Just about everyone reporting vibration damage from construction or blasting will be asked, usually almost immediately after their damage report, to have their damaged home "inspected" on behalf of the project contractor, contractor's insurer, the project sponsor and its insurer, the home owner's insurer, and, perhaps, others. In even rarer cases, the contractor will ask to carry out inspections and/or "studies" of various sorts before construction start. Because such inspections occur before the homeowner has had much experience in handling a damage claim, the potential for the homeowner to be misled or taken advantage of is very real. Following are some tips to help you in the conduct of inspections, avoid being a casualty of poorly supported or unscientific opinions, and challenge them factually, if they are offered by inspectors.

About Inspectors

The chosen inspector may be a contractor employee or executive, an engineer, a scientist, a technician or an insurance claim adjuster. The extent of the inspector's real knowledge about vibration damage can be highly variable, but almost never encompasses any significant scientific depth. Some experience with blasting vibration and standards does not automatically make one an expert in construction vibration, which has a whole list of significant differences from blasting vibration. Claimed "experience" in looking at damaged homes is no indicator of, or substitute for, genuine, in-depth, scientific knowledge of what vibration damage looks like, what levels of vibration can cause damage, and what vibration standards really mean in the context of the home and construction project at issue. 

Since most of the inspectors work for someone other than you, their likely inclination in a damage case is often predictable. Some inspectors may even cross the line from giving facts and real scientific opinions to offering "science-based" questionable assertions which ignore, or even directly contradict, scientific data and understanding. For these and other reasons, you or your attorney should identify and retain a qualified vibration damage expert of your own, in addition to an engineer expert, as early as possible.

Find Out the Facts

One way to get a sense of what you might expect from such an "inspection" is to look at the web site of the inspecting firm before the inspection. Most large firms who do inspections for insurers have such sites. Many of them have pages dealing with construction damage which say, in essence, that "construction can't cause damage". Such statements are clearly false, as a public video by at least one insurer of contractors shows.^[1] If the inspection firm has a web site with a page or pages devoted to construction vibration damage, be certain to print that page to both hardcopy and a PDF file. You can, if necessary, cite that information later to show that the inspection firm may be biased or unqualified, calling into question the reliability of its claims.

Human-Caused Cracking

It is common for inspection firm web sites, and even inspectors, to cite studies which show that human activities (running, jogging, exercise equipment as at right) can, in some cases, generate home vibration velocities comparable to some of the ground velocities caused by construction. Such statements are almost always irrelevant and misleading in the context of the house-wide damage, which is typical of most construction vibration damage examples. It has long been known that the potential for damage from human activities is confined to a very small area around the activity. In most examples, the vibrations caused by human activities decrease to well below construction vibration standard limits, even in the adjacent room.^[5]

Such citations are also misleading, in that they compare two different quantities; the human activity citation directly measures the house vibration within a few feet of the activity site; the other measures ground vibration, typically at 40-100 or more feet from the work site. The ground vibration measurement does not take into account resonant amplification in the home or building structure, which can result in a much larger structure vibration velocity than the ground vibration velocity. Vibration standard limits almost invariably cite ground vibration velocities, not home vibration velocities.

Human activities might, in theory at least, be a possible explanation for a hairline crack or two within a few feet of the most strenuous activities (e.g. stomping, jumping, door slamming) in extreme cases, but people simply can't generate enough power to do house-wide damage, let alone create damage affecting an entire property.^[5] By way of illustration, consider that a typical person can generate about 0.1 horsepower indefinitely and up to about 1 horsepower in short bursts. One construction excavator, a Caterpillar Model 320 BL (the one shown several times in the CVDG), has a specified net power of 128 horsepower, well over a thousand times that which a human can generate over the long periods that the excavator can operate.

Even if damage is confined to one location in which humans have been seen during the lifetime of the house, that mere fact doesn't prove that the damage is due to human activity. Supporting a human activity damage causation assertion would require far more real evidence, including detailed knowledge of the entire use history of all the sites in the home where cracking or other damage is observed and correlation of that history with damage appearance, at a minimum. Asserting human activities as a possible cause of house-wide damage is little more than unsupported speculation in the absence of such additional information.

Using the Scientific Literature

Insurer inspector reports or their company web sites may offer citations of 30-50 year-old scientific literature, usually involving blasting, not heavy equipment-caused vibrations, to support their "conclusions". Such literature, while useful in some aspects, is often misleading with regard to both more current literature of construction vibration damage and the use of modern construction equipment. More recent studies find that modern equipment is more damaging than the older studies imply (see Vibration and Distance for more, including printable full-size graphics which show expected vibration velocities for various modern equipment at different distances). As discussed elsewhere in the CVDG, vibration standard velocity limits have steadily decreased since 1970 (see right), as researchers have realized that the older standards and studies were underestimating the potential for both construction and blasting damage.^[2],[8]

Inspectors and their web sites may contend that they have "guides" or "calculations" which "prove" that damage cannot have been caused by construction. Ask why and on what basis they offer such a conclusion, including the scientific references they cite in drawing it. Ask for copies of those references to be supplied to you.  Such claims are often based on the use of parameters (equipment reference velocities and distance/velocity dependences) in vibration propagation equations which may well be inappropriate for your locale, the equipment used, or the way it was used. Also inquire as to the specific vibration propagation equation, written out for you, not just named, used to make the calculations. Ask for the numerical specifics of what reference values are being used in any such calculation or "guide" and what input parameters upon which the "guide" is based.

You can check the calculation conclusions you might be offered with our own free vibration velocity diagrams and safe distance diagrams (like the one at left), which registered users of the free CVDG e-book and CVDG Pro can either view online or download as a free PDF of all the diagrams. Registered licensees of the free CVDG PDF and CVDG Pro purchasers can also calculate vibration velocities and safe distances specific to their own construction situation, as well as blasting PPV's, maximum charge weights and blasting damage probabilities, with the free Vibrationdamage.com Ground Vibration PPV and Safe Distance Calculator. Direct free download links for the Calculator and the diagrams are included within the PDF's of both versions of the CVDG e-books in the Vibration Estimation Tools chapter.

Before the Damage Inspection

Arrange for the inspection to be done at a time agreeable to both you and the inspector, as soon after you note the damage as possible. On principle and for personal safety, if for no other reasons, you should not admit any inspector who simply appears at your door without prior arrangement. Do not allow another party's attorney to be present for any inspections, unless you have your representation present as well. Establish in advance how many inspectors will visit at any given time, their names and who they represent. If the advance arrangements are not honored, deny access to the home until other, more satisfactory, arrangements can be made. In most cases, you should allow no more inspectors in the home at a time than you have responsible adults in the house to accompany them. You should escort any inspector everywhere they go in the home or on the property. Anyone who escorts an inspector should be fully cognizant that anything he says "can and will be used" against him/her.

As I've advised elsewhere in the CVDG, it is wise, as a condition of access to get an inspector to sign a document^[3] in which he agrees to produce a copy of any and all video, photos and other documentation recorded during the inspection, as well as any subsequently compiled reports, within 10 business days of the inspection or of a request from you or your representation. The inspector may not produce those records, but such a document gives you another argument to force production later. You can also request to copy the video or camera memory card to your computer before the inspector leaves the premises or allow him to copy it on your computer. Insurance company photos can be particularly valuable as documentation, since nobody could believably argue that the insurer has any reason to overstate or fabricate the amount and type of the damage.

Real scientists produce (and publish) their data for examination, confirmation and evaluation by others. Remember to ask during the inspection for a copy of any report the inspector issues concerning your home or building, including all the supporting data. If the inspector refuses to make his data available, the refusal suggests that his real goal might not be scientific in nature. Make sure you document in writing any such refusal.

Conducting the Damage Inspection

Record on video everything the inspector does in the inspection. Indicate to him or his representative, when the appointment to inspect your home is scheduled, that you will record video of the entire inspection. If the inspection firm or the insurer refuses to allow video, deny access to the home. It is your right to keep records of anyone who may visit your home for the purpose of examining the damage. It is also your right to ask for a different inspector/firm if you believe, based on evidence (e.g. statements on a web site or a refusal to allow video of the inspection), that the one proposed may be unreasonably biased. Any insurer or other involved entity who insists upon one, and only one, inspector or inspection firm, may have suspect intentions. There are many insurance investigators and "public adjusters" in most towns and cities, so finding an alternate one should not be difficult. You should refuse conditions of inspection set by the inspector which you find unreasonable or unsupportable. You own the home, after all!

During the inspection, help the inspector to view all the damage, in the home and on the property, not just a few selected examples. If he refuses to do so, make sure he gives reason on your video for the refusal.^[7] Keep a rough count (and record it later) of the number of photos taken by the inspector, as this will allow you to know whether his report shows all the information collected or just the parts selected by the inspector to support his, often pre-conceived, opinions. Note the time of arrival and departure of the inspector; also observe whether he takes any written notes during the inspection or just does a "look-see". It is very difficult to depend entirely on memory for a detailed and scientific analysis of many damage sites in a home, as is the case in the typical damage instance.

You may be asked questions during the inspection regarding cause of damage, when you noticed it, and how you use the home, among others. You should be careful in answering any such questions, so as to avoid improperly biasing the inspector's opinions in any direction. It is the inspector's job, not yours, to perform the inspection, document it properly, and draw scientifically defensible conclusions from what he sees, and documents, in the inspection.

Neither argue nor agree with anything said by the inspector. Don't make legal threats. Don't allow him to intimidate you. The inspector is a guest in your home and should be treated, and act, as such.

Make sure you get his business card during the inspection visit. Ask the inspector to tell you his educational and work background on the video. Claim adjusters for an insurer usually don't have the training or knowledge to make supportable scientific judgments as to cause or timing of damage. If you would like to know more about how a damage inspection should be conducted, how to assign damage cause(s), how to deduce damage timing and how to draw scientifically supportable conclusions from an inspection, see our CVDG Pro chapter, Damage Assessment.

After the inspection, it is a good idea for you to write some timed and dated notes detailing what was said during the inspection by both you and the inspector, what was examined, and what was not examined, plus anything else you feel is noteworthy. If representatives for the contractor or project sponsor make any representations to the effect that they were responsible for the damage or would pay to fix it, be certain to record the name and date in your notes. If you have a videotape record, you can skip some of these notes, although you may find that having notes will help you find events recorded on video.

Other "Studies"

Companies or insurers facing possible damage claims will sometimes ask to perform measurements or "studies" at a home or building. Such studies may involve use of displacement gauges, strain gauges or inclinometers. Others may search for other kinds of evidence of "settling". The Vibration Measures chapter of the CVDG Pro has descriptions of these methods and their limitations. Although they can have some degree of value in some circumstances, these other types of studies address vibration effects on the structure. They do not determine ground vibration velocities, the standard by which probability of damage is judged, nor are they readily relatable to specific ground velocities.

More often than not, such requested studies will have more to do with litigation defense than they do with avoiding, or finding out the cause of, damage. Furthermore, they have very little value without some pre-construction studies of the same types to ascertain the prior condition of the home for comparison. Sadly, most of these studies are carried out only after damage is reported, making scientific interpretation of them all but impossible. Only occasionally can they be a part of answering the question of the cause and timing of damage. They are never a good substitute for well-done vibration monitoring before and during the job. If these other types of measurements are proposed to you, make sure you understand what they can tell you about the damage and how they might be misused in responding to a legitimate damage claim - before you grant permission to perform them.

Inspection Reports

After the inspection is completed, you should get a written report of the inspection from every inspector within two weeks of the date of the inspection. The report should indicate both the conclusions and the data on which the conclusions are based. Any inspection report filed more than two weeks after the inspection should be carefully examined for errors and unsupported conclusions.^[10] This is especially true in the common example where the inspector records some photos, but no notes at all, during the inspection.  Some inspectors will record neither notes nor photos, depending entirely on memory or their pre-conceived conclusions. You should make timely provision (within two weeks) of the report and any photos taken a condition of access to the building or home (see Conditions Documents in the CVDG Pro for some template documents for this purpose).

If the report bases its conclusions on photos recorded by the inspector, ALL those photos should be duplicated in the report or, alternatively, made available on DVD or USB drive. The specific location of each photo recorded is required (e.g. "west wall of family room"). If only a fraction of the damage is photographed by the inspector, the report should explain why some damage went undocumented by the inspector. Note any refusals to provide report copies and deny access. All inspection reports must be made available to both the homeowner and to other scientists for evaluation and comment. Any private or verbal only report (e.g. those made by adjusters to insurers) must be considered as unverified and scientifically unreliable.

Inspectors will usually offer "conclusions" to the effect that the damage was all "pre-existing" to the start of the construction work. Usually, such a conclusion is based only on a short visual inspection of some of the damage. Such conclusions from a simple visual inspection alone cannot be supported scientifically, as indicated briefly in the CVDG's Recognizing Damage chapter, and, with many more interior and exterior examples, in the CVDG Pro's Estimating Damage Age chapter.

Typically, inspection reports assert that thermal/humidity cycling and/or wind loadings may be responsible for the damage. Such causes can be responsible for limited hairline cracking in walls and exterior finishes. They are rarely responsible, excepting extreme cases (e.g. hurricanes, tornadoes, large earthquakes), for widespread, whole-home damage of the sort which is too often seen around construction sites employing heavy equipment.

Inspection reports often attribute damage to "normal settling". Most homes older than ten years or so will have a few (under 10) hairline cracks in drywall or plaster as a result of normal aging processes and minor settling. It is highly unlikely that one can account for a home near a construction site suddenly having developed hundreds of cracks throughout the home as reflective of normal aging.

Mere citation of the possibility of other potential causes of damage does not make that possibility a fact. It is the scientific responsibility of any inspector to prove his assertions and opinions with actual and fully representative data, objectively reflecting all his observations and directly supporting his conclusions. In the absence of such clearly relevant and unambiguous supporting data, such claims are little more than unreliable speculation, and easily challenged.^[9]

Opinions Based on Vibration Monitoring

Sometimes, inspector reports will include results of vibration monitoring as a part of the basis for the opinions offered. Others will quote vibration monitoring results. The typical report of only a maximum PPV for a given day or operation, often for only a fraction of the work days, is woefully insufficient to support any opinion regarding damage potential. A cornerstone of the scientific method is the ability, at least in principle, for the reported results to be verified by other scientists. Failure to include full information about all the vibrations observed and how the measurements were taken means that the data can neither be examined by someone else nor can the conclusions from the data be verified.

This means that reports which rely on vibration monitoring in any way should include, at a minimum: photographs of the seismograph transducer site and description of the means by which the seismograph is anchored to the ground, distance to the construction operation (or the point of closest approach) whose vibrations are measured, bearing to that location from the seismograph, exact location of the seismograph specified by distances from fixed landmarks or as GPS positions, a complete description of the construction operations occurring during the seismograph measurement run, histogram data for all seismograph measurements cited, seismograph setup parameters, and FFT dominant frequencies for all vibrations cited in the report.

These are only the minimum information which should be provided with the report. Ideally, all vibrations triggering the seismograph should have their waveforms included in the report. All the supporting raw, digital seismograph data should be made readily available in a timely fashion (within two weeks of request) to any person having a legitimate need or use for it, including the homeowner, his representation and his designated scientific aides.^[4] This means that a qualified vibration effects expert should be retained and brought in as early as possible to document the damage and analyze properly any vibration monitoring data.^[6]  The CVDG chapter, Vibration Monitoring, carries a brief list of some common faults in vibration monitoring and the reports summarizing it. The CVDG Pro provides extensive coverage of vibration monitoring, and issues which often arise from it, in multiple chapters.

Repeat Inspections

Sometimes, especially for vibration damage cases in litigation, the defendant(s) will request additional inspections. You should handle these in the same way that you did the initial inspection. If additional damage has appeared since the first inspection, as is typical, be sure to point out the new damage to the inspector. As in previous inspections, you should answer only questions which pertain directly to the damage itself. You are not the paid "expert" and are not tasked with explaining the damage in a scientifically acceptable and reliable manner.

Protecting Everyone's Interests

Inspections of damage by representatives of insurers, project sponsors and contractors need not be adversarial or confrontational. But, you need to remember that potentially large sums of money are at risk, for everyone concerned. Behave with appropriate caution and with consideration for how information gained might be both used appropriately and misused.

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[1]The Travelers Insurance Co. offers an online app for its contractor policy holders called ZoneCheck, which allows contractors to calculate what are claimed to be likely vibration interaction distances for various types of construction. Its accuracy and calculation methods are unknown, as is their suitability for the urban environments explicitly illustrated in a video describing it at https://www.youtube.com/watch?v=h3B5e8bMvQQ. The first line of the narration of that video (from the transcript) is, "You already know all about how ground vibration can cause damage to surrounding structures and you're probably aware that can cause serious profit losses to your job" ↩ [2] As discussed in our Vibration Standards chapter, blasting vibration standards are based on analyses of the probability of a single blast vibration, lasting less than "a few seconds", causing damage to a group of similarly constructed homes experiencing the same vibration, rather than vibration from multiple blasts, or long-lasting multiple vibrations from construction, causing damage to a single home. The multiple blast case is far more typical of damage instances from blasting. Acceptable vibration velocities for blasting in the U.S. are usually set at the 5% (two standard deviation) probability of damage, for a single blast producing a given ground peak particle velocity. It isn't clear if each individual blast can be considered truly independent in the statistical sense (i.e. each succeeding blast having a probability of damage unaffected by the preceding ones). Indeed, fatigue studies suggest that there may be a small increase in probability of damage for each successive blasting event. If the blasts were completely statistically independent, the probabilities from each succeeding blast would sum linearly. For example, three blasts, each of ground velocities having a 5% probability of damage, would have a 15% probability of causing damage at least once in the blast series, if the damage probabilities are unaffected by previous blasts. Whether or not such multiple blasts are truly statistically independent, it is very likely that multiple blasts increase the probability of damage over that assignable to a single blast. It is incorrect and misleading to state that any nonzero vibration velocity, associated with any single vibration event, when below an appropriately applied standard limit, has a zero probability of damage, even if the probability might be very low for very low PPV vibrations. As discussed in the CVDG's Vibration and Damage chapter, construction vibration is less amenable to statistical analysis of damage probabilities than blasting vibration. It is more variable, in velocity, frequency distribution, repetition rate, duration and cause, than blasting vibration. The distinctions in this footnote are rarely, if ever, mentioned in inspection reports about damaged homes, although (usually inappropriate) blasting standard limits, which are based on such probability arguments, are widely quoted in them. ↩ [3] The CVDG Pro, in its Conditions Documents chapter, has copies of sample documents which allow you to control access, get copies of records, and keep you own records of who has received what from you. ↩ [4] See the ISEE Field Practice Guidelines for Blasting Seismographs, 2020 Edition, International Society of Explosives Engineers (available online), for a more complete description of the proper use of blasting seismographs and reporting of data obtained from them. Note that construction uses of blasting seismographs require additional precautions to assure that data are not lost due to filling of limited internal event memory well before the end of the work day, as explained in the Seismograph Memory Limitations chapter of the CVDG Pro. ↩ [5] Blasting Vibrations and Their Effects on Structures, Harry R. Nicholls. Charles F. Johnson. and Wilbur I. Duvall, United States Bureau of Mines Bulletin 656, 1976, p. 21 ↩ [6]  When people bring in an attorney to help with a vibration damage claim, both they, and the attorney, tend to delay finding a scientific expert in vibration effects to evaluate and document the damage, at or near the time it is inspected by representatives for the opposition. This is usually done to save money. But, it is exactly the WRONG instinct. When you report damage, insurers and contractors will send their own people, with predictable opinions, to view the damage almost immediately. These folks often document only a fraction of the damage and only those parts which they think can be used to support their conclusions. People with claims often don't call in their own qualified experts until 2-4 years or longer after the damage has been done, usually as the case approaches trial, and long after the opponents' people have created, and distributed, their own view of the case. When the damage is first seen by one's own experts at such a late date, the experts' interpretations are crippled in many ways. If you have damage, make sure your attorney brings in a qualified vibration effects expert to view and properly document the damage as soon as possible after it is done. Make certain that his examination is thorough and his report complete. As damage develops, you may want to have your expert come in again to update his data and report. ↩ [7] I personally videotaped an "inspector" for a contractor completely ignoring two, over 10 feet long, quarter inch wide through cracks in a concrete patio, unambiguously attributable to the construction, in favor of recording a two foot long hairline crack in the same patio only a few feet away from the far longer and larger ones. When asked about the larger cracks, the inspector indicated that he saw them, but still didn't videotape them. That "inspector" (also the contractor's vibration monitoring technician) is no longer working in either business, after his appearance at trial in the matter. This incident, one of several such in the inspections done for this damage incident, is a good illustration why claimants should fully videotape the visits of every inspector. ↩ [8] "Soon after publication of the 2.0-in/sec safe level criterion, it became apparent that it was not practical to blast at this high vibration level. Many mining operations with nearby neighbors were designing their blasts to keep velocities as low as 0.40 in/sec." Structure Response and Damage Produced by Ground Vibration From Surface Mine Blasting, D. E. Siskind, M. S. Stagg, J. W. Kopp, and C. H. Dowding, United States Bureau of Mines Report of Investigations 8507 (USBM RI 8507), 1980, p. 3 ↩ [9] Lest you think that these issues are entirely technical and of little use to a homeowner, there is an example of a vibration damage case which was decided, both at trial and on appeal, by a debatable "expert" opinion. That expert asserted that the damage was all pre-existing, based on a scientifically questionable and largely unsupported claim that the appearance of the cracking was inconsistent with vibration damage. You must be prepared to address "pre-existing damage" assertions, both with your own evidence and by attacking the scientific basis of such claims by others, as they are almost certain to be made in a vibration damage case. See: Did the insured prove that ‘bad vibrations’ from a construction project damaged her home?, https://www.propertycasualty360.com/2017/07/05/did-the-insured-prove-that-bad-vibrations-from-a-c/?slreturn=20190911120226  ↩ [10] In one example of extensive and very well-documented construction vibration damage, an engineer inspector for the contractor didn't file any kind of report until more than a year after his inspection. The conclusions in that one page report (pre-existing damage exacerbated by construction vibration) were largely at odds with his witnessed verbal evaluation at the time of the inspection, where he indicated that the contractor "clearly caused this damage". When he appeared at deposition a year later, his testimony contradicted both his report and his conclusions the day of the inspection, as did his later trial testimony, where he indicated that the damage (over 600 damage sites on one property) was all "pre-existing". That "conclusion" was based entirely on visual inspection of some of the damage, known to be misleading and false, as indicated in the main text of this CVDG chapter. The photos he produced at deposition included only a portion of the ones taken of the home at issue. His production also included multiple photos represented as being of that home, but which were actually of an entirely different one. He had no credible explanation, either for the misattributed photos or the large number of "lost" ones.This example shows just how unreliable and biased damage inspection reports can be. ↩

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