This was originally published by Value Dry on April 9, 2015 and has been updated.
What is it that causes wet and leaky basements?
Well, the one-sentence answer is that it has to do with the soil composition in the area where we live and the way that home foundations for basements are typically constructed around here. Let’s start by explaining the soil side of basement waterproofing issue first.
If you live in Maryland, D.C., Virginia, Delaware, or anywhere else in the mid-Atlantic region, and you take a shovel outside into a grassy area and start digging under the top soil, it’ll become clear that the ground in our area is not nice, soft dirt, but a dense mix of soil and red clay. In fact, if you were to keep digging to a depth of about four to five feet, it’s likely that you’ll hit even harder-packed red clay, and at a certain depth, you’d have a tough time continuing without the use of machinery.
With a heavy rain or snow melt, water penetrates down into these layers of soil and clay. This groundwater needs to find a way back to rivers, streams, and other bodies of water to continue the rain cycle, and what many people don’t realize is that all this water travels through an underground route through the clay soil under our feet to accomplish this. Keep this in mind as we introduce a home into the picture.
When a new home is constructed, the site is first excavated in order to lay down the sub-grade foundation of the home. While this large hole is dug-up and exposed, the crews must have large water pumps handy in case there is heavy precipitation that causes water to accumulate in the hole during construction, as a significant amount of water can collect in these excavated holes quickly. It’s definitely important to note that the majority of this water build-up isn’t from water raining down into the hole itself, but is actually the result of rainwater soaking into the soil elsewhere, traveling underground, and seeping in through the side walls of the hole.
Another important thing to note is that once the foundation construction is completed and the dirt is filled back in around the foundation, the backfilled earth is much less dense than the pre-existing, hard-packed clay that was dug out. This creates a space of softer dirt between the foundation wall of the home and the pre-existing dense clay soil where water can collect after heavy precipitation (many within the basement waterproofing industry call this the “clay bowl” effect). You see, before any construction began, groundwater had been flowing through the property underground to make its way back to the nearest body of water, but when the area was dug out to build the home’s foundation, these pathways for the water were cut off and the water now runs into the area that was excavated for the home construction. This water is what builds up and causes hydrostatic pressure on the foundation, leading to basement waterproofing issues such as seepage, leaking, or flooding.
But aren’t foundations built to be waterproof?
Unfortunately, the answer is no. The reason is that when home foundations are built, the work is required to be done in steps to allow any concrete or cement to adequately cure before beginning the next part. This is true for your home whether you own a historic brick-built property in Alexandra, VA or a brand-new home with a poured concrete foundation in the Baltimore suburbs. Without getting too deep into the construction details, the foundation footer, floor slab, and foundation walls of a home are actually formed as separate pieces that are fitted tightly together rather than forming one single, solid base for the home. The result is that there are seams in the foundation where water can squeeze through located in the corners where the walls and floors meet with each other, and these are naturally vulnerable points in the foundation when hydrostatic pressure is present.
But don’t home builders install basement waterproofing on the home when they construct it?
Depending on the specific code, home builders are required to do a minimal amount of basement waterproofing either on the inside or the outside of the home. For the vast majority of homes in the Washington, D.C. and Baltimore metro areas, this usually means that the builder was required to apply a tar-like substance to the outside of the wall before replacing the excavated dirt around the house.
The truth is, this initial waterproofing may be enough to keep your basement dry for many years, but it could also fail within the few years of the home being built. The difference is not usually based on the age or type of the home, but more on the amount of water that is making its way underground next to the home and causing hydrostatic pressure on the foundation (which can be very unpredictable). This is why some homes that were built at the same time will have basement floods while others won’t, and why some homes that are 50+ years old will stay drier than a home built last year. If your basement or crawl space is subject to higher-than-average hydrostatic pressure, then the foundation waterproofing that was likely done at the time of construction will deteriorate faster than a house that experiences significantly less hydrostatic pressure.
So, that’s the short story on why basements leak in our area. Unfortunately, basement waterproofing and foundation seepage issues are very common in the mid-Atlantic region–regardless of the foundation type–simply due to the fact that many homes are built with basements and underground foundations. However, if you’re having basement leakage or flooding issues in your home, it is very likely that many other homeowners in our area are facing the same types of issues.
We at Value Dry have installed many different types of basement waterproofing, including sumps pumps, inside and outside french drains, outside basement sealing, battery back-up sump pumps, and window well/stairwell drains. We are confident that we have the experience and know-how to help you with your moisture issues.
Value Dry has also done basement waterproofing work on all sorts of homes all around the mid-Atlantic region, including stone foundations originating from the Civil War era near Frederick and Hagerstown, brick row homes in Georgetown, homes built on cinder block foundations all around Northern Virginia and Maryland, and have even helped home builders waterproof poured concrete foundations in new developments after their waterproofing efforts have failed.
If you’re in need of assistance in dealing with a moisture problem, or have any questions about basement waterproofing or why foundations leak, feel free to reach out to us to schedule an appointment. One of our expert inspectors or managers will advise you about your particular issue.