What is causing my basement to leak?

What is causing my basement to leak?

If you dug a hole in your backyard today and several inches of rain fell tomorrow, you would expect that hole to fill up with water, right? Now, imagine you built a house in that hole. What do you think will happen when it rains?

Built in a hole

When your home was first built, the builders dug a hole in the ground. Then, they built your home inside that hole. To establish a foundation, they poured a concrete footing to bear the weight of your home. 

On top of the footing, they poured the foundation walls. Then, they poured a concrete slab between the foundation walls for the floor. This three-piece foundation poured at three separate times forms your basement.

These homebuilders were wise and knew they were building your home in a hole that would fill up with water when it rained. So to combat the elements, they sprayed or rolled a damp proof coating of some kind on the outside of the basement walls. This coating is usually just asphalt, similar to driveway sealant. 

Then, they installed an exterior drain next to the footing. This footing drain consists of four-inch pipe with half-inch holes or slits to accept water. The builders poured rock around this pipe to function as a filter. Then, they backfilled the hole in the ground with soil and built the rest of your home.

Drainage system failure

Sometime after construction, the exterior drainage system failed. When it rained and everything was working well, the water would run down – through the loose backfill around your home – into the footing drain and drain away from your home. 

However, that water brought something along with it: dirt and silt. This created mud and sediment buildup around and inside the footing drain and the drainage system clogged.

For a little while, there were two things keeping your basement dry: the damp proof coating and the footing drain. The coating deteriorates over time, and the footing drain is now clogging or completely clogged. 

This is precisely why your home may have gone years without a water problem, but now you suddenly have a water problem that progressively gets worse and worse as the drain becomes more and more clogged.

Hydrostatic pressure

When it rains, the loose soil around your home becomes saturated. More rainfall means greater saturation. As the drainage system around your home clogs, less and less water is able to drain away from your home. When the drain is clogged and the water cannot drain away, the water builds up in the loose soil around your home.

So, the water builds up in that hole in the ground, but this isn't just any hole. Your home was built in this hole, remember?

Your foundation is not water-tight. The footing, the walls and the floor were all poured at three separate times. So, you have a porous structure with imperfect joints and cracks sitting in a hole in the ground that fills up with water when it rains. This body of water building up outside your foundation puts pressure on those imperfect joints. This is called hydrostatic pressure.

Hydrostatic pressure will build up around the foundation and force the water in at joints and cracks. As the water fills up in the backfill higher and higher, it puts more and more pressure on those imperfect joints in your foundation. 

Therefore, hydrostatic pressure creates two types of problems in your basement. One problem is leakage at the wall/floor joint, and the other problem is leakage up through cracks in the basement floor.

Wet basement repair

Initially, you may only notice symptoms of hydrostatic pressure, such as cracks and leaks, in certain areas of your basement. However, hydrostatic pressure is not isolated to just one corner, because the water fills up in the backfill all the way around your foundation.

Homeowners, like homebuilders, are also wise. Whether or not they're familiar with the term hydrostatic pressure, they do understand the concept. Some homeowners attempt to seal the water out from the inside by painting or spraying a sealant on the inside of the basement walls. Unfortunately, water has already seeped through the porous basement walls. At this point, the only thing holding the water back is a thin layer of paint.

Basement waterproofing methods have evolved over the years, and more advanced systems have been developed to keep your basement dry. There are certified contractors available who specialize in basement waterproofing. Often, these contractors will provide free inspections and estimates on wet basement repair.

You should always do some research before hiring a contractor. Read customer reviews, check company ratings with the Better Business Bureau or Angie's List, and consider your options carefully.

You don't have to live with a wet basement. You can keep your basement dry.

About this Angie’s List Expert: James E. Lord is a certified waterproofing professional with Woods Basement Systems, specializing in basement waterproofing services in St. Louis. For more than 25 years, Woods Basement Systems has offered basement waterproofing, basement finishing and foundation repair across Illinois and Missouri. You can follow this #ALExperts contributor on Twitter @WoodsBasement and on Google+.

As of April 7, 2014, this service provider was highly rated on Angie's List. Ratings are subject to change based on consumer feedback, so check Angie's List for the most up-to-date reviews. The views expressed by this author do not necessarily reflect those of Angie's List.

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