Mold growth on dirt & soil in, under, around buildings:

This article gives advice on how to find, identify, clean up or prevent mold growing on dirt or soil surfaces such as in building crawl spaces or in dirt floor basements.

Thanks to reader prodding we include five simple steps for dealing with mold growth on the dirt floor of a basement or crawl space.

Yellow mold in crawl spaces may be destructive Meruliporia fungus. White mold found on crawl space or basement dirt floor may be a basidiomycete. Photographs of mold growing on dirt crawl space floors - soil fungi under or in buildings. Indoor "mushrooms" growing in or on buildings.

Our photo (above) shows thick pale yellow fungal growth on dirt in a damp crawl area.

Q&A on Mold on Dirt in Basements & Crawl Spaces

These questions & answers about cleaning-up or preventing mold growth on soil or dirt floors were posted originally at MOLD on DIRT FLOORS - you will want to read the identification, hazard, and cleanup or prevention advice given there.

On 2018-09-04 by (mod) - just cleaning the heating system won't cure a building mold contamination problem

No, Rhonda.

If the building has a mold contamination problem cleaning the heating system will not fix a mold contamination problem that originates outside of the heating system air handler and ductwork.

You'd need to find and remove the mold and find and fix its cause.

Watch out: I agree that there are special risks when a forced air heating or cooling system is located in any moldy area for at least these reasons:

1. Mold contamination inside the air handler, blower assembly or ductwork may blow harmful or allergenic mold through the occupied building spaces
2. If there is an (improper) air return in the moldy area such as in the damp or wet or moldy crawl space then any contaminants (including mold) in that area are picked up and blown through the rest of the building.
   

On 2018-09-04 by Rhonda McVicker - dirt crawl space where furnace is located.

My daughter is renting an apartment that has a dirt crawl space where her furnace is located.

We did an air test for mold and it cultured out a lot of mold. If the furnace is serviced along with the ducts will this fix the problem or will the dirt basement continue to be a problem? The dirt has thick plastic over it and the ductwork is insulated.

On 2017-10-31 by (mod) -

yes

On 2017-10-31 by Kathy Dunleavy

Can it cause breathing problems.

On 2017-07-07 by (mod) -

Anonymous:

Regarding moisture in the soil of your crawl space from underground water:

Over at CRAWL SPACE DRY-OUT PROCEDURE https://inspectapedia.com/structure/Crawl_Space_Dryout_Steps.php
we describe a number of steps for wet crawl spaces. For your situation I suspect what's needed is 6 mil poly or heavier, over the crawl space floor and perhaps up the walls a foot or so.

If I'm right that you're near Melbourne, Victoria, Australia, the average morning relative humidity around Melbourne is 68% falling to 52% in the afternoons:

that's pretty humid. Humidity in that range invites mould growth on wood surfaces such as the subfloor over the crawl space. Additional steps such as running a dehumidifier that pumps condensate to a drain can make sense as the crawl space humidity may tend to be high too.

In sum, conventional best wisdom for crawl spaces is to give up on venting - that can actually make crawl spaces more humid in some conditions - and to convert the space to what we call "conditioned space" - that is, closed to outdoors and dehumidified for Melbourne.

With an average winter low of 16C in Melbourne I don't think you need to add heat to the crawl area but dehumidification might make sense.

On 2017-07-07 13:09:16.523199 by (mod) -

Wendy, we replied yesterday saying that the cost to clean up crawl space mold varies enormously depending on several factors that we listed - making any "guess" from here so specluative as to not be worth much - that is, the ballpark cost with no data about the situation can run from $500 to $15,000.

On 2017-07-07 07:27:59.615221 by Anonymous

I live in Ferntree Gully and face the Dandenong ranges there are underground streams and that is what causes the soil to be moist but not wet, I don't have much space under the house only enough to crawl in, it is only in the soil not the timbers, I appreciate your help and advice, do you do the actual work or can you recommend someone, Wendy

On 2017-07-07 by (mod) - cost of mold cleanup job

The cost of cleanup is going to depend on more than just the square footage of the crawlspace floor. Also significant are the ease of access that is the headspace which determines how easy or difficult it is to work there. Also significant is whether or not there is mold growth on the subfloor above.

Also important is to find and correct the source of water entry or high moisture.

Those are significant unknowns until you have had a more detailed on-site inspection including a cause of water entry.

Example: it's trivial to fix a downspout that needs to be extended away from the house but could be quite costly to have to regrade soil around a building. So I'm sorry but I can't guess at any reasonably close number.

On 2017-07-06 23:25:28.708537 by Wendy

I have pale yellow fungus almost covering my entire crawl space approximately 30met x18met, any idea how much it will cost to have this problem fixed

will you please respond to my comment that I posted at about 9 this morning, I just need an approximate quote, or if you need to come out to give me a quote on the job, or do you know who does clean upfungus under the house, thank you Wendy

On 2017-07-07 by (mod) re: what to do about moist soil in a crawl space in Melbourne Australia

Anonymous:

Regarding moisture in the soil of your crawl space from underground water:

Over at CRAWL SPACE DRY-OUT PROCEDURE https://inspectapedia.com/structure/Crawl_Space_Dryout_Steps.php

we describe a number of steps for wet crawl spaces. For your situation I suspect what's needed is 6 mil poly or heavier, over the crawl space floor and perhaps up the walls a foot or so.

If I'm right that you're near Melbourne, Victoria, Australia, the average morning relative humidity around Melbourne is 68% falling to 52% in the afternoons: that's pretty humid. Humidity in that range invites mould growth on wood surfaces such as the subfloor over the crawl space. Additional steps such as running a dehumidifier that pumps condensate to a drain can make sense as the crawl space humidity may tend to be high too.

In sum, conventional best wisdom for crawl spaces is to give up on venting - that can actually make crawl spaces more humid in some conditions - and to convert the space to what we call "conditioned space" - that is, closed to outdoors and dehumidified for Melbourne.

With an average winter low of 16C in Melbourne I don't think you need to add heat to the crawl area but dehumidification might make sense.

On 2017-07-07 by Anonymous

I live in Ferntree Gully and face the Dandenong ranges there are underground streams and that is what causes the soil to be moist but not wet, I don't have much space under the house only enough to crawl in, it is only in the soil not the timbers, I appreciate your help and advice, do you do the actual work or can you recommend someone, Wendy

On 2017-07-07 by (mod) re: the cost of cleaning up mold on dirt in a crawl space

Wendy: The cost of cleanup is going to depend on more than just the square footage of the crawlspace floor. Also significant are the ease of access that is the headspace which determines how easy or difficult it is to work there. Also significant is whether or not there is mold growth on the subfloor above.

So making any "guess" from here so specluative as to not be worth much - that is, the ballpark cost with no data about the situation can run from $500 to $15,000.

Also important is to find and correct the source of water entry or high moisture. Those are significant unknowns until you have had a more detailed on-site inspection including a cause of water entry.

Example it's trivial to fix a downspout that needs to be extended away from the house but could be quite costly to have to regrade soil around a building. So I'm sorry but I can't guess at any reasonably close number.

On 2017-07-06 by Wendy

I have pale yellow fungus almost covering my entire crawl space approximately 30met x18met, any idea how much it will cost to have this problem fixed

On 2015-12-20 by Anonymous

Dirty water from broken pipe was sit under house for long, problem was solved but I need to know What kind of absorbing powder should I spread on that crawl ground?

On 2015-11-11 by (mod) re: identifying yellow fungus on dirt as Meruliporia incrassata

If you are asking if the yellow fungus on dirt was Meruliporia incrassata - "the house eating funguys" - not in this case; but your inspection is defective if it did not include a careful examination of and report on the condition of the wood framing and other structural components that can be seen from the crawl space as well as from other areas.

Your report also needs to explain the causes and cures for a wet crawl space and the trouble that a wet crawl space makes for the rest of the building.

Search InspectApedia.com for "CRAWL SPACE DRYOUT" to see some suggestions.

On 2015-11-11 by Anonymous

Hi. We just looked at a house and the dirt in the crawl space was exactly like your picture at the top of this page. What is it? Is it the destructive one?

...

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