Home Miniature house How to Drain Swampy Yards and Stop Wet Basements

How to Drain Swampy Yards and Stop Wet Basements

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Ande lives in Puyallup, Washington, and reads my weekly column in his newspaper. She has a very common problem. In fact, tens of thousands of people suffer from it in places with heavy rainfall for several months of the year.

Ande’s garden turns into a miniature Okefenokee swamp when it rains. Its crawl space is also flooded. She asked for my help to solve the problem. Luckily, I have a college degree in geology with a major in hydrogeology — the study of groundwater.

Every spring, I receive hundreds of emails from homeowners suffering from water leaks in basements and crawl spaces. Most also have soggy courtyards. The good news is that in almost all cases, you can fix these problems with moderate effort and minimal expense if you can do most of the work yourself.

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I do a lot of phone coaching with owners like you, and in the vast majority of cases the builder caused the most problems. The three biggest pain points are:

· Water from the roof is discharged onto the ground next to the house.

· The ground has not been sloped from the foundation of the house.

· The lot was improperly leveled before the house was built, which prevented the drainage of surface water to the lowest natural point.

You’d be surprised how much water falls on your roof. If your home’s roof footprint is close to 1,600 square feet, a rainstorm that dumps 1 inch of rain will create just over 1,000 gallons of water falling off the roof. The last thing you want to do is dump all that water onto splash blocks at the base of the downspouts. This water must be directed to municipal storm sewers or to the lowest part of your land where the water would have drained naturally before the construction of your house.

The ground that touches your house must be away from the foundation. If your house was built on a mountain top, by default all the water would run down and away from either side of your foundation. You can achieve the same by making sure the top of your foundation walls are at least 18 inches higher than any ground within 10 feet of the foundation.

The building code suggests that the grade of the ground should fall at least six inches within the first 10 horizontal feet of the foundation. Note that this is a minimum standard. More slope is better.

Once the ground pulls away from the foundation on all sides, you do what is necessary to slope your yard so that the water runs down to the lowest point of your land. This takes care of all surface water. Now is the time to deal with the water flowing through the topsoil.

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When it rains, the water flows into the topsoil and takes up the space previously occupied by the air. The water is then pulled by gravity downwards and then laterally. Many soils have a clay component, and the deeper you go into the soil, the denser the clay becomes. That’s why in the Midwest, South, and many other parts of the United States, creating a pond is easy. The clay soil acts like a giant pottery bowl.

If you know this groundwater is coming down towards your home, you just need to intercept it before it reaches your foundation. You then redirect that water around your home and send it out to the ocean. This is where all the water wants to end up if given the chance, unless you live in the Great Basin in the Southwestern United States or similar places around the world.

I think the best way to intercept groundwater is to dig a trench six inches wide and about 24 inches deep. In most situations, this takes you into the dense clay subsoil. I like to put about an inch or two of clean rock in the bottom of the trench. This rock should be the size of large green grapes. Make sure there is no sand in the rock or small pieces of rock.

I then put a four inch perforated pipe over this gravel and then filled the trench to the top with the same grape sized gravel. Water flowing through the ground hits this gravel, immediately falls and ends up in the drainpipe.

The trench can be L-shaped or U-shaped as it wraps around your house in search of daylight. As the ground moves away from your house, the drain pipe will eventually come out of the ground if you keep the bottom of the trench level or have a very slight drop to the drain pipe by ⅛ of inch by foot. During wet periods, you’ll see enough water flow from the hose to fill a five-gallon bucket in a minute or two!

You can access a 90 minute step-by-step video showing you how to install one of these trench drains here: GO.askthebuilder.com/trenchdrain.

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©2022 Tim Carter. Distributed by Tribune Content Agency, LLC.