If you have a leaky or wet basement, or if you’re seeing symptoms of moisture like the peeling paint pictured above, you might be wondering why you’re having these types of issues. Well first, it’s important to note that the vast majority of homes in Maryland, Delaware, Washington, D.C., and Virginia are prone to basement waterproofing issues, and this is due to underground hydrostatic pressure caused by the rain water cycle and the soil conditions in the mid-Atlantic region.
However, hydrostatic pressure does not affect all home foundations in the same way, and the basement waterproofing issues you can potentially face depends on how groundwater interacts with the type of foundation construction of your home. In this blog post, we’ll discuss the most common foundation types for homes located in and around the Richmond, D.C., and Baltimore metro areas.
Poured Concrete Foundations
For more recently built homes, it is likely that the foundation walls, along with the foundation footer and floor slab, are constructed of poured concrete. Because of the difficulty of pouring the entire perimeter of the foundation walls all at one time, the concrete walls are often formed in sections, and each section must be allow to cure at least partially before the next section of foundation wall can be poured. In fact, if you have a poured concrete foundation with visible foundation walls, you may be able to see vertical lines between each section that was poured as you walk around your basement. These seams between the wall sections are natural weak spots in the foundation where hairline cracks can form due to settling of the home after construction as well as the presence of hydrostatic pressure. Hairline cracks also appear in the middle of the poured wall sections, but it more common to see these cracks originate in or near one of these seams.
Hairline cracks–while common to many homes and not usually not a structural issue–are one of the two main ways that hydrostatic pressure can force water into a poured concrete basement. We also know that there is also a seam that exists between where the floor slab and foundation walls meet, and that is the second main way that groundwater will seep and leak through poured concrete foundations due to hydrostatic pressure.
Cinder or Cement Block Foundations
Out of all homes in Maryland, Delaware, Washington, D.C., and Virginia, there are more foundations built with cinder or cement block walls than any other foundation wall type. This method was the primary type of foundation used for residences built from the 1930s-40s up to the 1990s, and many companies still choose to construct foundation walls using cinder block to this day.
If we take a look at the picture of a standard cinder block below, we’ll notice a few things:
First, the most prominent feature of a cinder block are the two vertical spaces in the block itself, called “cores.” When block walls are constructed, the blocks are stacked so that the right-side core from one block lines up with the left-side core with the block directly on top of it. This staggers the blocks as they build upwards, and you’ve definitely noticed this staggering if you’ve seen a block wall before. What you probably didn’t realize–and think about it for a moment–is that there are vertical cavities being formed in the wall as the cores in the cinder block line up. The reason for these empty spaces in the wall is so that steel can be inserted through these vertical spaces and then filled in with grout in order to add strength to the wall. However, this method is primarily done for larger, commercial constructions and this additional reinforcement is usually not necessary for smaller, private residential buildings. The takeaway is that there are empty columns built into cinder block walls.
Second, the concrete mixture that the block is made from is not 100% solid. The block itself is porous and has many small holes where water can seep through, and so by itself, a cinder block is not waterproof. (If you’re skeptical at all, try this: take a cinder block and pour water slowly onto the flat side of it so that the water does not run over the sides, and the small puddle that forms on top will soak into the block. If you continually add more water, water will eventually seep through the block and drip down.) This is why there is a layer of waterproofing material–usually a tar-like substance–that is applied to the outside of cinder block walls before the hole that was dug out for the home construction is filled back in order to help protect them from future groundwater.
With heavy rains and the resulting hydrostatic pressure, this initial waterproofing layer on the outside will eventually wear away and allow water to come in contact with the cinder block wall (the amount of time that this takes, however, is very hard to predict and can vary greatly depending on how much groundwater flows through your property and the specific waterproofing materials used). Water will then find its way through the pores of the blocks themselves as well as weak points in the mortar between the cinder blocks, but before entering the inside of the basement, the water first encounters the vertical spaces in the wall created by the cores in the cinder block.
What happens during a heavy rain or precipitation event is that water will collect and accumulate inside these columns of empty space within the wall before entering the home. The level of water inside the wall will build up while the ground outside stays saturated with water, and will go down once the ground has dried and the water can dissipate back into the soil. However, over time, the amount of water getting inside the wall will progressively increase, and the higher the build-up of water inside of the empty columns in the wall during heavy rains, the more hydrostatic pressure is exerted from the inside of the cinder blocks’ cores and on the mortar joints, causing stair-step cracks between the blocks. Just as hydrostatic pressure forced water from the outside into the inside of the block wall, the build-up of pressure will start to push water from the inside of the blocks to the inside of your home, and this is when you see water on the inside of your basement.
Take a look at the picture above. You can see water seeping through the cinder blocks themselves and from the floor-wall joint. You’ll notice that the signs of moisture are more pronounced towards the bottom of the wall, and this is because the weight of the water building up in the wall causes the most hydrostatic pressure to be applied to the insides of the blocks at the bottom. If you look right above the dark water stains, you can see a white, powdery substance on the walls. This substance, called “efflorescence,” is lime residue left behind by moisture being pushed through the pores in the block then evaporating, leaving the lime behind. If you see this on your cinder block walls, this is a symptom that there is some pressure inside of your walls, even if you do not see standing water.
Another symptom of hydrostatic pressure inside your block foundation walls is paint peeling, blistering, or chipping off of the wall. Many homeowners attempt to combat basement moisture by painting an elastic, waterproofing paint directly to the inside of the walls. However, these paints are not designed to permanently withstand hydrostatic pressure and will get pushed out of the pores in the cinder block wall when enough hydrostatic pressure is present behind it, leading to bubbling and cracking of the paint (see the picture at the top of post). This paint needs to be continually reapplied in order to stay effective and is therefore not considered a permanent waterproofing solution.
In Washington, D.C. and Baltimore, there are a lot of residences resting on brick foundations; it was the best material that existed at the time these structures were built, and many of the homes near downtown areas have been there for a long time. Often when homes are renovated for resale, the original foundation is not often replaced along with everything else in the home (this, of course, is to cut down on the cost of refurbishing the home on the part of the seller). As a result, a townhouse that appears to be newly built, especially in older, established neighborhoods, is usually only a new construction from above the foundation.
Older home foundations that are constructed with brick face similar issues with hydrostatic pressure as cinder block foundations. However, there is less likelihood of hydrostatic pressure building up inside of the bricks themselves because brick walls do not typically have as large of vertical cores when compared to cinder block walls (although this problem can still occur since some bricks have spaces bored out in them, which can line up). More often, basements with brick foundations have leakage issues simply due to the aging and decline of the brick walls themselves and groundwater is able to force itself through weak mortar joints between the bricks and through crumbling bricks, as well as from the joint where the brick wall and floor meet. Always remember: there is a seam where water can seep in between the floor and wall in most foundation types, including brick.
Stone foundations are prevalent in historic properties and other smaller structures built around the 1900s or earlier, especially if they were located in more rural areas at the time of construction (like farmhouses). A lot of times, the “basements” in these old home have low ceilings and are usually more like tall crawl spaces. Also, there may or may not have been a floor that was added when it was built because people didn’t typically use their basements as livable spaces.
As a result, stone foundations experience issues similar to that of brick foundations–seepage through the mortar seams and from the seam where the floor and wall meet–but additionally, if there is no concrete floor, water can also seep up from underneath the foundation through the middle of the dirt floor.
Value Dry can help with all foundation types.
We here at Value Dry have performed basement waterproofing work on all of these types of foundations; we’ve done work on historic properties near Frederick, MD and Alexandria, VA as well as helped builders waterproof brand new developments all around Maryland and Northern Virginia. Of course, we recognize that the effects of hydrostatic pressure are not just limited to leaks and seepage, but have the potential to cause structural issues in the foundation as well, and as foundation specialists, we have the resources and know-how to help you deal with that as well. On the other hand, if all you need is a sump pump and a battery back-up system to hold you over during heavy storms and power outages, we specialize in those as well!
Having wet basement issues and want to see how this applies to your home? Use the “Contact Us Today” button at the bottom-right of this page and we will have someone from our office reach out to you who can walk you through our process and schedule a free inspection with you.