed water rapidly into gutters
- Homes that experienced overflow with 5-inch gutters during heavy rain
- Significant tree coverage that can mat debris and restrict 5-inch flow
- New construction — the incremental cost is minimal when gutters are being installed for the first time
Our recommendation for Des Moines: For any home over 1,800 square feet, or any home that has experienced gutter overflow during heavy rain, we recommend 6-inch gutters. The upcharge from 5-inch to 6-inch is typically $1–$2 per linear foot — a modest investment for 40% more capacity.
Downspout Sizing Matters Too
A 6-inch gutter needs adequate downspout capacity to drain effectively. Standard 2x3 downspouts (appropriate for 5-inch gutters) may restrict flow on a 6-inch system. We typically recommend 3x4 downspouts with 6-inch gutters — larger opening, faster drainage.
Also, downspout spacing matters. One downspout per 40 feet of gutter is a rule of thumb for 5-inch systems. For 6-inch, one per 35 feet ensures the system drains before the next heavy rain event refills it.
Cost Difference
The upgrade from 5-inch to 6-inch seamless aluminum typically costs $1–$2 per linear foot. On a 150-foot home, that's $150–$300 more — a small premium for significantly better performance in Iowa's rainstorms. Almost always worth it on larger homes or any home with a history of overflow.
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Bottom Line
5-inch gutters are adequate for smaller homes and lower-pitch roofs. For any Des Moines home over 1,500–1,800 square feet, steep roofs, or homes with existing overflow problems, 6-inch gutters are the right choice. The cost premium is minimal; the performance difference is significant in Iowa's heavy rainfall events.