Home inspection methods: this free online class presents advanced building inspection techniques to improve the detection of subtle clues and to enable more accurate reporting of difficult-to-detect safety or costly defects in the system or building being inspected. These home inspection methods use a strategy and suggest methods which may be useful in the inspection of any complex system for defects. CONTACT us to suggest changes or additions to the text.

We discuss methods to improve the inspector's ability to "see" defects, even those for which there may be no immediately-obvious visual evidence. We discuss methods of accumulating evidence about the condition of a building (or any other complex system being examined) in order to cross thresholds of reporting, action, or determination of the level of importance of the evidence found.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Advanced Home Inspection Methods - Classes & Levels of Fear, and how to use them to find and report significant, hidden problems in the inspection of buildings or other complex systems

Daniel Friedman - Poughkeepsie, NY 12603 U.S.© 2013-1997 all rights reserved

We also discuss, and link to a more detailed article about the nature of vision and the human ability to "see" and to "notice" visual information, and we suggest strategies to improve the ability to "see" during inspections. This is an continuing-study topic and will be revised frequently. (08/31/2007) A power point classroom presentation of this paper can be read online at InspectAPedia.com/structure/x-ray-ppt.htm. In the photograph above, the severe damage to this building is obvious. The source of the damage is probably obvious too - leaks at a roof valley.

But the conditions that led to this severe damage and ultimate collapse of portions of a valuable historic (but unattended) building could have been spotted decades before. The damage could have been prevented by a minor repair.

Introduction: Dealing with "Hidden" Defects in the Inspection of Buildings or Other Complex Systems

Updated 3/8/2013 - priorities & maintenance
Updated 20 August 2010 - links, cross references, citations, reference books and texts found at end of this article
Updated 14 April 2007 - see links to subsections now stored as separate documents and web pages
May 1, 2004, 4^th Edition - Suncoast ASHI Seminar, Tampa FL 1 May 2004
Sinkholes, Termites, Inattentional Blindness, Comparison of Hidden Moisture Detection Methods, new case studies demonstrating collection and application of contextual clues to indicate hidden defects.
October 3, 1998 (Rev 3) - ITA's - Inspection Expo '98, Las Vegas NV Conference
August 8, 1998 (Rev 2) - Hudson Valley ASHI Conference, New Windsor NY
October 24, 1997 - Ontario Association of Home Inspectors, Inspection '97 Toronto National Seminar

• http://InspectAPedia.com/structure/x-ray.htm - this paper
• http://InspectAPedia.com/structure/x-ray-ppt.htm - Illustrated Power Point Version of This Paper
• http://InspectAPedia.com/vision/sinkholes.htm - Can X-Ray Vision Warn of Sink Holes?
  Contextual clues suggesting Wood Destroying Insect Infestation - a case study in photographs
• http://InspectAPedia.com/vision/vision.htm - The Nature of Vision - inspecting complex systems

What about "hidden" defects? What is hidden? If an inspector didn't observe [and report] a defect, it remains "hidden," in a practical sense since no action will be taken, regardless of how much direct, visible evidence was actually available.

The methodology discussed in this paper applies both to truly totally hidden defects and to those which were perhaps perfectly visible but which are "missed" by the observer. An inspector couldn't/didn't get up on a low-sloped rear dormer roof which is later discovered to be totally worn out - a condition which might have been predicted from the ground whether there was ready access for him to see it or not.

An inspector fails to explain in her report that evidence of a history of water entry in a finished, paneled basement means that there is a high risk of hidden mold, insect damage, or rot. Failing to provide this explanation of a field observation can leave a costly and potentially unsafe mold hazard or hidden damage in the building. It is "hidden" from the client even though there may have been overwhelming evidence of its presence.

Superman has X-ray vision. But even if he could see inside building components, would he understand the implications of what he was observing? Pretty nervy, talking about obligating us to report hidden damage! Can we really address serious problems for which there is no visual access? Should we? We don't promise to deliver real X-ray vision. We use something that may look like X-ray vision where we can to find faults which may otherwise go unnoticed or "hidden."

Warnings About This Paper - Increased Standard of Care

Discussing the detection of so-called "hidden" defects strikes fear into the heart of home inspectors.

It brings confusion to the legal profession.

It incites rage in the hearts and lungs of realtor - perfectly decent folks whose legal and contractual obligations to building sellers put them naturally in a position of conflicting interests with those of a property buyer. In other words, just slip your check under the door. Very close, thorough, detailed, building inspections make some folks nervous. This need not be so; it is unusual for even the most expert building or home inspection to discover defects which are so costly to cure that the purchase should be called into question.

Reading this paper or attending this lecture makes a tougher approach towards finding hidden defects part of our professional literature and thus raises the standard of due diligence for all of us. If you don't want to practice at this level you should stop reading this material or if you're seeing this in a classroom, leave the room now.

How to Detect & Report "Hidden" Building Defects - The Difficulties of How Clues are Presented

This topic divides home inspectors into camps: the ostrich camp (if we can't see it I'm not responsible for it and shouldn't have to even think about it), and the investigative camp (if there is a dangerous or costly problem for which we might find evidence and issue a warning we owe it to our client to do so).

For home inspectors, the fear is that if clues, even subtle ones, exist for a defect, we may be expected to find it. That's why it's difficult. Unlike a forensic engineer, we don't get to order destructive testing. Whichever camp is your tendency, better investigative skills can only improve your service to your clients and reduce risks for all.

The Nature of Vision - Predicting When You Will See or Don't See Something

This section of this paper has now been published as a separate article found as vision.doc and online as http://InspectAPedia.com/vision/vision.htm - The Nature of Vision - inspecting complex systems

The Nature of Inspection Clues and the Special Problems They Present

Let's look briefly at some underlying theory which will empower inspectors to see and think more forcefully and perceptively when they are in the field. Then we'll test the theory with actual practice. Finally, we'll see what conclusions we can make about how we might wish to modify our inspection practice.

Randomness Actually Aids in Building or Complex System Inspection

A natural, careful program? Sounds far too orderly! Home inspections are chaotic. There are people, control, and technical issues! Clues are often discovered randomly with respect to space and time.

Provided the inspector understands possible implications, provided the inspector maintains an inquiring mind, randomness is a help not a hindrance. It constantly presents fresh data, keeping the inspector alert for important information.

Randomness prevents the inspector from becoming routinized - an automaton which always sees, says, reports the same items is guaranteed to miss many costly and dangerous problems whose clues lie outside the habitual automatic range of action and thought.

The right attitude is essential. Cookbooks don't work. Checklists are incomplete. High-speed run-throughs cheat both the consumer and the property. Every house has a unique surprises. Look for them. Stay open to new, unfamiliar possibilities at every house. That's how to maximize the chance of discovering as much as possible about the property. Don't' assume! The last explanation for a familiar anomaly may not be correct this time.

Subtlety Hides Building or Complex System Defects

Little clues can point to hidden (or previously undiscovered) problems. Collect them.

Clues may be small visual anomalies, historical information, smells, sounds, both familiar and unfamiliar.

A small anomaly may defy understanding. That's ok. [1]

The most powerful clues are often simply construction practices which are known to lead to trouble.

If an anomaly doesn't lead to something, just keep it on mental file for a while.

Volume & Detail Obscures Building or Complex System Defects

Looking carefully at any complex system will produce a large volume of clues.

A large volume of clues will usually produce a large volume of "findings" or "defects."

This large volume is distracting, confusing, and makes for trouble for everybody.

How to Interpret & Respond to Difficult Inspection Conditions & Subtle Inspection Clues

Let's take a look at how to respond to these characteristics by seeing how we should respond to the difficulties cited above, and to sometimes subtle, context-dependent, or important but obscure building inspection clues.

Proper Building Inspection Focus: Handling the Signal to Noise Ratio Problem

Before you can start contemplating details, how do we deal with the signal-to-noise ratio problem?

That is, how do we select among the thousands of details available?

1. Stay away from unimportant details even if they "impress the client" (like testing stove burners) - they can cost big-time by diluting attention. An expert should sort detailed observations into clues that may justify further investigation and those that can with confidence be classed as a terminal point for an unimportant finding. For example, is a stain seen on a wall due to a hidden leak or due to soiling from a pet who rubbed against that area?

2. Avoid Selection Errors - making a mistake about which details get attention. Focus on the center of the large field of an easily-viewed steep-slope roof having no penetrations and in good condition should not be at the exclusion of a low-slope hard-to-see roof more likely to be worn and leaky.

3. Choose your focus based on the return on investment of your time and your client's money. Time spent assessing clues that suggest costly hidden problems is more important than time spent testing stove burners or determining which water lines are controlled by which shutoff valves (other than identifying the main shut-off).

If the clue (or actual defect) is likely to be connected to costly or dangerous findings, it should be pursued. If it is likely to be a dead-end, it should receive minimum attention. Why? Because the quantity and quality of your attention are limited and absolutely must be properly focused. [2]

Using a Promotion Theory of Observations To Detect & Report Building Defects

What is the Inspection Thought Process?

This is what most competent inspectors actually do:

1. make observations

2. consider implications

3. evaluate interactions among components and systems

4. weigh risks and probabilities of a potential defect - levels of fear

5. collect more data which increases or decreases level of concern (fear)

6. continue until the observations (fear) force the defect across thresholds of reporting

7. make recommendations

Using Building Defect Reporting Thresholds

As thresholds of reporting are crossed, report or act appropriately:

1. Lowest: consider but do not report - premature, keep the observation in mind and continue inspecting

2. Medium: report potential defects to client with advice: watch, investigate

3. High: report likely defects to client and advise further action

4. Extreme: report or find and identify virtually certain costly or dangerous conditions

Contextual Clues Can Expose "Hidden" Defects

Contextual clues, subtle little defects, visual or other anomalies, modifications, historical data, and site conditions may later suggest the presence of a costly or dangerous problem at probability high enough to justify a warning to the client even when there is no unequivocal, directly visible defect. (Example: very rusty old furnace in basement showing history of recurrent flooding, high risk of failed heat exchanger. Dangerous. Investigate further, reserve funds to replace unit.)

There is considerable argument among building inspectors about whether or not the inspector is obligated to report important building defects that are recognized by inference rather than by obvious simple visual data. We inspected a house with no accessible crawl space, a history of roof spillage around the foundation, trees close to the house, wood siding and framing below grade, and a bulged first course of aluminum siding all around the home. Anyone familiar with how aluminum siding is placed on a building knows that you start from the first or bottom course and hang siding up the wall. There is no way you could install a bulged first course. The bulge had to happen later - in this case from building settlement on crushing, rotted, or insect- damaged wood sills and floor framing. Yet outside there was no visible evidence of rot or insect damage to the house sills, since they were not visible (without invasive measures not part of a normal home inspection.).

The realtors present at this case study, and some of the building inspectors all argued that since one could not personally see a framing problem, there was nothing that should be reported. This camp argued that reporting a costly building damage condition was mere speculation.

I agree - that it is speculation, but I'd call it "informed" speculation. If the collection of contextual clues crosses a sufficient threshold of risk, such items should be reported. And of course, as most readers will suspect, later removal of siding showed very extensive sill and floor joist framing damage from termites and rot. At $100./linear foot just for sill repairs, this was a very costly problem that needed to be brought to the attention of the building buyer and owner.

Weighing the Risks in Deciding What To Report

Weigh the risk of angry realtor who feels that you should not be thinking so carefully about hard-to-see defects, or embarrassment of being mistaken by warning of a potential hazard against the risk of someone's injury or in the case of collapsing septic and cesspool systems, dangerous chimneys and flues, carbon monoxide and combustion air problems (can't see that one can you?), or even mundane falling hazards, there is risk of serious injury or even death!

How to Set Priorities for Building Repairs: - Dan's 3-D's

How do we cope with the quantity of details which present themselves? Focus attention on the high-risk topics.

When is the Building In Control of the Expenditure of the Client's Money?

Here are the classes of findings which deserve highest priority of attention. This little list can help the inspector and the inspector's client sort through the large volume of clues and "findings" that will be produced by any careful inspection of a building. For the following three items, the "building is in control of the client's money" in the sense that items in all three categories really need to be addressed promptly.

1. Things that are Dangerous [3]

2. Things causing rapid, costly Damage

3. Things that are essential that Don't Work [4]

Maintain this focus. Distinguish between what is potentially important (costly, dangerous, doesn't work) and what is not only unimportant (on a cost and risk scale), but can be a dangerous distraction. Don't waste energy, and don't mislead your client by permitting the client to think that the purpose of your inspection was to find defects.

When is the Client in Control of the Expenditure of the Client's Money?

Correcting other defects may be highly desirable, may make a building more economical to operate, or more comfortable, but they may be elective in that the client can decide when these expenses are to be incurred.

If a building has no insulation, the inspection and report need to point that defect out, and significant cost may be involved in its remedy. But delaying the installation of insulation means higher heating or cooling costs, not that the building is suddenly unsafe or deteriorating rapidly (excluding the freezing pipe problem in freezing climates). So this is an example of an item which, while important, can be deferred.

You may point out minor defects, as a courtesy or even as an added service, but keep yourself and your client focused on the purpose of the inspection: to reduce the chances of a costly or very dangerous surprise. Otherwise both you and your client will be very sorry later. Explain this focus to your client.

Isn't this what you're already doing? Then why talk about it?

Improving Defect Recognition By Thinking About Inspection Successes and Mistakes

Case studies show that serious defects are sometimes are discovered by a small triggering clue. Some would have been discovered anyway, some possibly not.

Study Inspection Successes

1. What did you find?

2. What was the first clue?

3. How did you follow it to a conclusion?

4. How glad were you that you found it?

Study Inspection Errors & Failures

1. What did you miss?

2. How was it later discovered?

3. How sorry are you that you missed it?

4. What could you have seen or thought that might have permitted an accurate guess, warning, prediction?

We can develop a very simple methodological way of thinking which is helpful without making us routinized. This paper uses mini-case studies of visible conditions to suggest interactions among systems and therefore likely areas where serious defects may be found.

Don't bother memorizing the specific case study conditions which follow.

The objective is to develop a way of

1. Thinking [the "Zen" of inspecting complex systems]

2. Seeing [the nature of vision for complex systems]

3. Thinking further [the promotion theory for inspection clues]

4. Investigating further [thresholds of action for inspection conclusions]

5. Concluding [a decision of the level of risk involved and an opinion of the need for action]

6. Advising [further investigation, repair, or notification of an immediate hazard]

to substantially improve the quality of a professional inspection by reducing risk for both the client and the inspector.

Some Conclusions About Inspection Methodology - What's Needed

Inspection performance can be substantially improved, adding value and reducing risk to all parties.

Techniques can improve visual detection of defects present on the system being examined, reducing inattentional blindness by a variety of methods

Techniques for focusing vision and avoiding distraction can improve visual detection of clues suggesting "hidden" defects

Methods of thought regarding collected clues can improve the accumulation of evidence, the promotion of possible to probable defects, and thus recommending appropriate action

Regardless of views about inspecting and reporting limitations expressed by inspectors, few clients would find acceptable an inspector who indicated that regardless of the possible implications of external evidence the inspector intends to refuse to warn about costly or dangerous hidden damage for which there was less than full clear visible evidence.

How to Monitor and Improve your Inspection Methodology

It should be possible for each inspector to significantly improve his/her field performance by making an ongoing study of those cases where a costly or dangerous defect was identified "just barely" or with difficulty.

Scrutinize your inspection process:

What is the significant finding that we made?

What was the very first clue that got us thinking about it?

What did we think then?

What did we do next?

How did we collect and correlate information?

When did we first understand that there was probably a serious defect?

What additional clue, observation, thought led us to that conclusion?

What additional information was we able to collect?

How did we find and correlate it to come to a final identification or other conclusion that this was, or was not, a significant concern?

In sum, what small anomaly did we observe that led to an important conclusion?

This approach by no means suggests that you cast out more strict and methodical investigative procedures. Checklists and procedures are most helpful for determining that something is missing, or that you've left something out. But no inspection checklist, no procedural guideline, can ever possibly cover every anomalous condition nor every possible major defect that may be present at a property.

Inspection Mind - Focus A final note about the Zen-mind of home inspection

We should always be asking: what's different here? What surprise is waiting? What's holding that up? How do air, moisture, people move in the building? How does that work? What was changed here? Why did they do that? Did it work? What did we later find out we missed at an inspection? How could we have seen it?

Addendum: Background thoughts behind inspection methodology:

Delivering value for fee as a professional consultant

What is the nature of the most valuable possible advice to a client regarding property condition?

- It is as complete as possible within the limitations of the process

- It is as accurate as possible both in conclusions and advice

- It is as reasonable and economical as possible both in priority and level of attention and repair.

Inspection Error Types:Borrowing from Statistics: type we and II Inspection & Reporting Errors

Researchers are concerned about Type we Errors and Type II Error. Or: the error of accepting a false hypothesis and the error of rejecting a true hypothesis.

Most inspectors think about the error of rejecting a true hypothesis.

A true (in this instance) hypothesis: "the fire chamber is leaky and dangerous."

An erroneous rejection of a true hypothesis:

"The furnace is new, we don't see any rust, so the fire chamber is ok."

Observations missed:

- burn marks on back of furnace jacket where flames escape a crack caused

during shipment - the confident inspector didn't look at all sides of the unit.

Why was this observation missed?

- assumption error (new equipment)

- attention error (tired inspector)

- distraction error (irksome realtor, client, kid, dog, owner, parent)

- inaccessibility - (but might the inspector have noticed something like a crushed cabinet corner that might have raised a question?) Here's "X-ray vision!"

Adverse Selection: Borrowing from the Insurance Industry - Making Safe but Bad (for the Client) Recommendations

Adverse selection of choices - when a consultant gives advice to the client in a manner which benefits the consultant (minimizing his risk or maximizing his income) rather than in a manner which most benefits the client (appropriate expenditures based on risks and probabilities).

Causes of Adverse Recommendations

Client makes the inspector nervous

Inspector knows s/he is not informed on a given topic

Inspector is a novice, knows it, and is afraid to show ignorance

Inspector is worried about hidden damage

Contractor takes the safe, profitable choice: replace all rather than fix

So the inspector recommends that a component be replaced, or that costly destructive inspecting be performed, when it's not necessary and not appropriate. The cost is a misapplication of both attention and money on everyone's part.

How to Avoid Making Adverse Recommendations

Engage in real risk management rather than simply giving advice that is intended to protect the inspector at the client's cost.

Real Risk Management for Home & Building Inspectors

Inspections are not about eliminating risk

We cannot reduce risk to zero. To attempt to do so would be to tear everything apart, replace everything, and in the course of reassembly, make new errors which would lead to still more problems.

Inspections are about reducing risk

We identify visually detectable problems, visually detectable risks for which there is sufficient data to suggest attention, and selecting levels of response appropriate for economic and safety reasons.

How can we push risk reduction further in a cost-effective way?

First, why should we work to further reduce risk?

Reducing risk for the client adds value to the inspection - it's good business.

Reducing risk for the client reduces also risk for the inspector.

We can substantially reduce risks of major costly or dangerous surprises. Estimates of payback at any competent inspection, comparing fee to the dollar-cost of previously unknown repairs plus the cost of savings accruing from early recognition of those topics range from 10:1 to 1000:1.

Second, how can we push risk reduction further, cost effectively?

Improve professional competence, learn details of construction, systems, failures, repairs, proper practices.

Improve inspection technique, practice methods which develop skill at recognizing problems

Numerous other topics (see end of this paper).

One technique for risk reduction: develop proper inspection focus

Home Inspection Case Studies Contextual Clue Detection, Interpretation, & Defect Reporting
StructAPedia ^®

Notice that we have clients in many of these photographs. Why?

Spotting Hidden Sink Holes at Sites

There are plenty of contextual clues that can raise a dangerous sinkhole condition to one needing to be reported, especially in states where sinkholes are a known issue. See our separate presentation on this: http://InspectAPedia.com/structure/sinkholes.htm - Can X-Ray Vision Warn of Sink Holes?

Termite & Carpenter Ant Hidden Damage

[Link to separate presentation & photos to be added here] Contextual clues suggesting Wood Destroying Insect Infestation - a case study in photographs

Hidden Building Leaks, Basement Water Entry, Moisture, Ice Dams

See Detecting and Correcting Attic Condensation and Preventing Ice Dam Leaks in Buildings and [Link to separate presentation to be added] "A comparison of methods for moisture detection in buildings" in which we tested multiple moisture detection methods and then disassembled the building to see where moisture actually was.

Spotting Hidden Building, Site and Environmental Hazards

See Indoor Environmental Issues.

Spotting Hidden Toxic or Allergenic Mold

See Inspect the property for mold, other contaminants, and mold-causing conditions

See Mold Investigation Tips for Home Inspectors

Spotting Lead Paint

Was the building built before 1978? Is there any paint?

Spotting Fiberglass Hazards

See Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation

Spotting Asbestos Hazards

See How to find and recognize asbestos in buildings - visual inspection methods, list of common asbestos-containing materials

Spotting Radon-Inviting Construction Details

Like open blocks at the top of a concrete block basement wall, cracks in the floor slab, basement toilets through slabs. And some areas are known to be over "hot" uranium-bearing rock, such as the "Reading prong." But one cannot know if there is a radon problem in a building without conducting a proper test.

Spotting Economic Issues - Defunct Hazards UFFI, Enviro-Scare

Spotting Hidden Underground storage tanks

Observations: steel pipe in small bald area of ground - blocked with wood chock; near the barn - ask yourself: What is it?

Implications: what about UST for old farm vehicles, now abandoned. Collapse and Environmental issues.

Observations: dual sump pumps, very wet basement - distracting and obvious older oil tank in basement, rusty - don't make an assumption error that there is no older tank

Look again next to those sumps!

dual-oil lines coming through basement wall, abandoned oil lines right at the furnace, flood lines on furnace wall - don't make a capture-error: note the furnace issue and go to consideration of the abandoned buried heating oil tanks

Implications: There used to be? Or still is a buried oil tank

Further observations: coffee can found under bushes, ignored before, this time, pick it up! - covers old tank, viewed with flashlight (not on hand at 1^st outdoor trip around) contains liquid

Implications: old buried oil tank, not in use, not properly abandoned, possible environmental issue/collapse hazard, significant cost and history of severe basement flooding, high risk of water damage or rusted heat exchanger on furnace, i.e. safety and cost issues

See Home Heating Oil Underground & Above ground Oil Storage Tank Problems & Solutions, and the inspection and testing articles linked-to from this page.

Septic Systems and Site Hazards- detection and reporting

Observations: microscopic site, lakefront house, crowded area, private well/septic, very rocky hill behind house, no room for septic components, debris outside, note pipes through wall and in ground outside kitchen; Recent pressure-treated platform roughly 3m x 3m abutting house wall; Limited area crawl space;

Question: where could the septic be?

More data available: note pipe routing in crawl space heads right for house wall near that wood "deck".

More observations: lift wood deck with help from client - very cautiously observe collapsing steel septic tank

See The Septic System Information Website
See Inspecting, Testing, & Maintaining Residential Septic Systems
See Class on Inspecting Septic Systems

Huge multi-section 3-story Old +"New" Barn, "repaired" for sheep, vehicles, storage - finding defects

Observations - recent structure attached to old barn - look at connections, new and esp. post and beam rot/insect damage? missing members? improper/inadequate repairs

Implications: amateur workmanship on connections, risk of collapse, cost to cure, control access pending repairs

More observations:

Old framing, be careful on that hay-covered floor! - child/kid hazard

New interior roof framing, rafters improperly supported on wall

Detail of above

Old framing repaired using pipe hangers - tons of load on single

Member tying together 3-story P&B walls!

Conclusions:

Unsafe conditions for kids - board up the barn pending repair

Inform client - avoid later discoveries that make client look as unhappy as this woman!

Warning: Don't let unfamiliar structures distract you! (boat-deck takes on a new meaning)

Farm Silo, Converted to Living Space ca 1985 - noticing defects

Observations, outside: missing steel tie-rod band at mid-height, rough surface - poor maintenance, modern windows back-sloping in wood shingle roof, some bands not level

Observations, inside: bands removed at bottom for entry to sauna, >open ceiling, heat tapes, repaired pipes, exposed wiring - history of freeze ups, bands removed at top for entry to bedroom, badly rotted windows

Warning: Don't let one dramatic finding cause you to miss something more important:

gaps in walls, open to outside, (similar gaps visible. in kitchen below, caulked, open, no pix)

Implications:

structural movement, risk collapse? poor choice of windows, extensive rot, risk concomitant insect damage

New/Recent construction, common maintenance by owners' association - common defects

Observation - recent construction: Siding at ground, Nearby trees (leaves blow into gutters), General maintenance company on-duty - may not care about details - just makes more work., Wood-landscape tie steps against front door and front wall - higher than probable sills, ROT

Implication:

Highly suspect insect/rot damage at sills.

Further observation in basement :

Removed insulation (not usual practice) to disclose gross sill damage-carpenter ants & rot

Old Construction, recent incomplete "repairs" to house structure - recognizing defects

Observations - insect damage/rot risk, no access below: slate patio poured against wood siding on old house (or new) slate settled, traps water

Implication: foundation cracking, insect and rot damage, (no further access, general warnings made consistent with next example, same house)

Observations - more insect-damage/rot risk, access below is possible: drainage towards house, ell forms inside corner, siding at ground contact, no gutters on roof eaves, deep drip lines below eaves, extensive structural repair in progress at wall bottom, repair left old damaged sills in place, new concrete block foundation on 1860 house

Implications: history of gross water entry, flooding, sill and floor and possibly wall rot and damage, also insect damage, probably water, earth, frost-load damage to previous foundation.

Question: what has been done to prevent damage to the new foundation and wall repair work?

Risk: future water damage, future sill crushing,

structural movement, costly repair

Prior repairs, jacking, temporary support, bulged wall, floor loads:

Observation: (same house) bulged side wall down-hill from previous damage/repair, window pushed out of wall

Implications: ongoing movement, movement caused during jacking for foundation repair, hidden rot/damage in wall

Further investigation: found post and beam floor joist tenons rotted off, not connected to sill, sill tipping and moving, amateur repairs with sister 2x6's face nailed to rotted sill and to joists, heavy load above floor from Franklin stove and slate hearth >and large amounts of tenant possessions, 3 teleposts adding supporting floor from below.

Implications: unsafe wood stove, incomplete and improper structural repair work, significant cost to cure, risk structural damage or collapse

Run-down Country Cottage - typical defects

*** This is an important case as it lets the inspector draw some important inferences: ***

Observations: drainage towards back of house, rocky hill (see hat), clogged gutters, heaved walk at rear wall, siding at ground, rot and hole in sill at back door

Additional Observations, Inside: buckled block wall, horizontal cracks in mortar joints, flood lines at bottom of furnace, exfoliating steel Lally column base, previous water heater rusted to death

Implications: history of water entry and recurrent severe flooding, unsafe furnace, (rusted heat exchanger?) (actually this is a different furnace, photographed through the inspection door), structural repairs needed at rear wall, drainage and site work may be needed outside, gutter maintenance needed, bug and rot damage to sills

Warning: Don't be distracted by funny construction: (trailer/house)

Chimneys - Hidden Defects: collapsing liner, frost damage, movement, loose, no rain cap - spot these defects

Observation: collapsing flue liner

Implications: unsafe blocked flue, improper heating system operation

Conclusion:

Unsafe conditions - risk total blockage,CO, etc.

Certain cost to repair chimney, possible whole flue re-line needed

Furnace or Boiler Chimney - clues indicating poor, possibly unsafe system operation

Observation: Soot at chimney top, fresh, (oil-fired)

Implications:

sooty heater operation, poor system operation, possibly just maintenance, could be very serious: blockage, draft, fire chamber, or other operating problem

Further Investigation: look for:

back pressure burn on boiler face at inspection port

pile of replaced ignition transformers damaged by back pressure and heat

damaged combustion chamber liner (obstructs flame, makes soot) (no slide)

Implications of these inspection clues:

Draft, fire chamber, oil burner defects, other possible defects:

condensation, CO, odors (depending on fuel gas or oil)

Conclusions:

Possible unsafe condition

suspect heating problems

possible costly chimney reline

Recommendations:

Competent service, look at chimney, boiler, system operation ASAP

Heating Flues - Interior equipment, long runs - spotting safety hazards

Observations:

long flue run on gas water heater into oil-fired boiler vent

burn and char marks around heater draft hood

Implications:

back pressure, draft problems, poor operation, unsafe venting,

risk of CO from water heater

Conclusions:

Potentially unsafe condition

Observations:

long vent run, shared with gas

burn marks at water heater top by draft hood

Implications:

back drafting oil appliance out gas fired water heater

history of draft problems

poor, possibly unsafe system operation

Observations:

long vent run

vent enters very bottom of chimney

no cleanout door lower than vent entry to chimney sealed-up barometric damper

Implications:

History of chimney/ draft problems, same as above.

Recommendation: check for unsafe chimney ASAP; system needs proper service.

Roofs - how to inspect, what not to miss

Roofs with limited access: how to warn about defects in areas not accessible - context inspection

Observations:

Roof valley runs into or abuts a chimney - promote the risk of leaks or ice dam leaks (in freezing climates)

Implications

clogging, debris, leak, shingle damage, ice backup

Conclusions

inspect, clean, repair, expect leaks

dividend: note bad flashing, shingles run up and tarred to chimney

Observations:

valley traps snow - promote risk

broken, missing shingles on recent roof

low near-flat area with roll roofing also traps snow

Implications:

ice dams, chopping damage, leaks

Observations:

low-slope, nearly flat roofs, from ground

Implications:

ice dams, damage, leaks - look at the ceilings inside, and in attic if accessible - promote risk

Observation: bags in attic - Implication: audience response.

Interior Inspection - Finding Defects

Previous building interior damage, repair, cover-up:

Observations:

missing flooring, semi-round hole, charred edges,

floored-over, charred marks at edges of hole

Implications:

previous fire, look for other damage

Insulation Defects in Buildings

Multiple materials may be present:

Observations:

Basement at wall bottom, vermiculite spilling out - was poured in walls (may contain asbestos), but *** avoid an assumption error - keep looking: and notice the UFFI oozing out from another building cavity - previous environmental issue, current MCS/marketing issue

Observations:

Rock wool at eaves - >*** avoid an assumption error, look in that gap by the entry into the attic!

Keep looking: funny corrugated material visible - looks like asbestos pipe insulation

Observation:

Unique area of snow melt - Implications: audience response

Observation:

Unusual flooring material - Implications: audience response

Plumbing, Wells, Water Supply - Detecting Common "Hidden" Building Defects

Abandoned equipment and recent repairs can tell history and predict future:

Observation:

Pile of old tankless coils in basement

Implication:

Hard water, recurrent clogging, bad hot water flow

Observations:

well located in pit uphill behind house, rusty rotting cover -

in well pit, bucket covers open well casing - implies unsanitary water

recent plumbing repairs (shiny pipes) - implies temporarily unsanitary water

well pit floods - implies unsanitary water

outside, old foot valve and piping found on ground - implies sloppy repair work, unsanitary?

outside old well pump found on ground - same

near house, wet soggy area in line with water pipe trench between well and house - implies leaky

water line from pump to house?

pump cycles periodically even when water is off in house - confirms leaky water pipe?

Implications:

history of unsanitary water -

unsafe cover over well - child/adult hazard

history of repairs to well - sloppy work, left debris

leaking well line between house and well may have burned up previous pump?

Further observation:

Amazing water runs into bath tub - predictable?

Inspecting Heating Systems - clues indicating important hidden defects

Leaky indoor oil tank - Detection & Reporting

Observations enabling the inspector to spot hidden oil spill oil tank concerns

oil odors entering basement - lots of possible explanations. What did you see at chimney top? What did you see outside about oil delivery piping?

recent delivery? recent service? oil spills found ? operating problem ? tank leak

Tank looks pretty clean, but there's a big wet area

also look at welded seams; also look for seepage at filler pipes;

Heating Appliance Combustion Air Safety Defects - Detection & Reporting

Observations:

boiler in small air-tight room in new house

3- dryer-vent in end-wall appears only air supply

outside vent is screened and jammed with stuck flapper

Implications:

inadequate combustion air, possibly unsafe operation

Bonus Inspection Expertise Questions - other unusual building observations and what they mean

Photos on file - to be added here

Catwalk

Attic air conditioning system

Tree fell on roof ( 2 slides)

Footnotes

[1] Your professional reputation is not reduced by saying you don't know, or you're not sure. Your professional reputation is destroyed, irrevocably, by bluster and bullying. Everybody (except you who do it) sees right through the baloney of arm-waving.

[2] Example: a bad burner on a range, while annoying, is 1. excluded from ASHI scope and 2. very unlikely to be connected to a significant expense at the property. Focus on this clue builds an inappropriate expectation in the mind of your client that the purpose of the inspection is to assure that trivial items are in order: stove burners, oven temperature accuracy, dishwasher cycling, gate latches. These are absolutely not the purpose of your inspection, and not only does attention to them ms-communicate to your client, it also dilutes your total attention and risks an increased probability that you fail to attend something costly or dangerous.

[3] If your neck is broken because you fell down the stairs (a boring defect but the most common source of injuries and lost time in North America) then it doesn't' matter a hoot that the roof leaks or the oven thermostat is inaccurate.

[4] Including things that don't work at contemporary standards of safety and reliability.

Conclusions from Case Studies

What did you see, learn, think, conclude

What supports those conclusions

What do you report

What are the priorities of concern?

tank abandonment issue

structural repair issue

immediate child hazard - lock up access

insect pest treatment?

Predictions:

Other inept repairs on the older structure - take a look

Frequently Asked Questions (FAQs) about virtual "x-ray vision" using clues to see subtle building & mechanical system defects or environmental hazards

...

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

• 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: johncranor@verizon.net
• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
  • Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
  • Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
  • 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.
• Dr. Jennifer Church, Vassar College, Poughkeepsie, NY
• Steve Vermilye, Shelter Systems, Inc. New Paltz, NY
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06

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.

• 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.,
• ...

Sinkholes and Sudden Land Subsidence References, Products, Consultants

• "A Hole in the Ground Erupts, to Estonia's Delight", New York Times, 9 December 2008 p. 10.
• History of water usage in Estonia: (5.7 MB PDF) jaagupi.parnu.ee/freshwater/doc/the_history_of_water_usage_systems_in_estonia.pdf
• "Quebec Family Dies as Home Vanishes Into Crater, in Reminder of Hidden Menace", Ian Austen, New York Times, 13 May 2010 p. A8. See http://www.nytimes.com/
• "Quick Clay", Wikipedia search 5/13/2010 - http://en.wikipedia.org/wiki/Quick_clay
• Florida DEP - Department of Environmental Protection, & Florida Geological survey (http://www.dep.state.fl.us/geology/default.htm) on Florida sinkholes: Effects of Sinkholes on Water Conditions Hernando County, Florida, Brett Buff, GIS in Water Resources, 2008, Dr. David R. Maidment, Photos - Tom Scott, Florida Geographic Survey - Web Search 06/09/2010 - http://www.dep.state.fl.us/geology/geologictopics/jacksonsink.htm
  and - http://www.dep.state.fl.us/geology/geologictopics/sinkhole.htm
  also see
  Lane, Ed, 1986, Karst in Florida: Florida Geological Survey Special Publication 29, 100 p.
  
• Foundation Engineering Problems and Hazards in Karst Terranes, James P. Reger, Maryland Geological Survey, web search 06/05/2010, original source: http://www.mgs.md.gov/esic/fs/fs11.html
  Maryland Geological Survey, 2300 St. Paul Street, Baltimore, MD 21218
• "Frost Heaving Forces in Leda Clay", Penner, E., Division of Building Research, National Research Council of Canada, Canadian Geotechnical Journal, NRC Research Press, 1970-2, Vol 7, No 1, PP 8-16, National Research Council of Canada, Accession number 1970-023601, Quoting from original source

The frost heaving forces developed under a 1 ft. (30.5 cm) diameter steel plate were measured in the field throughout one winter. The steel plate was fixed at the ground surface with a rock-anchored reaction frame. heave gauges and thermocouples were installed at various depths to determine the position and temperature of the active heaving zone. The general trend was for the surface force to increase as the winter progressed. when the frost line approached the maximum depth the force was in excess of 30,000 lb (13,608 KG). Estimates of the heaving pressure at the frost line ranged from 7 to 12 psi (0.49 to 0.84 KG/cm) square during this period. The variation of surface heaving force was closely associated with weather conditions. Warming trends resulting in a temperature increase of the frozen layer caused the forces to decline.

• "Geoscape Ottowa-Gatineau Landslides", Canada Department of Natural Resources, original source http://geoscape.nrcan.gc.ca/ottawa/landslides_e.php - quoting from that source:

  Leda clay slopes in the Ottawa valley are vulnerable to catastrophic landslides. More than 250 landslides, historical and ancient, large and small, have been identified within 60 km of Ottawa. Some of these landslides caused deaths, injuries, and property damage, and their impact extended far beyond the site of the original failure. In spectacular flowslides, the sediment underlying large areas of flat land adjacent to unstable slopes liquefies. The debris may flow up to several kilometres, damming rivers and causing flooding, siltation, and water-quality problems or damaging infrastructure. Geologists and geotechnical engineers can identify potential landslide areas, and appropriate land-use zoning and protective engineering works can reduce the risk to property and people.

  Deposits of Leda clay, a potentially unstable material, underlie extensive areas of the Ottawa-Gatineau region. Leda clay is composed of clay- and silt-sized particles of bedrock that were finely ground by glaciers and washed into the Champlain Sea. As the particles settled through the salty water, they were attracted to one another and formed loose clusters that fell to the seafloor. The resulting sediment had a loose but strong framework that was capable of retaining a large amount of water. Following the retreat of the sea, the salts that originally contributed to the bonding of the particles were slowly removed (leached) by fresh water filtering through the ground. If sufficiently disturbed, the leached Leda clay, a weak but water-rich sediment, may liquefy and become a 'quick clay'. Trigger disturbances include river erosion, increases in pore-water pressure (especially during periods of high rainfall or rapid snowmelt), earthquakes, and human activities such as excavation and construction.

  After an initial failure removes the stiffer, weathered crust, the sensitive clay liquefies and collapses, flowing away from the scar. Failures continue in a domino-like fashion, rapidly eating back into the flat land lying behind the failed slope. The flowing mud may raft intact pieces of the stiffer surface material for great distances.

• Kochanov, W. E., 1999, Sinkholes in Pennsylvania: Pennsylvania
  Geological Survey, 4th ser., Educational Series 11, 33 p., 3rd printing April 2005, Pennsylvania Department of Conservation and Natural Resources / Bureau of Topographic and Geologic Survey, DCNR Educational Series 11, Pennsylvania Geological Survey, Fourth Series, Harrisburg,
  1999 - web search 06/05/2010, original source: http://www.dcnr.state.pa.us/topogeo/hazards/es11.pdf - Quoting from the document introduction:
  The first 18 pages of this booklet contain an explanation of how sinkholes develop. In order to tell the sinkhole story, it is important to discuss a number of related geologic disciplines. The words used to describe sinkholes and these disciplines may be a bit unfamiliar. However, general explanations are given throughout the booklet to help clarify their meanings. Key words are printed in bold type for emphasis. The more important ones are defined in a Glossary that begins on page 29. The remaining sections, starting with “Sinkholes in the Urban Environment” (page 18), deal with sinkholes and their impact on our environment. This includes recognition of subsidence features and sinkhole repair.
• [1] Sarah Cervone, [web page] data from the APIRS database, Graphics by Ann Murray, Sara Reinhart and Vic Ramey, Vic Ramey is the editor. DEP review by Jeff Schardt and Judy Ludlow. The web page is a collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection contact: varamey@nersp.nerdc.ufl.edu [A primary resource for this article
• [2] Center for Cave and Karst Studies or the Kentucky Climate Center, both at Western Kentucky University
• Vanity Fair - web search 06/04/2010 http://www.vanityfair.com/online/daily/2010/06/what-caused-the-guatemala-sinkhole-and-why-is-it-so-round.html
• Sinkholes, Virginia Division of Mineral Resources,
• Virginia Department of Mines, Minerals and Energy, www.dmme.virginia.gov Virginia Department of Mines, Minerals and Energy Division of Mineral Resources 900 Natural Resources Drive, Suite 500 Charlottesville, VA 22903 Sales Office: (434) 951-6341 FAX : (434) 951-6365 Geologic Information: (434) 951-6342 http://www.dmme.virginia.gov/ divisionmineralresources.shtml - Web search 06/09/2010

Sink Hole & Related Engineering References

• Newton, J. G., 1987, Development of sinkholes resulting from man's activities in the eastern United States: US Geological Survey Circular 968, 54 p.
• Sinclair, W. C., 1982, Sinkhole development resulting from ground-water withdrawal in the Tampa Area, Florida: U.S. Geological Survey Water-Resources Investigations 81-50, 19 p.
• White, W. B., 1988, Geomorphology and Hydrology of Karst Terrains: Oxford University Press, New York, 464 p.
• Williams, J. H. and Vineyard, J. D., 1976, Geologic indicators of subsidence and collapse in karst terrain in Missouri: Presentation at the 55th Annual Meeting, Transportation Research Board, Washington, D.C.
• Barry F. Beck, A. J. (1999). Hydrogeology and Engineering Geology of Sinkholes and Karst. Rotterdam, Netherlands: A. A. Balkema.
• Beck, B. F. (2003). Sinkholes and the Engineering and Environmental Impacts of Karst. Huntsville, Alabama: The American Society of Civil Engineers.
• Beck, B. F. (2005). Sinkholes and the Engineering and Envrionmental Impacts of Karst. San Antonio, Texas: The American Society of Civil Engineers.
• Tony Waltham, F. B. (2005). Sinkholes and Subsidence, Karst and Cavernous Rocks in Engineering and Construction. Chichester, United Kingdom: Praxis Publishing.
• Whitman D., G. T. (1999). Spatial Interrelationships Between Lake Elevations, Water Tables, and Sinkhole Occurence in Central Florida: A GIS Approach. Photogrammetric Engineering and Remote Sensing , 1169-1178.
• Cited References from this article:
• #3. Detecting Sinkholes with Geophysics, Enviroscan, Inc., Lancaster PA 717-396-8922 email@enviroscan.com www.enviroscan.com 2003
• Sinkholes in Guatemala, Guatemala City, Wikipedia - web search 06/04/2010 - http://en.wikipedia.org/wiki/Guatemala_City