Why you should read this article

In this article we provide you with real life examples of what basement leaks look like so that you can recognize the cause of the water in your basement. This knowledge will speed up the process of getting the basement leak repaired if you have a leaking foundation.

Typical appearance of a leaking foundation crack

Introduction to basement leaks

Having conducted thousands of basement / foundation inspections over the years, we have concluded that approximately 90% - 95% of the causes of a damp, wet basement are attributable to one or two of the "usual suspects" as illustrated below.

Caution: There are many ways by which water can enter your basement and/or penetrate your foundation; therefore, the waterproofing repair method chosen must address the precise cause of the water in your basement. Without visual confirmation of the actual problem, or without absolute confirmation of the source of the leak using diagnostic equipment, many homeowners pay for basement waterproofing work far in excess of what is actually required, including waterproofing work performed in the wrong location, or basement leak repairs that are not needed because the source of the water in the basement is not attributable to a problem with the foundation at all.


Be sure to check out our page dealing with basement dampness. Simply click here.

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You might also be interested in our companion article on how to recognize basement leaks.

By examining the images below it will become abundantly clear that basement leaks are relatively easy to identify when a leaking foundation wall is exposed, and 99% of the time you will know without question what exactly is responsible for the water in your basement.

 Note: If a waterproofing contractor does not show you undeniable evidence of the source of your basement leak, there is a real risk that you will waste your money and/or not address the true cause of the water in your basement.


Where most leaks in the basement come from

basement leaks from foundation cracks basement leaks in poured concrete foundations
How water leaks through a concrete block foundation Water leaks in a cold cellar

Basement Leaks Often Cause Visible Mold on Walls

Basement leaks typically leave stains on the foundation walls. When a basement is finished, many basement leaks remain hidden; however, mold on drywall, baseboard discoloration and wet carpets are often the first sign that there is a leak in the basement. Here are some pictures of undeniable mould growth in a finished basement:

Mold growth on drywall in the basement Mold growing on drywall behind wainscotting
Mold of various colours growing on drywall in the basement

Here is what you can expect to see when the bare foundation walls are exposed:

Foundation Leaks from Cracks in Poured Concrete Foundations

Foundation crack with visible sediment Cracked foundation with visible sediment and mineral deposits
Wet foundation crack with mineral deposits

Leaking Tie-rod Holes in Poured Concrete Foundations

Basement leak from a leaking tie-rod hole Tie-rod holes with evidence of significant leakage
Actively leaking tie-rod hole in the foundation

Corroded Snap Rods in Poured Concrete Foundations

Snap rod with evidence of corrosion

Leaks from penetrations through the foundation to accommodate a conduit to the electrical panel and/or air conditioning and gas lines

Pipe penetrations for hydro often cause basement leaks Electrical conduit visible from interior

Honeycombing in Poured Concrete Foundations

Honeycombing between 2 tie-rod holes Large area of honeycombing with evidence of sediment

Water Leaking From The Top of The Basement Wall

Basement leak originating from top of foundation

Learn more about building envelope water leaks and what you can do to avoid them.

Water Leaking From an I-beam Pocket

I beam pocket leak

Water Leaking From The Top of Cold Cellar Walls

How water typically enters a cold cellar

Water Entering The Basement Below The Window Frame, or Through The Window

Evidence that water leaked between the window frame and the top of the wall Evidence of inadequate window well drainage
Evidence of window well drain failure and sediment contamination

Concrete Block / Cinder Block Foundation Leaks

If you are unfamiliar with leaks in concrete block foundations we encourage you to read our blog article on the fundamentals of block foundation leaks and repairs.

How water leaks through a concrete block / cinder block foundation Saturated concrete block with water gushing from weeping hole
Wet concrete block / cinder block wall corner

Concrete block wall with significant evidence of water leakage

Condensation Dripping Down The Foundation Wall From Behind The Insulation

This is typically seen in homes which are less than 5 years old or when there is warm and moist air in the basement which comes into contact with the cold foundation walls behind the insulation.

For more on this subject be sure to read the article: Why is there water inside the plastic of my basement insulation

Download offer - 10 tips for hiring the right waterproofer

Less Common Sources of Basement Leaks

On occasion, water will originate from one or more of the following sources:

      1. Plumbing leaks
      2. Water leaking from inside the fireplace or hot water tank chimney
      3. Water leaking from the roof to the basement behind the walls along the wood framing. This typically results from detached roof flashing around the chimney or from water backing up from clogged or ice-filled eavestroughs
        Rain water behind the flashing can leak into the basement
      4. Condensation dripping from very cold ducting or very cold water pipes in a high humidity environment
      5. An overflowing liner of an inoperative sump pump
      6. Water flooding the basement from beneath the floor slab
        A high water table that flooded a basement rapidly Water beneath the basement floor from a high water table could be the root cause of a basement leak
        Water beneath the basement floor introduces significant water into a basement

Click on this hyperlink for more information on basement leaks that originate beneath the basement floor due to a high or rising water table.

  • Water entering the basement from the floor drain due to back pressure from the storm sewer on the street
  • Water leaking from a chimney cleanout
    Rain water is entering the chimney on the roof and draining down the chimney to the cleanout

Homeowner Tip: Given the many potential sources of a leaking basement it is clearly necessary to positively identify the source of a leak in order to determine which type of repair is required. A truly professional waterproofing contractor will spend the necessary time to locate the source of the leak and explain how the proposed repair solution is best from both technical and cost perspectives; our Basement Waterproofing Repair Methods page provides a table detailing the available professional foundation repair methods to address wet basement issues. You may also want to have a look at our article on basement leak repair. Unfortunately, we have met many unhappy homeowners who either paid far more than was necessary to fix a basement leak or who have had their foundations excavated only to discover, thousands of dollars later, that the actual cause of the leak was not properly identified and therefore, not addressed.

If a waterproofing contractor has not conclusively proven to you how water has entered your basement, and then suggests that exterior excavation and waterproofing will correct the problem, we suggest that you hire a more professional company. Call us and we'll ensure that you get a correct diagnosis for the water in your basement.

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