What is a High Water Table?: Its Affect on Basement Foundations
Although the construction of buildings has come a long way and has never been more complex, and even though computers are used to test the most important parts of the design, there are still some problems even the most skilled and experienced builders cannot resolve. We are talking about high water tables, which are a cause of headaches for many homeowners.
Depending on what type of foundation you have, the water table on your property could be located above the crawl space or basement floor level. If the soil around and underneath your home is absorbent, this high water table can lead to damage and cause serious structural issues. When the level of the water table rises to the level of the basement, there is nothing you can do. Even if you regrade your yard and direct water away from your home’s perimeter, you won’t change anything, because when the water table rises, it rises over a large area, not just on your property.
What Is a High Water Table?
The water table is a zone in the ground between the soil surface and the layer where groundwater saturates all spaces between sediment and cracks in rocks. When water tables receive more water than they can drain off due to high amounts of rain or excess water from elevated grounds, they grow and are described as high. A high water table is usually above the level of the basement floor or crawl space.
The high water table can often occur in areas with poorly drained soils. However, it can also happen in other locations due to seasonal changes.
Types of Water Tables
There are two types of water tables that occur due to seasonal changes or geologic formations.
- Perched water tables: Just because your home was built on higher ground doesn’t mean it is protected against a high water table. A perched water table occurs when the zone above the usual subsurface groundwater consists of bedrock material or compacted clay soil, which doesn’t allow water to seep through it. As a result, groundwater becomes trapped in these pockets and creates a perched water table.
- Seasonal high water tables: During the spring or winter when there are a lot of rainy days or when snow begins to melt, the groundwater begins to rise. Water slowly penetrates the ground and pushes up the water table. If water cannot be drained during these seasons, you probably have a problem with a high water table.
Ways a High Water Table Can Affect You
There are several ways a high water table can impact your home. Here are just a couple of them:
- Foundation shift: If the water table is located too close to the surface, the groundwater can push against the footing of the foundation. Due to hydrostatic pressure, water can seep through the foundation and cause damage. If there is a lot of excess water and the pressure is extreme, foundation walls can shift.
- Humidity issues: If the walls are still in their place and cracks haven’t occurred anywhere, you could still have moisture problems. If water in the form of vapor has entered your basement or crawl space, it can lead to wood rot, rust, and mold growth.
Measuring the Water Table
If you want to determine the depth of the water table near your home, you can do it with tape by measuring the water level in a shallow well. In case there are no wells near your place, there are surface geophysical techniques that can measure the depth, such as acoustic or electric probes. If there is a pond near your home after heavy rainfall, it may be sitting on top of the water table.
Why Do Water Tables Rise and Fall?
Several factors affect the rise and fall of the water tables, such as precipitation, proximity to water bodies, tides, and irrigation. During the spring, when there are a lot of rainy days, the water table can become completely saturated. Some of the water that penetrates the ground is used by plants, but some of it is still shallow and won’t benefit the plants. As the water further penetrates the ground, it reaches the water table, causing it to rise. In the summer, due to the heat, a lot of water will evaporate, causing the water table to fall.
Possible Solutions
A high water table can give you a headache. Luckily, there are some ways you can minimize the impact it has on your home.
- Yard drainage: A surface or subsurface drainage system can direct rainwater away from your home and prevent it from causing damage to your foundation.
- Swales: Swales are shallow depressions that collect rainwater and direct it toward the municipal drain.
- Underground pipes: Sometimes surface drainage won’t get the job done and underground pipes need to be laid down. After a trench is dug below the soil grade, perforated pipes are laid in it. The perforations are used to capture water that tries to infiltrate the soil and the pipes are sloped towards the discharge point so the water is directed away from your home.
- Greenery: The roots of plants absorb the water, so combining them with a yard drainage system slows down runoffs and water infiltration.
- Basement and foundation waterproofing: Waterproofing solutions such as sump pumps and interior drains can minimize the level of water damage that often occurs in areas with high water tables.
In case there is a high water table near your Michigan home, there is no reason to panic. Contact the experts at FSM to schedule a free inspection and repair estimate. These professionals can install waterproofing solutions and mitigate water damage.
High Water Table FAQs
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Water can be much more problematic than you may think, especially since it can be damaging on its own and when combined with the soil underground. Homeowners that live in Lansing should be extra aware of these potential problems that water can cause and take the necessary precautions to prevent them. In order to understand how water can impact the structural integrity of your basement and foundation, you must first understand the two most common phenomena that cause water-related damages and issues. These phenomena are known as the clay bowl effect and hydrostatic pressure.
To build the basement and foundation of your house, contractors must first excavate a large hole so that they have enough room to construct both spaces. When construction has been completed, this hole will be backfilled by new soil. However, this soil is extremely loose and less dense in comparison to soil that has not been dug out. As such, this backfilled soil is more likely to absorb much more liquid, thus increasing the amount of water that collects around your foundation and basement. This collection of water is also known as a “clay bowl,” hence the name “clay bowl effect,” and can increase the likelihood of leaks and water damage in and around your basement or foundation.
Additionally, soils that become oversaturated with water—which may be common in Lansing due to constant rain—can result in hydrostatic pressure pressing against both basement and foundation walls and floors. As the weight of the water in surrounding soils increases, the more pressure that will be placed on your foundation and basement. This can result in the formation of cracks and holes, consequently leading to leaks and potential flooding through your home’s foundation and/or basement space.
Typically, standard homeowner’s insurance does not cover basement waterproofing or seepage, but separate flood insurance might cover some water damage.
Leah Leitow
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