GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Crawlspace flooding vs “right crawlspace design”

aimee00 | Posted in GBA Pro Help on

Hello – I’m looking for a long-term solution to my crawlspace and have received different information from basement contractors and what I’ve read on Green Building Advisor. Would appreciate the pro’s expertise on this matter. I’ve read the articles on ideal crawlspace design, and ours is quite the opposite. 

I have a home in CT with a vented crawlspace with concrete walls and concrete foundation (no dirt floor), built in the 60s. The house is sitting atop cinder blocks located in the crawlspace. Except for some pipes and electrical wirings, no other mechanical systems (e.g. HVAC) are located in the crawlspace. Typical fiberglass pink insulation in place.

Our backyard floods occasionally, but only a handful of times has the crawlspace been flooded since we’ve lived here in the 90s. Recently, Tropical Storm Elsa flooded our crawlspace. Two basement contractors gave two different solutions:
1. Joe said: Install a french/curtain drain from one of the drains closest to the crawlspace and run the pipe along the backyard to the other side of the yard and “redirect the flood” away from the crawlspace. The end of the french drain would have a drywell. Start planting some thirsty plants to help soak up water along the side of the house around the crawlspace entrance.

2. John said: the second opinion from John was the only thing I need to do is to sprayfoam the underside of the floorboards to protect the wood, and let the crawlspace be vented/flooded/humid because the any moisture (rain or condensation) will not affect the wood, and will recede back into the concrete foundation inside the crawlspace within hours. Because flooding is not frequently recurring, sump pumps and additional drains would likely not be a lot of “bang” for the buck. Better use of financial resources toward protecting the wood from mold and go natural by planting.

Based on articles all over green building advisor, I know I’m suppose to close the vents, insulate around the walls of the crawlspace/basement, and install a dehumidifier. But if my issue is flooding, and most of my neighbors have higher ground than me, then does it really make sense to protect and include the crawlspace as part of the building envelope and control humidity?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Deleted | | #1


  2. Jon_R | | #2

    When it floods, how long does it remain flooded? Is it creating a problem?

    1. aimee00 | | #3

      Only general fear of mold growth on wood/floorboards/beams

      yard/outside: once the rain stops, water will recede within 1-2 hours.
      inside crawlspace: 4-8 hours.. don't have a conclusive data point because it's infrequent and during last storm, we used a sump pump and wet vac afterwards

      1. Jon_R | | #4

        Re mold: I'd worry about a fix only if you see some signs of it.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |