How to Identify & Fix Exterior Sources of Foundation Leaks & Basement Water Entry
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How to identify and fix outdoor sources of water that cause foundation leaks, wet basements, wet crawl spaces, rot, insect damage, and mold contamination in buildings
Steps to prevent a wet basement and offers a few simple cures for existing wet basements
Questions & answers about troubleshooting wet basements: finding outside sources of water leakage

This article describes the common sources of foundation leaks and wet basement and how to find and fix them: sources of water outside and around buildings such as roof spillage, surface runoff, groundwater, mishandling of roof gutters and downspouts, and improper exterior foundation drains or footing drains.

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Eliminate Exterior Sources of Water that Cause Building Leaks, Water Entry, Flooding

Before launching a costly repair or retrofit to dry out a wet basement or crawl space it makes sense to check these common sources of basement or crawl space leaks and water entry:

Roof Gutters, Downspouts, & Leaders: the most common source of foundation leaks and wet basements

This article series discusses methods for preventing wet basements by attention to multiple best construction practices, including the basics of foundation dampproofing, poor site drainage, bentonite clay for basement waterproofing, foundation membranes to prevent leakage, foundation drain tiles, proper backfill, and proper finish grading. Our page top sketch of swale drainage construction is provided courtesy of Carson Dunlop Associates.

Our home page for diagnosing and curing foundation leaks and wet basements or crawl spaces is WATER ENTRY in buildings. Readers should also see BASEMENT LEAKS, INSPECT FOR and BASEMENT WATERPROOFING. Readers needing more extensive guidance on preventing or fixing basement leaks and moisture should see BASEMENT LEAKS, INSPECT FOR, or if your building includes areas over crawl spaces, see CRAWL SPACE DRYOUT PROCEDURES. If your building has been flooded, see FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP.

Roof gutters and downspouts - check to see that roof runoff is effectively disposed of away from the building, and that it is actually working.

See GUTTERS & DOWNSPOUTS for a guide to types of roof gutter systems.
See GUTTER DEFECTS LIST and DOWNSPOUT / LEADER DEFECTS for examples of common mistakes in handling roof runoff.

Most of the wet basements that we (DJF) have investigated were suffering from mishandling of roof drainage. Between gutter defects that spill large volumes of water close to the foundation and improper site grading, we estimate that 80 percent or more of basement water entry problems can be explained.

Do not tie the downspouts into the footing drains - you will simply overload the footing drain system and risk future basement water entry. We want to see gutters extended to release roof drainage no less than 10 feet from the home, more is better, and even more important, from the point at which water leaves the downspout end, it should continue to flow away from the building, not back towards it.

Add a splashblock to route surface runoff around a chimney whose side formed a water trap against the foundation wall

Improper Site Grading, In-Slope Grade May Send Roof Spillage or Surface Runoff into Building Basements or Crawl Areas

Site grading and control of surface runoff - see Finish Grading. Keep water away from the foundation. As we detailed at BASEMENT WATER ENTRY PREVENTION, this means proper site drainage that assures that surface runoff and roof spillage are conducted away from the building.

Our photo (above left) shows a home with an in-slope grade facing the house wall. It would have been relatively easy to install a swale draining hillside water and roof spillage around the left side of the home in this picture.

Instead the owners suffered decades of wet basements until the wet conditions made the home sills so attractive to termites that major

Guide to Finish Grading Details to Prevent Foundation Leaks & Water Entry

Swale used to control surface runoff (C) Carson Dunlop Assoc

At grade, the main object is to get water away from the foundation as quickly as possible. Finish grade should slope away from the building for at least 10 to 15 feet, and should not contain low spots that will make water ponds.

Swales: if one or more sides of the building face an upwards sloping hill, slope the finish grade away from the building for at least 10-15 feet, and then shape the finish grade at that point into a swale that itself continues to carry water around to the downhill side of the building.

A swale, illustrated by Carson Dunlop Associates' sketch at left, is a nice word for a "gentle ditch" - it does not have to be deep.

Details about proper surface grading to control runoff are found at SURFACE CONTOURING for DRAINAGE

Foundation ditches: Do not do what we have found at some flooding basements: an in-slope grade problem that was trapping surface and roof runoff against the house was "fixed" by digging a ditch right against the foundation wall in an attempt to carry water away. The ditch digger simply had built a water trap to guarantee that water would be sent against the foundation wall.

If a site absolutely has no room for a swale located 10-15 feet away from the foundation, you might make a workable drainage system by building a waterproof swale closer to the foundation wall by lining the swale or "ditch" with a heavy duty waterproof rubber or plastic membrane of the same material described at Foundation Waterproofing, Geotextiles and at FOUNDATION WATERPROOFING

Add an intercept drain at the entry of garages into which a paved driveway is sending water whenever it rains.

If you are planning to re-pave a driveway, that's a great time to go to the trouble of cutting in and installing a drain that prevents water from flowing into the garage.

Connect the intercept drain to a storm drain or to a new buried drain line that slopes to daylight well away from the building.

Don't connect the intercept drain to the building footing drain system - you may overload the footing drains and cause basement leaks.

Guide to Foundation Drainage Details to Avoid Foundation Leaks & Wet Basements

Footing drain to daylight (C) Daniel Friedman

Footing drains / foundation drains - check for presence of and check that water is flowing out of footing drains if water is in the basement. If the basement is wet and the footing drains are dry, they are not working. See FOUNDATION DRAINS & FRENCH DRAINS.

Our photo (left) illustrates a foundation drain that is "brought to daylight" at a property.

But this foundation drain (or "footing drain" extension) raises some questions: the use of perforated pipe far from the building may be ok.

And it's proper to use perforated pipes around the foundation footings themselves, so that water can enter the drainage system for disposal.

But if the pipes carrying this drainage "away" from the building are in fact perforated and are leaking it back into soils close to the structure, we may be simply recycling water rather than disposing of it.

Clogged footing drain (C) Daniel Friedman

Find the end of the footing drain system that used to drain to daylight - it may have become buried with mud or covered by backfill. Clear it open and check the end for water flow in wet weather. Our photo (above left) shows the footing drain that was excavated and removed at the home of a client whose house suffered recurrent flooding. The old footing drain was totally impacted with mud.

The photo at above right shows the ends of three new footing drains that were installed and carried to daylight. We remained a little nervous about just what the builder used for backfill - notice that silty mud coming out of the new drains? They may not have a long life.
Find and un-clog the footing drains: excavate at a building corner, find the footing drains, cut open the drain to see how full it has become with silt, and have the drains cleaned using high pressure water or other methods.
Reroute a non-working footing drain to a drywell if you can't get it to daylight
Add missing foundation footing drain sections that were omitted, such as around a chimney or building addition

Other Outdoor Sources of Basement Leakage & Water Entry

Repair foundation holes and cracks - see Seal Cracks in Concrete, How To
Storm drains - nearby storm drains should be un-blocked and not backing up onto the property.
Sump pumps - also check that if they are installed, the sump pump(s) are working and that water is pumped to a location that does not drain back into the building. Some properties use an outdoor catch basin and sump pump to dispose of roof runoff or surface runoff. See SUMP PUMPS GUIDE

Key building water entry diagnosis and cure articles:

BASEMENT WATERPROOFING - use of sealers to help keep basements and crawlspaces dry
BASEMENT LEAKS, INSPECT FOR - where and how water gets into basements and crawl spaces
CRAWL SPACE DRYOUT PROCEDURES - details about curing wet or damp crawl spaces.
EFFLORESCENCE, Salts & White / Brown Deposits - these white deposits are a great indicator of where moisture is penetrating a foundation
HUMIDITY CONTROL & TARGETS INDOORS - so how dry should a building be for comfort and mold prevention?
MOISTURE CONTROL in buildings - master list of detecting and controlling building moisture levels
MOISTURE PROBLEMS: CAUSE & CURE - moisture and building energy loss
SUMP PUMPS GUIDE - how and where to install a sump pump as an emergency backup against basement or crawl space flooding
WATER ENTRY in buildings - causes and cures of un-wanted building leaks in all areas
WET BASEMENT PREVENTION - how to stop basement flooding

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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EXTERIOR WATER SOURCE ELIMINATION - See detailed links at page left

[1] Scott Anderson, The Journal of Light Construction, December 2005 [1]. Mr. Anderson is owner of Tri-State Basement Systems in Berlin VT
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book 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. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

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Eliminate Exterior Sources of Water that Cause Building Leaks, Water Entry, Flooding

Roof Gutters, Downspouts, & Leaders: the most common source of foundation leaks and wet basements

Improper Site Grading, In-Slope Grade May Send Roof Spillage or Surface Runoff into Building Basements or Crawl Areas

Guide to Finish Grading Details to Prevent Foundation Leaks & Water Entry

Guide to Foundation Drainage Details to Avoid Foundation Leaks & Wet Basements

Other Outdoor Sources of Basement Leakage & Water Entry

Key building water entry diagnosis and cure articles:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair