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How to clean out a crawl space contaminated with mold, rodents, asbestos, or sewage. Here we discuss safety precautions and cleaning approaches for a dirty or contaminated building crawl space. We explain that first you should inspect the crawl space for visible signs of unsanitary or unhealthy contaminants. Cleanup methods need to include steps to prevent spreading contamination to other building areas. We include discussion of using vacuum cleaners and power washers in crawl areas. .
This article series describes the steps needed to get into, inspect, clean, and then dry out a building crawl space. We give a step by step crawl space entry, inspection, cleanout, dryout and keep dry guide explains how to get into or inspect a crawl space even if there is no ready access, how to assess crawl space conditions, how to stop water that is entering the crawl area, how to dry out the space, how to clean up and if necessary disinfect or sanitize the crawl space, and how to keep out crawl space water and moisture in the future.
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Is there asbestos insulation in the crawl space? Often we find a crawl area in which the asbestos pipe insulation is not just hanging (photo at left) but has fallen onto the crawl space floor.
Asbestos pipe or HVAC duct insulation that has been disturbed, damaged, or deteriorated, including asbestos that has fallen to the floor should be removed and cleaned up by a professional. Asbestos pipe insulation that is in good condition, that is not damaged, might be left in place or perhaps left in place and encapsulated.
Do not enter such an area without protective equipment; take care that you do not track hazardous materials out of the crawlspace and into other building areas.
Do not track asbestos debris back into other building areas.
Is there evidence of mold contamination such as areas of wood, paper, or other material covered with mold or mold-suspect material.
If the crawl area has more than 30 sq.ft. of contiguous toxic or allergenic mold it should be cleaned by a professional mold remediation company.
Beware: often the most serious mold we find in crawl spaces is not the mold you see on wood framing but rather the mold you don't see in fiberglass insulation in a damp or wet area. See Mold in Fiberglass Insulation for details.
Watch out: If the crawl space has a large area of mold (more than 30 sq ft) or if you suspect it may be contaminated with rodent droppings, chemicals, pesticides, (or electrical hazards) see CRAWL SPACE SAFETY ADVICE and CRAWLSPACE MOLD ADVICE. Do not enter such an area without protective gear.
Rats, mice & other crawl space rodent hazards
Hantavirus pulmonary syndrome (HPS) is a deadly disease from rodents. Humans can contract the disease when they come into contact with infected rodents or their urine and droppings.
HPS was first recognized in 1993 and has since been identified throughout the United States. Although rare, HPS is potentially deadly. Rodent control in and around the home remains the primary strategy for preventing hantavirus infection. -  US CDC
If it is necessary to remove rodent feces or urine-stinking soil (try using a "black light" to spot urine stains) your cleaning company may decide to actually remove the top few inches of contaminated soil in the most offensive areas, followed by sanitizing, sealing, and poly vapor barriers on crawl space floors and lower walls. See BLACK LIGHT & UV LIGHT USES and also see LIGHT, GUIDE to FORENSIC USE.
Watch out: don't remove so much soil that footings are undermined at foundation walls or supporting columns. If necessary, bring in and compact clean fill and gravel to fill low areas.
Is there or was there a crawl area sewage spill?
It's obvious that crawling around through sewage is not healthy unless you are wearing adequate protective gear.
But you may not realize that those same sewage pathogens may be carried on dry airborne dust.
See CRAWL SPACE SEWAGE CLEANUP for details.
Should we Use a Vacuum Cleaner to Clean up the Crawl Space?
Do not use a household vacuum cleaner nor an ordinary shop-vac to clean up crawl space dust and debris. Those machines will temporarily but significantly increase the level of airborne dust and debris. Since that dust and debris may contain harmful particles, tossing it into the air increases the risk of cross contamination from the crawl space into other building areas such as a basement or even upper floors in the building.
To vacuum and clean surfaces in a crawl area use a HEPA-rated vacuum cleaner that will trap very fine particulates, and select a vacuum cleaner model that does not have air bypass leaks that escape from the equipment when they should be passing through the filter.
Do we need to Set up Dust Containment and Negative Air to Clean Up the Crawl Space?
Negative air machines and dust barriers are procedures used by professional mold remediation companies, asbestos removal experts, and building flood damage restoration companies. These measures reduce the risk of blowing contaminated dust and debris into other building areas - an event which could be a health risk, especially to occupants who are in fragile health. Photo courtesy of Anabec, Inc.
Even an amateur, do-it-yourself cleanup project would benefit from these methods.
But you should recognize when your cleanup project needs the help of a professional. Here are some examples of conditions that mean you should hire a professional to clean up a crawl area:
There is asbestos material that needs to be removed
Should we use a Power Washer to Clean up the Crawl Space?
If there is room to work, a power washer is a very effective way to clean surfaces, but the increase in water and moisture in the crawl space can make mold or other building-related moisture conditions worse.
In some circumstances such as a crawl area or basement that can be well ventilated, in dry weather, that is well drained, and where other measures are taken to avoid sending a surge of moisture upstairs, power washing might be possible.
Alternative dry-spray surface cleaning methods called media blasting include use of dry-ice spray and baking soda or other abrasive particles, even sand or walnut shell fragments.
See MOLD CLEANUP by MEDIA BLASTING. Our photo shows the ceiling over a basement after cleaning by media blasting.
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Frequently Asked Questions (FAQs) about crawlspace de-watering: how to dryout the crawl space and how to keep that area dry
Question: crawl space insulation and vapor barrier retrofit questions
I live in Syracuse, NY in a 1920 colonial with full basement. I recently put on an 18'x 20' addition for my mom. Bedroom and bath. The crawl space is open to the full cellar via the former cellar window opening. The crawl space has water lines and p-trap for shower as well as heat/cold air runs. The contractor installed 1 small vent on each side of the addition. Should I permanently close off the vents and turn the crawl space into somewhat heated and conditioned space?
The contractor was going to install batt insulation on the underside of the floor- I told him to hold off. Should I install 10mil vapor barrier on the dirt floor and use 2-part closed cell spray foam insulation on the interior of the block? Or is it a better method to pour a concrete slab and use the 2-part closed cell foam? I understand I may need to cut a small register in the heat run as well as run a dehumidifier in the warmer months. I will also be installing a radon mitigation system soon. Thank-you very much for your response. - J.R. - Syracuse
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with air and moisture control for a structure that combines crawl and basement areas. That said, here are some things to consider:
First, kudos for packing so many good questions into a small (crawl) space:
The crawl space has water lines and p-trap for shower as well as heat/cold air runs.
The contractor installed 1 small vent on each side of the addition. Should I permanently close off the vents and turn the crawl space into somewhat heated and conditioned space?
The contractor was going to install batt insulation on the underside of the floor- I told him to hold off.
Should I install 10mil vapor barrier on the dirt floor and use 2-part closed cell spray foam insulation on the interior of the block? Or is it a better method to pour a concrete slab and use the 2-part closed cell foam?
Question: How do I dry out a crawl space quickly?
While this article did address the dehumidifier to a large extent, it really did not give instruction on how to rapidly dry out the crawl space after the water issues had been resolved so that the other remediation steps could be taken. More instruction on that would be extremely useful. - C. Brown
Reply: Rapid Crawl Space Dryout Procedure
Thanks for the comment C. Brown. In response to your well-put query, I have added material at How to Dry Out the Crawl Space Quickly in Three Steps, from which I excerpt below:
Question: using a sealer and vapor barrier in a crawl space
I live in the Wyoming mountains (9000 Ft) in a very dry climate, 15" of rain a year which includes average 3-4 feet of snow in the winter. The house is 45 years old. There were only two small vents in the crawl space. When an addition was built on the south end of the house 6 years ago,one vent was blocked by the addition which had a separate crawl space and vapor barrier installed. Last year we had record snowfall & high ground water, within 6" of outside grade.
I had a floor joists sagging in a bedroom and then I found white furry mold on a baseboard on the north end of the house. I pulled up the carpet and pad and on then inspected the crawl space below the two bedrooms found mold on the joists and subfloor with three joists rotting out under one bedroom and much less mold under the other bedroom which is on the other side of the main support beam..and a very wet space. The vertical two by fours in the walls and blow-in insulation inspected so far are dry and show no mold.
I had a contractor look at it and have decided to seal off the two bed rooms and remove the floors and joists completely in both rooms, remove a couple inches of dirt, dry out the crawl space, clean all the other visible mold by the methods you describe throughout the entire space, and rebuild the joists with pressure treated wood and new sub floors. And install more piers for support of the floor.
JR even in a dry climate that has just periodic rainfall, leaks and water entry are asking for a mold or rot or insect problem. Your cleanup sounds thorough but I didn't see much about tracking down exactly where the water is leaking in. It's better to keep water out than to let it in and then get rid of it or to try to waterproof the interior against it.
I have now found that the water was migrating up from snowmelt to the sill plate on the top of the foundation. The contractor that did some repair of dry rot rim joist on the north end of the house before it was resided with stucco. The contractor put Ice and Water Shield on the foundation down about 10 inches into the soil, and then had the Stucco contractor extend the 1/2" styrofoam board 12 inches into the soil as well thinking that all this would seal and insulate the foundation.
When I pulled off the ice and water shield and the blue styrofoam the foundation was soaking wet underneath. I have now removed all that mess and the foundation is drying out. With the amount of snowmelt that we have in the spring I think that is the main source of problem coupled with the reduced ventilation of only one small vent to the crawl space.
Question: how to dry out a crawl space after a toilet flood of more than 100,000 gallons into the crawl space
Our home flooded due to toilet break. 3 weeks water ran totaling 130,500 gallons of water. A company mediated our home, neglecting the crawl. I went under and dug down 6" the dirt was damp. How do we dry this out? - Ronald 7/22/12
Ronald I'd suggest starting crawl space dryout with a review of the suggestions in the article above - that's my best shot. When you've got the in crawl surfaces dry you'll want to take a look at the additional topics (see crawl space links near the top left of this page) such as how to put down a plastic moisture barrier to stop soil pumping moisture into the building.
Question: gutted house being renovated, mold like stuff on floor joists
I just bought a house that was mostly gutted when I got it. Neighbors tell of roof leaks and mold, though what was left on interior walls had no evidence of mold. Still, I finished the demo, removing everything down to stud walls and floor joists. Much of the subfloor (old chipboard and thin OSB - house was built in 1980) was rotted, to varying degrees.
There was much mold-like substance on the floor joists - (I've been all over your website trying to determine the type) but they include the black cosmetic mold, brown fuzzy mold (not the hair-looking stuff, but sort of looked like spun cotton candy), white stuff, a little bit of yellow stuff. I'm using the folded rag method to clean with water and anti-bacterial soap, with a little bit of bleach for good measure. It seems to be working well.
My builder is now putting down new Advantek subfloor, as I'm finishing the cleaning. I'm also cleaning out the crawlspace as recommended, removing all the debris, the old poly, all insulation, etc. There is water encroachment during rains from one corner of the house where the gutters aren't working and the ground slopes towards the house.
Obviously, those last two things must be corrected immediately. The crawlspace had a few areas of standing water after the last significant rain. It had dissipated by the time I started the cleanup down there. However, under the plastic, some of the ground (red clay, here in NC) is pretty wet. Where I had removed the plastic, it has started to dry out pretty quickly. (three days?)
So, is it okay to let my builder complete the subfloor installation while I continue to clean the crawlspace, or would I be better served to have him wait to complete until I'm done? Should I leave the plastic off for a period of time to let the ground dry out before replacing it? also, there are a few small visible roots under there that themselves look moldy - black and spidery. What of that? The ground is uneven and I'll smooth it out to eliminate the low spots, but I'm uncertain as to what is the best next step. - Charlene Blevins 10/21/2012
Question: how much will it cost me to dry out my crawl space?
hey first off great site, very informative.
My question is how much roughly would all that cost me and do you think it is a great idea to do so.
Question: what about drying out a crawl space over a radiant heat floor?
Thanks for all the info, very helpful.
Robert, it's an interesting question that I'll think about further, but my initial thought is that presuming you're talking about tubular radiant heat - tubes stapled up under the subfloor over a crawl area, I don't think that material's presence changes our normal recommendations for drying out a crawl space
Question: Hurricane Sandy flooded our Ocean City NY House - what do I do in the crawl space?
Hurricane Sandy hit my old Sears House (1930's)in Ocean City, NJ so the water was 1 foot deep on the first floor (the floor being 3 feet off the ground!) Sometime within the last 25 years the water was deep enough to get the insulation wet and it was removed at that time and not replaced (The house is not heated in the winter).
What should I do in the crawl space area? If I would encapsulate the crawl space, it would be like a swimming pool next time it floods. Ideas on a good solution? Is a spray insulating foam worthwhile for protecting flooring from underneath? Thanks!
I have also a home in Ocean City, NJ that got hit with Sandy. I have just pulled out the mostly wet insulation. I got water damaged in my first floor from the water seeping up from the craw space. Electric wires are down now and I am worried about structural damage.
Reply: tips for improving the resistance of crawl spaces to flood damage
Closed-cell foam products are somewhat resistant to wetting from flooding or other water intrusion in a building crawl space or anywhere else, but if a building area is actually inundated with floodwaters again after such an installation, I'd be concerned about the difficulty and cost of disinfecting or addressing the risks of sewage-contaminated floodwaters.
For this reason, just taking up some closed cell foam board can be problematic - how will you clean the space that was soaked with sewage waters between the foam boards and framing or subfloor above?
Talk with spray foam insulation contractors in your area about the water resistance of sprayed-in-place closed cell foam insulation. That product actually adheres to wood surfaces, a step that may resist sewage-contaminated water from entering the space between the insulation itself and wood surfaces that otherwise would need cleaning.
In addition, sealing the exposed wood and interior foundation surfaces with a sanitizing or fungicidal sealant (after they are thoroughly dry) will also reduce the moisture uptake (and sewage-contaminated water uptake) of those surfaces in future flooding, making surface cleaning and area dryout a bit faster after the next flood.
Frankly, if the home is likely to be flooded to a depth that submerges the first floor or higher, no crawl space encapsulation is going to completely protect the building; if you cannot afford to raise the building on a taller, flood-damage-resistant foundation or pier system, I'd be troubled about the prospect of recurrent, perhaps even increasingly frequent significant cleaning and repair costs from future area flooding.
Question: are my crawl space "dryout" fans blowing moldy wet dust and debris and maybe chemicals from a wet crawl space into the living area?
I recently moved to an 800 square foot single story historic house in Pacific Grove. The home has a very shallow crawl space (as little as 6" near the perimeter- the foundation is only 12" deep) and the crawl space was covered with a moisture barrier when I bought the home. It has a solid concrete wall bisecting the underneath of the house (the long way).
I had termites and was advised by the inspector that the house is very damp underneath. They recommended removal of the moisture barrier and installation of fans to dry out the space. I have been having symptoms like I get when I am exposed to dust (dry, red nose) and feel very uncomfortable ever since the fans went in. This is driving me absolutely nuts.
The crawl space is wetter now than before (it has rained). I can't put in a french drain because there is only about 6" clearance between my house's crawl boxes and the fence, also it is on top of the sewer lateral.
I live on a hill in an area known to have underground springs but nobody knows exactly where they run.
I think they should remove the fans and put the moisture barrier back.
Do you agree? Is there anything else I can do? Perimeter moisture barrier?
Thank you. There is lots of mold down here and I am concerned that just putting the moisture barrier back will cause mold or rot. - S.A. 2/7/2013
Reply: how not to "dry out" a wet moldy crawl space
Sounds as if you got some advice that was good in intent but not competent.
I do on occasion recommend adding a fan to increase air movement in a crawl area or basement where a dehumidifier is at work, as that will increase the rate at which the dehumidifier can dry out the area. But just blowing air around in a wet moldy crawl space seems like a bad idea.
Removing the moisture barrier from the crawl floor and blowing fans turns the crawl space into a moisture pump, moving moisture from soil into the crawl space air. Perhaps if the fans blew OUT of the crawl space that might have been better, but the proper approach is to find and fix sources of water entry, seal (poly is ok) the floor, and dehumidify the area.
Watch out: there is an added risk of blowing pesticide contaminated dust and debris into the home if the applicator used a surface spray - something that's not usually done for termites. Usually for termites the pest control officer places a termiticide in the soil around the home; but in a home with a dirt crawl space they may be unable to take that approach because of the risk of chemicals surfacing in the crawl area and entering the living area - making occupants sick. So I'm not sure what has been done about your termite issue but that too needs expert review.
I suspect that dust, possibly allergens (insect fragments, mold, even soil particles, potentially other particles) have been stirred up; and if the fans were not blowing out of the crawl area, it may have been pressurized by the air movement; if that's the case, the arrangement may have increased the movement of particles up into the living area from the crawl space.
More likely you need to stop the fans, find and fix outdoor water sources like roof or surface runoff spilling by the foundation, put the poly back down to stop pumping water into the crawl area, and after the mold problem has been evaluated and most likely removed (cleaning the wood surfaces, tossing out insulation), then you might get a fan and dehumidifier back at work to keep the area dry.
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