Gutter and Downspout Details (C) Daniel Friedman Roof Gutter Defects List Part II
Photo Guide to More Defects & Troubles at Roof Gutters

  • GUTTER DEFECTS, MORE - CONTENTS: More gutter and roof drainage system defects & photos. Definition and causes of "backflowing" roof gutters. Roof gutter installation errors, mis-placed drip-edge causes back-flow. Causes & cures for sagging roof gutters. Drip lines at ground level show history of roof gutter overflows or leaks. Missing gutter end caps, types of damage caused. Special problems with gutters installed on buildings with no roof overhang
  • POST a QUESTION or READ FAQs about troubleshooting roof gutters & drainage systems, problems with roof gutters, downspouts & roof drainage control systems

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Roof gutter leak problems, part II.

This article describes additional problems with roof gutters that cause leaks and building water entry, including backflowing gutters: leaks between the gutter and fascia board, and gutter installation errors (poor support, bad slope.

We explain the cause, cure or prevention of sagging gutters, and we explain how to notice drip lines on the ground close to a building beneath gutters - an indicator of the history of gutter spillage and a possible explanationof wet basements or crawl spaces.

We discuss the importance of gutter end caps. We also discuss the problems that occure when gutters are installed on a building with no roof overhang.

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Other Gutter Installation Defects, Leaks, Damage

Backflowing gutters (C) Daniel FriedmanArticle Contents

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Backflowing Gutters

"Backflowing gutters" is a term we coined to refer to the problem that occurs when water falling off the roof edge runs behind the gutter or between the gutter and the building fascia rather than falling into the gutter.

There are several principal causes of gutter back-flow:

  1. The gutters or roof drip edge have been improperly installed (or roof drip edge was improperly installed) so that the drip edge lower or vertical face is placed behind the gutter back wall rather than over the gutter trough.

    Details are at Roof Drip Edge Improperly Installed: Behind Gutters
  2. The gutters are loose or improperly installed too far out from the building eaves, or more likely, the gutters have become loose so that a gap has opened between the building fascia or wall top and the gutter back wall. When the loose gutter has moved far enough from the building fascia or wall top, roof runoff spills behind rather than into the gutter.

  3. Clogged gutters may also "backflow" - that is, sending water over the back edge of the gutter, depending on just how the gutter is sloped or supported on the building.


Often visual clues from the ground level can tell you that gutters have been back-flowing even if it's not raining at the time you are inspecting. But it may take an up-closer roof-edge from a ladder to see just what's going on with a backflowing roof gutter.

At a building inspection of a new home during a heavy rainfall we observed just this condition. Water was pouring down the roof, behind the gutter, and onto the front entry steps. Standing in the rain we (DF) knocked on the door. The builder answered and we spoke through a sheet of falling water.

"Look at all this water falling here! It's running behind the gutters. You might want to ask your gutter installer to take a look at this installation," we suggested with some tact.

"Ya know, " replied the builder, "we asked our gutter subcontractor about that. He said that it's normal, that 'they all do that'".

That observation was in a sense correct. All of the gutters installed by that contractor did backflow - they were all installed improperly. Often we find that when an installer is not up to speed on a building detail, the same mistake is made at every installation. "They all do that" can mean "they're all wrong."

OPINION: We divide home builders into two groups. Many are very well informed about good construction practices and make it their job (and what they're paid-for) to be sure that the job is executed properly, giving the new owner the best home with the least problems possible.

A second group of builders are folks who do not know construction practices, but perhaps are good organizers, arranging financing and scheduling subcontractors. If your builder is a member of group 2, s/he is at the mercy of the subcontractors, and too often, no one is minding the store.

Roof Drip Edge Improperly Installed: Behind Gutters

Installing the roof drip edge behind the rear wall of the gutter means that some roof drainage will run by capillary action down the drip edge and pass behind rather than into the gutter. If the gutter also happens to be a bit loose, not snug against the fascia and drip edge, still more water will pass behind it.

Our detailed photo (below left) shows a gap between the gutter back upper edge and the roof drip edge. Where this gutter is higher along the fascia, the drip edge is actually behind the gutter back wall.

Gutter and Downspout Details (C) Daniel Friedman Gutter and Downspout Details (C) Daniel Friedman

You may think the gutters are working properly, but if an inspection during rain shows a lot of water running from behind the gutters, either the gutters are clogged and overflowing, or the drip edge is improperly installed.

The stains on the fascia in our second photo (above right) often indicate a drip edge problem and gutter "backflow" behind the gutter itself, or a gutter overflow problem due to clogging.

Sagging Gutters Overflow

Sagging gutters may be caused by loose or lost gutter mounting hardware, improper or inadequate slope, or the weight of water or debris that cause the gutter to bend.

Gutter and Downspout Details (C) Daniel Friedman Gutter and Downspout Details (C) Daniel Friedman

At above left, when the roof is repaired (or replaced) the gutter needs to be replaced as well. At right it may be possible to repair this horrible gutter overflow by clearing a blockage and checking/correcting the gutter slope.

Drip Lines or Wash Areas on Ground Indicate History of Gutter Overflow

Simply looking at the ground under the eaves of a building may disclose a small "trench" or "wash area" that marks where soil has washed away directly under the building eaves due to roof runoff spillage. Finding a drip line under a building eaves is a good indicator that the gutters have been spilling in that location for some time.

Gutter and Downspout Details (C) Daniel Friedman Drip line below gutter (C) Daniel Friedman

At above left our photo shows a deep drip line from roof spillage outside of a building extension built over an inaccessible crawl area. There is risk of hidden water entry and water/moisture related damage in that area. At above right we show a wash area at the corner of a building. Often if you look "up" at this location you'll see the end of a gutter that has been spilling-over.

Even before entering the building to inspect its basement or crawl area for water entry or dampness, these clues are a red flag.

Gutter End Caps - Keep Them In Place

Since most folks don't spend a lot of time thinking about their gutters and leaders (until the basement is flooded), people don't notice that the end caps at some gutters have been omitted at original installation, are leaking, or have been lost. The result is often water splashing down walls, causing leaks, water entry, rot, or insect attack.

Gutter end cap leaks (C) Daniel Friedman Gutter End Cap Missing (C) Daniel Friedman

Installing Gutters on buildings with No Eaves Overhang

Gutters with no eaves overhang (C) Daniel Friedman

If your building design includes no eaves overhang (or soffit) it is especially important to maintain the gutters and downspouts.

That's because if these gutters overflow, water won't just spill onto the ground by the foundation, it will first soak the building walls or even enter at windows.

A close look at the gutter on this building shows so much debris on the gutter face that it's probable that the gutter has been overflowing down the home's walls.

Problems with the routing and disposal of roof drainage through downspouts or leaders are discussed separately at  DOWNSPOUT / LEADER DEFECTS.

This article series discusses how to choose, install, diagnose & maintain roof gutters & downspouts, & roof drainage systems to prevent building leaks and water entry.



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