Gutter/Downspout Discharge

I need some clarification on these statements regarding gutters/downspouts. In the “How to Inspect the Exterior” course, these two statements show up, in different parts of the course.

  1. “On buildings with multiple roofs, one roof sometimes drains onto another roof. Where that happens, water should not be discharged directly onto the roofing material. The best practice is to direct the water from higher gutters so that it discharges into lower gutters through downspout pipes.

  2. “First-floor gutters can overflow if second-floor gutters have been mistakenly directed to drain into them.”

What should I be looking for in the situation of second-floor gutters, as far as where they are supposed to drain to?


First, you need to understand that gutters are not generally required on a home. This varies by local and per your AHJ.

Next… Statement #1 is “generally” correct.

And… Statement #2 is also… but with certain parameters. Square footage of the drainage plane is critical. A large roof plane should not drain into a smaller roof plane gutter, thus the overflowing scenario.

Also… most inspectors never pay attention to the gutter sizing. It is often necessary for the lower gutter system to be larger than the second story gutter system to be able to handle the combined water volume. There is a lot more involved in getting it ‘right’ than just how much it will cost!


The first statement refers to the granule wear that will result from downspout discharge directly on the roof covering. This is often visible as a discoloration where the water has worn away the shingle granules
As you know the granules on a roof shingle provide a reflective surface that prevents the shingle from becoming brittle (dry). The other consideration is as Jeffrey writes above. Don’t overlook downspout discharge on the lawn or walking surfaces as potential problems.


I have an inspection Monday and after reviewing the listing pictures, I have already seen evidence of water discharge and “discoloration” on the shingles based on this exact same scenario. The upper downspouts should extend to the lower gutters and many builders won’t do it because of “looks”.


Same reason for too few downspouts… “cosmetic reasons”. Fine… then increase the gutter and downspout sizing to compensate for the additional square footage it needs to handle!


Course writers can make mistakes just like you or I can.

I like the above, if the lower gutters are sized to accommodate the additional flow as JJ said.


Thanks everyone,
I really appreciate all the input. It all makes more sense now.

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