08/19/2026
If your gutters overflow during heavy rain, cleaning them probably won’t fix it.
Every gutter system has a capacity limit — a maximum amount of water it can move per hour. That limit is set by three things: gutter size, how many downspouts you have, and how much roof is draining into them.
Standard 5-inch gutters handle a specific flow rate. A 6-inch system moves considerably more. But if a large roof is feeding an undersized system with too few downspouts, no amount of cleaning changes the math.
Here’s what makes it confusing: undersized gutters don’t fail gradually. They work perfectly through light rain, then overflow the instant volume exceeds the rate. Same gutters, completely different behavior — which is why homeowners assume it’s a clog.
The overflow goes somewhere. Down the fascia. Into landscaping. Beside the foundation. One storm won’t hurt. A decade of storms will.
If yours overflows regularly, the question isn’t whether they’re clean. It’s whether they’re big enough.