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WATER ENTRY IN BUILDINGS
AGE of MOLD - Old is the Mold?
BASEMENT CEILING VAPOR BARRIER
BASEMENT MOLD WATER IMPACT
BRICK WALL DRAINAGE WEEP HOLES
BUCKLED FOUNDATIONS due to INSULATION?
BUILDING DAMAGE ASSESSMENT & REPAIR
CONDENSATION on WINDOWS & SKYLIGHTS
DEW POINT TABLE - CONDENSATION POINT GUIDE
EFFLORESCENCE, Salts & White / Brown Deposits
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOD DAMAGED FOUNDATIONS
FLOOD VENTS & FLOOD PORTS
FLOODS IN BUILDINGS-mold
FLOOR DAMAGE DIAGNOSIS
FOOTING & FOUNDATION DRAINS
FOUNDATION BULGE or LEAN MEASUREMENTS
FOUNDATION CRACKS & DAMAGE GUIDE
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
MOISTURE CONTROL in BUILDINGS
MOLD INFORMATION CENTER
NOISE / SOUND DIAGNOSIS & CURE
ODORS & SMELLS DIAGNOSIS & CURE
SEWAGE BACKUP, WHAT TO DO
SEWAGE BACKUP TEST & CLEANUP
SEWAGE BACKUP PREVENTION
SEWAGE PUMP CLOG DAMAGE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
SWEATING (CONDENSATION) on PIPES, TANKS
TOILETS, INSPECT, INSTALL, REPAIR
TRAPS on PLUMBING FIXTURES
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
This article describes the steps needed to get into, inspect, clean, and then dry out a building crawl space. We add advice on how to keep the crawl space dry and clean so that this process doesn't have to be repeated. This 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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
How to Dry Out a Problem Crawl Space, Remove Mold, Rodent Debris Unsafe Materials, & Then Keep the Crawl Space Clean & Dry
Also see our other crawl space dryout and safety discussions beginning at CRAWL SPACE GROUND COVERS where we describe crawl space venting, crawl space poly over dirt, and crawl space heat, to illustrate current best-practices in keeping a crawl space dry. Separately our series of basement dry out, clean up and leak prevention articles begins at BASEMENT LEAKS, INSPECT FOR. Also see MOLD CLEANUP - MISTAKES to AVOID for a master list of the principal ways that people foul up mold cleanup projects.
Damp or wet crawl spaces or basements are often a source of health and structural problems in buildings. Wet areas beneath the occupied space invite mold contamination, insect attack, and structural rot and may also contribute to bacterial hazards. Keeping these spaces dry and clean is not difficult if we address the steps needed in the right order.
The crawl space shown in our page top photo was in our opinion not a readily accessible area because of flooding. This decision is made by the inspector on the scene, not by anyone else. The crawl space shown at left was tight and so junk-filled it could not be entered either.
We break down a thorough crawl space dryout and cleanup process into these steps:
Watch out: for steps 1-7 above, in some conditions, dust containment, negative air, and more protective gear or help from professionals may be needed.
Hazards in some crawl spaces include breathing moldy or unsanitary air, getting poked by a rusty nail, stirring up a hornets nest, getting shocked or electrocuted by unsafe wiring while crawling over wet ground, crawling through unsanitary water from burst waste piping, kneeling in unsafe pesticide chemicals left by an ignoramus, and the occasional spider, rodent, snake, or even trapped raccoon.
Wear appropriate protective clothing, use a good light, and don't work alone.
Take a thorough look in all areas the crawl space itself for water and dampness and for unsafe or unhealthy conditions such as
Here is a Step by Step Guide to Drying out the Crawl Area and Keeping it Dry
Step 1: Remove crawl space debris and wet materials - without this step the dry-out will be more difficult, take more time, and be more dangerous. Do not try to "dry out" wet or damp or suspect fiberglass crawl space insulation. Just remove and discard it. But don't insulate the crawl space yet. There is more cleaning, drying, and sealing work needed first.
Step 2: Remove standing water in the crawl space. This process can go on more or less simultaneously with debris removal.
Step 3: Remove moisture from the crawl space materials and surfaces. This means dry out wood framing, subfloor overhead, and the crawl space floor surface.
Do we also need to add heat to help dry out the crawl area quickly?
It depends. Warm air carries more moisture than cool air and thus will deliver moisture to the dehumidifier more rapidly. The answer is ... it depends on the relative humidity in the area and ambient temperatures. If the relative humidity (RH) is high, say over 60%, and temperatures are over 60 degF. (this is speculative opinion) you probably won't gain much by adding heat to the crawl space during dryout.
We don't want the crawl area so warm that we start sending moist, possibly moldy crawlspace air riding thermal currents into the occupied space of the building. But if crawl space temperatures are low, say below 50F, you will probably speed up drying by adding some warmth, beyond that already provided by the exhaust side of your dehumidifier fan motor.
Remove other Hazardous Materials Such as Asbestos in Poor Condition
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?
Should we use a Power Washer to Clean up the Crawl Space?
When Is it Good Practice to Use Biocides, Sanitizers, or Fungal sprays in a Crawl Space or in Other Building Areas?
For full details of this topic, please see MOLD SPRAYS, SEALANTS, PAINTS. The basics are just below.
When is it Good Practice to use Fungicidal Sealants and Encapsulant Sprays in a Crawl Space or in Other Building Areas?
For full details of this topic, please see MOLD SPRAYS, SEALANTS, PAINTS. The basics are just below.
Clean the crawl space, don't just spray it: Do not, however, permit the use of biocides, disinfectants, sprays, or encapsulants as a substitute for the physical cleaning that must come first.
Otherwise there is risk that you will leave harmful contaminants and particles in the building, and it is likely that cleanup will be inadequate. Look at the thick debris sprayed-over in this building. Simply stirring the debris shows that this approach was ineffective.
Fiberlok IAQ 6000 HD™ (above, left, misapplied right over a high volume of loose debris), Anabec X70™ waterborne sealant, and Fosters 4051™ (clear coating shown at above right) produce sealants frequently used by mold and flood damage remediation companies.
Once the crawl area has been cleaned of debris and moldy materials, and crawl space water has removed, and after we've eliminated the sources of crawl space water entry, we are ready to take the next steps to keep the crawl area clean and dry.
Details about use of fungicidal sealants and sprays are at MOLD SPRAYS, SEALANTS, PAINTS.
Below we focus on measures to take inside the crawl space to help keep that area dry. Things to do outside the building to keep water out of a basement or crawl space are outlined later at Exterior Measures for Crawl Space Moisture Control.
Crawl Space Surface Slope & Drainage Specifications
Crawl Space Floor & Wall Moisture Barriers: When, Where, How, & Why to Install Moisture Barriers, Heat & Dehumidification Equipment in the Crawl Space
Advice About Pouring (Placing) Concrete on Crawl Space Floors
A dehumidifier in a crawl space will also provide some heat in that area; if the crawl space is too cold (despite perimeter insulation) it may be necessary to add a small level of heat there. Some building also permit introduction of dry heat into these areas.
Make sure your crawl space electrical wiring is safe and meets current electrical codes. Receptacles (such as the electrical outlets you may want to use to power your crawl space fans or dehumidifier) should be GFCI protected and all of the circuits there such as wiring for lighting should be AFCi protected. See AFCIs ARC FAULT CIRCUIT INTERRUPTERS for details on the 2008 National Electrical Code requirements for AFCIs and GFCIs.
Add a heat source to the crawl area to help keep it dry. If plumbing supply or drain lines are in the crawl space that will be another reason to add heat if your building is located in a freezing climate. You don't need much. An air supply register cut into an existing supply duct in the crawl area may be enough, or a small section of heating baseboard if your building uses hot water heating. In crawl spaces where these heat sources are not convenient, add a small electric baseboard or oil-filled electric heater with a thermostat that turns it on at low temperatures.
It's always better to keep water out of buildings than to let it come in and then try to get rid of it. But some building sites and conditions may still justify one or more sump pumps in the crawl space. Earlier we stressed the importance of making sure that the crawl space floor drains to one or more points where as sump pump can be installed if needed.
Not like this! We cannot show all of the ways to foul up a sump pump installation in one article, but our photo at left is particularly disgusting. Don't just throw a sump pump into a low area in the floor. The resulting lake will continue to damage the rest of the building.
At SUMP PUMPS GUIDE we discuss types of sump pumps and how they should be connected to electrical wiring and to drainage destinations. Keep in mind that the time you are most likely to need a crawl space sump pump is during hurricanes or tropical storms or in northern climates during times of heavy snow melt.
During a storm is just when electrical power may be lost. If your electrical power is not reliable you should consider a battery-operated backup sump pump system with enough capacity to keep the pump(s) running until power is restored.
We noted earlier that it is almost always preferable to keep water from entering a building rather than allowing it to enter and then working to get rid of it. Here we refer to articles giving more detail on measures to keep unwanted roof runoff or surface or even subsurface water from entering a basement or crawl space.
Inspect the roof drainage system, gutters and downspouts to be certain that roof spillage is not ending up by the building foundation. Defects in handling roof runoff is the number one source of basement and crawl space dampness and water entry.
Key building crawl space water entry diagnosis and cure articles:
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.
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.
Questions & answers or comments about how to dry out a wet crawl space & prevent future crawl space water entry.
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