Water can enter a basement from many different weak points in a structure, but the 2 major causes of water intrusion is from either the leakage of groundwater or by surface water leakage.
Think of the exterior of any building as an envelope that has to be sealed tight so water cannot enter.
The most vulnerable points in all structures for water to enter is where 2 construction elements meet or "transition.
" These transition points make up about 3% of an average structure, yet they are responsible for over 90% of water entering the building.
Water always takes the path of least resistance.
Water can (and will) enter through cracks in your basement walls and foundation, but water can also enter through transition points and seems in the structure if they have not been built correctly or if the materials have deteriorated with time.
This areas of concern include, but are not limited to:

• mortar joints in the walls or foundation
• seems around windows
• window wells
• sewer pipe locations
• water pipe conduits
• floor drains
• sump pump
• concrete tie rod anchor holes
• clogged drain tiles

Water can also wick up into a structure through the foundation floor and walls.
The perfect example of "wicking" is when you dip the corner of a paper towel in water.
The water continues to absorb, or wick, traveling up higher than the original source of water.
This is also true for foundations and walls of buildings.
Cement is actually a porous substrate and can absorb water high above the ground water table or level.
Now that you are familiar with several of the various ways water can enter your basement, we need to look at the damage water can cause not only in your basement, but to the entire structure of your home.
Once water has entered your home, and especially if it is repeatedly entering your home, secondary problems will arise.
Water in your basement will begin to grow mildew and mold.
Mildew and mold are not only unsightly, but they cause an environmental hazard to you and your family.
mold spores can easily become airborne and cause a myriad of health problems for anyone in the home including allergic reactions, asthma, and significant breathing problems and diseases.
Not to mention the fact that insurance companies will not insurance a home with mold, will not cover a claim for mold and will not cover mold removal in most cases.
Mold removal is an extremely costly project.
Any building material that has been contaminated with mold is considered hazardous waste and must be treated as such.
We are talking about haz-mat suits and respirators for the workers along with wash down stations, and hazardous waste removal and disposal.
This is definitely a point you do not want to get to because the costs will hit the 10's of thousands to eradicate the problem in no time.
To avoid expensive costly repairs, the best bet is to have the appropriate basement waterproofing installed before water starts entering your home, but if you have already had water enter your home, the time you take to repair the problem is crucial.
The cost of waterproofing a basement through a contractor is a great "insurance policy" for your home and your peace of mind and a fraction of what a leaking basement can cost you in the long run.
The faster you fix the problem and stop the water from entering and clean up the effected areas, the less damage you allow to happen.