Guides
When the Upstairs Downspout Empties Onto the Porch Roof
October 22, 2026
Plenty of the two-and-a-half-story houses in Dubuque have something lower tucked under the tall roof, usually a front porch or a kitchen addition off the back. The gutter along the upper eave runs to a corner and drops into a short downspout that stops partway down the wall, its elbow aimed at the lower roof. Everything the upper roof catches comes out of that elbow onto one spot of shingles.
In a light rain it looks fine. The trouble builds over years, at the spot where the stream lands.
Is it a problem when an upper gutter’s downspout empties onto a lower roof?
Over the years, often yes. The outlet puts one whole upper roof plane’s water onto a single spot of the lower roof, and that spot takes the wear, the overflow and the winter ice. How much it matters depends on the roof it lands on. Deciding where that outlet should land is the planning half of downspout installation in Dubuque.
Think of the upper roof as a water source with one exit. The exit can land in three places. On the lower roof, the way most of them do now. Carried down the lower roof to that roof’s own gutter. Or brought all the way down the wall on a downspout of its own, so the lower roof never sees it.
The lower roof’s pitch decides how hard the first option is on it. A steep lower roof moves the water along before it does much. A shallow porch roof under a steep main roof lets the stream hit and spread.
What does that stream do to the shingles where it lands?
A stream that hits the same spot every storm wears that spot first. The granules on the shingle surface wash loose under the elbow and down the slope below it, and those shingles age ahead of the rest of the roof. From the yard, the tell is a darker or barer streak running from the foot of the downspout toward the lower eave.
The grit has to go somewhere, and it goes into the lower gutter. When we clean a lower run, the stretch right under an upper outlet often holds a little drift of shingle grit the rest of the trough does not.
On a low-pitch porch roof there is a second problem. In a hard rain the water hitting the shingles splashes sideways and back up the slope, and on a shallow roof some of it can get pushed up under the course above. A stain on the porch ceiling right below an upper downspout can start there. Replacing the worn shingles is a roofer’s job.
Why does the lower gutter overflow right where the upper water comes in?
The lower gutter carries two roofs’ water, its own and the upper plane’s, and the upper share arrives at one point instead of spread along the run. In a downpour the stream off the elbow skates across the lower roof and reaches the eave with speed behind it. At that one spot it can go over the front lip while the rest of the gutter runs fine.
It is a different overflow from the one under a roof valley, where two slopes meet and gather water between them. This one comes out of a pipe. In a hard rain, follow the sheet going over the lip back up the lower roof. If it lines up with the foot of the upper downspout, the outlet is the cause, and a clean trough will still go over there.
What happens under that downspout in a Dubuque winter?
On a sunny thaw afternoon the upper roof melts first, and its outlet keeps dripping meltwater onto the lower roof. If that lower roof sits in shade, a porch on the north side or an addition tucked behind the house, the water freezes there by evening. Freeze-thaw cycles through a Dubuque winter build that into an ice patch on the shingles and a row of icicles at the lower eave.
All of that ice sits on one corner of the lower gutter. The corner carries the weight until a real thaw, and that is where hangers pull and the front of a lower run bends out of line. How ice backs up at an eave in the first place is covered in our piece on ice dams and gutters. Here the outlet keeps feeding the same patch a little every sunny day, long after the rest of the lower roof has stopped melting.
That makes late fall the time to settle where the outlet lands, before the first hard freeze puts ice on the porch roof.
Can the upper downspout be carried down to the lower gutter instead?
Often, yes. The downspout from the upper gutter is extended down the lower roof, lying along the slope, to that roof’s gutter or out past its eave. The water stops landing on one patch of shingles, so the wear line stops growing and the splash at the landing spot goes away. It is usually a repair-scale visit, the same kind of work as downspout repair.
It has limits. A pipe lying across a roof catches leaves of its own, and under the big maples and oaks it can plug the way any downspout does. In winter it can fill with ice of its own. And if it ends in the lower gutter, it still feeds that gutter at one point, so a lower run that goes over the lip at that spot in a downpour may keep doing it.
Carried past the lower eave and on down to the ground, the run stops loading the lower gutter at all, which makes it nearly the same fix as a downspout of its own.
When should the upper gutter come down the wall on its own downspout?
When there is a wall for it to come down. A dedicated downspout from the upper gutter, run down an outside corner past the end of the lower roof to the ground, takes the upper roof’s water off the lower roof entirely. The lower gutter goes back to carrying only its own roof, and nothing drips onto the shingles below on a thaw afternoon.
The limit is the shape of the house. A dormer, or an upper run that sits wholly above the porch or the addition, may have no outside wall below it to come down. The lower roof is in the way the whole length. Those are the outlets that get carried down the lower roof instead.
Where a corner does exist, the question is what the new drop would pass on the way down, a window or a door in the way. That gets looked at on site, from the yard and from the ladder, before anything moves. If the gutters are due for replacement anyway, the upper outlets get planned into the new runs from the start, and our piece on when to replace gutters in Dubuque covers the timing.
A new drop ends at the foundation like any other downspout. What its water does from there is in where the downspout water goes on a hillside lot.