Why Is the Basement Leaking From the Floor?

Few scenes put fear into homeowners like spotting water on the basement floor for the first time, and rightly so too because this can be a sign of bigger problems and must be taken seriously. How and why water comes up from the basement floor can vary, so investigative work is needed before panicking.

Basement HDR
credit: © by Martin Deja/Moment/GettyImages
Why Is the Basement Leaking From the Floor?

Basement Water Leak or Flooding?

Before you enter, assess the danger. Any plugs, outlets or appliances that are in water or near it can conduct electricity, so turn off the power supply if needed and then grab a flashlight to do some investigating.

Next, make sure the water is coming up from the basement floor and not falling onto it from the pipes above. Once you're certain it's not flooding from pipework, it's time to find out the cause of the leak.

Common Causes of Flooding

There are a few questions to ask right off the bat.

  • Is your area known for groundwater issues with basements and foundations?

  • Has there been heavy rain or fast-melting snow lately?

  • Could there be a burst city pipe or construction by your property?

  • Has there been wind or other weather issues that could have shifted where your downspouts are dumping rainwater?

  • Has any piping under the concrete burst?

Groundwater and the Water Table

When it's not from pipes and plumbing, the leading cause of basement groundwater is the water table rising. The water table is where water saturation begins in soil, but the water table isn't static, meaning it rises and falls depending on weather and seasons. The water table near a lake, for example, is far higher and closer to the ground surface than in a plateau or desert area, and it rises far faster in poor weather, like after flooding or seasonal snow melting.

What happens with floods and snow melt is that water saturation continues to increase, so the level of water in the soil keeps rising until it eventually meets the ground surface. If your basement is in the way, and there are structural deficiencies or cracks in the concrete, then your basement becomes the path of least resistance, and the groundwater goes there.

Rising groundwater causes hydrostatic pressure, and that causes soil to push on your basement walls and floor. This can make cracks form in basement concrete, particularly in wet seasons, and is often why there's water in your basement after rain.

Water Entry Points

When groundwater and flooding are the issues causing your basement water problem, it can be difficult to identify from where the water is entering the basement. Hydrostatic pressure causes water to look for the easiest way into your basement. So, what's failing and where? Things like mold, efflorescence, mildew and stains might suggest from where a water problem has been coming over a longer period, but they won't be there if this is a new problem for you.

Here are some places of entry that could be the source of your water woes:

  • Window wells: These are designed to help more light come into the basement while keeping soil and water away from the window. Unfortunately, they can become clogged or filled with debris over time, and if they are not draining well, eventually water will make its way through deficiencies in the construction.

  • Wall cracks: This can be serious. A crack in the wall can be a structural problem with the foundation, and everything in your home rests on your foundation's integrity. If water gets into the crack and then the temperature drops, the water can freeze and further expand the crack. While hydraulic cement is considered a very good patching solution, much peace of mind could come from consulting with a professional to ensure that foundation integrity has not been compromised.

  • Honeycomb concrete: If concrete was poorly mixed before being poured for your foundation, air pockets can form that can eventually give way under hydrostatic pressure, giving water entry points of all sizes in random spots.

  • Mortar joints: Especially in older homes, mortar can eventually crumble or deteriorate, losing water resistance. On one hand, this is a problem that can be repaired. On the other, it could mean there are multiple leaks, and each is quite hard to diagnose, as the cracks can be small and tricky to locate.

Dealing With Water in the Basement

Basement leak repair can be costly. If you have cracks occurring in the basement floor, and it's because of hydrostatic pressure, the good news is that it can be mitigated, but it will be pricey. The solution is installing drain tile, which is when concrete is cut to install a network of piping that directs the water build-up away from possible entry points into your basement. It relieves the pressure and saves your slab.

Waterproofing your walls and concrete floor is an option. There are products you can apply, but it is very labor intensive, as you'll need to patch all cracks first and then wire-scrub and clean all surfaces so the proofing adheres properly. It's not as effective unless the exterior is done as well, which must be completed by a professional waterproofing outfit.

Outside Solutions to Leaky Basements

When the problem isn't coming up from the underground water table, it means the problem is coming down to the basement, and a big cause of that is weeping and perimeter water damage. The first culprit might be clogged gutters. Debris preventing proper drainage down gutters can mean water is overflowing and seeping down along your home's perimeter and soaking the soil by the basement walls.

After that, consider the grading. Is the property's pitch leading away from the house or leading to it? Some simple landscaping can mean you alter the path water takes, simply guiding it away from your home and saving the day.

Weeping or drain tile failures can also be an issue. It's unlikely the length of weeping tile will fail, but it's possible you have sections that are clogged and nonfunctional, causing water to pool along the wall in that area and resulting in the floor issues. Sourcing problems in the weeping tile is a trickier solution and might need intervention from contractors who specialize in foundation repairs.

Maintain Your Plumbing

Sewer and water lines are big culprits in water damage of any kind in homes, as they can clog and back up, causing water or waste leaks. Even worse, they can crack and break under pressure, creating a very costly repair. Be proactive to avoid this and have a plumbing company flush your lines every 18 to 24 months. Warning signs are when water starts to drain slowly, or you hear gurgling in the pipes.

Do not flush wipes even if they claim to be flushable. Do not ever pour fats, oils, starches or coffee grinds down drains. Don't put anything larger than a pea down the kitchen sink.

While it can seem inconvenient to not pour things down the drain, repairing plumbing can be one of the most expensive problems a home can face depending how pervasive it is. Practicing good habits with what goes down may help prevent what comes out or up.


Steffani Cameron

Steffani Cameron

Steffani Cameron is the daughter of a realtor and interior decorator mother and a home contractor father. Steffani is a professional writer with over five years' experience writing about the home for BuildDirect and Bob Vila. Raised with a mad love for decorating, Steffani gave up her Art Deco apartment to travel and work remotely for five years. She's in love with experiencing traditional decor around the world, including stays in Thai teak plantations on the Mekong River and cave homes in Turkey.