I am preparing to install a perimeter drain in my crawlspace. I will be using NDS-EZ drain pipe. My question is Where is the proper place to dig the trench? Next to the foundation or 1 foot away from it? I was planning on digging right down next to the foundation, which in this area is only 18" max but I have since read where it should be 1 foot away from the foundation. If this is correct, why?

1 Answer 1


Typically a perimeter drain system is installed within 12 inches of the foundation wall. The gravel backfill then rests against the foundation and the pipe is 6 inches or so out from the wall.

In your case, I don't think it would make much difference in the performance of your drain. Not sure exactly what you meant by 18" max. Is the foundation only 18" deep or your drain to be installed no more than 18" deep? You definitely don't want to dig deeper or too close to a shallow foundation so as not to undermine it. Good luck.

  • I was refering to how deep they trench for the foundation or the frost line depth. Most foundations in this area are no deeper than 18" to the bottom of the trench and then the concrete footer is poured inside that. thanks for your answer.
    – user2156
    Commented Mar 25, 2011 at 20:54
  • "undermine" heh heh -- does anyone actually thinking about the origin of the term Commented May 12, 2014 at 15:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.