Crawlspace question.

I also posted this in the Emergency section, but was hoping someone could give me their feedback.

I did an inspection this morning in the Denver area, and the house had a crawlspace with a structural wood floor above it. The crawlspace was dry, with a humidistat controlled air exchange system (Which was not running based on the humidistat setting).

There was no obvious black mold like substances, but there was this white color (mold like substance?) on the bottom of some of the structural floor joists. Not exactly sure if it needs to be written up, and how it should be.

Thank you for any Advice


Yes, it is mold. Usually happens on the bottom of floor joists due to moisture evaporating from the ground, such as no moisture barrier.

No insulation?

No vapor barrier?

Thank you for the responses. Recommending further testing of white substance. And yes the vapor barrier , and insulation are noted.

Thanks Again.

When I see something like this i will usually check humidity areas in the area to verify my findings.
9 times out of 10 it is a gutter/downspout/grading problem.

Hey Rick,
I have a few questions about your statement and if you can take the time to answer, I’d appreciate it as we’re always learning.
How do you come to this conclusion? Are you saying if all this stuff you mentioned is ideal, there wouldn’t be this white stuff on the bottom of the joists or high humidity wouldn’t exist? Do gutter/downspout/grading problems cause moisture issues, including high humidity, in crawlspaces 9 out 10 times? If you fix this stuff at the exterior, will crawlspace moisture issues be solved…9 out of 10 times? If the crawlspace has functional/properly installed drain tile system, and walls are intact/moisture-proofed, will the gutter/downspout/grading systems make a huge difference, 9 out of 10 times? Do you tell clients what you stated when you run into moisture issues in crawlspaces?

Just trying to understand and stay educated, so I don’t misinform clients.
Thanks in advance.

Water?! is it in an area that was effected by the recent flooding? Recent as in w/I last few years.
Is the flooring new? Efflorescence. Some one correct me Please. These are my first thoughts on this pic and info alone. Next is how old is the house. Sometimes the truss and Beams for a house sit on ground for a while before the building and get wet and have discoloration. but the white on the steel beam too…moldy looking.

I have a property that had the same mold. No moisture barrier,very similar pictures. It cost $1300 to clean,treat and install plastic on the ground. The end results were done very well. It has to remedied. No one will buy the property knowing this.