Crawl Space Encapsulation French Drain

Crawl space french drains are optional in many encapsulation projects. Do you need a waterproofing drain in your crawl space? What about a sump pump? These are the questions many homeowners ask when faced with the expense of dealing with standing water in the crawl space.

Remember, a crawl space in need of waterproofing has the potential to create a humidity problem. Humidity problems can lead to mold and wood rot fungus. Wood rot fungus can destroy your homes foundation or at least create sagging floors.

Make sure you don't make the wrong decision when it comes to a crawl space french drain.

Do You Need a French Drain in Your Crawl Space?

French drains in the crawl space are designed to move standing water to a sump pump. They can also be installed to move the water out through the foundation wall. If you have water intrusion in your crawl space after heavy rains, waterproofing drains are needed. Keep in mind, there are right and wrong ways to install them.

Which is Better, Sump Pump or French Drain

French drains are no better or worse than sump pumps. They each do something unique and many times work together. For large areas french drains are needed to move the water to an exit point, like a sump pump. If you have just a small area of water intrusion, the sump pump may be all you need.

It is possible to install a french drain and not use a sump pump as long as the contractor knows what they are doing. Many of the issues we see with this type of install is the waterproofing drain is not draining to daylight. We have seen them stop in the block wall or just past the footer in dirt.

Image of NDS ezflow

The NDS Ez-Flow Drain Pipe

As you can see in the picture above, our french drains use a perforated corrugated pipe, aggregate and sock. The sock keeps soil and debris from entering. The aggregate gives the pipe space to allow water to channel more rapidly to the pipe. The perforated waterproofing drain pipe allows the water to enter and travel to the exit point.

We feel all three of these components are crucial to a proper french drain. No sock can allow clogging and failure. No aggregate can slow water making it into the pipe. During heavy floods this can be a problem. No perforations keeps water out of the pipe.


I have seen french drains installed above the dirt. I have seen them not connected. I have seen them installed to try to carry water up hill. I have seen them installed with no exit point.

Read our last article:

Crawl Space Encapsulation Sump Pump

Normally french drains installed incorrectly are not noticed for a while (until the next heavy rain). Plus many times they are covered with a new vapor barrier which can also hide its incorrect installation. Hiring a crawl space encapsulation contractor with a great reputation for customer service can protect you from wasting money on waterproofing installs.

Below is a video of a crawl space we had to redo for many reasons. One was the french drain pipe was installed above the ground. There are many other problems with the install of the french drain. See if you can spot them.

I hope you found this information useful. Please comment below if you have any questions or would like to say hello.

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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.


  1. Nathan Suhl on August 17, 2021 at 5:40 am

    Hi, I have ordered the Aprilaire e080 and vent fan and will be ordering anabec advanced cleaning solution plus to fog my crawl space and then do an encapsulation. I’ll also be sealing the other vents and installing insulation on the walls. I would like to install the French drain system myself but not exactly sure of the best way to slope it. For instance, the long back wall of my crawl space is 60ft long and straight. Any ideas of the best way to slope that? My sump pit will be at the low end of that wall trench. Thanks in advance

    • Michael Church on August 17, 2021 at 1:07 pm

      Hi Nathan, if the crawl space floor is level the inside of the pipe has a built in slope (air space). If you will slope the last part of the pipe that enters the sump pump pit, it will draw the water in the pipe to it faster. If you want the water to move even faster towards the pit, a 2 to 3 inch slope along the majority of the wall with maybe a 4 to 6 inch slope into the pit will move the water quickly into the basin. Keep in mind most footer drains and interior basement drains are not sloped due to the air space inside the pipe that acts as a natural slope as long as the pit/pump is lower than the pipe. Hope that helps.

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