Gutter and Downspout Details (C) Carson Dunlop Associates Roof Downspouts & Leaders: Defects, Leaks, Repair Guide

  • DOWNSPOUT / LEADER DEFECTS - CONTENTS: Downspout or gutter leader defects, clogging, overflowing, holes corrosion, leaks that cause wet basements or crawl areas. Proper installation of buried downspout extensions. Proper installation of French drains & seepage pits at flat sites. Gutter & downspout defects cause wet basements & crawl areas. Roof gutters downspouts & roof drainage control systems
  • POST a QUESTION or READ FAQs about roof drainage systems: downspouts & leaders: installation, maintenance, repairs, leaks, screens, routing, clogs, and just about anything else.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Gutter roof drains, downspouts & leaders: Here we decribe the types of defects or leaks in the downspouts or leaders for roof drainage systems: leaks or other defects that cause basement or crawl space water entry.

Our page top sketch is provided courtesy of Carson Dunlop Associates.

Green links show where you are. © Copyright 2015, All Rights Reserved.

Roof Downspout or Leader Defects

Downspout empties too close to building (C) Daniel FriedmanThis article series discusses how to choose, install, diagnose & maintain roof gutters & downspouts, & roof drainage systems to prevent building leaks and water entry.

Article Contents

Quoting from Carson Dunlop Associates' Home Reference Book:

Downspouts collect water from the gutters and discharge it into drains or onto the ground. Underground drains (usually made of clay tile, cast iron or plastic) become clogged or break below grade. If an underground downspout malfunctions, water problems will likely develop in that part of the basement. There are two options.

Exterior digging and repairs can be undertaken; however, it is faster and cheaper to simply disconnect the downspout and redirect it to discharge away from the house. It’s also easier to monitor the performance, and problems are corrected easily. Downspouts should discharge above grade onto the ground at least six feet from the home. The slope of the ground in this area should be away from the house, to direct water away from the basement.

Common Downspout Defects Causing Building Water Entry or Leaks

Our list of common downspout or leader defects shown just below is followed by illustrations or photographs of many of these conditions.

  • Downspout empties too close to the building, concentrating water against the foundation, a very likely source of basement or crawl space water entry.

    Details are at Downspout Extension Spills Too Close
  • Downspout empties onto soil that slopes back towards the building. Details about controlling surface runoff and roof drainage disposal by proper site grading are found at Surface Contouring to Dispose of Surface or Roof Drainage Runoff
  • Downspout connections facing wrong way - leaks.

    Details are at DOWNSPOUT LEAKS
  • Downspout buried sections using perforated pipe near the building. D

  • Downspouts connected to footing drains, building interior drains, floor drains, or sewer system (storm drain connections are ok). This is a common but serious mistake made by uninformed builders. Adding the load of roof runoff to building foundation drains overloads that drain system and invites basement or crawl space water entry and even flooding.

    Watch out: A basement flood from this mistake can happen very suddenly, often less than 10 years after new construction, when a hand full of leaves or other debris enters and clogs the footing drain system through the gutter and downspout system.

  • Downspouts clogged at gutter connection, elbows, or anywhere in their routing.

  • Downspouts damaged by clogging, ice, frost, animals: splits, holes, tears, leaks.

  • Downspouts disconnected, loose, or missing.

  • Downspouts (& gutters) missing from upper or secondary roofs.

  • Insufficient size or number of downspouts to handle roof drainage water volume. In general, provide a downspout for every 35-40' of gutter length. More downspouts may be needed around complex roof structures.

  • Buried downspout lines made of perforated pipe close to building.


Downspout Extension Spills Too Close to the Building

Gutter and Downspout Details (C) Carson Dunlop Associates

The sketch at left illustrates a major cause of wet basements and crawl spaces: the downspout ends too close to the building, backfill at the building has settled, and in addition, the original grade left from the excavation to build the foundation remains as hard-packed soil that directs spillage back towards the structure.

Sketch courtesy of Carson Dunlop Associates.

Our photos below illustrate downspouts emptying too close to the building.

At below left you can see erosion that is sending most of the roof runoff out of the downspout and right down the foundation wall.

At below right a downspout is terminated on the deck surface. That detail can lead to slip/fall hazards (slippery algae-covered deck boards) and basement water entry (due to in-slope grade towards the building, hidden below the deck surface.)

Downspout empties too close to building (C) Daniel Friedman Downspout spills on deck (C) Daniel Friedman

Downspout Empties onto Settled Backfill

Gutter and Downspout Details (C) Carson Dunlop Associates

Here we show the most common roof drainage system error that leads to basement or crawl space water entry: the downspout empties too close to the building foundation wall.

This mistake, combined with settled backfill that slopes back towards the building sends this concentration of water from the roof right into the building.

While there are rules of thumb for the length of downspout extensions (minimum of six feet, or more from the building), the common sense downspout rule is:

When the water leaves the end of the downspout, it should keep going away from the building, not back towards it.

Sketch courtesy of Carson Dunlop Associates.

Downspout Empties onto Sloped backfill over compacted in-slope virgin soils or clay

Gutter and Downspout Details (C) Carson Dunlop Associates

A more subtle version of the "downspout too close to the building" problem we described above is illustrated in the sketch at left.

After a building foundation and structure have been completed, backfill may have been spread around the building and may appear to slope nicely away from the structure.

But because the new backfill is less compacted than virgin soil, even though it slopes away from the building, water soaking through the backfill may encounter below-ground hard-packed original soils that slope towards the structure.

The result is a hidden in-slope grade problem sending roof spillage or downspout spillage right back into the building.

Sketch courtesy of Carson Dunlop Associates.

Gutter defects are discussed in detail separately at GUTTER DEFECTS LIST


Continue reading at DOWNSPOUT LEAKS or select a topic from the More Reading links shown below.

Suggested citation for this web page

DOWNSPOUT / LEADER DEFECTS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

More Reading

Green link shows where you are in this article series.


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Questions & answers or comments about roof drainage systems: downspouts & leaders: installation, maintenance, repairs, leaks, screens, routing, clogs, and just about anything else.

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References