DOWNSPOUT DEFECTS, MORE - CONTENTS: Downspout 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 gutter downspouts & roof drainage control system problem diagnosis and repair articles
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Common mistakes in roof leader or downspout systems causing leaks & damage:
This article describes defects in roof leaders or downspout systems such as inadequate number of downspouts to handle the volume of roof drainage, missing, lost, or damaged downspouts. This article series discusses how to choose, install, diagnose & maintain roof gutters & downspouts, & roof drainage systems to prevent building leaks and water entry.
More Downspout Defects & Downspout Installation Details and Mistakes
Missing gutter and/or downspout on upper or secondary roofs
Our photo of an upper roof with no gutter (below left) shows how seriously water splash-up may stain or affect building walls. Not shown (not visible) in that photo is wear on the roof shingles from water splashing from above. Our photo at below right shows algae growth on shingles from a downspout spilling across roof shingles.
[Click to enlarge any image]
We often see early roof shingle wear, staining, or even roof leaks on lower roof slopes in areas where drainage from an upper or secondary roof slope spills onto the lower roof slope.
A solution to the wear problem caused by spillage from upper roof slopes onto lower roof slopes is the installation of gutters on the upper roof slope combined with a downspout to conduct that upper gutter's drainage contents directly into a lower roof gutter or even directly to the ground.
As Carson Dunlop Associates' sketch illustrates, if a small auxiliary roof extends far enough from the building foundation wall you might get away with a simple elbow that spills onto a splash block rather than a full downspout and extension installation.
Watch out: in the illustration shown if the splash block does not conduct water far enough away from that basement walkout stairwell water may cause damage to the stairwell sides.
Especially in freezing climates we often see frost heaves and collapsing concrete block stairwells that have been exposed to main roof or small auxiliary roof water runoff.
As we've stated earlier, a rule of thumb is to install a downspout for every 35-40 feet of length of gutter. But there are some other considerations to keep in mind.
If the roof design prevents good gutter slope (less than 1" of gutter drop in 200" of run) then adding more downspouts can help prevent gutter overflow in periods of heavy rain.
Adding more downspouts (and larger gutters) can reduce the frequency of gutter overflow due to clogging on roof slopes close to trees, especially pines and firs whose smaller needles wash into and clog gutters and screened gutters.
More downspouts will be needed for discontinuous runs of gutters along irregular roof eaves or slopes.
Use of strainers both helps and hurts with the downspout and gutter clog and overflow problem.
Installing a strainer in the gutter where it empties into a downspout helps keep the downspouts clear of debris and clogs. As Carson Dunlop point out, the gutter itself will clog more quickly with a strainer installed however.
Watch out: if your downspout system includes buried lines, clearing a clogged buried drain line can be difficult and expensive. For buried drain line systems we recommend that you always keep strainers installed at the downspouts at the gutter drain points.
[Click any image or sketch to see an enlarged, detailed version.]
It's usually easier to clean the gutter than to clean the buried downspout drain line. Sketch courtesy of Carson Dunlop Associates.
Animal Damage to Downspouts - Dog Bites Downspout?
Our photos below show unusual downspout extension damage - doesn't it look as if something has "chewed" the aluminum downspout ends? in fact that was just the case. The building owner explained that when a squirrel or other rodent entered the downspout the family dog became quite excited by the animal's noise or odor even though the humans were unaware of their visitor.
The dog, frantic to get to the now trapped animal, tore up the downspouts with its bare teeth. The second downspout dog bite photo (below right) was the same phenomenon observed at a different property. More than one dog with strong jaws finds downspouts interesting.
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. 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 for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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