Crawlspace concerns

House Repair Talk

Help Support House Repair Talk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


New Member
Aug 17, 2023
Reaction score
Hello, new here to the forum. Where I live (NW Indiana) we recently got 5"+ of rain in an afternoon. I realized we got 8" in our crawlspace the same day we got the rain. I was able to use a sump pump to remove the water the next day. Our crawlspace is about 20" tall and we have no drainage system. Today a crawlspace contractor showed up to check for mold, any damage and give me a quote for a drainage system. We do have a little bit of mold, (concerning, but not major). I was quoted $8700 for mold remediation, crawlspace encapsulation, drainage installation and installation of exterior crawlspace entry door. One question I really had that I have never heard of is after the encapsulation is put in and the crawlspace is completely sealed up, he mentioned putting in register vents in the ductwork, to condition the space to reduce the mold growth, with the added benefit of keeping the pipes from freezing in the winter and warmer floors. Everything made sense to me, but I had never heard of it as well as wondering if there is any concerns of doing this. I should mention my house is a 1200 sq. ft. brick ranch built in 1948.
It rarely gets below freezing where I live so others may have a more relevant view - so, take this with a big grain of salt. If there is any visible mold, it is almost certainly due to long term damp conditions, not rain a couple days before. That suggests that if you fix the drainage so your crawl space stays dry you might not need to do anything else. If you can keep it dry there is no reason to clean up the existing mold - unless you have reason to believe it is making someone sick. Serious health impacts due to mold can be real but the whole "toxic mold" scare was mostly just a cash cow for lots of consultants and contractors.

If there is no evidence of previous sub-floor flooding, what changed to cause it this time? If you need to make changes to improve drainage, your best option is to re-grade the surface so that water flows away from the house. If that is not practicable, the next best option is to capture water at the surface then drain it away in solid pipe. The least desirable option is a french drain or other system that collects the water in the subsurface.
Conditioned crawlspaces are the preferred method these days. To do one you need to encapsulate the crawlspace, insulated the walls, close off the vents and install supply and return lines from the HVAC into the crawlspace. Alternatively, you can install a dedicated dehumidifier with a drain-line running to daylight outside of the crawlspace. Vented (open to the outside) crawlspaces are very common here, but given our hot and humid summers are really a bad choice. Our winters don't usually stay cold for very long, but you do run the risk of frozen pipes with an open/vented crawlspace. From what I've seen the price quoted is pretty typical.