Buying a home, especially for the first time, is a huge undertaking.
A bad choice or missed sign of trouble can result in costly repairs or financial losses at resale so homebuyers are well-advised to be painstaking in their search. There are lots of “red flags” that homebuyers are urged to heed along with the usual research on schools, property taxes and comparable pricing.
One thing that typically turns a potential buyer off to a home is any sign of a wet basement. Understandably, potential buyers who may not be familiar with the causes of and cures for a wet basement are likely to see it as a huge problem and move on to the next listing.
Of course, a wet basement may be a sign that major repair is required to make the basement waterproof or to fix a damaged foundation but it is equally true that the problem could be fixed by a quick, simple crack repair that could be done permanently for a few hundred dollars.
So, how’s a potential homebuyer to know the difference? It helps to understand why and how a basement leaks.
What Causes a Wet Basement?
Water that ends up in the basement starts out in the soil around the foundation. It is rare that falling rain or melting snow flows directly into a basement before being absorbed by the soil and some kind of external pressure is needed to force the water in through opportunistic openings.
Water is contained in the soil that surrounds the foundation to a degree that depends on the type of soil found in the area. For example, sandy soil, such as that found in northwest Indiana, drains very quickly and absorbs very little water. Clay soil, common in the Chicago area, is very absorbent and holds a great deal of water.
The area immediately around a home’s foundation is particularly susceptible to absorbing water because it contains soil that was disturbed during the original excavation to build the foundation. This backfilled soil is less compacted than the undisturbed soil around it and has more space surrounding soil particles to contain water.
Water is also contained in soil below the foundation. This water occurs nearly everywhere, sometimes very deep in the ground in more arid areas, and is referred to as ground water. The level to which this water rises in the soil is called the “water table,” which is a relatively static measurement but one that can change for the short term after heavy rainfall or snowmelt.
When the soil surrounding the foundation absorbs water it expands and creates pressure against the foundation walls. This lateral pressure can force water into the basement and can also cause structural damage to the foundation.
Similarly, when the water table rises, pressure is created below the foundation, called “hydrostatic” pressure. Hydrostatic pressure can also force water into the basement and can create cracks in relatively thin concrete basement floors.
But, how does the water get in?
Sources of Basement Seepage
No matter how much water there is outside the basement there has to be an opening of some kind for it to get into the basement.
These openings, as mentioned earlier, can be caused by pressure against basement walls or floors, but can also be caused by foundation settlement and small errors during construction, even by the nature of homebuilding itself.
The most common type of residential foundation is one constructed of poured concrete and the most common source of seepage in such a foundation is a non-structural crack in the wall. These cracks can be caused by lateral pressure or by the foundation dropping or settling. The cracks are narrow, generally less than 1/8”, and occur randomly in walls, sometimes emanating from openings like windows or utility penetrations.
Cracks can also occur in masonry foundations, whether built of concrete block, stone or brick. Cracks in these foundations occur in the mortar joints between masonry units and will usually be found in a “stairstep” pattern.
Another very common source of seepage is through what is called the “cove joint.” When a foundation is built, the first step after excavation is to build the footings, a wide pad of poured concrete that describes the perimeter of the foundation and serves to create a stable base and spread the load of the house more evenly.
When the foundation wall, either concrete or masonry, is built on top of the footings, there remains a tiny gap between the two structures. After the wall is finished, the basement floor is poured to sit on top of the inner edge of the footings and a small gap remains there too, between the floor and wall. This is the cove joint and hydrostatic pressure can force water into the basement through it.
The floor cracks caused by hydrostatic pressure can also seep water and, because basement floors play no structural role in the foundation and are typically thin, these cracks are very common.
Less common are porous spots in poured concrete, caused by a “dry spot” in the concrete mix or insufficient vibration to settle it when freshly poured. Water can seep through these spots, as it can through concrete block because they are considerably more porous than poured concrete.
Seepage can also occur around poorly fitted basement windows, improperly sealed utilities such as plumbing, electrical conduits, HVAC connections and sewer lines.
Finally, when exterior construction, such as a deck or patio is improperly pitched to cause water to drain back toward the house, water can enter the basement over the top of the foundation wall, between the concrete or masonry and the wooden sill plate that is the base of the aboveground construction.
Lots of places where water can enter the basement – can they all be fixed?
Fixing a Wet Basement
For each of the ways that water can enter a basement there is at least one method of permanent repair.
For those cracks in a poured concrete foundation wall, the best repair is to inject them from inside with expanding polyurethane to fill and seal the crack. The polyurethane material remains flexible when it cures to prevent re-cracking from minor foundation movement and the repair can be completed in less than one day.
If the crack is inaccessible from the inside it can be repaired on the exterior by creating a pliable, permanent barrier against the exterior wall with sodium bentonite clay. This repair is invisible once completed and can also be done in less than a day.
Injection is not appropriate for cracks in a masonry foundation, however. Seepage from these cracks can be managed on the interior of the basement (more on that later) or repaired by sealing the outside of the wall with an exterior waterproofing membrane.
After excavating the affected wall or walls, a thick coating of asphalt-modified polyurethane material is troweled onto the wall to form the membrane, which can be covered with insulating material and/or plastic drainage board to channel water downward.
An exterior waterproofing membrane also prevents seepage through porous poured concrete or concrete blocks and water entering the basement over the top of the foundation wall. It’s a pretty major repair and may require several days to complete, depending on how much of the foundation is affected.
Seepage caused by hydrostatic pressure, whether through the cove joint or cracks in the basement floor, requires a method of alleviating the pressure and providing an alternate route for the water that causes it. This is done by installing interior drain tile.
Interior drain tile is a system of perforated plastic pipe that is embedded in washed gravel under the basement floor next to the footings. The water that would otherwise be forced through the cracks or cove joint is instead forced into the pipe, which carries it off to a sump pump for discharge from the basement. Interior drain tile is maintenance-free.
Interior drain tile can also be used to manage seepage through the wall, usually in company with a vapor barrier covering the wall. No matter how it is used, it is a surprisingly convenient installation and can typically be done in a fairly short time.
Drain tile can be installed on the exterior of the foundation to alleviate lateral pressure. It is often installed when an exterior waterproofing membrane is used, especially when ground water is high.
So, should you buy a home with a wet basement? It depends on the appeal of the home, the price and lots of other factors but at least you can make your decision knowing what causes the water problem and how it can be fixed. A wet basement doesn’t have to be a deal-breaker.
If you decide to buy the home, you’ll need the advice and assistance of a full-service basement waterproofing contractor that can accurately diagnose the source of the problem and recommend a permanent, cost-effective repair. At U.S Waterproofing, we’ve rescued the dreams of many a homebuyer in our 57 years in business and we proudly count more than 300,000 satisfied customers who no longer have to worry about wet basements thanks to us. Why not ask for our free advice?