Photograph of a collapsing roof and attic structure on a historic building in Saugerties NYAdvanced Home Inspection Methodology - Developing your X-Ray Vision
A Promotion Theory for Forensic Examination of Complex Systems

  • ADVANCED INSPECTION METHODS - CONTENTS: Advanced building inspection methods and strategies are suggested in order to improve the completeness and accuracy of the inspection of any complex system. Complete, free online text on advanced home inspection techniques. Home inspection methods & procedures to maximize the chances of finding important defects
  • POST a QUESTION or READ FAQs about forensic building inspection, home inspection, environmental inspection & testing

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Home inspection methods free online course:

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.

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 2017, All Rights Reserved.

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 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 5/19/2014Updated 3/8/2013 - priorities & maintenance; updated 1/6/2014 cross-references.
Updated 30 April 2015
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, 4th 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

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.

Article Contents

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 - 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]

The Fear-o-Meter: Promotion Theory of Observations To Detect, Investigate Further, or Report Building Defects & Hazards

Enviro scare curve of fear vs time (C) Daniel Friedman

As thresholds of reporting or action are crossed, the inspector musty report or act appropriately to her or his overall assessment of the level of risk. We pose first a simple four-point fearometer scale, followed for those who perfer, a ten-point fearometer scale.

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

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

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

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

Contextual Clues Can Expose "Hidden" Defects. And the inspector must weigh these risks in deciding when to recommend further investigation as well as when to conclude that a significant cost or safety hazard is present even when information is of necessity, incomplete.

See FEAR-O-METER for complete Details about these concepts.

Set Priorities for Building Repairs

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? Dan's 3-Ds

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]

More about setting these priorities is at FEAR-O-METER

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: - 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

Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues

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 1st 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!


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)


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


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


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)


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)


Possible unsafe condition

suspect heating problems

possible costly chimney reline


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

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


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

burn and char marks around heater draft hood


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

risk of CO from water heater


Potentially unsafe condition


long vent run, shared with gas

burn marks at water heater top by draft hood


back drafting oil appliance out gas fired water heater

history of draft problems

poor, possibly unsafe system operation


long vent run

vent enters very bottom of chimney

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


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


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


clogging, debris, leak, shingle damage, ice backup


inspect, clean, repair, expect leaks

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


valley traps snow - promote risk

broken, missing shingles on recent roof

low near-flat area with roll roofing also traps snow


ice dams, chopping damage, leaks


low-slope, nearly flat roofs, from ground


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:


missing flooring, semi-round hole, charred edges,

floored-over, charred marks at edges of hole


previous fire, look for other damage

Insulation Defects in Buildings

Multiple materials may be present:


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


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


Unique area of snow melt - Implications: audience response


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:


Pile of old tankless coils in basement


Hard water, recurrent clogging, bad hot water flow


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?


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


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


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


Attic air conditioning system

Tree fell on roof ( 2 slides)


[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?


Other inept repairs on the older structure - take a look


Continue reading at VISUAL PERCEPTION ERRORS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see FEAR-O-METER a promotion theory to convert risk of hidden defects & hazards into action thresholds

Suggested citation for this web page

ADVANCED INSPECTION METHODS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman