How to Install a Drainage System Around the Foundation of a House

Co-authored by Elmer Bensinger

Last Updated: December 10, 2024 References

Is rainwater coming into your basement? This can be a real nuisance, not to mention the damages it causes. Installing a drainage system around the foundation of your house will help. Here are a few steps to prevent rainwater coming into your basement:

Steps

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The trench will need to be dug down to the footers of the foundation and be about 4' wide. You will also need to dig a trench away from the foundation to either a percolation trench, dry well or to daylight if the slope of the land allows.^{[1]
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Elmer Bensinger
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Expert Interview} (Percolation trench is also called an infiltration trench similar to the trench you have around the foundation. You will then add perforated pipe at the percolation trench. This is the best way to manage the run off. A dry well is either a pit filled with crushed stone or a structural camber. The easiest way is running it to daylight if the building site has a steep enough slope).^{[2]
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Along the bottom of the trench, you will unroll the filter fabric, lapping the filter fabric up the sidewalls of the foundation. Smooth the remaining fabric away from the foundation.^{[3]
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Cover the filter fabric with a 3-4” layer of crushed stone. Now, install the 4” perforated pipe around the whole perimeter of the foundation. Perforated pipe can be installed on level ground. Use a solid 4” PVC tee to connect the ends of the perforated pipe. You will now connect the solid 4”PVC pipe to the tee, which will leads to a percolation trench, dry well or to daylight. Cover the pipe with crushed stone, 8-10” above the footing of the foundation. Then, pull the excess filter fabric over the crushed stone, making sure it laps against the foundation. It is important that the fabric completely cover the crushed stone, this will prevent the soil clogging the pipe.^{[4]
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Fill with a minimum of 6” of gravel or coarse sand is recommended to prevent soil getting under the fabric and clogging the drainage system. Now back fill the trenches. The soil should slop away from the foundation.^{[5]
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You have your drainage system almost completed. Lay a layer of filter fabric over the soil. Plant your favorite shrubs and cover filter fabric with bark mulch or pea stone. Not only will you have a dry basement, you will have lovely landscaping.^{[6]
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Which way should the holes be facing on the pipe?

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They should be facing down. If the holes face up, then silt will eventually fill the pipe. Also, with the holes down, the drainage from the pipe begins at the lowest level (bottom) of the pipe instead of at the top of the pipe; a 4" difference in water removal depth.

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If holes are on the bottom of the pipe, what keeps the water in?

Andrew Trenholm

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The holes are on the bottom left and right (do not set a line of holes straight down). Between the holes is just enough gutter (usually about 1" inch high) that works just perfectly for sending water down the pipe.

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It seems like removing the soil from the side of my foundation would upset the structural integrity. How deep should I dig below the level of the foundation?

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Your pipe needs to be 3 inches below the foundation's footer. Nothing to worry about; most of the house was built on the foundation before the dirt was put against the foundation.

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Install gutters around overhang to direct rainwater away from your foundation.^{[7]
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Elmer Bensinger
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Make sure you glue the pipe together!

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Apply a good quality waterproofing material to your foundation walls before you back fill. There are many different kinds on the market today. Water-based material is easier when it comes to clean up. Do your research.

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Warnings

Some waterproofing materials are really only damp-proof.

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Check local codes for guideline on percolation trench, dry well or to daylight.

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Wear protective gloves and eye goggles.

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