Trask Research, Inc. - Mold Problem Solving

How to Get Rid of Mold in a Crawl Space

By: Jim Dobbins, Sr. Mold Remediation Specialist

CONTAIN - the mold from spreading into uncontaminated areas;

KILL - the mold;

REMOVE - the dead mold and materials used for remediation; and

PROTECT - the cleaned out area against future mold infestations.

Mold in the crawl space is one of the top three mold problems common to a home, affecting 1 in 3 crawl spaces in the United States . Left untreated the health effects can be disastrous to you and your family.

If you have mold in your crawl space or suspect it, it is a good idea to do a mold test inside your home for mold. The mold from your crawl space may have infected your home from small drafts and HVAC systems which blow spores throughout your home.

The only way to be sure is to conduct a laboratory mold test.

Before entering an area infested with mold, you’ll need personal protection equipment ( PPE ): P100 respirator, gloves, goggles, protective clothing (coveralls with hood). In lesser mold infestations a Tyvek isn’t necessary, but keep skin contact with mold to a bare minimum.

1.) First fix the problem that caused the mold to form.

Mold in the crawl space is generally caused by increased humidity and moisture. The source of the moisture can be from the ground in the crawl space, improperly or too few installe d c rawl space vents, improperly or no installed plastic sheathing or visqueen, water leak allowing water to stand in the crawl space from new construction, a leaky water pipe, or any other source of moisture. A dryer may have been vented improperly into the crawl space or crawl space vents may either be closed or there may be too few vents to support the moisture in the crawl space.

ALL crawl spaces must be vented properly, even during the winter. A common misnomer is that the crawl space vents should be shut during the winter season. This is not true. As moisture builds in the space, mold will form on the ground, floor joists, plywood, or any organic material which serves as food for mold. This can lead to mold spores migrating into the home an d c an potentially, if left untreate d c ause a total loss of a home from severe mold infestation.

2.) Get the area as dry as possible before starting your remediation project or it will not be a successful remediation.

You must either pump out standing water (if you can see it), and then start the process of drying out the space by using at least two fans. One to circulate the air inside the area (more fans may be required for larger areas, and another fan to pump inside air outside of the crawl space. Some remediators will bring in HEPA filters or positive air machines during this process to prevent mold spores from moving inside the home and outside of the crawl space. Some crawl spaces will require the use of a dehumidifier to remove excess water from the space.

The crawlspace will need to be as dry as possible (below 40-50% relative humidity) before remediation can begin. The drier the surfaces are the more effective the treatment will be.

- Some crawl spaces may need to have new 6 mil plastic placed down over the dirt after the remediation process is completed.

- Some crawl spaces may have to be concreted in to prevent water from entering the crawl space. (This is common in wet, swampy areas of the country)

- When HVAC systems and ducting are run under a crawl space, it is possible that the mold may have penetrated into the HVAC system and therefore blown around the entire home. The home and HVAC should be thoroughly tested for mold. You can order a mold test at this link. If there are elevated levels of mold present in the home, it will be necessary to remediate the home as well.

4.) All areas of the crawl space must be treated with a fungicide to kill the mold

Even if the mold is just in one area of the floor joists, you must treat the entire crawlspace (dirt, visqueen (plastic), all floor joists, and foundation) with Oxy Mold MX-501™ with a minimum of two full treatments, letting it dry in between each treatment.

There are two ways to treat the crawl space: Fogging and pump spraying.

- Fogging is a method of dispersing atomized product into the crawl space area without having to go under and pump spray everything which is a very uncomfortable and tedious task with Personal Protective Equipment ( PPE ) and respirators on.

- Break the crawl space area into quadrants of about 15’ x 15’ areas. You will move the fogger to each quadrant, fogging generally 45 minutes per quadrant

- If you are fogging it is more convenient to use a cheap 1 hour timer to turn the unit off after it has finished.

- Put the fogger in the middle of the crawl space (It may be different for different crawl space layouts) and turn the unit on facing the one of the corner quadrants such as the example above.

- Simply fill the 1 ½ gallon tank on the unit with EPA approved fungicide, turn on the fogger, set the timer for 45 minutes and leave the area. If you are going to be in the space while the fogger is running, you must wear protective eyewear and a P-100 rated respirator. Repeat the process for each quadrant.

- No one should be in or near the crawl space while the fogger is running. Do not re-enter the space until the fog has settled for an hour.

- Pump spraying is also a way to accomplish this task, keeping in mind that you must do at least two treatments with EPA registered fungicide Oxy Mold MX-501™ soaking all floor joists, plywood, foundation, and dirt/plastic, letting it dry in between treatments. Wear a P100 respirator protects against organic vapors while pump spraying in confined areas.

5.) Mold remediators would HEPA VAC any visible mold areas

A HEPA vacuum can be used to vacuum away dead mold spores in the crawlspace. This is not always required in situations of limited mold contamination, but is a good practice. Even dead mold spores can be a health hazard.

6.) Mold killers do not remove stains from mold on your floor joist and plywood.

It is possible to kill mold without the mol d c hanging much in color. Molds have VERY strong pigments, and the roots of the mold actually grow into the wood. This causes in some cases permanent staining. You may try using bleach to get the stain out prior to using a fungicide. This bleaches the mold but does not effectively kill it. If you are concerned with the stains you need to decide what type of fungicidal coating to use (white or clear) to either cover the satins or seal them in.

The other option is to "brush" or sand the stains out. This is a tedious task that remediators get huge sums of money to do, but it does remove the stains. After the sanding, you can use a fungicidal coating to seal the areas in.

7.) Mold prevention is all about controlling moisture and fixing leaks and other moisture problems immediately.

After the mold is dead (from 2 treatments) be sure that there are no improperly installed vents and that the crawlspace is dry and well ventilated. It may be necessary to install a crawlspace dehumidifier to keep humidity below 50% year around. If there are any lingering moisture or ventilation problems, it will be necessary to retreat with Oxy Mold MX-501 every 1-3 months.