Reliability Study: Using Moisture Meters to Screen Buildings for Leaks, Moisture Traps, Rot, Insect Damage, or Mold
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Field study compares the ability of popular moisture and leak detection tools to find leaks in building wall cavities and ceilings
Importance of visual inspection in assessing the leak risk or mold, insect damage, or rot risk at buildings
Guide to detecting and evaluating leaks and water entry into buildings

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Report on the Reliability of Moisture Meters to Screen Buildings for Hidden Moisture, Leaks or Mold Contamination

This article explains the use and reliability of different types of moisture detection equipment to find water entry problems on buildings.

Our page top photo shows our client pointing to flood lines on a heating system expansion tank, indicating that this building was subject to severe deep flooding. We learned from neighbors that a nearby river had flooded this home and others in its neighborhood repeatedly over the 60 year life of the building.

Question: will my inspector test for moisture?

I am scheduling a pre-purchase home inspection and my real estate agent asked a question about moisture detection: he wants to know if the home inspector will check the moisture level in Sheetrock? - C.W., New York, NY.

Reply: ... it depends ...

Moisture meters, particularly pin-type probing moisture meters that detect moisture by sending an electrical signal between two probes inserted into a material (such as the time-tested Delmhorst™ twin-point electronic resistance moisture meter shown at left) are one of the first tools that many building inspectors purchase after a flashlight, ladder, and screwdriver.

Relying on any test instrument alone, as we discuss at Warnings re instruments for detection of gases, is not a good substitute for a careful inspection. While using a moisture meter is a popular tool among home inspectors and building environmental inspectors or "mold investigators", and a useful one, the visual inspection of a building for leak history is much more critical than a general "check" using a moisture meter.

After all, the building could have had a history of leaks in the past, as well as hidden rot, insect damage, or mold, related to leaks or trapped moisture, but the leak spot could happen to be dry at the time of testing.

Absence of evidence of moisture when using a moisture meter in a building is not evidence of absence of a history of building leaks, and there is a long list of visual clues that readily tell the story of a building's leak history or the risk of building flooding. .

So properly a moisture meter is, in our opinion, useful principally to confirm that a leak is current.

We also find moisture meters useful, particularly radio-signal based non-probing moisture meters such the Tramex™ electronic moisture encounter, to check for hidden leaks behind ceramic tile walls in bathrooms and kitchens where probing is impossible. Our photo (above left) illustrates use of a Tramex™ moisture encounter to check for leaks into the EIFS stucco covering of a building's window sill. Details are at SIDING EIFS WALL LEAK POINTS.

And certainly "spot checks for moisture" done randomly at a building would be nonsense.

Study Comparing the Effectiveness of Moisture Detection Methods in Buildings

In a field study this author (Daniel Friedman) conducted in February 2004 we compared the effectiveness of various methods to test for moisture in the walls of a home reported to have suffered leaks from ice dams at its roof eaves. We surveyed the inside surface of building exterior walls of the entire second floor front and rear building surfaces using the following methods:

Surface checks for evidence of moisture using a Tramex™ Moisture Encounter (shown above on an exterior window sill). This instrument is non-invasive, does not leave surface marks, and can be slid rapidly along building surfaces, making it easy to scan large areas for moisture. [Tramex also makes pin-type moisture meters like the model shown at left.]
Surface checks for evidence of moisture using a Delmhorst™ pin-type moisture meter with short pin probes that penetrated less than 3/4" into the building drywall. This type of water leak detection device is the most commonly-used one during home inspections.
Long probe moisture meter: Spot checks for moisture at highly-suspect areas, wall tops, around windows, and wall bottoms above baseboard trim using a long-probe Delmhorst pin-type moisture meter.

Test cuts into wall and ceiling cavities at highly-suspect areas for recent leaks, including wall tops, around windows, and wall bottoms above baseboard trim using a drywall knife and making 2" x 4" or 4" x 4" inspection openings to examine the wall insulation, wall framing, cavity side of drywall, and the inner surface of exterior building wall sheathing.

Our photo (left) shows a wall test cut made and then closed over a window and where from outside we had seen evidence of leaks into the building soffits - caused by ice dams.

Note: destructive or invasive inspection practices are not normally used during a pre-purchase home inspection but may indeed be appropriate during more extensive building investigations (with owner permission). [In this case we were studying the building for an insurance company who was investigating ice dam leaks.]
Demolition and strip cuts or complete removal of the drywall throughout the suspect building walls of the second floor of the home to expose all of the wall cavity framing and exterior wall sheathing, including demolition of a bathroom that had been built using ceramic tile wall covering.
Use of infrared or thermography to detect moisture in buildings is a widely-used practice that was not tested during this study. Our OPINION is that not only do IR or thermographic scans of buildings face the same limitations of moisture meters (old leaks are not detected), but as well, the operator needs the skill and experience in IR image interpretation to account for other sources of temperature differences across a building that may be caused by other conditions than water leaks.

Conclusions of Moisture Detection Equipment Study

Any moisture meter properly used did a good job of detecting moisture that had penetrated the building interior drywall provided that the drywall was still sufficiently damp at the time of our inspection.
An electronic moisture encounter could detect wet insulation in the wall cavity that had not yet led to drywall in that location being sufficiently wet to show up using a surface or pin type moisture detector.

But the same device could be "fooled" into reporting wet conditions where there were none if there any metallic substance was in the wall cavity, including electrical wiring, plumbing pipes, expanded metal lath, and foil-faced building insulation.
A long-pin type moisture meter was capable of detecting moisture in the wall cavity insulation that did not show up in surface tests, and might not show up using an electronic moisture encounter, provided that the inspector was astute enough or lucky enough to probe exactly correctly to stab into moisture.

For example, in one wall cavity water from a roof leak was running down the side of a wall stud (photo at left) but staying close to the exterior wall. This type of leak was missed by most of the test and inspection methods, but would show up eventually in the ceiling below if the leak continued long enough or in great quantity.
Old leaks were not detected: None of the moisture detection devices was able to detect points of prior leakage that had dried at the time of the study, but indeed when we demolished the building interior walls, we found both water stains and carpenter ant damage in the bathroom walls from old plumbing leaks.

Note: Pin-type moisture meters, in the hands of a very experienced inspector, might detect a suggestion of previous, leaks in areas dry at the time of inspection (provided the surface can be probed AT ALL and is not covered by a hard surface such as ceramic tile) because on occasion mineral salts left behind when a leaked-into-area dries will give a higher moisture meter reading (higher electrical conductance) than surrounding areas even though the surface is dry.

Visual evidence of leaks (C) Daniel Friedman

Visual inspection of a building, its construction, materials, maintenance history, ventilation, and the myriad of visual clues that can indicate a history of water entry, leaks, or trapped moisture is critical in assessing the level of risk of moisture or leaks at a building. Articles shown at the left of this page discuss various inspection points that indicate a history of building leaks, flooding, moisture, or mold problems.

Our photo (left) of a window in a shower and duct-tape "repairs" along the window edge would be a very strong suggestion of a leak history in this bathroom shower - without using any moisture meter instrument whatsoever. Similarly, the mud-line on the heating system expansion tank shown at the top of this page shows that the building had actually been flooded.

Observing evidence of the frequency, extent, source, and causes of leaks, water entry, and actual building flooding is a critical step in evaluating a building as well as in planning the cure for building leaks, water entry, and mold.

Home buyers and home owners are right to worry about building leaks and moisture - water where we don't want it is at the top of the list of sources of building problems. If you have a particular reason to be suspicious about something be sure to let the inspector know.

Also see VISUAL PERCEPTION ERRORS - an exploration of the theory of vision and visual errors that illustrates to building inspectors that it is important to actually inspect, and to be aware of distractions that keep us from "seeing" critical clues even if we are "looking" right at them - inattentional blindness.

Watch out for "show and tell" tools that impress the client during a home inspection but are a poor substitute for doing a good job.

OPINION: Of these questionable practices, the most hilarious (and dishonest) use of thermography that we have found popular in some areas is that made by "mold inspectors" and a few mold remediation companies who claim that their IR camera is a "mold detector".

Like any good fib, there' s just enough truth in the statement to confuse things. Sure, a leak may show up under a thermographic scan, and a leak into building cavities are a high risk for mold. But what about old leaks, now dry, that launched a large mold problem? What about air leaks that lose energy and show up on the thermographic scan, but have not led to moisture and mold contamination? [Perhaps some readers will recall the old replacement window scam that used light meters as "energy loss" meters. ]

Key building water entry diagnosis and cure articles:

BASEMENT WATERPROOFING - use of sealers to help keep basements and crawlspaces dry
BASEMENT LEAKS, INSPECT FOR - where and how water gets into basements and crawl spaces
CRAWL SPACE DRYOUT PROCEDURES - details about curing wet or damp crawl spaces.
EFFLORESCENCE, Salts & White / Brown Deposits - these white deposits are a great indicator of where moisture is penetrating a foundation
HUMIDITY CONTROL & TARGETS INDOORS - so how dry should a building be for comfort and mold prevention?
MOISTURE CONTROL in BUILDINGS - master list of detecting and controlling building moisture levels
MOISTURE METER STUDY - reliability of methods for screening buildings for leaks, water, moisture, mold
MOISTURE PROBLEMS: CAUSE & CURE - moisture and building energy loss
SUMP PUMPS GUIDE - how and where to install a sump pump as an emergency backup against basement or crawl space flooding
WATER ENTRY in BUILDINGS - causes and cures of un-wanted building leaks in all areas
WET BASEMENT PREVENTION - how to stop basement flooding

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MOISTURE METER STUDY
MOISTURE PROBLEMS: CAUSE & CURE

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book 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. InspectAPedia.com ^® editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for certain articles found at this website. All rights and contents to those materials are ©Journal of Light Construction and may not be reproduced in any form.
Appliances and Home Electronics, - energy savings, U.S. Department of Energy
Avongard foundation crack progress chart for structural crack monitoring
Basement Moisture Control, U.S. Department of Energy
Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
The Circular Staircase, Mary Roberts Rinehart
Construction Drawings and Details, Rosemary Kilmer
Crawl Space Moisture Control, U.S. Department of Energy
Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328
This book is an update of a long-established text dating from at least 1988 (DJF); Quoting:
This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations. THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.
Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
Domestic Building Surveys, Andrew R. Williams, Kindle book, Amazon.com
Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting:
A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
Guide to Domestic Building Surveys, Jack Bower, Butterworth Architecture, London, 1988, ISBN 0-408-50000 X
"Avoiding Foundation Failures," Robert Marshall, Journal of Light Construction, July, 1996 (Highly recommend this article-DF)
"A Foundation for Unstable Soils," Harris Hyman, P.E., Journal of Light Construction, May 1995
"Backfilling Basics," Buck Bartley, Journal of Light Construction, October 1994
"Inspecting Block Foundations," Donald V. Cohen, P.E., ASHI Reporter, December 1998. This article in turn cites the Fine Homebuilding article noted below.
"When Block Foundations go Bad," Fine Homebuilding, June/July 1998
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Log Homes: Minimizing Air Leakage in Log Homes, U.S. Department of Energy
Manual for the Inspection of Residential Wood Decks and Balconies, by Cheryl Anderson, Frank Woeste (Forest Products Society), & Joseph Loferski, October 2003, ISBN-13: 978-1892529343, $39.00 at Amazon.com or at the InspectAPediaBookstore
Masonry structures: The Masonry House, Home Inspection of a Masonry Building & Systems, Stephen Showalter (director, actor), DVD, Quoting:
Movie Guide Experienced home inspectors and new home inspectors alike are sure to learn invaluable tips in this release designed to take viewers step-by-step through the home inspection process. In addition to being the former president of the National Association of Home Inspectors (NAHI), a longstanding member of the NAHI, the American Society of Home Inspectors (ASHI), and the Environmental Standard Organization (IESO), host Stephen Showalter has performed over 8000 building inspections - including environmental assessments. Now, the founder of a national home inspection school and inspection training curriculum shares his extensive experience in the inspection industry with everyday viewers looking to learn more about the process of evaluating homes. Topics covered in this release include: evaluation of masonry walls; detection of spalling from rebar failure; inspection of air conditioning systems; grounds and landscaping; electric systems and panel; plumbing supply and distribution; plumbing fixtures; electric furnaces; appliances; evaluation of electric water heaters; and safety techniques. Jason Buchanan --Jason Buchanan, All Movie Review
Masonry Design for Engineers and Architects, M. Hatzinikolas, Y. Korany, Canadian Masonry (2005), ISBN-10: 0978006100, ISBN-13: 978-0978006105
Masonry Structures: Behavior and Design, Robert G. Drysdale, Ahmid A. Hamid, Lawrie R. Baker, The Masonry Society; 2nd edition (1999), ISBN-10: 1929081014, ISBN-13: 978-1929081011
Masonry, Engineered: Using the Canadian Code, J. I. Gainville, Cantext publications (1983), ASIN: B0007C37PG
Masonry, Non-reinforced masonry design tables, Hans J. Schultz, National Concrete Producers Association and the Canadian Masonry Contractors Association (1976), ASIN: B0007C2LQM
Moisture Control in Buildings, U.S. Department of Energy
Moisture Control in Walls, U.S. Department of Energy
Quality Standards for the Professional Remodeling Industry, National Association of Home Builders Remodelers Council, NAHB Research Foundation, 1987.
Quality Standards for the Professional Remodeler, N.U. Ahmed, # Home Builder Pr (February 1991), ISBN-10: 0867183594, ISBN-13: 978-0867183597
R-Value of Wood, U.S. Department of Energy
Slab on Grade Foundation Moisture and Air Leakage, U.S. Department of Energy
Straw Bale Home Design, U.S. Department of Energy provides information on strawbale home construction - original source at http://www.energysavers.gov/your_home/designing_remodeling/index.cfm/mytopic=10350
More Straw Bale Building: A Complete Guide to Designing and Building with Straw (Mother Earth News Wiser Living Series), Chris Magwood, Peter Mack, New Society Publishers (February 1, 2005), ISBN-10: 0865715181 ISBN-13: 978-0865715189 - Quoting:
Straw bale houses are easy to build, affordable, super energy efficient, environmentally friendly, attractive, and can be designed to match the builder’s personal space needs, esthetics and budget. Despite mushrooming interest in the technique, however, most straw bale books focus on “selling” the dream of straw bale building, but don’t adequately address the most critical issues faced by bale house builders. Moreover, since many developments in this field are recent, few books are completely up to date with the latest techniques.
More Straw Bale Building is designed to fill this gap. A completely rewritten edition of the 20,000-copy best--selling original, it leads the potential builder through the entire process of building a bale structure, tackling all the practical issues: finding and choosing bales; developing sound building plans; roofing; electrical, plumbing, and heating systems; building code compliance; and special concerns for builders in northern climates.
"Vapor Barriers or Vapor Diffusion Retarders", U.S. DOE: how vapor barriers work, types of vapor diffusion barriers, installing vapor barrier
Ventilation for energy efficient buildings, Purpose, Strategies, etc.,
...

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Report on the Reliability of Moisture Meters to Screen Buildings for Hidden Moisture, Leaks or Mold Contamination

Question: will my inspector test for moisture?

Reply: ... it depends ...

Study Comparing the Effectiveness of Moisture Detection Methods in Buildings

Conclusions of Moisture Detection Equipment Study

Key building water entry diagnosis and cure articles:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair