Homeowners commonly report that a heavy rain or thunderstorm has left them with a leaky basement. Before you start getting stressed out about spending thousands of dollars on basement waterproofing, there are some facts of which you should be aware. In this post we discuss leaky basement reports that are commonly associated with heavy rains, and some little known facts or details which are very relevant when trying to properly fix the cause(s) of water leaks in your basement.
This blog post is a must read because many homeowners get duped and spend thousands of $ on basement waterproofing when waterproofing the basement is not going to solve the underlying cause of a wet basement.
Important Facts About Leaky Basements and Heavy Rains
It is commonly unacknowledged, even by prominent waterproofer contractors, that heavy rains test the integrity of the entire building envelope of a home. Heavy rains commonly put your building envelope in general under alot of stress; here are some examples that we will discuss further in this post:
- Heavy rains put your entire roof to the test; if there are any vulnerabilities, they will reveal themselves;
- Heavy rains pound against your windows, doors, and the brick veneer or siding on the exterior of your home;
- Heavy rains cause your eavestroughs to spill over the side and your downspouts to discharge potentially hundreds of gallons of water in a very short period of time;
- Heavy rains can flood your backyard and introduce significant amounts of hydrostatic pressure against your foundation walls and cause the water table to rise; and
- Heavy rains can overload the storm sewer system on your street and cause your basement floor drain to back up.
Having A Leaky Basement Does Not Mean Your Basement is Leaking
Can you believe this headline? Strange but true.
When discussing heavy rains, building envelope leaks and leaky basements we need to acknowledge the role that gravity plays in bringing rainwater to its final destination. To add relevance to this statement consider this, if your main floor kitchen sink plumbing is leaking into the cabinet beneath it, don't you think that this water will ultimately end up in your basement? Count on it.
Obviously, if during a thunderstorm you can plainly see water coming through a foundation wall, then you clearly have identified a bona fide basement leak. However, if your basement is finished, establishing the cause of your leaky basement is much more difficult.
Incorrect assumptions, cursory inspection and waterproofing contractor greed are the three primary reasons that homeowners spend money waterproofing a basement that isn't actually leaking. If the source of the leak in your basement isn't plainly visible you risk spending $1000s to fix a problem you don't have!
Heavy Rains And Your Leaky Basement
Getting back to the impact of heavy rains on the building envelope, here's what tends to happen:
Rain Penetration of The Roofline
When rain penetrates your roofline, the water enters your home. When you have a roof leak you won't necessarily see water pouring out of your ceiling (unless the leak is major). In many cases, minor roofing leaks result in water travelling along the roof trusses and then down the wood framing of the interior walls supporting those roof trusses. It is common for the rainwater to eventually make its way into your basement. That "leaky" basement may not be leaking at all!
There are numerous possible points of water ingress through your roof. We recently consulted a roofer that we trust, we asked how to best identify the location of where water penetrated the roof. According to the roofer, the only way to positively identify the precise location of a roof leak is to be in the attic during a fairly heavy rain in order to observe exactly where the water is entering. In most cases, the remedy is to re-seal the location where the water has entered; in general, the complete reshingling of the roof is not required.
Pounding Rains Against Windows, Doors and Exterior Walls
Over the years we have concluded that, when homeowners report a wet basement after having had rains from a certain direction, the reported basement leak is usually attributable to a water leak through the building envelope.
Window frames and door frames (including patio doors) are effectively inserts in the building envelope, making it necessary to seal around the frames with caulking to prevent water from penetrating the building envelope. Since caulking shrinks and dries as it ages, deteriorated caulking separates from the door frame and wall surfaces over time. When it rains onto deteriorated caulking, or gaps in the caulking, the rain water often penetrates the building envelope. This water, by gravity, drains down onto the top of the foundation wall(s) and often results in reports of a leaky basement.
Similarly, if rains are able to breach the building envelope through cracked mortar joints in your brick veneer walls or through cracks between bricks or stone slabs on window ledges, water will run down the back side of the brick walls and end up in the basement as well.
It is crucial that you regularly maintain the building envelope of your home in order to avoid a leaky basement attributable to building envelope leaks.
The Role Eavestroughs and Downspouts Play in Basement Leaks
Many homeowners report that they have a leaky basement as a result of water pouring over the side of their eavestroughs.
When water pours over the sides of an eavestrough, insteading of draining via the downspout, water permeates the soil along the foundation walls. This situation causes a rise in the height of the water table next to the walls resulting in increased hydrostatic pressure (water pressure against the foundation walls).
The fact that the water pours over the sides of the eavestroughs is not the real reason why there is a basement leak; instead, the real problem is that the water is able to breach the foundation walls. If the foundation walls are properly waterproofed, water is not able to enter the basement.
Downspouts, to a much greater extent than leaking eavestroughs, introduce significant hydrostatic pressure against a foundation. Again, a properly waterproofed foundation would not leak. To reduce hydrostatic pressure against your foundation, it is recommended that downspouts drain water 8-10 feet away from the house.
The Impact of Heavy Rains in General
Like eavestroughs and downspouts, heavy rainfall causes a rapid rise in the height of the water table and consequently, a rapid increase in hydrostatic pressure against the foundation. When there is sufficient hydrostatic pressure, cracks and other deficiencies in your foundation are more likely to leak. Under these conditions, cracks etc., which do not typically leak, begin to leak. Again, waterproof foundation walls would prevent water ingress and a wet basement.
Storm Sewer Capacity and Floor Drain Backups
During very heavy rains, sometimes the storm sewers under the street are overloaded and incapable of handling all of the water entering them. Such conditions, can cause the storm sewers to naturally relieve pressure via the path of least resistance. In some instances, this path of least resistance is the floor drain in your basement. Many flooded basements are the result of water "backing up" through floor drains. The only way to avoid this situation is by installing a backwater valve in the drain pipe from your floor drain. These backwater valves allow water to travel from your floor drain to the storm sewer but prevent water from flowing from the storm sewer into your basement.
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