Crawl spaceguide_

Introduction – Crawl Space Cleaning 

Mold in crawl spaces is very common and can often be corrected with a little patience and hard work. We have been saying for years that there is no such thing as a crawl space with no mold growth in it. While this is probably an exaggeration, it certainly isn’t far from the truth. It is a very common problem that, while oftentimes not a health issue, is a growing resale issue that requires attention prior to listing a home for sale.

The cost of cleaning up crawl spaces can be very expensive. Indiana Mold Remediation (IMR) has always sought to find the best solution to mold problems that meet both remediation needs as well as account for the available resources of the homeowner. While we have worked hard to provide a high value for our cleaning services in crawl spaces, this guide is designed as an instruction manual for the do-it-yourselfers trying to address this hidden problem themselves and save the cost of hiring a professional. Keep in mind, cleaning up mold in a crawlspace can be very labor-intensive and quite messy, it isn’t for the faint-hearted! Understanding your own abilities is an important first step before taking on a project of this size and scope. 

Mold growth occurs in crawl spaces for a variety of reasons. The most common is simple humidity from two primary sources, evaporative moisture from the ground and humidity present in the warmer air of Indiana summers. Uncovered ground in a crawl space allows for evaporation of groundwater into the surrounding environment leading to chronically elevated humidity levels. While ground cover (plastic sheeting) is currently building code for new homes in Indiana, older homes may not have any, or it could have been removed from newer homes for a variety of reasons. More often than not, crawl space vents, intended to help control moisture issues, can also allow the introduction of humid air into the space from outside. Given enough time, the humid air from outside can lead to mold growth. It’s important to consider that foundation vents weren’t originally intended to prevent surface mold growth, they were about keeping the foundation from rotting.  Of course, flooding, foundation leaks, and plumbing issues can be primary or secondary sources of moisture and, subsequently, mold growth.  

Before cleaning up any visible mold growth from a crawl space, all moisture sources should be identified and a plan of action for correcting them made. Drainage around the home should be evaluated and corrected as needed. This includes cleaning gutters, extending downspouts and addressing grading issues (does the ground around the home slope towards the foundation wall?). Plumbing leaks should be addressed, drainage systems installed or repaired and a plan for controlling ambient (airborne) moisture in the future established. The installation of encapsulation systems (plastic sheeting that is installed on the ground and the foundation walls), dehumidifiers or powered vent fans can all be researched and considered. While these systems are not required to clean up the mold, they could provide the key to preventing the need for similar cleaning in five years. This guide isn’t about all of the various ways that mold can be prevented from entering the space, it is about the cleanup. We are, however, happy to discuss the various systems and solutions for crawl space moisture and prevention. Just contact our office if you have additional questions. 



Some items that you will need for your cleaning include:

Possible Cleaners:

–  Oxiclean (or other percarbonate powder)

–  Bleach

– Soap (Dish Soap, Simple Green, Castile Soap)

– Borax 

– Washing Soda  

– Botanical/Natural Cleaners (Benefect, Theives, Vinegar, etc.) 

Personal Protection Equipment (PPE) 

Pump Sprayer or other Spray Equipment 

Soft Bristle Brush 

High-Pressure Fan or several low-pressure fans

Extension Cord


Cleaning Procedure


The goal of remediation in crawl spaces is to remove surface mold growth (visible) and the staining that is present from the mold growth on structural framing. The vast majority of mold growth found in crawl space can be cleaned with a simple soap and water solution. Ideally, when completed, the structural components of the crawlspace will just look like clean wood when you are done. The use of sealants or other protective coatings is not the best choice to protect the future value of the home. 


Suit Up! 

Make sure that you protect your body, it’s the only one that you have. In the cleanup industry, protective clothing and supplies are referred to as PPE which stands for Personal Protection Equipment. You will need to wear a respirator of some kind. We recommend that at a bare bones minimum an N-95 particulate mask is used, Higher levels of filtration are better, and we encourage the use of full face respirators with organic vapor cartridges. If you choose to use less respiratory protection, cover your eyes with goggles or safety glasses to prevent cleaners from splashing into your eyes as well as the mold that your cleaning. Full face respirators are available online and provide both respiratory and eye protection. The use of protective gloves is a necessity. Finding thick, waterproof gloves to wear during the work will help to keep cleaning solutions and other contaminants from getting onto your hands. Disposable gloves are available online or at hardware stores, make sure that they are waterproof and chemical resistant.  Wear clothing that completely covers the body. Disposable coveralls are available at most hardware stores or can be ordered online. These suits can be reused until they are worn out. Buying several at one time generally makes sense, especially if more than one person is performing the cleaning work. Moisture (or splash) resistant coveralls are preferred over synthetic dust suits or clothes.  

PPE is ideally worn as follows. Wear older, long sleeve clothing. Cover the clothing with your protective coveralls. Having coveralls with attached boot covers and hoods allows for maximum protection and prevents carrying into the home what you’ve cleaned in the crawlspace. Pull the gloves on with the cuffs over the coveralls. We typically use tape to attach the gloves to the coveralls. This prevents dirt, debris and cleaners from getting directly into the coveralls and onto your skin. The use of duct tape usually works well for this. Once these items are on, put on your respirator (and goggles or glasses if needed). Make sure that the respirator is tight against the face and that the only air coming into the mask is through the filters. For full face respirators, placing your hands over the cartridges and breathing in should draw the mask to the face, no air should seep in through the seal. Men with beards can have an especially hard time getting a good seal and shaving may be needed. With all of this gear on, you’re ready to begin the cleanup. 

A quick note on safety. This is what is considered confined space work. Don’t do the work without someone knowing you are in the space and within reasonable earshot of the crawlspace. Make sure that if there is trouble, someone will know to come and help you out. Ideally, this work is completed in teams or pairs. The more hands available, the lighter the load for any one person. 


Insulation and Debris Removal

All cleanup work begins with the removal of any insulation, plastic sheeting and debris from the crawl space. Bricks, Stones, Cement Blocks, Old Pipes, Cans, Trash, Electrical Wiring bits, and many other things can all be present in a space. There may be stored items that have been left in the space for many years that are now moldy and just need to be discarded. All of these items need to be removed prior to any cleanup efforts. Heavier items that cannot be removed (like old cast iron drain pipes that were cut and left in place) can be left, but they should be moved out of the main area of the space as your strength allows. Some bricks, stones or blocks can be left in the space as well (assuming there aren’t that many) and used later to weigh down plastic sheeting or other ground cover. 


All fiberglass insulation should be removed from the space. This in and of itself can be a very large job, but is needed to do a sufficient job of cleaning. Over time, fiberglass insulation becomes soiled with mouse droppings and other contaminants not to mention mold spores that have accumulated between the fibers over time. Insulation is removed, and either shuttled out of the space in pieces or bagged first and then removed. Bagging should be done with the understanding that, ultimately, the bag needs to fit through the space. A typical, fully insulated crawl space could require 50-100 contractor size trash bags to empty the space of insulation. Once removed, the use of a hauling service or a dumpster delivery service may be needed to remove the trash from the property. Foam insulation, either rigid foam board or spray-on foam, can generally be left in place assuming there hasn’t been an adhesive failure. These types of insulation can be cleaned if needed on the surface and rarely support mold growth any deeper than the surface. Any paper that is present on the floor joists may have to be meticulously peeled away if the installers used a lot of staples. Very small amounts of paper under staples are unlikely to cause any additional trouble in the future and can be left in place, everything else needs to be removed.  We don’t recommend that you insulate crawl spaces with fiberglass insulation between floor joists. Insulation can hold moisture at the wood surface, right where we don’t want it. 


Cleaning Floor Joists and Decking

Choosing the right cleaner can help save a lot of time in the future. We recommend a test of the surfaces to be cleaned with a couple of different methods. Using a soft bristle brush and a handheld sprayer, spray a solution of dish soap and water on the surface. Scrub with the brush. If the mold on the surface appears to go away with no underlying staining, you are in luck! You should be able to clean the entire space with soap, general cleaners like Simple Green, or a sanitizer like Lysol.  In these cases we recommend the use of percarbonate solutions (like Oxiclean). The carbonate residue left behind can help prevent mold in the future and some stain removal and brightening of the wood will occur. Some minor staining that may remain when you are completed can be bleached out later, so don’t worry if there are a few small areas that don’t appear to come completely clean. The percarbonate solution we recommend is two cups OxiClean (or equivalent off brand) with one gallon hot water. To improve your overall cleaning power, a quarter cup or TSP (trisodium phosphate) can be added to the solution. TSP is available at most hardware stores. 

If, after the soap and water test there is still a significant amount of staining (like dark black spots), you’ll have to use a stronger cleaning solution that includes bleach if you want the space to look good when you are done. In either case, the cleaning steps will be similar, but the use of bleach throughout the space increases the risk to the cleaner (due to the irritation that bleach can cause to skin, eyes, and the respiratory system). If bleach is needed throughout the space, the use of full face respirators will be required with no exception. An effective bleach solution that will still provide some residual prevention when done is two cups bleach, one cup of Borax, one teaspoon of dish soap and one gallon hot water. 


Final Touches

Once the cleaning is completed and you are happy with the overall cleanliness of the space, you may want to consider treating the wood with additional preventative treatments. A treatment of sodium carbonate (washing soda), sodium bicarbonate (baking soda) and a little soap can be effective and inexpensive. Borate salts like boric acid, borax or Tim-Bor (sodium octoborate tetrahydrate) are also possible choices. If you’d like to discuss available preventative measures with IMR, please give us a call.

A plastic vapor barrier is code in most areas of the country, so it’s something that will be required if you are preparing the home for resale. A vapor barrier is helpful in minimizing ground water evaporation into the space. If you need additional drainage or water prevention measures, you can call us for some advice or consider hiring a foundation repair professional to install drainage. Most drainage is a matter or trenching and routing incoming water to a sump pit. This is also something you can do, but it is beyond the scope of this guide to discuss it. 

Once your cleaning work is completed, you may want to add an exhaust fan into the space. Active ventilation helps to exchange air in the space and prevent moisture build up. Closing all crawlspace vents and actively drawing air from the crawlspace and sending it outside can create a negative pressure that helps draw conditioned air from the home into the crawlspace. This is the ideal way to condition the space and prevent moisture problems in our opinion. If you’d like to discuss this further, please give us a call. 

We hope that this cleaning guide has been helpful. As always, we are available for questions or clarifications. As daunting as the task may be, careful, methodical work will often achieve the results you are looking for.