Choosing between 5-inch and 6-inch gutters requires a whole-system assessment. Nominal width alone does not tell you how much water a particular installation can collect and discharge. The roof catchment, local design rainfall, gutter profile and slope, outlets, downspouts, and discharge route all belong in the decision.
Start with the roof area feeding each run
A house can have several roof surfaces feeding different gutter sections. Its floor area is not a reliable substitute for that drainage layout. A valley can also concentrate flow at a local point, which is a different observation from a long run filling evenly.
The Minnesota Stormwater Manual calls for rainfall intensity and suitable hydraulic sizing methods when selecting roof drainage. USDA NRCS’s PA-1 worksheet illustrates that gutter geometry, slope, design rainfall and compatible downspouts are considered together. Those references are design background, not automatic approval of either size for a residential property.
What to ask about each proposal
- Catchment: Which roof surfaces feed each gutter run?
- Rainfall basis: What local design criterion or product sizing method is being used?
- Profile: What shape and dimensions are proposed, rather than only a nominal width?
- Outlets: How many are planned, and where will they be located?
- Downspouts: Are their size and routing coordinated with the gutter proposal?
- Discharge: Where will water go, and are connected drains included in the assessment?
A larger collection channel does not establish that an unchanged outlet or downstream pipe can accept the increased flow. Similarly, retaining the existing size may be reasonable only after the cause of any overflow has been explained.
Compare scope, compatibility, and maintenance
Ask whether the quoted work includes new supports, roof-edge adjustments, outlets, downspouts, removal, and repairs to damaged backing. Confirm how the chosen system fits the roof edge and how guards, if proposed, affect inspection and maintenance access.
A useful written explanation might state why the current drainage layout is adequate after a restriction is corrected, or why a different profile and outlet layout are required. “Six inches is always better” is not an adequate explanation. Neither is a universal percentage increase in capacity without stating the profiles and design assumptions being compared.
When overflow is the reason for upgrading
Document the symptom before comparing quotes. The provider should distinguish collection problems, restrictions and downstream issues. A size upgrade addresses only the parts included in its design and installation scope.
Begin with heavy-rain overflow, compare the types of gutter service work, and use our cost guide to check whether two estimates include the same components.
Sources and editorial review
Reviewed October 28, 2026. Design background: USDA NRCS PA-1 roof gutter and downspout worksheet and Minnesota Stormwater Manual design criteria. We do not reproduce a sizing table or supply a project-specific design calculation.