Crawl Space Mold Remediation

One of the top three areas where mold can be found in a dwelling is a crawl space.  For the most part, mold in a crawl space is a direct result of outdated building codes.  The codes have inadequate moisture controls which allows mold to grow in areas that are not conditioned.  By conditioned I mean heated and cooled, using your HVAC allows a structure to maintain environmental conditions that inhibit mold growth.  Case in point you will not see mold growing in your bedroom or family room (unless you have a water leak).   In a crawlspace mold will have an opportunity to grow when moisture and temperature conditions are conducive to mold growth.

To be fair a crawl space is called  a crawlspace due to size and access, most people never go in their crawlspace so if mold is growing, there is a water leak or water entry it goes sight unseen.

History of Crawlspace Mold

The historic common building practice was to insulate the floor above the crawl space and to leave the crawl space’s wall vents open, for ventilation.   The idea of installing vents was the belief that any moisture buildup in a crawlspace would vent to the outside, a seriously flawed design even today.   Instead of expelling moisture (at least in areas with humid summers), the open vents allow moist air into the space that would mix with the cool surfaces of the crawl space, allowing condensation. The mixture of hot and cold air allows moisture to drop out of the air.   The proof of this is drooping insulation in a crawl space (insulation retaining moisture, which adds weight) and mold on the exposed wood ceiling.

Bottom Line on Crawl Space Mold

We find mold in crawlspaces often, its in the top 3 areas.

If mold is below your living space you have an exposure pathway where mold spores and mycotoxins and MVOC (both a by product of mold growth) can impact your indoor air quality.  Most crawlspaces have HVAC ducts which are a super highway for air in your home, no one wants their ducts sitting in a mold infested space.  Mold growing on the outside North facing wall of your house, not so much because its outside the building envelope.

How do you remediate mold from a crawlspace?

You remove insulation

You clean the wood surfaces of staining

You fog the space with a fungicide to kill and remnant spores (this reboots the space)

Lastly you treat the wood surface that is the molds food source with a fungistatic coating. Fungistatic means mold won't grow on it. The better ones have 10 year warranties.

The photo below shows this white fungistatic coating.

Example of a remediated, vented crawl space. 

Crawl Space Remediation Cost

The average crawlspace remediation can cost between $2,000 and $5,000. The cost is relative to the size of the area, bigger cost more expense.   Larger spaces take more time and consume more fungistatic coating.

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Crawlspace Mold Prevention

After you remediate a crawlspace and apply a fungistatic coating, you have in essence mold proofed the space as you are sealing the wood food source with anti mold coating (fungistatic).

But some crawlspace have a high moisture environment, perhaps down the shore, poor grading outside which leads to water entering the space.

Some more modern crawl spaces or crawl spaces that have been upgraded, can include conditioning of the space. Basically, sealing the space, insulating the walls and heating and cooling the space. Typical conditioned crawlspace improvements can average $5,000.00 plus or minus depending on specific site conditions. Not a huge fan of conditioned crawl spaces since you are heating and cooling an area that is not habitable. Also no one is going to compliment you on the crawlspace.

Alternate approaches to conditioned spaces is moisture management, which can take many forms both within and outside the footprint of the area including outside wall insulation.

Most Bang for Your Buck

The most bang for your buck in controlling moisture in a crawlspace is adjusting outside grading so water flows away not toward the house.  This can be easily performed.  Add a dehumidifier to the space and seal outside air and you can control the moisture in the space and  have a dry Egyptian style space that is inhospitable to mold.

Crawlspaces can be affordably sealed to manage humidity levels including proper operation of a dehumidifier to keep humidity down. Dehumidification should operate continuously with a drain hose, so manual emptying is not necessary