The Washington PostDemocracy Dies in Darkness

How to drain swampy yards and stop wet basements

If the footprint of your house’s roof 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. (iStock)

Ande lives in Puyallup, Wash., and reads my weekly column in her paper. She’s got a very common problem. In fact, tens of thousands of people suffer from it in places where there’s abundant rainfall for many months during the year.

Ande’s backyard turns into a miniature Okefenokee Swamp when it rains. Her crawl space also floods. She asked for my assistance in solving the problem. Fortunately, my college degree is in geology with a focus in hydrogeology — the study of groundwater.

Each spring, I receive hundreds of emails from homeowners who are suffering from water leaking into basements and crawl spaces. Most have soggy yards as well. The good news is that in almost all cases you can solve these problems with moderate effort and minimal expense if you can do most of the work yourself.

More Builder: Why you need a covered front porch on your home

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

· Roof water is dumped onto the ground next to the house.

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

· The lot was improperly graded before the house was built, impeding drainage of surface water to the natural lowest spot.

You’d be surprised at the amount of water that falls onto your roof. If the footprint of your house’s roof 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 this water onto splash blocks at the base of downspouts. This water needs to be piped to municipal storm sewers or piped to the lowest part of your lot where water would have drained naturally before your home was built.

The soil that touches up against your home must slope away from the foundation. If your home was built on a mountain peak, by default all the water would slope down and away from each side of your foundation. You can achieve the same thing 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 slope of the ground should fall at least six inches in the first horizontal 10 feet away from the foundation. Note that this is a minimum standard. More slope is better.

Once you have the ground sloping away from the foundation on all sides, you do what’s necessary to slope your yard so water flows to the lowest point of your lot. This takes care of all surface water. It’s now time to deal with the water flowing through the topsoil.

More Builder: How to repair a bathroom window with wood rot — and preventing it in the first place

When it rains, water flows into the topsoil and occupies the space previously taken up by air. The water then is pulled by gravity down and then sideways. Many soils have a clay component, and as you go deeper into the soil, the denser the clay becomes. This is why in the Midwest, South and many other parts of the United States it’s easy to create a pond. The clay soil acts like a giant pottery bowl.

If you know that this subsurface water is moving downslope toward your home, you simply have to intercept it before it hits your foundation. You then redirect this water around your home and send it on its way to the ocean. That’s where all water wants to end up if given the chance unless you live in the Great Basin in the U.S. Southwest or similar locations in the world.

I feel the best way to intercept the subsurface water is to dig a six-inch wide trench about 24 inches deep. In most situations this gets you into the dense clay subsoil. I like to put about one or two inches of clean rock in the bottom of the trench. This rock should be the size of large green grapes. Be sure there’s no sand in the rock or smaller pieces of rock.

I then put a perforated four-inch pipe on this gravel and then fill the trench to the top with the same grape-sized gravel. Water flowing through the soil hits this gravel, immediately drops down and finds its way into the drain pipe.

The trench might be L- or U-shaped as it goes around your home looking for daylight. As the ground slopes away from your home the drain pipe will eventually pop out of the ground if you keep the bottom of the trench level or have a very slight fall to the drain pipe of ⅛-inch per foot. In wet periods you’ll see enough water flow out of the pipe to fill a five-gallon bucket in a minute or two!

You can get access to a 90-minute step-by-step video showing you how to install one of these trench drains going here:

(Subscribe to Tim’s free newsletter at Tim now does a live stream Monday through Friday at 4 p.m. Eastern time

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

More from The Home You Own

The Home You Own is here to help you make sense of the home you live in.

DIYs you can actually do yourself: Don’t be intimidated by those home projects. Consider which renovations add the most value to your home (including the kitchen and bathroom), what you can actually get done in a weekend, and everything in between.

Your home + climate change: Whether you’re trying to prepare your home for an electric vehicle or want to start composting, we’re here to help you live more sustainably.

Plants and pets: Your furry friends and greenery add more life to your spaces. For your green thumb, find tips for saving money on houseplants and how to keep your plants alive longer. Pets can make a house a home, but stopping your cats from scratching the furniture isn’t always easy.

Keeping your home clean and organized: We breakdown the essential cleaning supplies you need, and point out the 11 germy spots that are often overlooked. Plus, hear hacks from professional organizers on maximizing counter space,

Maintaining your home: Necessary home maintenance can save your thousands in the long run. From gutter cleaning and preparing your fireplace for winter, to what to do if your basement floods.

Contact us: Looking to buy your first home? Do you have questions about home improvement or homeownership? We’re here to help with your next home project.