Why Use a Dehumidifer? In spaces that are naturally more damp, such as basements and crawl spaces, a dehumidifier will help dry the air, reducing musty odors and preventing mold growth and other issues caused by excess moisture.
A basement dehumidifier helps maintain an ideal indoor relative humidity (RH) level in the space. The Environmental Protection Agency suggests that the indoor relative humidity be kept between 30-60% to help prevent mold growth. A home with relative humidity above 60% can also be a breeding ground for pests and wood rot
When constructed properly and with the appropriate air conditioning and ventilation, a basement should be dry. But many basements are particularly prone to dampness because of their poor design and ventilation. Dampness like this is a perfect breeding ground for mold and mildew, especially in basements where old books, magazines, clothing and suitcases are stored.
When the humidity level goes over 50%, the water vapor in the air can cause furniture to warp, moisture to condense on walls and floors and promote growth of fungus. It will also accelerate wood rot. For those family members with allergies, a basement dehumidifier is crucial to lessen the health risks linked to toxic mold and fungus.
Many of the most common causes of allergies, including dust mites, mold, and mildew, thrive in humid environments. Whether you live in a humid climate, or you just have a living space that tends to be more humid, you may be suffering from these things. Small living spaces with limited ventilation, such as bathrooms or kitchens in a small apartment or basement apartments, are common areas where moisture can build up, even in dry climates.
Moist, damp air is the ideal environment for mold to flourish (50-65% humidity), and a dehumidifier can remove the surplus moisture while preventing new mold from growing. If you or anybody in your home suffers from frequent asthma attacks or if you see mold growing in various places, then you should strongly consider getting a dehumidifier for your home.
But before you go off to purchase a basement dehumidifier, consider taking some time to investigate the reason behind the high humidity, and then repairing the underlying problems. For example, your basement should ideally be the same temperature as the rest of your house, and not an isolated cool temperature zone. Try adding weather-stripping to any basement doors and windows. If the basement is uninsulated, youll have to weigh the costs of adding insulation against that of running a basement dehumidifier.
Buying a basement dehumidifier will require a little planning. Know the cubic footage of the basement space that it will be going into. Also you will need to decide on getting a permanently installed unit versus a portable dehumidifier. An other shopping point is to consider are the size of the unit- will it fit in the space you are planning for it? Also be aware that some models are noisier than others, so ask for a demonstration before you buy.
Noise levels – The noise level of the specific basement dehumidifier is also crucial. For basement use, I’d advise you to go with a unit that emits more noise. But you shouldn’t invest in one that is extremely noisy. I’d recommend that you go for a unit that’s moderately noisy. It will tell you if the unit is running or not. If you are thinking of using the same unit in your living room or bedroom, the more silent model is probably your best option.
During home inspections in Barrie Ontario, I come across many basements with running dehumidifiers, which is not unusual, but if the basement still has damp feeling or smell, then it is very important to check all exterior walls with moisture meter and thermal imaging camera.
Thermal Imaging measures the temperature of walls, ceilings, and floors. The infrared camera shows a colour screen indicating a visual picture of either moisture or hot spots. This is especially useful for finding hidden moisture, missing insulation or electrical hot spots. Thermal Imaging identifies changes in an items thermal structure that the human eye cannot see.
Options for Basement Flooring. Getting ready to finish your basement? Then you’re probably wondering what kind of flooring to use. There are various options that you should and can use, and we’re going to take a look at three of the most popular types of flooring.
Carpet is the most commonly used flooring coverings and is the most commonly used for basements. It is inexpensive, and also is a great and commonly used material. However, carpet can be more easily stained than some other materials we’ll discuss. One of the greatest things about carpet is that the installation is quick and it is easy on the feet.
Ceramic tile is another common option for flooring in a basement. It is one of the most attractive options, and spills are easily cleaned up without worry of stains. Ceramic is more expensive than carpet. It requires more floor preparation, and it is often recommended that a special base layer be installed to prevent tile from cracking if your concrete floor settles. Ceramic tile can be hard and cold on the feet, especially in basements which tend to be cooler than upper levels.
Laminate and hardwood floors are really a nice touch in a basement. These options are about the same cost as that of ceramic tile, and just like ceramic require a substrate installed before laying the hardwood. Homeowners often find laminate and hardwood to be their favorite material option. Laminate can now be bought which only requires a roll of dimpled vapour barrier to be laid down first. This simplifies installation and reduces costs.
In summary, there are 3 primary options for flooring in your basement. Hardwood, ceramic and carpet. Remember, hardwood is more expensive but very beautiful and most experts would never recommend hardwood to be used in basement due to the ease of which is will wick up moisture, causing visible cupping of boards. . Ceramic is a bit easier and can deal with a little moisture with no problems. Ceramic tile is also great for bathrooms. But both hardwood and ceramic last a very long time, and are good for cleaning and maintenance. Carpet can be durable as well, but is more susceptible to staining. Balance the initial costs of each, along with future maintenance costs and longevity, and you will be happy with your ultimate selection.
Remember that some flooring such as hardwood will require a special sub-floor to cut down on moisture absorption and cupping of the individual boards. The Barrie Home Inspector uses a moisture meter to assess the basements moisture content and also included Free thermal imaging scans.
Solving Basement Water Problems. Many “how-to” magazines run articles touting miracle products that stop water from permeating through foundations or basement walls and floors. While some products may be effective at mitigating water migration through cracks or flaws in a wall, blocking groundwater can be as tough as keeping water from leaking through split seams of a wooden boat. So long as any part of the boat is in the water, a certain amount of water is bound to find its way inside.
Never wait until water enters the basement or permeates the foundation before treating the root cause. The resulting dampness is both distasteful and potentially dangerous, even if there is no noticeable standing water.
There are four ways that moisture can permeate foundations or enter and collect in basements:
High groundwater table Surface (rain)
water leaking through openings or flaws in the walls Condensation Broken plumbing and/or irrigation runoff High Groundwater Table
Wet basements are a very common problem, particularly in low-lying areas or mountains where high water tables are common. This means that the ground water level has risen up to its high point for the year due to melting snow, spring rains, lack of water pickup by the trees and plants, and the absence of sun to dry the ground during the winter. Some soils such as clay bind water tightly, keeping the water table high for extended periods. Porous soils including sands and gravels pass water quickly, yet often have high springtime water tables, especially in low areas due to excess springtime runoff. Unfortunately, many homes are built with inadequate protection from groundwater, even though site conditions may be well suited for the proper installation of a simple and cost-effective drainage system.
Once a water problem is discovered after a house is built, it is very difficult and expensive to remedy. If left unchecked, structural and health-related problems may persist. Excessive moisture not only results in a musty smell or damage to carpet and wood flooring materials, but it promotes growth of mold spores, which can result in asthmatic symptoms in many people. For this reason, the use of vapor barriers under slabs as well as other drainage techniques are essential to keeping your home dry year-round.
To help illustrate the high groundwater problem, imagine a 12″-high pile of sand in the middle of your bathtub — with six inches of water in the tub around it. If you were to dig a six-inch-deep hole in the sand, you would find water at the bottom of the hole. By adding more water to the tub, the water level in the hole would rise as the surrounding water reached equilibrium due to hydrostatic pressure. This simulates the effect of a higher water table acting on a foundation. Now, inserting a watertight box into the hole would cause it to float. If there were holes in the box, water would seep inside. In this analogy, the box is the basement or foundation, and the tub water is groundwater.
Wrong Culprit
Years ago I did a job for a homeowner who insisted that her basement became wet only after a rainstorm. After lots of digging and waterproofing, (and continued water in the basement) I was left with a serious question about the real source of the water. Finally I started checking the house plumbing and discovered a leak in the water heater! I’ve learned to more be suspicious.
Keeping Water Out Ironically, making residential basements absolutely watertight can lead to other problems if not properly engineered. For example, basements of many commercial buildings in highly developed areas are built watertight.
However, their construction costs are extremely high compared to typical residential basements because their foundations and floor systems are built to far more stringent specifications. This is not only to keep water out, but to keep the high pressure of outside water from causing structural damage.
Consider this real-life situation that occurred a few years ago: During one extremely rainy night, a family awakened to a strange sound coming from their basement. Apparently, excess rainwater had saturated the ground around their home given its location in the lowest section of their development. The extreme pressure from the accumulated ground water actually buckled up the basement floor, causing the soil from under the floor to erupt six feet, covering their washer and dryer. The sudden soil displacement undermined the overall foundation, causing one of the walls to fall over a foot. The house was abandoned for massive structural repairs. Although this is an extreme example, it demonstrates the powerfully destructive force of water. This foundation was built in a manner similar to many residential basements. Yet, by allowing the groundwater pressure to rise without relief, failure resulted in the weakest part of the structure which, in this case, happened to be the concrete floor. Ironically, if homes were absolutely watertight, they might even float like the box in the bathtub, resulting in an unstable structure.
Current building codes require homes have sump pumps to discharge out any water that might leak in which could otherwise damage the basement. Fortunately, as water is pumped out of the basement, the water table around the house is lowered, (like pulling the plug on the bathtub drain) relieving the “hydrostatic” pressure. This is why floating houses or erupting floors are rare.
One effective way to check the water table near a house which has a dug well is to uncover the well and measure the depth from the ground surface down to the water. Compare this depth to that of the basement floor below grade and the difference equals the depth to which the basement would flood if the water were not removed. Even if the house is located on sloping terrain, the water table remains approximately the same distance down from place to place as groundwater tends to follow the contour of the surface.
Perimeter Drains
In many situations, particularly in mountainous regions where the land is seldom flat, it is possible to drain water away from most foundations and basements by gravity rather than by pumping. The traditional method specifies a perimeter drain around the outside of a building during its construction. The drain outlet slopes downhill away from the house until it reaches the surface of the ground where it can freely discharge by gravity flow. The advantage of this method over pumping water out of a sump is that it lowers the water table around the house, preventing water from ever reaching the cellar in the first place.
In many instances where experts have been asked to troubleshoot wet basement problems, a common finding is drain pipes that were installed above the foundation footing, which allows water to rise to the level of the floor. If the builder made the additional mistake of installing the drain pipe with the weep holes facing up, then the level of water has to rise to the top of the pipe before the pipe can pick up any water. Other times there is little or no porous bedding material and pipe inlet holes can become plugged. Another problem occurs with large bedding stone. Migration of the original soil into the bedding plugs up the stone, leading to failure. Often a combination of problems may coexist.
Conventional perimeter drains are usually constructed with 4″ pipe laid at the base of the footing. Most contractors use 1 1/2″ crushed stone around the outside of PVC or thinwall perforated septic system pipe which has 1/2″ or 5/8″ holes every few inches. Usually this is entirely satisfactory, though in some cases capillary action (wicking) within the soil can make the basement floor damp even though it is a few inches above the artificially lowered water table.
Due to the severe conditions encountered when building a home several years ago, the following example illustrates an improved method. Just as sitework started, the property was deluged with rain. The rain aggravated an already difficult groundwater situation, threatening postponement of construction. However, with patience (and a good pair of rubber boots), perimeter drains were installed four feet outside of where the house was to be located. Within days of installing the drains, excavation for the basement was able to proceed as if it were a dry summer. The home is built into the ground about six feet deep on a gently sloping hill. Several years have since passed and the home has never been bothered by moisture in the basement. This is in spite of the original springtime water table just two feet below the surface of the ground. This same procedure is excellent for drying out existing wet basements where conditions permit.
Ensuring Effective Drainage
The first consideration is setting the drain pipe deep enough to lower the water table well below the floor in order to reduce the effects of capillary action (wicking). Another way to reduce this effect — generally limited to new construction — is to install a layer of crushed stone entirely under the basement floor. Water cannot “wick” through this coarse aggregate. Although this is more costly, it is good insurance for a dry basement. Alternatively, installing the drain pipe a little lower may be a very cost-effective alternative, assuming there is sufficient side hill grade to ensure gravity discharge well away from the structure.
For new construction and retrofit situations, place the drain pipe a foot or more lower than the footing whenever possible and far enough away to avoid undermining the foundation. Generally 2′ to 4′ or even more is necessary to protect landscaping or porches and similar structures. In retrofit situations, installing a drain on the upgrade side of the house can yield a significant improvement, as it is usually only necessary to intercept water moving through the ground toward the house to eliminate the moisture problem. This type of drain is considered a “curtain drain” rather than a footing or perimeter drain, especially if it is several feet from the house. Its job is to lower the water table downgrade in order to protect the house. The curtain drain method is an important consideration particularly for retrofit installations as it can reduce site disruption and the resulting cost of excavation.
some checking and told the folks that a gravity drain could probably solve the problem. They went ahead and had one installed and have had no more trouble with unexpected flooding or pump maintenance since. What is surprising is that it took a college education and several years in the construction field before I was able to make such a simple and obvious recommendation. Yet I know of similar situations that exist today, and houses that are being built where sump pumps are expected to do what could have been done with a few pieces of pipe and some planning. Many basement drainage companies still rely on sump pumps for all installations, regardless of whether or not gravity could be used to discharge the water. This creates a long-term dependence on a mechanical device. Sump pumps can get plugged up, wear out, fail to come on after months of non-use, or stop because of a power failure. Unfortunately, it is often during the worst weather conditions when power is lost in rural areas while, at the same time, excessive rainfall is causing the water table to rise. About the only assured way to protect a basement is to install a redundant pump and a separate circuit coupled with a battery-powered back-up system that automatically kicks in when all else fails. Such systems are now on the market but represent additional investment and occasional maintenance to keep them in working order. They use an automotive-type battery for power, similar to safety lights in public buildings. If there is no choice but to install a sump pump, selecting the right pump should be based on the severity of the situation. There are many types market, but the extra money spent for a high quality submersible style with a built-in switch is well worthwhile, especially in extreme situations. Excessive dampness can quickly corrode unprotected motors on pedestal pumps and a power failure that allows water to completely cover an unprotected motor can require replacement of the entire pump. Also, there are automatic switches now available that allow sump pumps to draw water down to within a fraction of an inch of the floor and to turn on when water is only slightly deeper. This can be helpful for occasionally dewatering a basement without digging a sump hole through the concrete floor. Filter Fabric: Synthetic cloth-like material that is used for several different types of construction related applications such as erosion control, road stabilization and soil separation. Can consist of either woven or non-woven fibers in varying thicknesses or weights. Available in 12 to 15 foot wide rolls several hundred feet in length. Woven fabrics (usually black) resemble the stuff that modern day grain bags and weed control fabric are made from while non-woven fabrics can resemble a range of materials from soft felts to the stiff shiny house wrap (to which they are closely related) usually seen enveloping homes under construction.
Maintenance
It is essential to keep the drain outlet running freely. The rodent guard must be kept clear of any debris. The area below the outlet must be kept cleared of leaves and debris, especially if the drain empties into a ditch. Sometimes drains that have clogged up internally can be cleared by the use of a pressure washer (or even a garden hose) to break up the clog. I’ve cleared obstructions from perimeter drains and had water drain out of the basement just like water leaving a bathtub.
Properly installed perimeter drains create an “island” out of the house site by lowering the water table completely around the house. They keep water from entering under the footings and, in my experience, provide the surest protection against any type of dampness in a basement resulting from groundwater.
There are some situations where perimeter drains are not necessary, however. A thorough knowledge of the site, or an exceptionally low water table indication from a septic system test pit, can provide such a determination. If you happen to be one of those folks already blessed with an unwanted indoor swimming pool each Spring, whether in a new or existing house, rest assured that there usually is something that can be done. However, since soil conditions vary so greatly, it is wise to consider your circumstances carefully before deciding on a course of action.
Also see the University of Minnesota Extension Bulletin Moisture in Basements: Causes and Solutions Filter material: According to the American Iron and Steel Institute’s Handbook of steel drainage and Highway Construction Products, 1967: “Early subdrains consisted of a trench filled with coarse rock (“french” drains) which quickly silted up. Extensive research by the U.S.Waterways Experiment Station at Vicksburg, Mississippi, shows that a graded material roughly equal to concrete sand (AASHO Specs) has been found most suitable. Such material gives better support to the sidewall of the trench and thereby reduces erosion and silting. Filter material should be placed in layers and tamped.” Leaks in Foundation Walls Another condition that can sometimes appear to be high ground water leaking in may simply be surface water entering over or through the foundation at bulkheads or window openings, seams between walls, and/or, flaws in the foundation.
Poor surface grading can direct water toward the lip of a bulkhead or towards basement windows where it can spill over into the basement. By not paying attention during heavy rains, a homeowner can sometimes end up blaming the wrong culprit.
Surface water leakage
Surface water leakage is reasonably easy to locate once you get on track. The solution often involves regrading to drain water away from the foundation. In the case of foundation windows, however, it is not always possible to shed water away since the bottom of the windows are often too far below the adjacent ground, requiring the installation of window wells. These often consist of corrugated galvanized steel half circles but can also be made of pressure treated wood or masonry. The goal is to make the top of the window well high enough to be able to slope the surrounding ground surface away from the house. A problem arises when the window well is directly below the roof drip, especially in cold, wet climates where rain gutters are seldom used (because snow and ice fills them, making them useless, or ripping them from the building!)
The solution is either to cover the window well with a clear plastic dome which also keeps out leaves and critters or to create a mini-drywell under the window well to allow rainwater to soak away into the ground before it can rise up and find its way through the window. This leads to another issue: porosity or flaws in the wall itself. If a foundation wall is totally watertight there is little problem with letting water run down against it all the way to the perimeter drain. If the wall has had adequate damp-proofing and/or the water drains quickly through the soil, there is little to be concerned about. The problem is that many foundations are have defects and hairline cracks which allow water infiltration.
Sources of Leaks in Foundation Walls
Concrete block foundations often crack in the grout joint between blocks. Even poured concrete or ICF walls can develop shrinkage or settling cracks in addition to water channels from anchor bolts and form ties. Honeycombing due to improper vibration and consolidation is another source of leakage, wherein the concrete aggregate became separated leaving voids in the wall. In addition, poured walls often have seams between different stages of the pour.
Another problem exists with many of the older foundations that are constructed of various sizes and shapes of cut granite and round fieldstone. With or without mortar between, these foundations typically exhibit numerous passages for water to follow. Water can enter walls around utility penetrations such as sewer, water, gas or electrical conduits. There are several instances where I’ve been engaged to dig around existing buildings and to waterproof walls and/or install drainage systems only to discover that the actual problems were unrelated to groundwater. Having been under the direction of an architect in some cases, I’ve had to follow his recommendations rather than follow my instincts to determine the problems.
Consider this example that involved an old house with a loose stone foundation. The original work that was done under the direction of the architect only aggravated the wet basement problem. Digging a shallow perimeter drain actually allowed more water through the porous basement wall. This was the same mistake many people make when they dig out next to their foundation wall and replace the original backfill with crushed stone either for appearance and splash protection. Putting crushed stone directly over the original soil, even with the installation of a perforated drain pipe often causes more water to enter the ground. The crushed stone becomes a dispersion system in the same way it does in a septic drain field. Usually little water enters the drain pipe, except in a deluge, and more water soaks into the ground next to the foundation where it makes its way into the basement.
What I did to solve the problem was to seal the outside of the wall with a coating of concrete that directed surface water away from the foundation as it soaked into the ground, keeping it from streaming through the loose stone foundation. The addition of a bituminous asphalt coating or a Bituthene membrane can also help to keep water from penetrating the foundation wall. The success with this project has prompted me to use this technique in many other situations. Rather than using concrete, however, in most cases I rely on a layer of rubber or plastic to direct water away from the wall. Usually I excavate just a few inches below the surface next to the building and three to four feet lower at a distance of four to five feet from the wall, sloping the soil down on a 30 to 45 degree angle away from the building as I go. I rake the earth smooth, remove all rocks and sticks, and tamp it firm. Then I install a layer of rubber or a couple of layers of 6 mil polyethylene over the slope, right up to the wall. I don’t usually worry about sealing against the wall, as my primary concern is to direct the majority of the surface water away from the wall and out into the earth where it can soak harmlessly away, leaving a “dry zone” beneath the membrane next to the wall. I use this same technique under a window well if there is any question about the integrity of the wall below the window. I dig out a few extra feet, slope the soil, install the plastic membrane on the slope, place crushed stone as a mini drywell for any rainwater that may enter, install the window well structure and then backfill to the surface as discussed.
This technique of installing a membrane just below the ground surface is similar to installing “flashing” around a chimney or other structure on a roof. One of its biggest benefits is that it can eliminate the need to completely excavate a foundation wall all the way to the footing and attempting to waterproof it. It is somewhat similar to installing a full length “splash block” mentioned in other basement drainage articles on the Internet except that it is out of sight. I’ve also had success with this technique even when attempts to make the wall watertight below have failed.
Concrete foundations are of two types – poured concrete and concrete block. Poured concrete is a modern manner of laying foundations, while concrete blocks are more traditional. Concrete blocks are preferred for their visual appeal and strength. Yet, as time passes, there may be degradation of concrete.
The prime cause of cracks in concrete foundation is seepage of water. Such cracks caused due to leakage of water are thin and hairline. They may widen over time, but they are present only in those areas where the seepage occurs. In order to repair leakage cracks, it is necessary first to investigate the source and the point from which the leakage originates. There may be other reasons for concrete foundations to crumble. Soil may lose its moisture content in summer. There may be underground roots which may wither and die. Such natural causes make the soil shrink and hence the foundation may move. Though this movement is gradual, overtime it will cause cracks to occur. These cracks will be large gaping ones, running across the entire length of the foundation. They may even be in the form of tiny holes in certain places. Whatever be the reason, cracks in the foundation are very perilous if ignored. Repair must be done as soon as possible.
Difficulties involved in the repair process are influenced by how big the cracks are. For tiny moisture created cracks, the repair is relatively simple and can be done by almost anyone. These cracks must first be brushed clean with a wire brush. A jet of water may be passed to remove any loose concrete particles within the crack. The crack is then allowed to dry completely and filled with concrete caulk. If the crack is large, then it is packed with patching materials that are specifically available for concrete. These patching materials must be wet when applied. They are limestone based, and they expand as they dry, filling up the crack completely. The finishing touch is to apply a sealant to the repaired crack. But if the crack is sinister and not the do-it-yourself kind, then it is most prudent to shell out a few dollars and hire some good repairmen. Such cracks occur due to rods which may have rusted inside and snapped or because of deterioration of the materials present within the concrete.
Some leakage cracks when ignored can also reach dangerous levels. Such cracks are more found in poured concrete. Contractors treat the concrete foundation with urethane injections to extract the embedded water. They may even excavate the area around the foundation and replace the faulty tile or construct a provision for the water to lose contact with the foundation.
Foundation Repair
The principal function of a foundation of a home is to transfer the weight of a structure to its underlying soil and rocks. One of the factors that bring about the need for foundation repairs is improper foundation settling. Foundation settlement can devalue structures and also render them unsafe. Building on expansive clay, compressive or improperly contracted fill soils and improper maintenance in and around foundations are some of the major reasons of improper foundation settling. Another reason for improper foundation settlement is undetected or unsuspected air pockets in the ground below the area of construction. These may cave in and cause the integrity of the foundation to be compromised.
General symptoms of a structure needing foundation repairs are bulging or cracked walls and doors that don’t close properly. Building on expansive soils is the main culprit for foundation settlement. When only one part of the foundation either settles or heaves, cracks are formed in the foundation.
The exterior warning signs of improper floor settling are rotation of walls, displaced moldings, cracked bricks and foundation and separation around doors and windows from the walls.
Interior warning signs of improper floor settling are cracks on the floor, sheet rock and misalignment in doors and windows. There are many ways of doing foundation repair. Cement, stone, steel or wood were used extensively in past techniques. They would be forced into the ground in a bid to salvage the strength of these foundations. However, this type of repair work has been known to be futile.
Two of the most successful ways of foundation repairs are slab jacking and the Piering method. Piering is also known as hydraulic jacking. Slab jacking is the process of adding grout beneath a slab or beam. This produces a lifting force and restores the said beam or slab to almost its original elevation and adds to its strength. Care should be taken that the amount of sand should be perfect while adding grout. During Piering, steel posts are driven through unstable soil. Hydraulic jacks are used to stabilize concrete slabs which are weakened due to the changes taking place in the underlying soil. Steel beams are used in the Piering method because concrete has great compressive strength. Though Piers are able to transfer huge downward loads without the help of reinforcing steel, steel is used in the piers for prevention of the pier from being pulled apart or sheared by forces of the expansive soils. The repairs normally take 21 to 30 days, however this time frame can vary depending on soil conditions and weather delays. This article is for general knowledge only, always consult with an expert regarding any structural design issues or faults.
The Barrie Home Inspector has inspected over 8,000 foundations. For more information on foundations or water penetration visit blog on home maintenance and tips.
Many “how-to” magazines run articles touting miracle products that stop water from permeating through foundations or basement walls and floors. While some products may be effective at mitigating water migration through cracks or flaws in a wall, blocking groundwater can be as tough as keeping water from leaking through split seams of a wooden boat. So long as any part of the boat is in the water, a certain amount of water is bound to find its way inside.
Never wait until water enters the basement or permeates the foundation before treating the root cause. The resulting dampness is both distasteful and potentially dangerous, even if there is no noticeable standing water. There are four ways that moisture can permeate foundations or enter and collect in basements:
High groundwater table
Surface (rain) water leaking through openings or flaws in the walls
Condensation
Broken plumbing and/or irrigation runoff
Wet basements are a very common problem, particularly in low-lying areas or mountains where high water tables are common. This means that the ground water level has risen up to its high point for the year due to melting snow, spring rains, lack of water pickup by the trees and plants, and the absence of sun to dry the ground during the winter.
Some soils such as clay bind water tightly, keeping the water table high for extended periods. Porous soils including sands and gravels pass water quickly, yet often have high springtime water tables, especially in low areas due to excess springtime runoff. Unfortunately, many homes are built with inadequate protection from groundwater, even though site conditions may be well suited for the proper installation of a simple and cost-effective drainage system.
Once a water problem is discovered after a house is built, it is very difficult and expensive to remedy. If left unchecked, structural and health-related problems may persist. Excessive moisture not only results in a musty smell or damage to carpet and wood flooring materials, but it promotes growth of mold spores, which can result in asthmatic symptoms in many people. For this reason, the use of vapor barriers under slabs as well as other drainage techniques are essential to keeping your home dry year-round.
To help illustrate the high groundwater problem, imagine a 12″-high pile of sand in the middle of your bathtub — with six inches of water in the tub around it. If you were to dig a six-inch-deep hole in the sand, you would find water at the bottom of the hole. By adding more water to the tub, the water level in the hole would rise as the surrounding water reached equilibrium due to hydrostatic pressure. This simulates the effect of a higher water table acting on a foundation. Now, inserting a watertight box into the hole would cause it to float. If there were holes in the box, water would seep inside. In this analogy, the box is the basement or foundation, and the tub water is groundwater.
Wrong Culprit Years ago I did a job for a homeowner who insisted that her basement became wet only after a rainstorm. After lots of digging and waterproofing, (and continued water in the basement) I was left with a serious question about the real source of the water. Finally I started checking the house plumbing and discovered a leak in the water heater! I’ve learned to more be suspicious.
Keeping Water Out
Ironically, making residential basements absolutely watertight can lead to other problems if not properly engineered. For example, basements of many commercial buildings in highly developed areas are built watertight. However, their construction costs are extremely high compared to typical residential basements because their foundations and floor systems are built to far more stringent specifications. This is not only to keep water out, but to keep the high pressure of outside water from causing structural damage. Consider this real-life situation that occurred a few years ago: During one extremely rainy night, a family awakened to a strange sound coming from their basement. Apparently, excess rainwater had saturated the ground around their home given its location in the lowest section of their development. The extreme pressure from the accumulated ground water actually buckled up the basement floor, causing the soil from under the floor to erupt six feet, covering their washer and dryer. The sudden soil displacement undermined the overall foundation, causing one of the walls to fall over a foot. The house was abandoned for massive structural repairs. Although this is an extreme example, it demonstrates the powerfully destructive force of water. This foundation was built in a manner similar to many residential basements. Yet, by allowing the groundwater pressure to rise without relief, failure resulted in the weakest part of the structure which, in this case, happened to be the concrete floor. Ironically, if homes were absolutely watertight, they might even float like the box in the bathtub, resulting in an unstable structure. However, many homes have sump pumps to discharge out any water that might leak in which could otherwise damage the basement. Fortunately, as water is pumped out of the basement, the water table around the house is lowered, (like pulling the plug on the bathtub drain) relieving the “hydrostatic” pressure. This is why floating houses or erupting floors are rare.
One effective way to check the water table near a house which has a dug well is to uncover the well and measure the depth from the ground surface down to the water. Compare this depth to that of the basement floor below grade and the difference equals the depth to which the basement would flood if the water were not removed. Even if the house is located on sloping terrain, the water table remains approximately the same distance down from place to place as groundwater tends to follow the contour of the surface.
Perimeter Drains
In many situations, particularly in mountainous regions where the land is seldom flat, it is possible to drain water away from most foundations and basements by gravity rather than by pumping. The traditional method specifies a perimeter drain around the outside of a building during its construction. The drain outlet slopes downhill away from the house until it reaches the surface of the ground where it can freely discharge by gravity flow. The advantage of this method over pumping water out of a sump is that it lowers the water table around the house, preventing water from ever reaching the cellar in the first place.
In many instances where experts have been asked to troubleshoot wet basement problems, a common finding is drain pipes that were installed above the foundation footing, which allows water to rise to the level of the floor (Figure A, level Y). If the builder made the additional mistake of installing the drain pipe with the weep holes facing up, then the level of water has to rise to the top of the pipe (level X) before the pipe can pick up any water. Other times there is little or no porous bedding material and pipe inlet holes can become plugged. Another problem occurs with large bedding stone. Migration of the original soil into the bedding plugs up the stone, leading to failure. Often a combination of problems may coexist. Most contractors use 1 1/2″ crushed stone around the outside of PVC or thinwall perforated septic system pipe which has 1/2″ or 5/8″ holes every few inches. Usually this is entirely satisfactory, though in some cases capillary action (wicking) within the soil can make the basement floor damp even though it is a few inches above the artificially lowered water table.
Due to the severe conditions encountered when building a home several years ago, the following example illustrates an improved method. Just as sitework started, the property was deluged with rain. The rain aggravated an already difficult groundwater situation, threatening postponement of construction. However, with patience (and a good pair of rubber boots), perimeter drains were installed four feet outside of where the house was to be located. Within days of installing the drains, excavation for the basement was able to proceed as if it were a dry summer. The home is built into the ground about six feet deep on a gently sloping hill. Several years have since passed and the home has never been bothered by moisture in the basement. This is in spite of the original springtime water table just two feet below the surface of the ground. This same procedure is excellent for drying out existing wet basements where conditions permit.
Ensuring Effective Drainage
The first consideration is setting the drain pipe deep enough to lower the water table well below the floor in order to reduce the effects of capillary action (wicking). Another way to reduce this effect — generally limited to new construction — is to install a layer of crushed stone entirely under the basement floor. Water cannot “wick” through this coarse aggregate. Although this is more costly, it is good insurance for a dry basement. Alternatively, installing the drain pipe a little lower may be a very cost-effective alternative, assuming there is sufficient side hill grade to ensure gravity discharge well away from the structure.
For new construction and retrofit situations, place the drain pipe a foot or more lower than the footing whenever possible and far enough away to avoid undermining the foundation. Generally 2′ to 4′ or even more is necessary to protect landscaping or porches and similar structures. In retrofit situations, installing a drain on the upgrade side of the house can yield a significant improvement, as it is usually only necessary to intercept water moving through the ground toward the house to eliminate the moisture problem. This type of drain is considered a “curtain drain” rather than a footing or perimeter drain, especially if it is several feet from the house. Its job is to lower the water table downgrade in order to protect the house. The curtain drain method is an important consideration particularly for retrofit installations as it can reduce site disruption and the resulting cost of excavation.
Properly installed perimeter drains create an “island” out of the house site by lowering the water table completely around the house. They keep water from entering under the footings and, in my experience, provide the surest protection against any type of dampness in a basement resulting from groundwater. There are some situations where perimeter drains are not necessary, however. A thorough knowledge of the site, or an exceptionally low water table indication from a septic system test pit, can provide such a determination. If you happen to be one of those folks already blessed with an unwanted indoor swimming pool each Spring, whether in a new or existing house, rest assured that there usually is something that can be done. However, since soil conditions vary so greatly, it is wise to consider your circumstances carefully before deciding on a course of action.
Leaks in Foundation Walls
Another condition that can sometimes appear to be high ground water leaking in may simply be surface water entering over or through the foundation at bulkheads or window openings, seams between walls, and/or, flaws in the foundation. Poor surface grading can direct water toward the lip of a bulkhead or towards basement windows where it can spill over into the basement. By not paying attention during heavy rains, a homeowner can sometimes end up blaming the wrong culprit.
Surface water leakage
Surface water leakage is reasonably easy to locate once you get on track. The solution often involves regrading to drain water away from the foundation. In the case of foundation windows, however, it is not always possible to shed water away since the bottom of the windows are often too far below the adjacent ground, requiring the installation of window wells. These often consist of corrugated galvanized steel half circles but can also be made of pressure treated wood or masonry. The goal is to make the top of the window well high enough to be able to slope the surrounding ground surface away from the house. A problem arises when the window well is directly below the roof drip, especially in cold, wet climates where rain gutters are seldom used (because snow and ice fills them, making them useless, or ripping them from the building!) The solution is either to cover the window well with a clear plastic dome which also keeps out leaves and critters or to create a mini-drywell under the window well to allow rainwater to soak away into the ground before it can rise up and find its way through the window. This leads to another issue: porosity or flaws in the wall itself. If a foundation wall is totally watertight there is little problem with letting water run down against it all the way to the perimeter drain. If the wall has had adequate damp-proofing and/or the water drains quickly through the soil, there is little to be concerned about. The problem is that many foundations are have defects and hairline cracks which allow water infiltration.
Sources of Leaks in Foundation Walls
Concrete block foundations often crack in the grout joint between blocks. Even poured concrete or ICF walls can develop shrinkage or settling cracks in addition to water channels from anchor bolts and form ties. Honeycombing due to improper vibration and consolidation is another source of leakage, wherein the concrete aggregate became separated leaving voids in the wall. In addition, poured walls often have seams between different stages of the pour. Another problem exists with many of the older foundations that are constructed of various sizes and shapes of cut granite and round fieldstone. With or without mortar between, these foundations typically exhibit numerous passages for water to follow. Water can enter walls around utility penetrations such as sewer, water, gas or electrical conduits. There are several instances where I’ve been engaged to dig around existing buildings and to waterproof walls and/or install drainage systems only to discover that the actual problems were unrelated to groundwater.
Condensation
The effects of condensation can be as devastating to a home as water leakage, causing rot, mold, mildew and generally disgusting and, possibly unsafe conditions. (I have seen mushrooms growing inside on occasion). Since so many local dwellings in remote areas are vacation homes, many are lived in only a part of the time. This can mean inadequate ventilation (as houses are closed up much of the time) which is often aggravated by colder-than-normal internal temperatures. Many of these homes are only heated to just above freezing during much of the winter, if at all. When folks arrive for the summer, they open the house, letting in warm, humid air that condenses its moisture against cool basement surfaces. Perhaps the best solution for this is to have the house opened earlier in the springtime, allowing the basement temperature to equalize. Air conditioning can also help, but at least one basement drainage expert warns that dehumidifiers may actually cause more damage to basements. Written by Russell H. Lanoie, Rural Home Technology at www.ruralhometech.com
Remodelling your basement is one of the easiest and most cost-efficient ways of adding new living space to your house. Besides the traditional recreation room, more and more people are using basements for self-contained granny flats, rental suites or home offices.
No matter what the renovation purpose, ensuring that the space is clean, dry and healthy is a critical part of the project and something that must be done before anything else.
Common Situations
Moisture is the most common problem in basements; either entering from outside sources or being produced inside by the occupants activities. The soil around the walls can contain a large amount of moisture from surface water that is seeping down or from a high water table. Water can find its way inside by gravity or through a crack or flaw in the water protection layer of the foundation. Water can also be pulled up by a wicking action or pushed up by hydrostatic pressure from the soil under the walls or floor.
In summer, warm moist air from outside can enter the house and lead to condensation on the cool basement walls or floor. Daily activities also produce moisture that can be trapped inside the home.
Basement moisture problems often include:
Foundation cracks that leak.
Standing water.
Efflorescence (white, chalky stains).
Wet decaying wood in contact with concrete.
Damp or moldy walls or floor.
Condensation on windows, pipes and other fixtures.
Wet insulation.
Moisture damaged finishes.
Musty or damp carpets.
High humidity.
Stuffy, damp smells.
Healthy Housing Renovating is an ideal time to make your house healthier for you, the community and the environment. When assessing your renovation project, be sure to consider the five essentials of Healthy Housing.
House as a System
A house is much more than just four walls and a roof, its an interactive system made up of many components including the basic structure, heating, ventilation and air conditioning (HVAC) equipment, the external environment and the occupants. Each component influences the performance of the entire system. A renovation provides an opportunity to improve how your house performs.
Basement moisture problems can have a huge effect on the durability of the entire house structure and on the indoor air quality (IAQ) throughout the house. Avoid Surprises Moisture problems are caused by a buildup of a variety of water sources. Whether it comes from surface or ground water that leaks in, water that wicks up or water vapour that condenses, it must be controlled. The easiest way to control moisture is to stop it from coming in and to exhaust the water vapour produced in the house to the outside.
Here are some of the likely situations that people encounter. However, every situation is unique. You may need to hire a qualified professional to do a thorough investigation, find the moisture problems and suggest the best solutions.
Do the roof, eavestroughs, downspouts and grading direct surface water away from the house?
Repair or replace a leaky roof.
Ensure that eavestroughs and downspouts with extensions direct water away from the building.
Slope the grade away from the house. A poor rain drainage system will continue to provide a large volume of water that can leak in or overwhelm basement drainage systems.
Do window wells drain freely? Install drainage below window wells. Water may accumulate in the wells, leading to possible leakage into the basement through or around the window.
Does water leak in through cracks in the foundation wall or floor? Patch small cracks from inside with cement-based material or use an injection-type foundation repair system. Fill large cracks from inside (and outside if possible) with hydroscopic material that expands as it dries. Consult a structural engineer or basement specialist concerning multiple, severe or expanding cracks. Water may penetrate cracks, continue to deteriorate the existing house, affect IAQ and any proposed renovations.
Severe or active cracks may be an indication of future structural problems or even present unsafe conditions Without exterior protection and drainage, water will eventually find its way inside. Are there any pools of water on the floor or damp spots on the walls?
Is there a working floor drain at the lowest point of the floor? Is there a working sump pump in a covered sump pit? Has the basement ever flooded? Dampproof or waterproof the outside of the foundation walls. Install a perimeter drainage system. Install a floor drain with a trap and a sump pump in a covered pit. Make sure that the sump cover is tightly sealed.
If future flooding seems unavoidable, do not install interior insulation or finishes that will be damaged by water. Without a floor drain, any water spilled inside cant get out. Working sump pumps may help, but open pits can be another source of humidity and soil gases. If future flooding is possible, interior insulation and finishes give mold a place to grow and will cause more difficulty and expense in flood clean up.
Is there a complete concrete floor? Install a concrete floor over a sealed polyethylene moisture barrier. Dirt floors are a huge source of moisture and soil gases.
Are there any white, chalky stains (efflorescence) on the walls or floor? Provide better drainage and dampproofing to the outside. Efflorescence indicates water evaporation of moisture that has wicked through the foundation wall. Continued efflorescence is a sign of ongoing moisture problems.
Are there any black, white or green mold stains or fuzzy growth on the walls or floor? Clean up mold according to CMHC guidelines. Remove the sources of moisture. Some molds are toxic. Clean up must be done carefully to avoid health hazards. Are there any wet or decaying wood windows, sill plates, columns or beam ends in contact with concrete? Replace decaying wood. Provide a capillary break between wood and concrete. Seek professional advice as damage may compromise structural strength. Wood in contact with concrete will continue to decay and will eventually result in structural problems. Are floor tiles lifting? Are carpets damp or musty? Damp concrete causes lifting floor tiles and damp carpets. Improve foundation drainage. Install a polyethylene moisture barrier over the concrete floor as part of a retrofit floor system. Replace carpets with hard surface flooring. Tiles wont stick to damp floors. Damp carpets will continue to be a haven for dust mites and mold.
Is there any wet insulation, framing or moisture damage on finished walls? Remove wet insulation or finishes. Fix the moisture source before refinishing. Materials that are wet from any source (leaks, capillary action or condensation) will get moldy and decay, leading to unsightly finishes, durability problems and hazards to health. Is there any condensation on windows, pipes or other surfaces? Is the air humid? Does it seem stuffy, damp or smelly? Are basement windows open in summer? Is a dehumidifier or air conditioning used in summer? Is there any ventilation or air circulation? Is the basement heated the same as the main floors? Does a clothes dryer in the basement exhaust outside, using a minimal length of duct? Is wet laundry hung to dry in the basement? Is firewood stored indoors?
Install energy-efficient windows, insulate cold water pipes and insulate walls (and floors, when possible) to achieve warm surfaces. High humidity plus cold surfaces results in condensation. Keep basements ventilated and heated. In summer, use a portable dehumidifier or air conditioning to reduce humidity. In warm, humid weather, keep basement windows closed. Run the furnace fan continuously to circulate house air. Provide ventilation to get rid of humidity. Run dryer exhausts directly outside. Do not hang wet laundry or store firewood inside. Opening basement windows during warm, humid weather will make basements wetter with no chance to dry out. Adding humidity to already damp basements will only make problems worse. High humidity will result in condensation on cold surfaces. Are there a lot of stored items in the basement? Get rid of unused items. Store items on shelves. Avoid storing in cardboard boxes that readily absorb moisture. Allow air to circulate. Too many stored items, especially on the floor, will allow hidden corners to get even wetter and encourage mold growth.
Rewards
Correcting foundation moisture problems can improve the durability of your home and eliminate some dangerous health hazards. A dry, clean basement space will provide a good starting point for your other planned renovations.
Skills to Do the Job
Some tasks such as a thorough basement cleanup dont require special skills. A homeowner with good fix-it skills may be able to do a lot of the other work too, including: Roof, eavestrough and downspout repairs. Grading and landscaping. Patching small basement cracks. Clean-up of small mold patches. Removing damp insulation, finishes or carpets. Insulating cold water pipes. Installing dryer venting. Installing storage shelves. Hire a professional renovator for exterior, below-grade water protection and drainage problems, large or moving foundation cracks, concrete placement or major structural repairs. You may also need a heating contractor to install heating, cooling and ventilation equipment.
growth. A home with relative humidity above 60% can also be a breeding ground for pests and wood rot
dehumidifier. An other shopping point is to consider are the size of the unit- will it fit in the space you are planning for it? Also be aware that some models are noisier than others, so ask for a demonstration before you buy.
