Dig a Drainage Trench to Avoid Basement Flooding
This post originally ran about a year ago. I thought it was pretty informative but was still able to add a few more details.
Flooded basements are a very serious problem that can result in considerable damage to your property and possessions. It’s also a health concern as wet basements promote mold. It’s important to resolve poor drainage issues rather than clean up the aftermath year after year. Plus, flood insurance will only protect you for so long.
If you’re in this situation and you’re considering professional help, Basement Systems is a company that provides a service to link homeowners with basement water problems to professionals who handle this type of work. Here’s the link for Basement Systems. The form is quick and someone will contact you usually within 24 hours.
If you’re looking for a DIY solution, French drains and drainage trenches are a great way to divert water away from your home.
How a French Drain Works
Water will follow the path of least resistance. A French drain provides an easy alternate route for water, allowing you to direct it away from your home. You accomplish this by using perforated pipe and gravel. Water would much rather flow through open pipe or around small rocks than through compact soil but there are some important things to keep in mind to ensure your drain works properly. Read on as we cover how to install a drainage trench.
How to Install a Hidden Drainage Trench
The overall idea is to dig a trench that slopes away from your house. Next, embed perforated pipe within gravel for water to flow through, and protect the whole setup with landscape fabric.
Plotting your locations: First, you need to decide where to install your drain. Examine the grade of your yard and determine sloping areas that direct water toward your house. Even gradual slopes can enable water to collect at your foundation. Ideally, you’ll cut off these pathways and redirect the water somewhere harmless. Storm sewers are the best endpoint for runoff, but it may be difficult to achieve that connection. The next best solution is to expose the drain end to daylight. Here are some considerations for where you direct the runoff.
- Neighbors – Sending water toward the neighbors is not a good idea. It may result in flooding problems and ultimately a law suit.
- Sidewalks – Sidewalks can become icy in winter or slippery in summer.
- Play area – You want to be able to enjoy your yard. Don’t create a soggy marsh that you can’t use.
Mark off the locations for your drains. Before breaking ground, check local code for any guidelines and call “Call Before You Dig” at 811. Call Before You Dig will get a local utility to come out and mark the utility lines on your property.
Digging your Drainage Trench: Trench widths can vary. I’ve seen them as small as 6 inches or as wide as 24 inches. Often, trench width is dictated by the equipment you are using and how much you want to dig. A backhoe makes it easy to dig a wide trench while shoveling is a lot of work. Wide trenches do afford several important advantages.
- They can collect more water.
- Working in a wide trench is easier.
- Wide trenches last longer because they will not clog as easily.
Drains should be at about 2-3 feet deep. Deeper soil is more compact and will better funnel water to your perforated pipe. Whatever depth you choose, remember to account for the downward slope. Also, place your drain about 6 feet away from the foundation, else it will pull water toward your house.
Sloping the trench: Your trench should maintain a 1% grade. That means a 1 foot drop for every 100 feet of length. A steeper slope is not a bad thing but 1% is the minimum. Use the 1/100 ratio to determine how far your trench should drop. Here’s an easy way to measure the grade as you work.
- Grab two stakes and place them next to the trench, along it’s entire length.
- Run a string between the two stakes. Adjust the string height until it’s perfectly level (using a level of some kind).
- Measure from the bottom of the trench to your string to determine the change in depth.
Fill with gravel: After digging out your trench, it’s time to fill. Begin by lining the trench with permeable landscaping material- fabric or plastic. Plastic landscape material can be easily damaged. I suggest using fabric landscape material.
This fabric will allow water to pass through while keep dirt and debris from clogging your drain, making it less effective. Be sure to overlap any seams and to allow extra for wrapping over top. Next, put down two inches of washed gravel taking care to maintain your slope. Be sure to select a large gravel that it won’t clog your pipe.
Many people use corrugated, flexible pipe in their drains however a rigid plastic pipe has some additional benefits.
- It’s easier to maintain the proper slope with a rigid pipe.
- Rigid pipes can be cleaned with a sewer snake, while flexible pipes would tear.
Place your perforated pipe on the gravel, holes facing downward. It may seem counter intuitive, but remember, the water pools from the bottom up. Placing the holes on the underside allows water to enter much sooner. Slowly fill the trench with gravel, taking care that the pipe stays in place. Fill the trench with gravel until you are 2 inches below ground and cover with the landscaping fabric. Add dirt with grass seed, or lay sod to conceal your drain.
Waterproof Your Basement Walls
Another important tactic to consider is waterproofing your basement walls. You can seal below grade concrete, brick, stone, or masonry walls to prevent moisture penetration. The best way to accomplish this is by applying a portland cement-based powder waterproofer. These waterproofers have chemicals that are activated by water and dry as a waterproof barrier.
What do you think? Ever install a French drain before?
Image courtesy of Jeff Tidwell
Enjoy this article? Share it with your friends...
Share
June 24th, 2009 9:13 am
Several years ago, after two costly basement floods caused by poor drainage and the roof spill falling too close to our foundation, we installed french 4 drains around our house, and I’ve never regretted it. It was a big job and labor intensive, but made much easier by our son-in-law who could borrow a backhoe from work. The sacrifice in grass was worth it!
Another thing that we did to push run-off away from the house was to build raised gardens around the low side and back where most of the problem lay. We used 12-inch landscape stones to wall in the garden to 2-4 layers above ground. The underground pipes from downspouts to drainfield pass under the gardens and drain safely 6-20 feet out. So far, no more floods!
[Reply]
June 24th, 2009 1:30 pm
Chris, You mention a good point. Typically, multiple drains are required to divert enough water. And there are other measures like building up the grade around your home that can help too.
[Reply]
June 29th, 2009 9:40 pm
Ethan,
Great article! Best description of how to do it that I have seen yet, and I have been reading quite a few!
Thank you.
[Reply]
March 31st, 2010 4:30 pm
We just bought a house and 2 days later got an ncredible amount of rain. Needless to say, the whole basement flooded with about 3″ of water. I am uncertain about what method of waterproofing to go with. The indoor french drain w/sump pump or outside cutrain drain. I was told that the indoor drain detaches the basement wall from the floor so now you have a floating basement floor and affects the footings. I got a price of $6k to do the inside french drain w/pump. Whatever method we go with, we are do it yourselvers and would like to do the waterproofing ourselves. How much labor is involved with the exterior curtain drain?
[Reply]
March 31st, 2010 7:03 pm
@Julie, Sorry to hear about the flooding. That’s not what you hope for from a new purchase. I’ve never installed a french drain myself so it’s tough to compare. When I helped dig the drainage trenches, we used a backhoe. It took care of a lot of the heavy lifting, but your trench may not be as big- meaning less digging. Another thing to consider is laying the gravel.
I definitely think DIYers can handle the drainage trenches and that’s the choice I’d go with in your position. Good luck!
[Reply]
May 29th, 2010 7:11 pm
Hi, I am digging a trench in my yard and I keep coming across white roots. I have no plants around it and I’m not sure if I should be digging them up or not. Can anyone help?
[Reply]
August 4th, 2010 7:16 pm
Ethan –
Thanks for the informative article. This is something I’m planning to try to prevent the large amount of water that comes into my basmenet sump well. In my case, I’m less concerned about the yard, and mostly concerned about water making it’s way to my foundation and basement.
I have a general concern about this method. I’ve been told by some contractors that basically the entire lot of your house should be considered loose / water hungry water as it was all disturbed during the foundation pouring. Is this a falicy? I’m not sure how else this method would work, as it assumes we hit clay / dense soil after 2-3 feet.
I also have some questions on my setup. I have a deck on half of my backyard, and I can’t get under it. Would it be wise to create two separate drains – one that is 6′ from the foundation on the open half, and one that is right up against the deck (12′ from the house) on the other side? I’m assuming I would not want to connect these, but maybe that would be OK. If not connected, I guess I would cap off the end.
The rear of my backyard is a huge hill, followed by 20′ of flat ground before the house, and then we start going downhill in the front yard. I picture the drain being parallel to the house in the back (aside from the jut out for the deck) and completely level throughout the back. It will then make 90 degree turns after it’s 6′ to the sides of the house and head forward. The natural slope of the yard would lead the water to the front. But what about the level pipe in the backyard that is parallel to the house? Will the pressure caused by the dropoff as we move towards the front yard pull the water from the long and level pipe running in the back?
Finally, I’m wondering if I need multiple trenches in my situation. I’m thinking that the base of the hill is a big spot where water might sneak down, so a pipe might be good there. Then of course the one closer to the foundation to catch anything between those two spots. Does that sound fair? A diagram would be easier
Thanks!
[Reply]