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Where do Leaks Occur at Roof Downspouts or Leaders?
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Roof drainage downspout leak points: this article describes the places where you are most likely to find leaks in the building roof drainage system downspouts or leaders. This article series discusses how to choose, install, diagnose & maintain roof gutters & downspouts, & roof drainage systems to prevent building leaks and water entry.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Common Leak Points on Downspouts & Downspout Connections
Also see DOWNSPOUT DEFECTS, MORE or start this topic at DOWNSPOUT / LEADER DEFECTS; also see GUTTER DEFECTS LIST for other sources of wet basements or crawl spaces caused by problems with the roof drainage system.
Common leak points at downspouts include:
- Upper elbow below the gutter, leaking at seams and elbows due to damage from clogging and frost
- Downspout leaks at vertical seams that have burst from swelling wet leaves or frost
- Clogged lower elbows near the lower end of the downspout
Sketch courtesy of Carson Dunlop Associates. |
Downspouts Split by Leaves, Swelling Wet Debris, or Frost
Downspouts may be split and damaged from swelling organic debris (leaves) or by freezing. The result is leaks against the building wall and foundation. Keeping a strainer at the gutter-to-downspout connection will protect the downspouts from becoming clogged and thus splitting.
Of course, if the downspout is connected to a buried drain line that is also blocked, water backing up into the downspout will, in freezing climates, still freeze and burst the downspout.
Downspout Leaks at Connections & Elbows
You might be surprised but the dislocated downspout "connection" shown at below-left is very common. Don't assume that the building's downspouts are all connected - it's worth a close look, especially if there are signs of water entry or dampness in the basement or crawl space.
At above right you can see two downspouts descending the building wall. The left hand unit is leaking a bit at the elbow. The right hand downspout has lost its elbow and extension, and leakage has rotted the building wall.
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What is the proper direction or "female" end to "male end" of downspout joints?
The sketch at left illustrates the direction of water flow off of a roof - in this case a "flat roof" that drains to two roof scuppers.
The enlarged section of downspout connections (circled detail at lower right in the illustration) explains that downspout section connections and downspout elbow connections need to be installed so that water flow will always be directed to the interior of the next or "down-slope"
downspout component.
Sketch courtesy of Carson Dunlop Associates.
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Downspout Extensions that Lack Adequate Slope
Our downspout extension line photos below show what happens if the downspout extension is too flat, or if it ends aimed "uphill" from the downspouts themselves: the downspout extension simply backs up and during heavy rain, spills by the building. The photo at below left shows a black flexible 4" drain line and tee intended to conduct roof spillage away from the building. But following the drain line we found it ending pointing "up hill".
A closer look into the downspout extension connecting tee (below right) shows that the line contained standing water and was not draining.
Downspouts Emptying Below Decks & Porches
An often hidden basement water entry problem is traced to a downspout that the building owner thought was safely handled below an attached deck or porch.
On closer inspection we may find that the downspout spills below the deck and against the building, or that an extension has fallen off, or as we show at left, the downspout extension slopes up-hill.
Notice the water stains on the foundation wall near the downspout?
Particularly because many builders construct the deck before final backfill and grading, soil below the deck slopes back towards the building, increasing the risk of basement or crawl area water entry. |
Sometimes desperate measures are needed to successfully extend a downspout out from below a deck. The photos below show a combination of a downspout that was spilling below a deck, an inside building corner, and a wet basement (not shown).
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission to InspectAPedia to use illustrations from The Illustrated Home which illustrates construction details and building components. Carson Dunlop Associates' home inspection education products include
- The ASHI-adopted Home Inspection Training Program, and Commercial Building Inspection Courses
- The Home Inspection Home Study Course, and publications such as
- The Home Reference Book, a reference & inspection report product for building owners & inspectors
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones
- Home Inspection Report writing materials including the Horizon report writer
- Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF - ** Particularly useful text **
- Dampness in buildings, Diagnosis, Treatment, Instruments, T.A. Oxley & E.G. Gobert, ISBN 0-408-01463-6, Butterworths, 1983-1987 [General building science-DF
- Certainteed Weatherboard fiber cement siding and trim products - see certainteed.com/ or see certainteed.com/resources/sidingandtrimspecsheet.pdf
- "Flashing: the plain solution to leaky walls", Thomas E. Remmele, Manager, Technical Services, Sto Corporation, Building Standards, November/December 1999 p. 21-25.
- "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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