How to Inspect, Diagnose, & Repair Problems in Building Crawl Spaces
CRAWL SPACES - home - CONTENTS: How to inspect, diagnose, repair problems in building crawl areas and other under-floor spaces. Scope of crawl area inspections, limitations & advice on handling areas that are inaccessible or unsafe to enter for inspection.
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Building crawlspace inspection procedures & topics:
This building crawl space article series explains how to inspect, diagnose problems in, and repair building crawl spaces, including crawl space insulation & leaks or moisture control.
Information is provided about visual clues of crawl space problems, such as
evidence of a history of leaks, mold contamination, insect damage, structural damage, flooding, as well as evidence of hazardous materials and conditions such as the probable presence of animal allergens, asbestos, or mold.
Crawl Areas: Defect Recognition, Repair, Prevention for Building Crawl Space Leaks, Mold, Insulation & Ventilation
The page top sketch of the role of a dirt floor crawl space in building moisture and mold problems (above) is courtesy of Carson Dunlop Associates. Photo at left is of the author, Daniel Friedman, peering into an inaccessible crawl space while suffering from a broken leg. Photo courtesy of Arlene Puentes.
[Click to enlarge any image]
The list of concerns or problems in or due to building crawl spaces is long as would be a list of opinions about what to do with crawl spaces, wet crawl spaces, moldy crawl spaces, or crawl space insulation and ventilation.
Good building science combined with a lot of experience has led to some good information on how to correct crawl space problems. Here we list crawl space problem inspection, diagnosis, and cure. Here are some things to watch out for in a building crawl space:
Crawl spaces may be unsafe to enter due to risk of asbestos, chemicals, collapse, hantavirus, mold, rodents, sewage, snakes or even electrical shock hazards.
Crawl spaces may be a source of building water, moisture, leaks, mold -
see CRAWL SPACE DRYOUT - home - this is the key article on dealing with wet or damp crawl spaces and related problems in buildings.
For avoiding foundation collapse in areas prone to flooding, also
see FLOOD VENTS & FLOOD PORTS. WATER ENTRY in BUILDINGS is the home page for our series of articles on the causes and cures of high indoor moisture, wet basements, wet crawl spaces, and moisture related problems like attic condensation and mold.
Crawl spaces may be a cause of building energy loss or increased heating bills, especially if the crawl space is improperly insulated and/or vented.
See CRAWL SPACE DRYOUT - home where we also discuss the change in thinking between the old-school idea of venting crawl spaces to the current best practice of converting crawl areas to a conditioned space, explained further
at CRAWL SPACE GROUND COVERS.
Crawl spaces are often a reservoir of hidden structural, rot, insect, mold, water, contaminant, or other problems, largely because most crawl areas are difficult to enter and are rarely inspected.
WOOD DESTROYING INSECTS carpenter ants, powder post beetles, & other wood destroying organisms are a special risk in crawl areas, especially if fiberglass insulation was run from crawl space floor right up the wall and onto building framing or flooring.
Crawl spaces may be cluttered with debris impeding inspection and inviting pests or rodents. Crawl spaces are required to be kept clear of debris; some such as wood scraps increase the risk of termite risk. For example from the 2012 IRC:
The under-floor grade shall be cleaned of all vegetation and organic material. All wood forms used for placing concrete shall be removed before a building is occupied or used for any purpose. All construction materials shall be removed before a building is occupied or used for any purpose. 
Key Crawl Space Inspection, Diagnosis, Repair articles
AIR BYPASS LEAKS - stains on insulation may help spot air leaks from a crawl area into the occupied space
EFFLORESCENCE SALTS & WHITE DEPOSITS - don't waste money testing white goop for crawl space mold if it is efflorescence, but efflorescence does indicate a source of crawl space moisture that needs attention
FIBERGLASS INSULATION - can become mold contaminated in a crawl area, leading to mold contamination in the occupied space above
WOOD DESTROYING INSECTS carpenter ants, powder post beetles, & other wood destroying organisms are a special risk in crawl areas
Thermal Tracking & Stains how to recognize thermal tracking or thermal bridging & how to diagnose Stains on Ceilings & Walls, Building Air Leaks & Insulation Defects, as well as other indoor air quality or building concerns
Question: What is the Best Approach to Drying out a Flooding Crawl Space?
I have been battling crawl-space moisture and ponding water problems for about 2 years now and am desperately requesting your pro-bono assistance and consultations. I am living in a senior citizen retirement house that I inherited from my deceased parents. I am on total permanent Social Security Disability for almost 10 years now. This is my only income which is $1300 per month.
After many many hours, weeks, and months of calling people, searching the internet etc., I came across your excellent article and web-site. I knew from reading your material that you are the people I need to help me navigate properly through all the people and companies I have been in contact with. I didn't, (and still don't) know where to start first.
This house was built in a senior citizen community where the water-table is high and the ground gets soaked around the perimeter of the foundation and other areas of the property during heavy and even not-so-heavy rains. I have a dirt crawl-space that gets puddles in it and had a termite inspector put a not-so-good sump pump in it that the water never reaches.
Then another person told me I had mold in there and several other people told me I didn't. Had an excavator look and he told me the dirt needed to be pitched and leveled but he's never done that in a crawl space before. Even when the termite guy dug some trenches, the water just sat in the trenches.
I had water-proofing companies come and tell me differing things, all wanting thousands of dollars and none guaranteeing anything. Some say encapsulation and inside french drains, some say that's not good and outside french drains, some say putting more wall wells and vents in or digging the dirt out more so that water won't come in the vents. I consulted with a hydro science company that also said to just clean the gutters (which I already had done and they have that netting over them so they weren't too bad) and clean or get new downspouts. And it goes on and on and on.
I want to get the right people to start at the right place but am thoroughly confused now. I got free weatherization from the state because I am on limited income and on medicare, paad, and food stamps. They wrapped the pipes down there and put in a cheap black moisture barrier and fiberglass insulation on top.
I have heard and read that may make the moisture and mold problems worse. Recently I have noticed a mildew-like moldy smell coming from my forced-air gas baseboard registers and read when I put the heat on it will spread and contaminate the house even more with mold spores.
I know my carpeting needs to be removed and house painted but have been putting if off because I realize I need to get the water/moisture issues identified first as well as the mold problems corrected. I had the bathroom painted in April and shortly after I noticed the paint cracked on the ceiling which is near the attic where I suspect there may be water/mold damage.
This, I think is probably from a couple of years ago when my central air was dripping and we had a new a/c put in.
So I am asking you for your help in testing for molds and dust particle analysis as well as directing me to the correct professionals in the proper order to resolve all these issues.
Thank you very much for your kind consideration and assistance in advance,
- B.B., Toms River NJ
Reply: A Step by Step Approach to Wet Crawl Spaces
Thank you for the interesting or I should say challenging water entry question - it helps us realize where we need to work on making our text more clear or more complete.
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem.
That said, here are some things to consider,interspersed with your remarks from your own note:
I have a dirt crawl-space that gets puddles in it and had a termite inspector put a not-so-good sump pump in it that the water never reaches.
Puddles in a dirt crawl space below a home, even just wet soils, invite problems with building mold contamination and wood destroying insects such as termites and carpenter ants. It's certainly a problem that needs correction. Divide your wet crawl space solution thinking into these three main topics:
how to stop water from entering the crawl area
how to get rid of water and moisture therein
how to evaluate the building for related damage (mold, termites) that may need attention
Then another person told me I had mold in there and several other people told me I didn't.
If mold is not visible and there are no health complaints there might not be a big mold problem, or there may be one but as mold does not affect everyone to the same degree, you may not have noticed it.
See our article on MOLD / ENVIRONMENTAL EXPERT, HIRE ?, for help in deciding if it is cost justified or otherwise appropriate to perform some expert inspecting and testing for mold. Don't rely on mold tests without an inspection by an expert.
If your expert finds that there is a significant mold problem originating in the crawl area, also see CRAWLSPACE MOLD ADVICE.
Had an excavator look and he told me the dirt needed to be pitched and leveled but he's never done that in a crawl space before.
I agree with your excavator - if the crawl space is not sloped to a common drain point you cannot easily remove water therein. It's best not to have water enter the crawl in the first place since if we let water enter but then pump it out, we are still facing mold and insect troubles stemming from high moisture in the area.
Even when the termite guy dug some trenches, the water just sat in the trenches.
This means that the soil has a slow percolation rate. Trenches need to be pitched to a common drain point where a sump pump removes water.
I had water-proofing companies come and tell me differing things, all wanting thousands of dollars and none guaranteeing anything.
The number one water entry step is gutter and leader maintenance.
You think your gutters are "clean" but a mere handful of leaves can clog a downspout and lead to gutter overflow and spillage around the building so you will want to inspect the gutter and downspout system during a heavy rainfall. Make sure downspouts drain far enough from the building that water does not enter at those locations.
Some say encapsulation and inside french drains, some say that's not good and outside french drains, some say putting more wall wells and vents in or digging the dirt out more so that water won't come in the vents.
Simpler and less expensive are steps to stop water entry from outside, combined with a sloped crawl surface to a common sump pit (see SUMP PUMPS), combined with 6 mil poly over the dirt to stop pumping soil moisture into the area (see CRAWL SPACE VAPOR BARRIER LOCATION).
I consulted with a hydro science company that also said to just clean the gutters (which I already had done and they have that netting over them so they weren't too bad) and clean or get new downspouts.
Your hydro science company was pointing to the number one cause of wet crawl spaces
Question: Problems with odors from poly vapor barriers on crawl space floors
I have a dirt crawl space under my bedroom floor which is causing me some health problems. I am extremely allergic to mold and my husband put 6 ply visqueen on dirt floor & 2 vents in block. I became extremely sick from visqueen order and I removed it, still feeling sick but not as bad. I am closing off the 2 vents to avoid anymore air flow in crawl space.
However, I want to put something down overtop the dirt floor and adhere it to the concrete walls to avoid any further allergy problems plus have cleaner air flow in our bedroom....but the plastic's are mostly made of polyurethane which might be sensitive too also or with the combinations and exposure to the dirt floor caused more airborne mold spores & allergies.
Even in the middle of the night I feel like something is crawling & biting me....and my husband is coughing something awful and we both have headaches & sinus, breathing problems too, nausea, disoriented and confusion. I am very worried about this and want it repaired ASAP before its too late. I am looking for something to cover & seal the dirt flooring but want something that is chemical free. I would also like to know if it would be wise to put insulation up underneath the bedroom floor to help prevent from coming up thru the floor into the bedroom? Any information, suggestions, ideas would be greatly appreciated. thank you! - Suzanne
Suzanne, When choosing a poly vapor barrier for a crawl space beneath your home, indeed it makes sense to do a sniff test - some of the white 6-mil plastic vapor barriers I've seen used by building remediators were virtually odorless;
In other cases we placed the poly outdoors in the sun for a few days to help it complete its outgassing before putting it down in a crawl area. Indeed I've been bothered by horrible odor outgassing from some poly ground covers too.
You could also pour a concrete floor in the crawl area - a more costly solution that has its own concerns with temporary high moisture levels. More suggestions are at CRAWL SPACE GROUND COVERS where we describe ways to cover up dirt and stop moisture movement into the structure from the crawl space floor. Also see VAPOR BARRIERS & CONDENSATION in BUILDINGS.
But I wouldn't be too hasty to assume that plastic odors are the only concern, perhaps not even the main one, in your home. A damp dirt floor crawl space could have led to a mold problem or there could be other health and IAQ issues coming from that location or even elsewhere in the building. For example there could be hard-to-see mold contamination on wood surfaces or in fiberglass insulation if it has been exposed to wet or dampness. (See INSULATION MOLD CONTAMINATION TEST).
At MOLD INFORMATION CENTER (article link at the "More Reading" links at the bottom of this article ) you can find MOLD / ENVIRONMENTAL EXPERT, HIRE ? - that might help you decide if it's appropriate to bring in an expert for a more thorough building inspection and perhaps some tests. I'd be reluctant to ONLY blame the plastic odors (though those have bothered me too at times).
Question: What should be inspected in building crawl areas?
I am the VP for a condo association. The units are approximately 35 years old and when the last couple of unit have sold, the home inspector found a number of issues within the crawl spaces. The units (42) are individual town home type with individual unit crawl spaces. Some are physically divided by foundation, and some are divided by fire rated dry wall.
We would like to know if you have any examples of what we should expect from an inspection of the crawl spaces as we are going to engage a firm to do the inspection for the association. - Anon. 1/2/2014
Perhaps because the range of components and building systems that may or may not be present in a crawlspace is so great, I had not though of making a crawlspace-specific inspection list or topic, though indeed inspectors have strong opinions about the inspection of that area of any building.
I'll make some general suggestions below. If you want to send me examples of what reports & photographs have already been provided for your buildings I can then form a better view of the nature of the construction of the townhomes and thus would have a more specific opinion.
I agree that crawlspace inspection is important: problems tend to develop further and to a more severe extent precisely in building areas that are difficult to access.
First: the inspection report must indicate whether or not a crawlspace exists at the building; presuming that one is present beneath each of the 42 units in your case, the report must indicate whether or not the crawlspace was entered and inspected or not. Some conditions such as flooding, unsafe wiring, contamination, or limited safe access space can either limit or even preclude actual entry of a crawl space.
Ultimately the decision to enter or not enter a crawl area must be up to the inspector in the field, as s/he may observe specific safety concerns that would lead the inspector to decline to enter the space. In that case the report must indicate the inspection limitations and if the space was not entered, the report needs to explain why. If I were writing such a report, based on what I could determine about the building and its risk points, I'd have additional recommendations for inaccessible areas. For example where a crawl area is completely inaccessible one needs to decide based on other site and building observations whether or not there are clues suggesting either damage or risk of conditions serious enough to justify destructive or invasive measures to gain view or access to the area. .
Second: for entered crawl spaces surely the scope of inspection will cover all structural and mechanical systems and components that are present therein. For example (this cannot be a complete list as I know nothing of building specifics) the inspector would report
nature of & condition of construction: visible materials of the foundation, piers, footings (if present/visible), framing, insulation, presence of mechanical components, wiring, etc.
fire barriers: where the building is a multiple occupancy/multiple living unit, the presence & condition of fire barriers between crawl spaces as required by local building codes should be reported
evidence of water entry, flooding, drainage problems. At InspectApedia you'll find that many of our articles address water and moisture related problems in crawl spaces.
evidence of visible damage to the foundation walls
evidence of rot or wood destroying insect damage to the building and depending on qualifications and contract, evidence of activity of wood destroying insects
visual evidence of mold contamination or other obvious hazards (burst sewage pipes, damaged or improper wiring)
if insulation is present, and if so, installation or condition defects
if mechanical components are present, such as under-floor heaters, water tanks, or other equipment are located in a crawl space their condition should be inspected and reported just as for other building mechanical systems, with the added notation that limited access can often interfere with proper inspection and maintenance of mechanicals
While many inspectors stop the scope of their service at the level of reporting their direct observations (materials, conditions, defects) in my OPINION a true professional will also be sure that you, the client, are given to understand the significance of these findings and are told clearly where there is evidence of unsafe conditions or the need for repairs. For example, water entry in a crawl space can affect the entire building, inviting insect damage, rot, mold contamination, wiring damage, damage to mechanical components, and even moisture problems in other building areas, even in the building's attic.
Watch out: in my OPINION what would not be helpful or particularly useful would be an "inventory checklist" type of inspection report that simply indicates the type of construction and materials. And a limited report that lists observations but gives you no idea of their relative import nor of the need for repairs nor of safety hazards is also of limited value.
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Dickson, Bruce. Guide to Closing and Conditioning Ventilated Crawlspaces. US Department of Energy, Energy Efficiency & Renewable Energy, 2013.
De Haven, E. S. "Approximate hazard ratings and venting requirements from CSI‐ARC data. An up‐to‐date review of methods for analyzing single‐and multiple‐reaction data from adiabatic‐reaction calorimeters." Plant/Operations Progress 2, no. 1 (1983): 21-26.
 International Residential Code, IRC Section R408, Under Floor Space, http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_4_sec008.htm, retrieved 3/2/2013
 International Residential Code, IRC Section R406, Foundation Waterproofing and Dampproofing, http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_4_sec006.htm, retrieved 3/2/2013
 Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees (Bylaws, Standards), as well as HVASHI Chapter President. Ms. Puentes can be contacted at firstname.lastname@example.org
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: email@example.com
Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program. Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Home Reference Book, a reference & inspection report product for building owners & inspectors. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
Asbestos: How to find and recognize asbestos in Buildings - visual inspection methods, list of common asbestos-containing materials
Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
How could homes be designed and built more efficiently?
What kinds of construction and production techniques worked well and which did not?
How did people use different kinds of spaces in their homes?
What roles did community planning, zoning, and interior design play in how neighborhoods worked
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Fiberglass: Indoor Air Quality Investigations: Health Concerns About Airborne Fiberglass: Fiberglass in Indoor Air from HVAC ducts, and Building Insulation
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
Rubblestone Wall Filler: See this Lartigue House using exterior-exposed rubblestone filler between vertical timbers of a post and beam-framed Canadian building.
Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or
ISBN 10: 1-933264-01-2,
available from the publisher, Lawyers ^ Judges Publishing Company,Inc., www.lawyersandjudges.com firstname.lastname@example.org and also from the InspectAPedia Bookstore (Amazon.com)
Manufactured & Modular Homes: Modular Building Systems Association, MBSA, modularhousing.com, is a trade association promoting and providing links to contact modular builders in North America. Also see the Manufactured Home Owners Association, MHOAA, at www.mhoaa.us. The Manufactured Home Owners Association of America is a National Organization dedicated to the protection of the rights of all people living in Manufactured Housing in the United States.