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Causes & Solutions

Understanding The Problem
Building Materials
What Is A Foundation
Waterproofing & Drainage
Causes & Solutions

Causes & Solutions

At some point in time, every home and building with a below grade foundation will have a wet basement or crawl space (or cellar). It may take 2 years, 20 years, even 50 to 100 years or more, but regardless of when it happens, if you can understand the causes then maybe you can comprehend and understand the solutions.”Basements are not designed to be waterproof…” Iowa State University, “Building Basements in Wet Locations” March 1994.
DISCLAIMER: This quote comes from an engineering department. It generally applies unless your home is custom built by a Foundation Expert who understands Structural Engineering and waterproofing science. But, you’ll need to spend the money to install a system that will keep the basement dry for 100 years or more. We have the knowledge, expertise, and experience to build waterproof foundations and basements that last a lifetime!The Multiple Paths Water Takes To Enter Your Basement (or Crawlspace)
Below is an image of a foundation and basement with normal or common water problems. In the diagram, the wall illustrated on the left is a block wall made of concrete (cinder) block, or if very old, brick, terra cotta block or stone. The wall depicted on the right is a concrete wall, either poured or cast-in-place, or pre-cast concrete walls manufactured at some factory and shipped to the construction site. The type of wall in your home is easily identified because one is solid concrete, as opposed to hollow core 8″ X 12″ blocks, or bricks bonded together with mortar joints or seams; stone is evident, but terra cotta blocks have ridges that run vertically or horizontally. The following image illustrates the various paths through which water can enter your basement. They are:

Through the wall:

  • Tie rod (the metal pieces which originally held the forms together when the wall was poured or cast in place)
  • Window wells
  • Mortar joint
  • Foundation wall crack – simple or structural
  • Porous concrete
  • Concrete block (concrete blocks are not only hollow, they are porous and water accumulates inside the cores)
  • Penetration through an existing pipe (gas, sewage, water, cable, etc. )– around and through pipes, which enter your basement through the wall
  • Stairwells & doorways

Through the floor:

  • Cove, the joining or joint of the wall and the floor
  • Sump pit or well, which occurs when the sump pump fails
  • Floor drain, which can occur when the storm drain system backs up, or the floor drain has failed due to clogging
  • Penetration from pipe – around and through pipes which enter your basement through the floor
  • Floor crack

Understanding the Problem

“Water comes in four forms: solid, liquid, vapor, and adsorbed. All four forms can cause grief to building owners, designers and contractors. When water causes building problems, investigating and diagnosing the problem can be challenging because water constantly changes its form inside a building and within its materials. The investigator must hunt down the water, thinking like water.” Joseph Lstiburek, Ph.D. in Engineering, who understands more about building science than anyone in the United States (author’s opinion)

Soil, water, drainage, acid, concrete, concrete block, brick, stone, mortar – these are the elements and construction materials in and around your home and foundation which are subject to water. The noticeable effects are concrete wall cracks, humidity, dampness, white powder (efflorescence , flaking paint; structural issues, mold, mildew, insect infestation – the result is pain, misery, and the associated costs to resolve these problems.

The most destructive element isn’t necessarily the water. The water tends to be the catalyst of a variety of activities or mechanisms, which contribute to the overall decay and destruction of your foundation. But in that water, and in the soil surrounding your house, are acids, or more specifically, sulfates which contributes to the slow but steady corrosion and destruction of your foundation, the concrete, the mortar, etc.

Soils (clay, silt, sand and gravel) have a high degree of sulfates (acids) and so does rainwater (hence the term “acid rain”) – acid being below 7 on the pH Scale. The concrete, concrete block, brick, stone, and mortar are construction materials that receive their structural integrity, their strength, from mixtures of calcium and lime, which are alkaline – above a 7 on the pH scale. Acid and Alkaline are natural enemies which neutralize each other. If the cement, concrete, concrete blocks, and the mortar, are neutralized, then the components of your foundation are being corroded and losing their integrity. The end result will be structural – it is only a matter of time, unless these issues are corrected… Properly! And then it is still a matter of time, but now a much longer period of time.

Sulphates (acid)

Acid Deposition or Acid Rain: From the Columbia Encyclopedia – a form of precipitation (rain, snow, sleet, or hail) containing high levels of sulfuric or nitric acids (pH below 5.5 – in the D.C. Metropolitan area it can be much lower). These acids are produced when sulfur dioxide and various nitrogen oxides combine with atmospheric moisture; acid rain can also contaminate and damage vegetation, aquatic life, drinking water, and absolutely does erode and corrode the outer faces of buildings, foundations, and monuments.

Wikipedia defines Acid Rain as: rain or any other form of precipitation that is unusually acidic. It has harmful effects on plants, aquatic animals, and infrastructure.
Other adverse effects – Acid rain can also cause damage to certain building materials and historical monuments. This results when the sulfuric acid in the rain which chemically reacts with the calcium compounds in the concrete, concrete block, mortar, stones (limestone, sandstone, marble, and granite) to create gypsum, which then flakes off. This is referred to as efflorescence.

Wikipedia: Sulphates (acid) in solution (water) in contact with concrete can cause chemical changes to the cement, which can cause significant micro structural effects leading to the weakening of the cement binder.

In other words, the sulfates are corrosive to all cement products – concrete, mortar, concrete block, mortar seams between the blocks, stone, or between the bricks.

And then we have clay surrounding your home, sometimes referred to as shrink / swell, or expansive, sometimes classified as marine clay. Marine clays are soils that were deposited by rivers flowing into the Atlantic Ocean millions of years ago and can be found in widespread areas surrounding Interstate 95.


Silt, Clay, Sand, Gravel – excluding minerals such as gold, silver, etc., organic (vegetation) and refuse, these are the geological components of soils.

Clay is an Expansive Soil

Clay is an impermeable soil, meaning it holds water, as opposed to permeable soil that allows water to rapidly drain, like a gravel or sand. It is also an expansive soil, such as the marine clay which predominates in states such as Maryland, Virginia, and D.C., which when shrinking or expanding, can damage foundations and structures. The shrink and swell movements are due to changes in soil moisture. Providing uniform soil moisture next to and under your foundation is the single best thing you can have to reduce or minimize the damaging effects which expansive soil movements have on your structure. Unfortunately, the trade off is having a saturated soil, creating constant hydrostatic pressure which can also exert damaging water pressures, which we will discuss later in this dialogue.

Structural Problems

Footing Damage

The more common problem caused by marine clay is the settlement and heave of house footings. During dry periods, the soil loses moisture, and as a result, it shrinks and settles into the void left by the evaporating moisture. This causes voids and gaps under the foundation footings. If the house then settles, this results in cracked masonry walls, interior cracks in dry wall, plaster, and warped door and window frames. See Figure 1 below.

Trees and shrubbery with deep root systems, planted near the house or right next to the walls, contribute to the problem by drawing water from the soil through their root system causing further moisture loss, resulting in further shrinkage. Foundations that have settled during dry periods will sometimes rebound or return somewhat to the original position after enough rainfall replenishes the soil moisture, which causes the soils to swell again. After several cycles, the rebound of the foundation may become progressively less resulting in larger cracks.

Typical Foundation Cracks from Marine Clay


The footing support must extend to deeper and hence more stable soils. In new construction, footings can be placed further below the ground surface; the exact depth is determined by an engineering soils investigation. Trees and shrubbery should be planted at least 20 feet away from the house.

On existing construction, helical piers or underpinning are often necessary to reinforce a foundation damaged by settlement. Underpinning a house consists of new footings that extend below the original footings throughout the damaged area. Helical piers are steel anchors that are drilled into the ground to a deep depth and attached to the existing footings. Underpinning and installation of helical piers requires an engineer’s report and a county permit (and it is expensive). Once the foundation is reinforced and underpinned, a wall rebuild is often necessary.

Foundation Wall Damage Caused by High Shrink Swell Clays in the Backfill

Basement Wall Damage

Soil Compaction Changes
When your home was built, an area approximately 6 to 10 feet from where your house is currently located was excavated, footings were formed, your walls constructed, etc.. Then that area was in most situations, backfilled with the same clay that was originally excavated. Damage to foundation walls is caused when marine clays are used as backfill. This practice, now prohibited, but County inspectors do not sit around job sites watching as crews place backfill. Code violations are something that we find on a regular basis when conducting inspections – and it does not matter if the home is worth $100,000 or $5,000,000. New Home Building Contractors love to skimp and save money wherever possible.

In any case, this soil was not properly compacted to what we call a pan hard density. It was loosely backfilled, and rightfully so. Otherwise, the compaction would have imploded the walls that were not fully cured to begin with. As the years went by, and your house aged, the soil around your home compacted. During dry periods, the clay shrinks, settles into the voids left by the moisture, and then when the moisture returns, swells again. Damage is caused from these yearly cycles of pressure exerted by shrinking and swelling of the marine clay in the backfill. See figure 3. Swelling pressure of the soil can be compounded by improper drainage around the house from rainwater.

All concrete structures will crack to some extent. Concrete will crack due to tensile stress induced by shrinkage or stresses occurring during setting or use. Contractors pour walls, or build block walls, and before the concrete and/or mortar can cure properly or adequately, up goes the rest of your home, and there is the stress we are talking about. In many large structures, expansion and contraction joints or concealed saw-cuts are placed in the concrete as it sets to make the inevitable cracks occur where they can be managed and out of sight. In residential construction this rarely occurs.

Shrinkage cracking
Shrinkage cracks occur when concrete members undergo restrained volumetric changes (shrinkage) as a result of either curing or drying, self-generated shrinkage or thermal effects. Once the tensile strength of the concrete is exceeded, a crack will develop. The number and width of shrinkage cracks that develop are influenced by the amount of shrinkage that occurs, the amount of restraint present and the amount and spacing of reinforcement provided. Some cracks are immediately apparent, visible within 0 to 2 days of placement, while drying-shrinkage cracks develop over time.

Tension cracking
Concrete members may be put into tension by applied loads. The size and length of cracks is dependent on the magnitude of the bending moment and the design of the reinforcing at the point under consideration.

Porous Concrete Block
When water comes into contact with concrete block, the concrete block soaks up the water like a sponge, at which point, the acid starts to corrode and weaken the block and the mortar that holds it in place. This can ultimately result in a weakened block wall, which can then bow inwards, as illustrated above. The fix is below.

Repair or Replacement of a Damaged Wall

Depending on the extent of damage, foundation walls may need to be replaced (pictured above) while others can be repaired. Interior solutions can be wall bracing, I-Beams, Carbon Fiber, epoxy injections, interior drain tiles, and other types of repair. We now have interior elastomeric applications to waterproof concrete blocks from the inside, if the block is unfinished. Outside solutions involve excavation, crack repair, wall rebuilds, helical piers and anchors, home leveling, waterproofing, drain tiles, etc. To prevent future damage, the clay must be removed and the backfill replaced with, according to code, a minimum of fifty-one percent (51%) sand and/or gravel.

Indicators of Expansive Soil Movements
Listed below are indicators you can look for to determine possible expansive soil related movement and / or structural damage. The probability that your foundation has experienced some movement increases with the number of indicators observed, their frequency, and location in the structure.

Exterior Indicators:

  • Bowed or non-vertical walls
  • Sagging brick lines when sighting along a wall
  • Separation of concrete driveway, patio, or sidewalk from foundation
  • Diagonal (stair stepping) Cracks in brick walls. Cracks may go through brick or mortar and vary in width
  • Separation of wood trim joints at corner
  • Tilting of landscaping/retaining walls

Interior Indicators:

  • Bowed or non-vertical walls
  • Bottom of wall separating from the floor Cracks at wall corners
  • Cracks above doors
  • Cracks in sheetrock walls or ceilings
  • Cracks in ceramic or vinyl tile
  • Cracks in concrete floor 1/16th inch across or wider
  • Sticking doors. (warped door frames)
  • Sticking windows
  • Sloping floor surface

Soil Moisture Changes
Observing soil moisture changes around your foundation is possible, but what about under it? Moisture can move from outside to under your foundation through a property of soils known as suction or capillary action. Soil suction is similar to placing just a corner of a dry, compressed sponge in contact with a puddle of water. In a short time, the sponge has drawn water throughout itself and grown in volume. While a water source is present, the sponge will continue to absorb water until it is saturated. If the water source is cut-off, then water already in the sponge will distribute itself evenly, but the sponge will not reach saturation.

Water can move horizontally and vertically through the soils under your foundation in a similar manner. As clay soils draw water to themselves, they too grow in volume (swell or heave) causing your foundation to move. Drying outside your foundation reverses the process. The moist soils will lose volume (shrink) as soil moisture moves out from under your foundation, the clay will crumble and settle into the voids left by the moisture, creating voids under the footing, causing the foundation to settle. Shrinking and swelling soil motions can lead to damaging your foundation and structure.

See Approach 2 below for Proper Drainage Solution

Rainfall StatisticsFor Average Residential Property, Single Family
Total of 1” Rain on Your ¼ Acre Property = Approx. 8,408 Gallons
17.7 % (1491 gallons) of the water reaching your foundation is surface water, subject to proper grading, downspout extensions, surface obstructions such as patios, roofs, driveways, etc.
82.3% (6914 gallons) of the water reaching your foundation walls comes from below the surface through the ground!Most homeowners are under the impression that surface water is causing their water and foundation problems. While it is always recommended to extend your downspouts, and grade away from the home (compacting the soil, not just dumping dirt next to a wall), most of the water is rising as a seasonal water table around your foundation, causing extreme hydrostatic pressure. (See below)
1” of RAIN on 1 ACRE of LAND = (approx.) 27,660 gallons of Water. Imagine a rainfall that dumps 10” of rain in 3 days or less! In 2008, in the DC Metro Area (VA, MD, DC) we had two torrential downpours each of which dropped 8-13 inches of rain! Mother’s Day (May 2008) and Hurricane Hannah (September 2008).

Hydrostatic Pressure
A Simple Analogy
If we go outside to your lawn, and turn on the hose, the water doesn’t run away on the surface – it soaks into the ground. Water seeks the path of least resistance. It runs downhill or to grade, meaning that all water that touches down on the Eastern side of the Appalachian Mountains will find its way to the Atlantic Ocean by way of ground water and those tributaries which transports the water. One Inch of Rain equals 6914 gallons reaching your foundation walls from below the surface through the ground!

Imagine an empty pot, a top, and your kitchen sink. First, we stop up the drain in your sink to simulate the absence or ineffectiveness of drainage around and under your home. We then put a top on the pot, simulating your roof, and we place this empty pot in your sink and turn on the faucet, simulating the rain. It doesn’t matter if the water hits the top (your roof) or around the side of the pot (your lawn, your neighbor’s lawn, your neighbor’s neighbor and so on).

As the water continues to run (rain, rain, rain), the water starts to accumulate around the pot, eventually lifting it like a boat bobbing on the water. Why? Because another characteristic of water is that it reaches its own level – self equalizes. The water at the bottom of the pot wants to be at the same level as around the pot and it therefore lifts it up. This is what we call hydrostatic pressure.

In fact, the water on the side, wants to get into the pot. Pop a hole in the side of the pot under the water line, and the pot will fill until the level inside is the same outside. This is what happens to your basement. Create a hole or seam, which is natural to the construction process of your home, and eventually water will seep in. Pop a hole where the side meets the bottom or in the bottom, water will seep in even quicker.

Now pop that drain under your pot (or house) or drill holes in the sink around the outside of the pot, and it doesn’t matter if you turn on two more faucets, the water will now drain from around the pot, or around the foundation of your home, and the water in theory will not build up because the drainage won’t allow it to build up.

Please do not confuse surface water as the reason why water enters your home. If your home were waterproof, the water would not be able to enter, regardless of where it was originating. Think about that – if your home, including the walls, the floor, and where the wall meets the floor, were waterproof, the water would not be able to enter your basement.

The Virginia, Maryland, and DC Metro area is in essence a swimming pool into which we sink foundations and basements. The natural and seasonal water table is very high – rivers, streams, creeks, and lakes abound. Look around and notice, maybe for the first time, the names of your streets and communities. Falls Church, Riverdale, Silver Spring, Great Falls, Potomac, Chesapeake, Rock Creek Park; Falls Road, River Road, Cold Spring Lane – We are literally surrounded by water.

Go sit in a pool of water, and eventually even you will start to leak. Concrete is not waterproof. Neither is your home. It may have temporarily been waterproof, but the technology to do never really existed until now, the 21st Century, where even a man of color can become President of the U.S.A. Everything is possible. It is even possible that there is a Foundation Expert, a great waterproofing company out there that can apply 21st Century Technology to residential construction and waterproof a home – long term!


See Approach 2, and Approach 5 through 8 below.

The Wet Basement “Solution”- External Drainage Iowa State University, “Building Basements in Wet Locations” March 1994
“Basements are not designed to be waterproof, only water resistant. When water in the soil is only a few inches above the basement floor, water can find openings and seep or flow into the basement. Water creates such high pressures that sealing cracks will not prevent water from leaking into the house if the soil around the house is saturated. For example, when the soil is saturated to 3 feet above the floor level, the force of the water is more than enough to lift the concrete floor slab. Obtain professional design assistance if you feel you will need a “water-proof” basement.

All primary drainage systems near the house must be located below the finished floor height.” Sub-surface drain systems must be adequate to keep the water level from rising to the top of the basement floor level. Often sub-surface drainage is needed at one or more of the following locations: around the foundation footings, and alongside the interior footing, under the basement floor.

Understanding Foundations, Moisture Sources, Hydrostatic Pressure, and Drainage
Moisture problems in basements and crawl spaces are very common, but are not understood or if they are, not properly treated. Forgetting for a moment possible structural concerns, basements are connected to the rest of the house through ductwork or other openings. In addition, basements are increasingly used as finished living and bedroom spaces.

Molds and mildew can grow in damp carpets and beneath floor and wall coverings – basically, where there is moisture and where you have organic materials, like wood, and the paper on drywall, mold can grow and proliferate on these surfaces. In these cases, moisture problems are not only annoying and uncomfortable, but can lead to significant health problems.

Basement water problems are solvable, but there is a cost to doing it properly. Finishing a basement without first dealing with the moisture problems can result in making health conditions worse and lead to significant damage as well.

Sources of Water
To properly correct your basement water problems, it is necessary to understand and determine where the water is coming from – which mechanisms are allowing or permitting the water to enter the basement. There are only three sources of water and/or moisture:

  1. Exterior liquid water (as opposed to vapor) from ground water, water tables, springs, or rain.
  2. Exterior vapor in the form of humid air that enters the basement and condenses on cooler surfaces.
  3. Interior sources of moisture – unvented clothes dryers, humidifiers, cooking, water vapor from bathrooms and the moisture that remains in concrete long after construction is finished and slowly dissipates.

Moisture is transferred from the outside of the building to the basement interior by four mechanisms:

  1. Liquid water flow
  2. Capillary suction , adsorption
  3. Vapor diffusion
  4. Air movement

Of late, we constantly find that these types of problems are traced to poor construction or cheap materials. This may be evident with wall cracks and settling foundations. In many cases, although the basements and foundations can be structurally sound, they were not properly built to handle water drainage. Failure to slope the ground surface away from the foundation or lack of a good gutter and downspout system is a common occurance. Missing or nonfunctioning subsurface and foundation footing drainage systems are also encountered with increasing frequency as homes get older and leak for the first time.

All of these problems can be analyzed and properly corrected by experienced professionals. If you have any of the following symptoms, then you should have some concern and should address these issues immediately:

  • Odor, mold, and mildew
  • Deterioration of carpet or wood
  • Rot and decay of wood headers, joists, sill plates, and columns
  • Staining and blistering of wall covering
  • Efflorescence, spalling of concrete or masonry
  • Standing water on floor
  • Saturated base of concrete block walls–a ring of dampness
  • Damp, humid air
  • Condensation on cold walls and floor in summer
  • Water trickling out of walls
Rainwater and Groundwater
In a one-inch rain, 27,660 gallons will fall on 1 acre of land, 1,250 gallons will fall on the roof of a 2,000-square-foot house. Without proper grading, gutters, and downspouts, some of this water flows into the basement Some. Well over 80% of the water problems are caused by water coming from the ground up. The below-grade water table whether it is seasonal or not, will rise due to flooding or seasonal site conditions. This is why exterior and interior drain tile systems are recommended around basement walls even in sandy or gravel soils which drain quickly.
Interior Moisture Sources
Moisture is generated inside of basements from people and their activities. Common sources are humidifiers, unvented clothes dryers, showering, and cooking. When basements are finished, these activities increase. Another source that can be thought of as internal is the moisture contained in new concrete after construction. In a typical house, this can amount to 0.2 gallons per square foot of wall, and 0.1 gallons per square foot of floor. It may take many months or even years for a new house to come into equilibrium with its environment.
Ventilation with Humid Outside Air
In the summertime, basement windows may be opened for fresh air. If the outside air is warm and humid, it will condense on the cool basement wall and floor surfaces. Many homeowners see this moisture and believe they are experiencing basement wall leakage, when in fact the accumulated moisture is from condensation.Perform a Simple Condensation Test
If you suspect that condensation may be the problem, there is a simple test. Tape and fasten securely a 10″ x 10″ piece of plastic wrap onto the basement wall in an area where you have noticed dampness, sealing the edges of the plastic wrap with the tape. Over the next few days, check on the plastic. Eventually you will get moisture: if the moisture is on the room side of the plastic, you have a condensation problem; if the moisture is on the wall side of the plastic, you have a leak..
Typical Causes of Basement Moisture Problems
Inadequate Grading
PROBLEM: If the ground around a foundation is level or slopes toward the house, water may be directed into the basement. The soil next to the house is often backfilled without proper compaction and later settles. This is especially true under stoops where settlement has allowed water to collect next to the basement wall.
Defective or Missing Gutters and Downspouts
PROBLEM: Missing or clogged gutters and downspouts cause rainwater to be directed toward and around the foundation perimeter. A downspout without an adequate extension (splash-blocks don’t work either) is worse than no downspout at all. Without proper extensions, the roof is depositing huge volumes of rainwater in a single concentrated location near the basement.

Install Proper Gutters and Downspouts:
Regardless if your home is new or old, downspout maintenance is always recommended. They should be cleaned at least 6 times a year, unless you have gutter guards, gutter helmets, or whichever brand you have that will keep leaves from clogging your system. Downspouts should always be extended at least 8 feet from the foundation walls. If your home is new, less than 5 years, maybe grading, if done properly, with compaction can help.

Regardless, if you have water in the basement, it is because there is a path through which the water is entering, whatever the source. All too often, the entire solution to basement problems is misdiagnosed by a home inspector, because they do not understand this science, or they are working for the Realtor who is trying to sell a home, or both.If water is entering the home, yes, poor grading and absence of downspout extensions may be playing a contributing factor. But the fact remains, water has accelerated the corrosion and deterioration of you waterproofing and drainage systems. Water is getting in somehow, and usually it is because 1) your walls are no longer waterproof, and 2) the drainage that should be around the footing is not there, or if it is, it is not functioning effectively, most probably clogged with silt and clay or roots and gravel. Hence, water in your basement.

If you want to spend money grading, which we do not recommend, then Do Not Place Dirt Higher Against The House as this will cause water problems to flow into your first floor, and rot the following:

  • The Wood Sill Plate – Or Mud Plate, Which is a Pressure Treated 2X6 Or 2X8
  • Your Floor Joists or TGI or Wood I-Beams
  • Timber or Oriented Strand Board – OSB
  • Tieback or House Wrap

Finish grade to the first wood component of the structure should be a minimum of 16” BELOW the sill plate!
If you want to try grading as a possible solution, then first go out about ten feet from your house and start digging down. Excavate away from your house, and create a slope away from your walls, which should have been done when the house was built. If you place earth around the house, do not go up so that you are above the top of the basement wall. Make sure that it slopes away from the foundation wall a minimum of one inch per foot for at least six to ten feet. Then compact the dirt to a pan-hard surface with pneumatic or gas powered compactors.

Otherwise, you are only adding more spongy material that will soak up more water. Author Note: In my 35 years, I have never seen this to be effective after the fact. There is so much water in the ground, that any grading effort will actually worsen the problem as non-professionals, i.e. – landscapers or DIY’s do not understand soil compaction and proper grading.

Improperly Designed Window Wells
PROBLEM: Window wells are similar to having a drain right next to the basement wall. They are often improperly constructed so that any water is directed toward, rather than away from the foundation.SOLUTION: In a perfect world, window wells should be excavated down to the footing and a window well drain installed which will drain to the exterior drain tile system, assuming it is still functioning. If the home only has a functioning interior system (if not, one needs to be installed), at the very least, excavate down 2-3 feet, install a drain through the wall and then down to the interior drain system. In either case, window wells should be refilled with 3/8- to 3/4-inch round washed gravel to 2 feet below the windowsill. In a situation where the drain tile system is non-existent, and you don’t want a system installed, a sump pump can be installed in the window well with the discharge line out and above grade. For egress windows, drainage is an absolute, because you just built a mini-swimming pool, plus it is code!
See Approach 2 through 7.
Ineffective Drain Tile and Sump Pit
PROBLEM:Many existing houses simply have no subsurface drainage system. This comes from a time when basements were not used as habitable space. In other cases, the systems do not work for a variety of reasons, such as the builder didn’t care or know how to install one correctly; someone who called themselves a waterproofer, was not; collapse of the pipe; clogging of the pipe with silt and/or tree roots, or a broken connection to the sump. The sump pit usually contains a pump designed to lift the water to the ground surface and discharge it outside the foundation wall. This pump can fail or may not be strong enough for the discharge line distance, or both.We encounter these situations all the time, in homes which are old, and homes which are 2 years old. Older homes were usually built correctly, and drainpipe failure is simply a matter of time, which deteriorates almost all things. We get old, buildings get old, appliances fail; so do properly installed drainage systems from 20 to 50 years ago. Anything less should be attributed to poor construction by the original builder for improperly installing the drain tile system, i.e. – using inferior drain tile, no gravel, a cheap pump, the list goes on.Cheap plastic pumps fail all the time. Cast iron, commercial grade Zoeller Pumps, around since 1939, are great pumps which rarely fail. I have seen them work for 35 years without failing. My first waterproofing job was an old home in Falls Church, Virginia, with a Zoeller, which was 35 years old and was still pumping out water from an old terra-cotta drain tile system, which had finally crumbled due to age.

SOLUTION: For detailed approaches on drain systems, give us a call or see the following approaches 2 through 7. These are basic designs, some good, some not recommended.

PROBLEM: Concrete and concrete block foundations usually develop some cracks. They can be severe if floor joists are not properly connected to the foundation wall, thus permitting the wall to move. Also, soil settling causes cracking. Places where walls meet rigid structures like the fireplace often crack as well. Usually, drainage removes the water from cracks, but repair may be necessary. See Concrete Crack Repair and See Approach 2

Outside Excavation – Waterproofing and Exterior Drainage System

Installing an exterior drainage system on an existing building is the most costly, but also the most effective water control approach. This requires excavation – digging up the area around the foundation, installing a new foundation drain system, waterproofing the wall, except now we can do it with 21st Century technology. It also requires digging up shrubs and other obstacles around the house.

Usually, waterproofing and insulation are installed at the same time, in addition to making any repairs to the structure. The traditional exterior drainage systems use free-draining gravel and sand in the backfill. Drain tile must be placed beside the footing or the water level can and will reach above the floor. Level drainpipe installations are satisfactory. A minimum of 12 inches of coarse aggregate should be placed around the drain tile.

Free-draining Membrane or Board
It can be expensive to haul pea rock or sand to a site for backfilling purposes. Instead, a drainage mat can be placed against the foundation wall and then backfilled with any soil on site. The drainage must have a free-flowing path to the perforated drainpipe below.

Draining to a Sump
All exterior drainage systems must drain to gravity (usually not possible) or to a sump that can pump and discharge the water out and a few feet away.

Interior Drainage Channel above the Concrete Slab

In most cases when water is entering the basement, an interior drainage system is installed next to the footing under the floor (see approach 5 through 8). The most primitive, least costly, and least effective approach is a cove plate, which is a drainage channel adhered at the base of the wall and the floor slab. This is a temporary patch solution that some companies will install and charge the same amount as a professional company installing a much more comprehensive solution as illustrated in approach 5 through 8. The cost for cove plate systems should be approximately $25 a foot, although it usually isn’t worth even that amount because they fail in the short-term. A band-aid, not a healing aid.This solution is only recommended when outside drainage is impossible, and the foundation and floor slab are monolithic. We do not recommend this system. Sometimes this system is employed in crawl spaces that also do not have a footing. However, this is allowing the moisture into the basement interior. Water is collected and drained into a sump using another channel placed on top of the slab, then through a trap to the sump basin. It does not solve the problem in masonry walls because water remains in the block cores at floor level and the water level is only lowered to the top of the slab. With this approach, the water is not completely removed from the space. The result is that humidity, mold, and mildew can still be a problem. This system cannot drain groundwater from under the floor slab. NOT RECOMMENDED.

Interior Drainage Channel within the Slab Edge

Another low cost technique and approach, utilized primarily by Franchisee and Licensee type companies, is to place a box shaped drainage channel, with large round holes, at the base of the wall on top of the footing. This requires removing and then replacing a small amount of the concrete along the slab edge – a trench approximately 5”-7” wide and only 3”-4” deep – which is the average thickness of most floor slabs. The drainage channel is connected to a drainpipe leading to the sump.Serious Drawbacks
This is a “cookie-cutter” approach that requires little training or experience, and would not pass a county inspection. It is not ‘up to code’ – county and municipal codes, and engineering standards, require 4″ Perforated Drain Tile, installed in gravel, next to the footing, not in the floor slab. These systems should not cost more than $25 per linear foot since there is one-third the labor and material cost compared to a properly installed drain tile system.Moreover, the size of these box shape drains is not sufficient to handle large volumes of water. These systems have different shapes and prices depending on the Franchised or Licensed product installed. Also,they have no flexibility, which means they cannot go around corners, or around obstructions, or around pipes, which may sit next to the wall, or around the 90⁰ corner which all basements have.

The worst feature of this system is the 1″ or 2″ of concrete that is replaced back over top of this flexible

plastic pipe. This is a flexible plastic which has no compressive strength. This flooring will not last very long as it is not the required 4″ of concrete that is minimal code, and any attempt to finish your basement, i.e., nailing a base plate on top will crack the ‘new’ cement, and will just not adhere – there isn’t sufficient concrete. Also, no gravel. A real interior or exterior drain system consists of 4” pipe, alongside the footing, below the floor depth, surrounded by gravel, which in and of itself, also acts as a drainage system.

Interior Drainage System Beneath the Slab

One of the most effective interior drainage systems is comprised of a 4″ perforated drainpipe installed inside the perimeter of the footing, in a wide, sloped, trench, with round washed gravel completely surrounding the drain tile. This requires removing and replacing approximately 12″- 18″ of concrete at the slab edge. By placing the drainpipe beneath the slab, it drains the area to a lower level.

These interior systems are almost as effective as an exterior system, sometimes even more effective, as long as they connect to a sump, which discharges the water outside. A critical component of this interior approach is first, drilling holes in the bottom course of block; poured concrete walls have a keyway where water can enter under the wall. The the placement of a drain material (dimpled plastic sheeting called Miradrain ® 2000R or other similar brands) placed at the base of the wall and beneath the slab edge permits free drainage of the wall into the drainpipe. It is less expensive than many specialized drainage channel systems. In low permeability soils, which is exactly what we have in the MD / VA / DC Metro area, this system cannot accept rising groundwater unless there is a sufficient aggregate layer under the slab (round washed gravel).


When a new home is being constructed, this is the time to properly install drainage systems inside and outside, to properly waterproof the walls from the outside with rubber type elastomeric membranes, modern day drain mats, to backfill with a gravel / sand mixture, and to install an interior wall system that is water and mold proof. Although basements are usually not designed to be waterproof, The Foundation Expert can and does design waterproof basements. We do it all the time!

Restoring your House
With The Foundation Expert, you need not worry about any water damage repair. From a free of cost preliminary damage assessment to completely restoring your house just the way it was, we are there at every step of the way – offering tailor-made support at a budget-friendly cost.

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