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"Performing Residential Home Inspections, Radon Gas Sampling and Mitigation, Home Energy Audits, and Stucco Inspections for Southern New Jersey, Delaware, and Eastern Pennsylvania"  

Table of Contents:

1.    Basement Dampness

2.    Foundations

3.    Damp-Proofing, Vapor Barriers

4.    Ventilation

5.    Underground Water Table

6.    French Drains

BASEMENT DAMPNESS

Damp, moist, wet or overly humid basements are like the common cold. Any body can get one and they usually come with wet weather. Unlike the common cold, this is predictable and avoidable.

RAIN CAUSES DAMP BASEMENTS. All water comes from the sky. It is rain that dampens the earth, feeds creeks, streams, rivers, the underground water table, and eventually, the ocean. But, water doesn't like to flow through solid objects (like dirt), so it stays largely on the surface. Water would rather travel miles to the ocean than a few feet through solid or even semi-solid ground.  Damp basements result from conditions that allow water to get into the foundation back-fill.

SO WHY IS IT OOZING IN MY BASEMENT? When water does get into the ground, it continues to flow downward and away, unless something slows it. Even when it slows down or stops, water is so energetic and so determined to keep moving, that it will change form and escape another way. Damp basements result from conditions that allow water to travel downward into the foundation area and then gather or stop there. Secondary effects occur as a result of the water being there, and what it does to try to leave.

WHY DOES THIS HAPPEN? When a building is constructed, with a basement, the first thing done is to dig a big hole, called an excavation, to contain the foundation. Once the foundation footing (a strip of concrete approximately one foot deep and two feet wide) is laid and the foundation wall (usually of concrete block) is up, there remains an area between the foundation and the un-dug, or undisturbed soil, about two to three feet wide. This area is then refilled, or back-filled, with soil left over from the construction site. This back-fill material is loose and porous and will never be of the same nature as the original soil which was packed down by nature over thousands of years. This loose, air filled, "disturbed soil", will let water pass through it readily (as compared to undisturbed soil). The only saving grace is that water will not easily pass through dirt, especially if it is sloped so that the water keeps moving. Wherever there are flat areas or areas where the soil is sloped toward the building, any water that falls on or flows toward the foundation area (the ground around the building up to three feet from the foundation wall), will soak into the foundation back-fill area. Depressions in the soil around the building, which often occur from normal settling, also encourage this. The soil beyond the back-fill, called "undisturbed soil", is packed down by nature over a long period of time; where it is high in clay content it is almost totally impervious to water penetration. Thus, any water that makes its way to this area ultimately gets trapped (in the back-fill soil) between the "undisturbed soil" and the foundation. Continual additional inputs of new water can keep this area saturated; since the water must leave by either evaporation or capillary action, both of which are slow processes.

THEN WHAT HAPPENS? Constantly saturated soil next to the foundation structure ultimately results in secondary effects. Some of these effects are: damp walls, as the moisture migrates through the concrete; wet walls as water runs between cracks in the joints and fills hollow areas; mineralization or efflorescence, caused by long term dampness as moisture migrating through the wall evaporates, leaving minerals behind; appearance of water at the floor level, as the saturated soil drains itself of excess water, through the joint between the wall and floor, or some other opening. The presence of water in any form against the outside of the foundation means water pressure in various forms, and will always result in the intrusion of water and/or moisture into the interior. Secondary effects can be more serious including cracked or bulged walls, settled foundations and sunken or buckled floors.

Water and moisture buildup in the back-fill soil around the foundation has several negative effects. Two of the most severe affect the footing and the foundation wall. The footing is affected by water gathering at the bottom of the original foundation excavation (the bottom of the back- fill). When this area stays moist or wet for a long period of time, or when it gets extremely wet for short periods, the soil becomes plastic (or soft, mucky) and the heavy weight of the building pushes downward (sinks) slightly. When this happens, it almost always does so unevenly and the result is cracks in the foundation. The cracks are either shear cracks (vertical cracks) or step cracks (follow the mortar joint in block and brick). When the back-fill becomes thoroughly saturated with water, it also becomes heavy and plastic (plastic means pliable), exerting greater pressure on the foundation sidewall. During extremely cold weather, when this saturated soil freezes (and expands), tremendous pressures develop against the wall. When the wall can no longer resist these pressures it moves slightly inward, bulging, and splitting horizontally on the interior side. This weakens the wall and simultaneously reduces its waterproofing qualities. When the soil warms and thaws, the soil shrinks and settles downward occupying the new volume of space available to it which has been provided by the moving inward of the wall. This in turn provides an even lower area on the ground surface, at the same location, which in turn invites more water to gather and enter the soil; accentuating and promoting further deterioration.

WHAT CAN BE DONE ABOUT IT? Make sure that any surface water traveling across the yard is directed away from the building. Keep the gutters clean and in good working order; do the same for the downspouts and downspout drains. Provide a soil curb at the exterior of the foundation by building up the soil, preferably of clay soil or clay bearing soil (the more clay, the better for sealing purposes --top soil is spread on the finished surface only), at the foundation wall so that it is six to eight inches higher at the wall than it is two to three feet away.

Proper ventilation will facilitate and maintain the drying out process. Windows should be opened and perhaps a fan installed to force air through the basement or other damp areas. Simply placing a common room fan on the floor to circulate air is an improvement. A dehumidifier may also help, but its use should only be temporary or occasional. All basement areas should maintain good ventilation.

SOME COMMON BUT IMPROPER APPROACHES: This problem is so pervasive, that a myriad of approaches has been invented to attack it, most of them ineffective or even destructive. A common approach is the use of "French Drains". French Drains should not be used next to the foundation as they invite water into the ground. Sometimes French Drains are useful at the base of a hill or as area drains when at least seven feet away from the building. French Drains should not be confused with foundation perimeter drains (or footer drains), which are normal in many homes.

Footer drains, found at the exterior base of the foundation wall are safety drains drawing away water only when all else fails. When a footer drain becomes a working drain, it eventually clogs up and becomes useless, eliminating its safety protection.  There is absolutely no product or procedure that can be used on the interior of a foundation wall to dry it up; they just don't work. Of course, so-called "Waterproofing Company" practices should also be avoided. The information we give you here is, remarkably, not common knowledge; therefore, when hiring a workman to make corrections, do not rely on his expertise; you must take charge and make your instructions very clear.

THE COMPARATIVE COST: Generally speaking, filling in soil around the foundation is somewhat less expensive than all other approaches, but tends to be a more permanent solution. Especially since the work can often be done by the owner on a few weekends.

The preceding information is applicable to about 98% of all damp basements (including commercial buildings), especially in areas where the soil is high in clay content and, for the sake of clarity, is simplistic in its description; there are rare situations where water, causing damp basements, is from another source. Sandy soils can be treated similarly, especially if there is some clay available in the area to mix with and enrich the characteristics of the soil at the surface immediately around your building.

FOUNDATIONS

Although a wide variety of techniques and materials used in foundation construction exist, for our purpose we need only discuss those commonly appearing in the construction of local urban homes. A foundation is a stone, block or concrete system of walls build upon, or up from, a footing (usually poured concrete) so as to form a structure which supports the above ground main framework of the house. Foundations that extend partially or totally below ground level create a "basement" as well.

It is important to remember that any penetration of the ground interferes with natural drainage. Therefore, an appropriate drainage system should always accompany the construction of the foundation.

STONE

The earliest foundations were commonly build out of locally occurring or locally quarried sandstone or limestone, the most common material being sandstone. Less frequently, other materials were used such as granite While some sandstone foundations were laid up of beautifully cut stone (occasionally up to 400 pounds or more per stone), most foundations were laid up of rubble of uneven sizes and shapes. These foundations were usually 18" to 24" thick, more even on the inside than the outside, and mortared with low-grade material. The mortar served more as a filler than a bed and bonding agent (the manner in which mortar is now used), since the stones were actually layered directly in contact. Some of the oldest stone foundations were fitted up dry (no mortar) and only later sealed with a surface of clay or plaster wash.

Sandstone is a naturally porous material that allows moisture to pass through freely. In combination with the type of construction used, these foundations are difficult to waterproof and often are related to a damp basement. Another characteristic of this type is its ability to shift and move, particularly vertically. This is often caused by poor drainage. On the positive side, sandstone foundations are extremely durable, often remaining long after a building has burned or torn down and the foundation has been left exposed to weather for extended periods of time.

 BRICK

Brick foundations, a step up from stone, first made their appearance in the Eastern USA area in the mid to late 1800s when brick and masonry labor were relatively inexpensive. The period of popularity for these was relatively short and few remain today. The carry over from the brick foundation is seen when the brick chimney is carried down to (or build up from) the footer. One tendency shared by both brick and mortar chimney construction and sandstone foundations is porosity. This means that in spite of its strength, this can be an area where moisture is found penetrating into the basement.

POURED CONCRETE

Poured concrete is by far the strongest and most waterproof of all foundation materials. Its use in residential construction began in the USA around 1910. During the early late 1920s it gave way to modular concrete block which proved to be easier and cheaper to use. However, poured concrete is still used and preferred whenever the situation requires extreme water resistance, great strength, or is simply affordable under the design circumstances. More recently with the use of re-usable steel forms, poured concrete walls are becoming the builders’ choice of foundation construction.

CONCRETE BLOCK

Concrete block, the result of mass production and standardization in the masonry business, has been the preferred foundation building material since it became available, and for several reasons gets the most discussion.

Virtually all residential foundations built since the early 1940s are of this material. It exhibits good strength, water resistance and ease of handling. Since its inception, the concrete block manufacturing industry has continuously re-engineered concrete block gradually making it lighter and not as strong or water-resistant.

A less common factor in concrete block foundation malfunction is the thickness. Concrete block comes in 6 inch, 8 inch, 10 inch and 12 inch sizes commonly available, with 14 inch and larger being available on special order. Although they are rare, foundations requiring larger, or wider dimension, may have various thicknesses of block doubled-up to get the desired overall dimension. Very clear guidelines exist as to how thick a given foundation must be relative to the depth of soil it is to support and the actual load it will bear. Generally most foundation must be 10 inch to 12-inch block. Rarely, a shallow or utility foundation may be 8-inch block. The generally accepted vertical strengthening practice on very long/wide dimension foundation walls is to add periodic columns sometimes called "pylons", where the block is simply turned out and back in again in a tight structure that looks like a 16 inch wide square column protruding from the wall and rising from the bottom to the top of the wall. Horizontal strength is gained by adding standard reinforcing bar or specially made "zigzag" or running "H" bar every two or three courses of block. Extreme strength is gained by dropping reinforcing bar vertically down through the hollows of the block and filling the hollow portions of the block up with concrete (basically making a solid wall).

Concrete block is almost always hollow, since each individual block is constructed with voids or hollow areas.  This "hollow" characteristic of concrete masonry units allows some peculiar behavior such as "tanking" or the holding or water inside of the hollow block while the interior of the wall appears relatively dry. This hollow characteristic also allows air movement and vertical as well as horizontal travel of water inside the wall. Tanking occurs because the interior of the wall normally has tightly finished joints while the outside of the wall is often not as carefully finished or "struck" during construction. Tanking and interior water retention in concrete block walls often leads to much confusion about what is going on when a wall starts to "sweat" or "leak" water.

DAMP PROOFING, VAPOR BARRIERS

DAMP PROOFING as discussed here, is a material or system of materials designed to prevent the passage of moisture, dampness or minor amounts of water from the outside to the inside.

As it applies to building foundations, it is most commonly an application used on the exterior of masonry foundations. These systems are not capable of withstanding, and not intended to withstand hydrostatic pressures (standing liquid water). Necessarily, damp proofing is different from waterproofing and is usually cheaper and less complicated. Its purpose is to retard (slow down) the transfer of moisture/dampness.

Typical examples are plastic draped along the outside of a foundation wall, or a cementitous coating troweled onto the exterior of concrete block, or a tar, asphalt, epoxy, acrylic or silicon sealer. Liquid water will pass around seams in the plastic or through cracks in the concrete block mortar joints, and will eventually overcome most applied sealers. This is true especially when cracks appear in the masonry structure, from normal settling and stress adjustments. But in the absence of constant liquid water, damp-proofing materials will effectively retard the transfer of moisture from outside to inside thus inhibiting development of chronic damp conditions in basements and crawl spaces. Good performance of a damp proofing system requires the existence of proper and effective drainage (surface water control) around the exterior of the building.

VAPOR BARRIERS are used on the interior side of habitable rooms to retard vapor transfer into or through the walls, from the inside to the outside. Vapor barriers are some type of film or membrane through which vapor cannot readily pass. Water vapor is the gaseous form of water. Typical membranes used for vapor barriers are polyethylene plastic, tarpaper (roofing felt), or aluminum foil. Vapor barriers are always installed on the interior side of building walls and just under the interior finish (such as plaster or drywall). Many forms of wall insulation have built-in or pre-attached vapor barriers. Vapor barriers, when properly installed, are never installed on the exterior side of an outside wall; and never face down, or face out, in a crawl space. The purpose of a vapor barrier is to prevent warm, moist interior air from coming into contact with the interior surface of cold outside walls where it can condense to water. The presence of this condition (warm moist air against a cold surface) inside the wall cavities or on interior roof surfaces always results in damage to the structure. Such a condition encourages rot, mildew, deterioration of fasteners, peeling of paint, sagging of drywall and deterioration of plaster, de-laminating of plywood, discoloration of wallpaper and other problems.

EXTERIOR WATERPROOFING refers to a material or a system intended to prevent the passage of liquid water through roof, walls and floors.

VENTILATION

STRUCTURAL VENTILATION

One of the least understood and most often overlooked features of wall and roof construction is structural ventilation. The purpose of which is to remove excess water vapor and moisture from attics, crawl spaces and wall cavities. Or, to remove superheated air from under roof areas. Inadequate ventilation can allow condensation to occur and water content to increase in enclosed areas. This provides an environment that will encourage rot and insect attack and, deterioration of framing. It can cause warping; buckling or de-lamination of plywood and other wood products; and degrade insulation and interior finishes such as plaster and drywall. Deficient ventilation in attic areas can cause early failure of roof covering from summer heat build up, plus increase summer cooling cost while decreasing comfort. Proper ventilation will extend the potential life of the structure, reduce the frequency of repairs and increase the safety and welfare of the occupants and contents.

Ventilation of living spaces is important for the maintenance of the proper balance of interior temperature and humidity. Ventilation of roof, crawl spaces and wall cavities do not necessarily (and should not) interact with the ventilation of interior space.

Older homes are usually not tightly sealed and therefore provide a high rate of air changes per hour (ACH).  Newer homes are more tightly built (starting in the 1950's). Tighter homes have a lower ACH and are somewhat more energy efficient. The ventilation needs of these can normally be achieved by the use of windows and common ventilator fans.

UNDERGROUND WATER TABLE

Possible definition: an ubiquitous formless inscrutable monster hiding just underground, waiting to suddenly, unexpectedly surface, terrorize, overrun and submerge everything within reach.

The term "water table" and "high water table" are buzzwords. The water table term is widely used to mean different things, depending on to whom you are talking, and about what. The various definitions of what a water table is are beyond the scope of this article However, for simplification a few things may be said:

·        A water table may exist where water gathers in a level body.

·        True water tables do not change much (one inch per century is a large side of direct major human intervention.

·        Most true water tables are many feet down (usually 50 feet to hundreds of feet).

·        In developed locales where a true water table is "high" or not very far down, such as in many parts of southern coastal Florida, houses are, by law, not permitted to be built with basements.

"French Drain,” means a buried drain system used to collect and channel water in a controlled manner. Not unlike a storm sewer or underground pipe, but different in that the pipe may be perforated or have loose joints, may collect water along its entire length and usually is utilized for subtle, slow moving, or small-but-steady amounts of water such that a ground surface drying affect is produced in a given area.

An exterior French Drain used to remove surface water, is constructed by digging a trench or ditch a given depth and length, filling the trench up with a fairly solid but permeable material such as river gravel or crushed stone; usually with a perforated pipe laid at the bottom of the trench and traveling its entire length. The bottom of the trench should be below the frost line, but sometimes at or below the lowest point of a structure it is intended to protect (to intercept the water and direct the it away from the structure). The bottom of an exterior French Drain ditch must be sloped downward if it is not cut into a hill or natural slope. When used to collect surface water, such as at the base of a hill, it is often left open at the top (so the gravel can be seen at the surface); when intercepting significant amounts of surface run-off, if the gravel or stone does not travel all the way to the top of the surface (to "daylight"), it may not work well, or at all.

All French Drain installations are improved and protected when accompanied by ground surface treatments such as terraces (on hills), swales, curbs, dikes or crowns; and by sealers on the exterior of foundation walls.

The one use of French Drains that surpasses all other uses in commonality, concern and misunderstanding, is the almost universal footer drain. Footer Drains, also known as perimeter drains and foundation drains; are used at the outside base of building foundation walls to protect against and prevent ground water entry. The use of these drains is a science and a controversy in themselves, with many variations having been added in recent history. The one universal application of the foundation French drain, which is most proven and most widely accepted is simply the placement of a drain pipe covered with gravel at the outside base of a foundation; followed by adding dirt from the building site (back-filling) to the top of the excavation.

You may be getting the feeling that French drains are found everywhere. Quite simply, structures can not survive without them in any climate where there is moderate rainfall, snowmelt or a frequent frost-heave cycle. So, they are nearly universal. But, they are also nearly universally out of sight.

So why are they so mysterious, or why all the confusion. Given that they are expected to last indefinitely --a misconception-- they are put in place at the time of construction and buried, usually without any type of access or maintenance feature. It is generally assumed they are there, but the average person never sees one. A failure gives rise to suspicion and speculation without benefit of direct observation. Often the worst is assumed: that some sort of subsurface water source exists or has suddenly arrived, and overcome the capacity of the original French Drain. Other factors contribute to misunderstanding such as the phenomenon of water showing up a day or two after an extended period of rainfall, and continuing to run for some days after the rain has stopped. Water coming in immediately during a rain and stopping with the rain can be equally confusing to some that don't make the connection between rain and basement water. Sometimes once the water begins to enter it just never stops, which seems mysterious, because it just "suddenly" appears. The owner has little way of knowing that slow changes around his building have set him up, the process has fermented and the last rain triggers the final act --water coming through the foundation.

Much confusion exists because of decades of armies of "Water Proofing" salesmen bleating about underground springs.

Further confusion exists because of decades of armies of "Water Proofing" salesmen bleating about underground springs (which mainly exist in the imagination of the salesmen) and other less than likely scenarios; but infect the unschooled building owner with panic. The "Water Proofers" get a great degree of credence because most lending institutions and banks, self servingly endorse this quick fix. Even plumbers get in on the act --why not. But the real cure is too cheap and too easily done by just about anyone to get any marketing finance. Like a lot of things, only the complex, hard to understand, short lived, but easy to execute approach gets any salesmen going to bat. Think about it, wouldn't it be a lot easier to sell something that requires work just a little beyond the capability of most homeowners, but not so difficult as to require specialized trades, is buried and not readily accessible for criticism when done, and resolves a homeowners panic without the liability of digging up their yard. And, appears to be a quick fix. But with little factual intelligence left behind by the person only interested in making a sale, the salesman does little to diminish confusion. When these often short lived, instant fixes fail again, the salesman is usually "no longer available". Panic is un-assuaged. Misunderstanding continues. Factual information is unavailable.

Information on the proper use of French Drains is something you can get access to. Any time you face the task of using French Drains, consult with a proven independent expert. That should be the first step. This is true with solving water collection and dampness problems in general. An expert can save you a ton of money and a world of aggravation from effects of dampness.