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How to Prevent Basement Leaks & Water Entry InspectAPedia®  -     Steps to prevent a wet basement and offers a few simple cures for existing wet basements Multiple defenses are the best guard against basement leaks Foundation dampproofing & correcting poor site drainage to stop basement leaks Using bentonite clay for basement waterproofing Using foundation membranes to prevent basement or foundation leakage Using foundation drain tiles, proper backfill, proper finish grading are discussed as basic steps towards a dry basement Case report of foundation collapse due to settlement & wet soils Photographs of basement waterproofing methods & procedures Simple cures for wet basements without major work - steps that might work Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices

This article discusses 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 . A case study of a foundation collapse is described and we offer a few simple steps that might cure a wet basement without major work. Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Readers should also see BASEMENT WATERPROOFING. Readers needing more extensive guidance on preventing or fixing basement leaks and moisture should see BASEMENT LEAKS Moisture or Mold, 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. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

How to Prevent a Wet Basement - causes and cures for basement water entry may be more basic and easy than you think

• Keeping Basements Dry: Wet Basement Prevention - PDF form, use your browser's back button to return to this page
• Keeping Basements Dry: Wet Basement Prevention & Cures - part 2

The text below paraphrases, quotes-from, updates, and comments an original article original article (see links just above)"The Almost-Too-Tight-House" by Steven Bliss.

Wet Conditions Lead to Building Foundation Collapse

This article begins with a pair of foundation collapse case studies, describing poor site drainage and wet soils that led to the foundation bursting into the home. Our photo (left) shows an example of severe foundation damage and ultimate collapse due to water and wet soils outside the foundation wall. Mr. Bliss points out several factors that led to two foundation catastrophes that he investigated:

• The site was sloped, and each foundation collapse was on the uphill side of the building
• The land was sloped so that water collected behind the foundation and soaked into the ground
• While original site grading might have sloped away from the foundation it was inadequate, so as excavated soils settled around the building ground sloped in towards the foundation wall
• Surface or perhaps roof runoff collecting close to the foundation saturated the soils, increasing the soil's mass and ultimately bursting in the foundation wall
• No sub-surface foundation drainage system was installed, or if there had been one, it was no longer working
• In-house basement wall waterproofing, if present, might actually have contributed to the foundation wall collapse by failing to provide another possible path for water (and its pressure) to escape from outside the foundation wall

Bliss notes that foundation leaks are said to cause more callbacks than any other problem in new home construction. Some building sites with good natural drainage are unlikely to result in a leaky basement even if the builder does not follow all of the best foundation water entry prevention steps during construction and site work. But others are a catastrophe waiting to happen - or as above, a catastrophe that has already happened.

Living With a Basement that Floods is Unnecessary and It's a Bad Idea

Living with periodic basement flooding - which some people manage, is not a great strategy, risking moisture-related damage such as toxic mold contamination (photo at left), building rot, termite damage, or even shorter roof shingle life.

One of our clients (DJF) lived for thirty years in a house that flooded repeatedly in wet weather.

The owners told me (DJF) that as city people, they didn't think anything was amiss when on first visiting the home on a rainy day, the original owner was standing in the basement in hip boots with a garden hose spraying down the basement walls. "I'm washing out the basement" he told them - a creative cover up for serious basement flooding. When I saw the house it had been flooding for 30 years. A wooden upright piano that had been stored in the basement had so badly rotted that it was only two feet tall.

The owners had later been told that "nothing could be done" because the basement was built over an underground stream that flooded in wet weather.

Starting by noticing that basement leak stains originated high on the foundation walls I was sure that even if there was an underground stream, basement water was also coming off of the roof or from bad surface drainage. Outside I found that a concrete patio had been poured against the foundation wall, later settling and tipping towards the home.

Tall pines near the home made sure that the house gutters were constantly clogged with pine needles and clogged, overflowing onto that patio at every rainfall. Water ran across the patio and down through the foundation wall. A simple experiment of cleaning the gutters and temporarily routing the downspouts well away from the home using above-ground flexible extensions was enough to immediately stop the basement water entry.

Steps to Prevent Basement Water Entry - the Basics

Soil Testing Predicts Soil Drainage Ability

For new construction, start with a few soil tests to understand what the house is being built upon. Any civil engineering manual will include a soil guide describing soil types and their drainage characteristics. Watch out for clay soils and silts that are unstable and expand when wet or frozen.

Conduct a soil percolation test to get an accurate idea of how soils drain around the home. If a septic system is to be installed you're going to need soil perc tests anyway. See Septic Soil PERC TESTS and PERC HOLE SPECIFICATIONS. Remember that if your perc tests are performed in the dry season you may get over-optimistic results. And if living space in the home is going to include below-grade areas, consulting with a soils engineer may be good insurance.

Water Entry Prevention Priorities

• Keep water away from the foundation. This means proper site drainage that assures that surface runoff and roof spillage are conducted away from the building. Most of the wet basements that we (DJF) have investigated were suffering from mis-handling 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. \

Our photo (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 structural damage had occurred.

• Dampproofing: traditional dampproofing is a bituminous coating that is rolled, brushed, or sprayed (least effective) on the foundation wall. Dampproofing is not waterproofing, and water will leak through a coated foundation wall wherever there is the combination of cracks or other openings and water.
  
  What dampproofing does is slow the flow of water vapor through the foundation wall by breaking the capillary flow of water through the masonry. Without dampproofing, water evaporating from the more dry indoor side of the wall actually pulls moisture through the foundation wall. But we're talking about moisture, not flowing water. If water never accumulates against the outside of the foundation wall, leaks and moisture won't be flowing through the wall.
• Amateur foundation waterproofing: as extra insurance, some builders drape plastic against the dampproofing coated foundation wall. This is a very inexpensive step that certainly reduces foundation leaks, even if the plastic is somewhat damaged during backfill. However amateur waterproofing alone does nothing to prevent a foundation collapse if lots of saturated soil is pressing against the foundation exterior.

True Foundation Waterproofing Method Details

• True foundation waterproofing: for poorly drained soils, investigate true foundation waterproofing, such as heavy textured plastic or rubber membranes that are placed against the foundation wall and that conduct water down the wall to a foundation drain system to carry water safely away from the building.
  
  Our foundation waterproofing system photographs above show (photo above right) the plastic membrane, protected by a geotextile to combine good water drainage down the foundation wall (and into the footing drains) with gravel backfill to nearly the top of grade (photo above left). This system was installed on a home that had suffered recurrent basement flooding due to a combination of in-slope grade at the rear and right side of the home combined with improperly installed and non-working footing drains, aggravated by wet soils in the area.
• Bentonite clay waterproofing: bentonite clay can be pumped into soils around the building foundation wall - an old basement waterproofing method that in some installations works quite well to slow or stop foundation leaks. Watch out - by leaving water in soils near the foundation wall, the risk of foundation collapse may remain.

Foundation Footing Drain Details to Prevent Basement Water Entry

• Foundation drainage - drain tiles also called footing drains and by some folks "French drains" (a mistake),: water flows in the path of least resistance. Perforated 4-inch PVC or flexible ABS are the least costly and most foolproof foundation drainage conduits. Foundation drains should pitch at least 4 inches in every 100 feet of length.
  
  The top of the foundation drain, should be below the top of the finished basement or crawl space slab. From the low corner of the building, the foundation drain should continue to daylight or, if permitted by local codes, to a storm sewer, so that water will drain away from the building without relying on an electrical sump pump or other magic.
• Footing drain hole perforations face down: if you use perforated footing drain tiles that include perforations only on one side, face the holes down. Water collects on the bottom.
• Footing drains to a drywell? Some builders of homes on flat sites where drainage by gravity is not possible install a drywell to collect and store storm drainage from around a building. Watch out: in areas of wet soils, in wet weather drywells are often not dry at all and may themselves fill-up with water from nearby soils, making this scheme simply not workable.
• Footing drains to a sump pit? One of our clients plagued with water entry at a flat site installed new foundation drains around her home, combined with an outdoor, frost-protected, duplexed, and battery backup sump pit system to pump foundation drainage to a nearby storm drain. Without the battery backup detail, this system might not have worked: guess when electrical power (for the sump pump) is most likely to fail?

Foundation Drainage Backfill Details to Prevent Basement Water Leaks

• Bury the footing drains in gravel, both under and above the drain tiles. Extend the gravel backfill at least two-thirds of the way to the top of finished grade. Gravel helps water flow easily into the drain system instead of seeking a way into the building, and the removal of water outside the foundation wall also avoids foundation collapse later. The gravel size needs to be larger than the holes in the drain tiles.
  
  Our sketch (left) shows a less than optimum footing drain installation because the artist placed soil too close to the drain pipe.
• Footing drain geotextile covers: some builders also install synthetic fabrics (geotextiles) over the footing drains before covering them to further slow the footing drain clogging by dirt and silt. Other builders place a layer of 15-pound building felt on top of the drainage bed to slow soil clogging of the gravel itself as well as to protect the footing drains.
• Clay foundation drain cap: the top foot of backfill over the footing drains should be a low-permeance clay cap to keep surface water (those spilling-over gutters) away from the foundation. If plantings are intended, add 4 to 6" of loam on top of the clay cap.

Finish Grading to Prevent Foundation Leaks & Water Entry

• 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 is a nice word for a "gentle ditch" - it does not have to be deep.
• 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 above at True Foundation Waterproofing.
• If the building roof system includes gutters and downspouts, 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.

Simple Retrofit Repairs Can Cure Basement Leaks

• First identify where water is entering the basement or crawl space. See  BASEMENT LEAKS Moisture or Mold for examples of common leak points that might be hidden behind finish walls or paneling. Our photo (left) shows a previously-hidden foundation wall crack that was sending water into a finished basement and under the raised wood basement floor from the time the home had been built until severe flooding in the basement motivated the owners to remove wet walls and find this leak.
• Patch leaky foundation wall penetrations or holes: Mr. Bliss reports stopping a substantial basement water leak (a couple of gallons per rainstorm) by chipping out around a waste pipe where it passed through the foundation wall, and patching that area with hydraulic cement.

• 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

• Add a splashblock to route surface runoff around a chimney whose side formed a water trap against the foundation wall
• Use a basement waterproofing paint on porous masonry block foundation walls - we have had excellent results with Thoroseal™ but don't expect an indoor foundation waterproofing paint to hold back a flood. See BASEMENT WATERPROOFING for details.

See BASEMENT HEAT LOSS for a discussion of foundation and basement insulation methods. See POLYSTYRENE FOAM INSULATION for a guide to using this material in below-grade applications. See TERMITE SHIELDS vs TERMITICIDE for a discussion of avoiding insect damage when foam insulating board is used below or at ground level.

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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WATER ENTRY in BUILDINGS
  ATTIC LEAKS Moisture or Mold
  BASEMENT De-Watering Systems
  BASEMENT HEAT LOSS
  BASEMENT LEAKS Moisture or Mold
    Cold Pour Joint Leaks
    Form Tie Leaks
    Wall Crack Leaks
    Floor-Wall Joint Leaks
  BASEMENT WATERPROOFING
    BASEMENT DE-WATERING SYSTEMS
    EXTERIOR WATER SOURCE ELIMINATION
    FOUNDATION DRAINS & FRENCH DRAINS
    FOUNDATION WATERPROOFING
    GEOTEXTILES & DRAINAGE MATS
    SEALERS, Basement Floor & Wall Moisture
    SITE DRAINAGE
    SUMP PUMPS GUIDE
    WINDOW LEAKS INTO BASEMENT
  WET BASEMENT PREVENTION
  CRAWL SPACE Dryout Proc
  Chimney Leaks
  CRAWL SPACE Dryout Procedures
  DEW POINT CALCULATION for WALLS
  DEW POINT TABLE - CONDENSATION POINT GUIDE
  EFFLORESCENCE, Salts & White / Brown Deposits
  FLOOD Damage Assessment & Repairs
  FLOOD DAMAGED FOUNDATIONS
  FLOOD VENTS
  FLOODS IN BUILDINGS-priorities
  FOUNDATION WATERPROOFING
  HUMIDITY CONTROL & TARGETS INDOORS
  HOUSEWRAP AIR & VAPOR BARRIERS
  LOG HOME Leak Diagnosis & Cure
  LOG HOME Condensation &Moisture
  MOISTURE CALCULATIONS
  MOISTURE PROBLEMS: CAUSE & CURE
  MOLD in BUILDINGS
  SEWAGE CONTAMINATION
  SUMP PUMPS GUIDE
  WET BASEMENT PREVENTION

• Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
  
• 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.

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