How To Fix A Moldy Crawl Space!

You just got the bad news. It normally comes in the form of a home inspection or engineer’s report. The house you are trying to sell or buy has a moldy crawl space. Now what? The following post describes the parts of a standard crawl space repair so you know what to expect when undertaking the project.

You Don’t Have A Crawl Space Mold Problem…

You have a crawl space moisture problem! A moldy crawl space is the direct result of one thing. Its exposure to long term high humidity. If you do not address the humid conditions in the crawl space, over time, the mold will eventually grow on the floor joist and subfloor…Period!

Furthermore, even if you hire the best crawl space remediation company in the world to remove the mold, if you don’t solve the underlying moisture problem, THE MOLD WILL GROW BACK! Make sure you understand this before starting a crawl space mold removal project or your effort could be in vain.

Step #1 – Control Water Before It Enters

Ideally, it is best to stop the water before it enters the crawl space. Stopping the water outside first is usually the best practice. Unfortunately, addressing all of the exterior drainage problems is not an automatic guarantee that the water will stop coming in. The flow of water around a building is unpredictable. Storm water can enter a crawl space in many ways and the ways in usually never cut and dry.

The depth of crawl space floor compared to the outside ground surface also plays a part. The deeper the crawl space, the more water can enter via gravity.

Installing an interior perimeter drain is a more reliable way to capture and control water in the crawl space. Water that quickly enters the the drain won’t be available to undermine footings and raise humidity levels inside of the crawl space. The water drains to a sump basin normally located at the low end of the crawl space and pumped out down gradient from the building foundation.

Step #2 – Mold Removal – Clean it Up!

Remove the crawl space insulation if moldy or if mold is found on the subfloor. Removing the insulation exposes the entire wood floor system and areas of hidden mold easily treated. Cleaning all of the mold in a crawl space helps reduce the chance of regrowth. After all, a mold colony starts with one spore.

Popular methods to remediate mold in the crawl space include dry ice blasting & hand cleaning. Dry ice blasting uses accelerated dry ice pellets to micro-abrade the wood surface removing mold. Use dry ice blasting for large, moldy or fire damaged areas.

Interestingly, the rise of advanced hydrogen peroxide cleaners provide excellent hand mold cleaning results that rival the micro-abraded surfaces of dry ice blasting. The process is safer, quieter and less intrusive that blasting and perfect for the majority of crawl space cleaning applications. Click on our recent blog post Expert Tips For Removing Mold From Floor Joists for an in depth discussion on the subject.

Step #3 – Crawl Space Encapsulation or Vapor Barrier?

The current mantra of the big crawl space franchise companies is “The only way to fix a crawl space is to encapsulate it!” Agreed, encapsulating the crawl space provides superior water vapor control, increased curb appeal, with modest energy savings compared to the standard vapor barrier install.

Full encapsulation is a relatively recent solution that help reduce crawl space moisture problems. Does every crawl space need encapsulating? In retrospect, a crawl space rated dehumidifier paired with a standard 6-mil vapor barrier have been solving humidity problems long before the advent of the encapsulated crawl space. It comes down to how you want the final result to look like compared to how much you are willing to spend to get it.

Step #4 – Control Humidity with a Dehumidifier

A moldy crawl space can develop anytime the relative humidity rises above 60%. The installation of a properly sized dehumidifier removes moisture from both airborne water vapor & solid building materials alike. The installation moderates crawl space conditions and keep relative humidity below the mark needed to grow mold.

The first part of the installation is to close the foundation vents using foam board insulation to reduce the communication of air from the outside environment. Install the dehumidifier on a brick pedestal and set the control to below 60%. Route the dehumidifier discharge outside of the building in a spot that is down gradient from the foundation.

Step #5 – Annual Crawl Space Inspection

Count on taking at least one annual trip through the entire crawl space to inspect and to make sure that there are no major changes. Stringy insulation, insect / animal infestation and areas of mold growth are red flags.

Environmental forces that affect the crawl space change with the seasons. The best time of the year to determine how good your crawl space handles humidity is checking in July & August. It is the period of highest regional humidity & temperature. A few drops of condensation here & there are normal. Reduce crawl space humidity if visually wet conditions are observed.

Check the crawl space for moisture intrusion after large regional rain events. Look for evidence of water coming through the foundation walls near plumbing penetrations and previously repaired areas. Check for standing water in the low areas of the crawl space and around pier footers. Check to see how the crawl space drain & sump pump are handling the water under peak conditions.

Using these tips on how to fix a moldy crawl space will help keep you clean & dry year round. Remember, out of sight should never be out of mind when dealing with a crawl space.