How to Inspect and Correct a Vented Crawlspace Article

How to Inspect and Correct a Vented Crawlspace

This article explains the issues and concerns with conventional ventilated crawlspaces and outlines prescriptive measures for improvements that will create healthier and more durable spaces.

Home inspectors should use this how-to guide as a tool to help them perform inspections of crawlspaces, identify indications of defects associated with crawlspaces, and properly recommend strategies to convert a traditional crawlspace with open foundation vents and poor design and construction into an unvented, insulated, and conditioned space.


I had a situation where the contractor wrapped the wooden support columns as depicted in your Graphic #21 & #22, which rotted out the bottom of the posts causing settlement and extensive drywall cracking. The water vapor trapped under the plastic accumulated around the wood posts. I would not recommend wrapping steel or wood posts.



Thanks Randy.

Hi, Randy. Great images. The rot may have been more likely caused by the untreated wood being in contact with dirt, and less likely because of insulation wrapping. I would think that the builder wrapped the post with insulation to hide an improper installation of a load-bearing post and footer. In the image, wicking of moisture from the bottom of the wood is apparent, and the water marks are the result of the wicking and do not reflect the position of the insulation. Great catch. Your clients must have been very pleased.


You can’t tell from the photos but all the posts were sitting on concrete footings above grade. I was called in to do a structural inspection concerning all the drywall cracks and sloping floors when I discovered the problem in the crawlspace.

That is fantastic and spot on! Thank you!

I particularly like the checklist.

Capillary action for sure. Thanks for posting this Randy I will look at these things differently.

Awesome Ben. Nice Job.

In Chicago I automatically recommend conditioning the space. Absolute minimum is to provide a vapor barrier and plastic sheet is never a good answer. If they leave Vented it seems rare the heating ducts are insulated.
Agree with Randy that wrapping wood is a dumb idea.