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How Far Away Is "Far Enough"?
Although such questions are often asked and conclusions often given, there is no single answer to the question, "How far away must my building be from a vibration source to be considered 'safe' from vibration damage[?]".
Buildings have different degrees of resistance to vibration damage depending on design, construction materials and age, among other factors.[28] As discussed
in the CVDG's Vibration and Distance chapter, both vibration source properties (e.g. blasting or pile driving vs. compaction) and the way vibration velocity decays through movement in the
ground can be very different, depending on locale, presence or absence of structures and other obstructions which can damp, reflect, refract or modify vibration waves. Resonance effects in homes
and other buildings can turn an "allowable" ground vibration velocity
into a structure vibration velocity which is damaging at considerably greater distance than the direct ground vibration itself might be. Document the construction!I have served as a consultant in many cases of apparent construction-related vibration damage. Although most people experiencing such damage do a good job of documenting it in their homes or buildings, it is rare, indeed, to see cases in which they have also created a good record of the construction itself. Without such documentation, your damage claim is pretty much at the "mercy" of the contractor. I have seen contractors outright lie about their construction operations under oath - even when there was video showing them doing repeatedly the very things they vigorously denied. Other contractors have provided conflicting, constantly shifting, stories of what they did and how they did it. It may be too time-consuming to record photos or video of every operation in a large construction job lasting weeks or months. However, if you can anticipate or otherwise know in advance of certain kinds of work to be done, you can significantly reduce the burden of documenting the job. There are only a few kinds of operations - blasting, compaction, pile driving and demolition - which can be expected to produce vibrations which might be damaging, if your home is close enough to the work. If you can get good records, including dates and times, of these operations, you will have covered most, if not all, eventualities. Make sure to also record any evidence of vibration monitoring in progress during the job, as some contractors will be reluctant to admit to having such data when there is a damage claim. You can find out much more about documenting damage and construction at https://vibrationdamage.com/recording_damage.htm. Some Sobering StatisticsWe have been maintaining databases of vibration damage reports to Vibrationdamage.com since 2013. These come from over 2700 registrations of the free version of the Construction Vibration Damage Guide for Homeowners (https://vibrationdamage.com/download.htm), plus over a hundred more reports from emails, our Damage Report form and phone calls. While a full description of what we have learned from analyzing that data is far too involved to examine here, following are some basic excerpts from that data analysis which show how serious the problem is around the world.
Although this is just the barest outline of the data, we can see that vibration damage reports are common just about everywhere. It's time to address this issue, not simply pretend it can't happen. Want to Avoid a $100,000 or More Mistake?If you have construction in progress nearby or about to start, take an hour or so to walk around your home documenting its contents and condition on video. If you have cracks, video them carefully, noting on the sound track their exact location and approximate length. If you don't have any, be sure to video the corners of wall penetrations, where construction vibration damage is likely to become evident first. An hour spent this way could easily save you $100,000 or more if damage is done by the construction. Handling a Vibration Damage Claim - The Short ListPursuing a claim for vibration damages to your home can take a lot of time, though it is usually accomplishable in evening and weekends. Spending even a half hour per day on some basics can markedly improve your chances of a fair resolution of your claim. Here's a much abridged version of our chapter at https://vibrationdamage.com/homeowner_checklist.htm - itself much abridged from the full content on the site. This short list is pretty much the bare minimum that a homeowner with vibration damage can expect to do to move a claim forward.
Some of this work can be done by others, but it will cost you a great deal of money to pay them to do it. About Insurers' "Earth Movement" Exclusions
Most home insurance policies now carry "earth movement" exclusions. These were originally used to exclude damage from natural causes (e.g. earthquakes), but have increasingly been used by insurers to exclude just about any kind of
damage to a home, save, perhaps, a fire. Courts have been divided about whether such exclusions can be invoked for man-made vibrations. Although widely cited by insurers to evade paying for damage, the ways such exclusions are used
almost never stand up to scientific test. Fortunately, the insurer of the construction job itself cannot use such exclusions. If you have vibration damage, it's virtually a certainty that your home insurer will invoke an "earth movement"
exclusion. To help you prepare for handling that properly, read our full chapter at
https://vibrationdamage.com/pursuing_a_claim.htm.
How Much Vibration is Too Much?Construction companies often cite, inappropriately, the OSM blasting standard limit of 0.75 in/sec, when construction causes damage. There are many reasons why such a citation is inappropriate. However, consider this: The Swiss standards for construction vibration set the vibration velocity limit for timber-framed homes at 0.2 in/sec. The U.S. FTA adopts a slightly revised version of the Swiss limits having the same numeric value. A scientific paper by one of the original workers on the Swiss standards indicates that damage is "to be expected" when the vibration level is at twice the Swiss limit. Thus, those who use the OSM standard for construction situations are, at nearly FOUR times the Swiss limit for construction, HIGHLY LIKELY to cause damage. This may go a long way toward explaining why damage often occurs when people try to apply blasting standards to non-blasting construction vibrations. For more on this topic, and the original paper reference, see Vibration and Damage and Vibration Standards. Drywall Cracking Summarized in One Photo
"Fixing" Drywall Cracks by Painting
Vibration Monitoring Contractual Requirements
About Safe Distances
Just above are some safe distances calculated for the four building type classes of the U.S. Federal Transit Administration vibration standard. The classes indicated on the diagram are defined in that standard in terms of the nature
of the home construction type as:
Class I. Reinforced-concrete, steel or timber (no plaster) In this and our other safe distance diagrams, distances greater than the relevant calculated one can be considered "safe", within the limitations of the calculation algorithms. Those less than the calculated one are considered "unsafe". Because such safe distances have all the probability-related uncertainties of the standards on which they are founded, as well as those introduced by the known limitations of vibration propagation equations, any such calculated safe velocity should be considered as a MINIMUM value. We recommend a factor of two multiplier on any calculated safe distance to account for these limitations. You can find this diagram and additional ones calculated as a function of other variables from the FTA vibration propagation equation on our page at https://vibrationdamage.com/vibration_and_distance.htm. A free PDF of full-size versions of this and other safe distance and vibration velocity diagrams can be downloaded free by registered users of the CVDG for Homeowners and the CVDG Pro. Look for Vibration Monitoring
About "Scaled Distances" in BlastingAlthough Vibrationdamage.com and its Facebook page emphasize construction effects of vibration from heavy equipment, blasting is sometimes done in construction contexts to remove rock or level sites on rock. Construction blasting differs substantially from mine and quarry blasting in the typical amounts of explosive used per delay and the frequency distribution of the produced vibration. Of course, it differs from heavy equipment vibration production, too. You can find an introduction to blasting and its effects in the CVDG chapter, Blasting Vibrations.  Because of these differences, blasting vibrations are usually depicted differently in scientific contexts than other kinds of construction vibration.
The diagram shows that blasting vibration velocities are usually plotted vs. a quantity called "scaled distance". The scaled distance is just the measured distance between the blast and the seismograph, divided by the square root
of the charge weight of explosive used per explosion delay time. Such charge weights per delay (usually around 8-9 milliseconds between detonations) are always reported in documents to local regulatory authorities, along with the
measured vibrations at the seismograph locations.This is usually called "square-root scaling" in the scientific literature, since its goal is to remove the effect of differing amounts of explosive, placing a series of blasts on the same source energy basis. For point source blasting, sometimes cube root scaling is used. When plotted with logarithmic scales on both axes, the equation describing the vibration intensity produces a line, whose slope is related to the type of soil through which the vibration moves. This may be more information than most people want to know about construction blasting, but, if your home is ever damaged by it, it is likely that you will be presented with a plot like the one shown here. I hope this explanation will help you understand what you're seeing. The CVDG and CVDG Pro have considerably more information about blasting vibration and its effects on homes. Facing a Home Inspection?Just about anyone reporting damage from construction will be asked to have their damaged home "inspected" on behalf of the contractor's insurer and/or the home owner's insurer very shortly after they describe the damage. These inspectors work for the insurer, so their inclination in a damage case is predictable. However, many may cross the line from "inclination" to outright "bias" or even falsehood.[1] One way to get a sense of what you might be able to 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 web sites. Many of those sites have pages dealing with construction damage which say, in essence, that "construction damage can't happen". Such implications are clearly false, as a public video by at least one insurer of contractors shows. 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 cite that information later to show that the inspection firm may be biased and its statements unreliable. For much more information on how to handle damage inspections, see our chapter, Damage Inspections. Historic Structures and Vibration DamageMany people around the U.S. and the world live in structures which are historic in some sense. Such homes may be built upon rubble foundations or, in desert areas, from adobe. These require lower vibration standards and larger safe distances than homes built to modern standards. Note that the standard for use of these lower limits is NOT necessarily formal historic designation, but the nature and age of the construction. The OSM velocity limit for blasting and the much lower construction-based FTA Class III limit for timber-framed homes are not applicable for historic structures or those which have already suffered vibration damage. Typically, among the higher limits recommended in the scientific literature for such structures is the FTA Class IV limit of 0.12 in/sec (cf. FTA Class III limit of 0.2 in/sec shown in the diagrams above). A limit of 0.08 in/sec has been advised for the thousand-year-old Pueblo Bonito in Chaco Culture National Historic Park in New Mexico, USA.[2] Vibration velocity limits as low as 0.05 in/sec appear in the literature for other historic structures.[3] These lower limits have the effect of increasing safe distances for historic structures. For more on this topic, see https://vibrationdamage.com/vibration_and_distance.htm Can Construction Cause Damage?The Travelers Insurance Co. has just released a loss control 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 operations. Its accuracy, validation and calculation methods are unknown 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 is, "You already know all about how ground vibration can cause damage to surrounding structures..." Apparently, the many contractors who say things like "construction can't cause damage" haven't gotten the memo! About Pre-construction SurveysPre-construction video is sometimes recorded to document home condition prior to the job. It is often required of the contractor under the terms of the construction contract, whether or not it is actually carried out. It can be useless or extremely valuable, depending on how it is done. In one example, the pre-construction video, which covered only a tiny fraction of the homes along the job route, lasted a grand total of 42 seconds in front of a home with over 100 feet of street footage. There were no close-up views whatsoever, as the frame capture below from the video, the closest to most of the homes, shows. That video was useless for any feature more than 10 feet from the video camera (e.g. the entire home structure). Note that the logo on the trash can is illegible, at over 4 inches in height. Thus, even a crack in the home a half inch across would not have been visible in this video! Extensive damage (over 600 damage sites in at least one case) was done in that job to numerous houses 40 feet or more from that street. This example is a good one showing how not to do meaningful pre-construction documentation. Contractors On StandardsPeople who report damage from construction or blasting are often told that the work "met standards". Such statements might be reassuring to some. But, they have virtually no meaning from a scientific or legal standpoint. First, which standards were "met"? Blasting standards, like the US. Office of Surface Mining standard, are widely recognized throughout the scientific literature as inappropriate for construction or traffic settings, but are still routinely cited and relied upon by contractors and their paid vibration monitoring firms. Standards considered much more appropriate for construction, like the "Swiss" and related U.S. FTA standards, are rarely acknowledged, let alone adhered to, by contractors.
Second, what is the frequency distribution of the vibration(s)? Most standards set lower allowable ground vibration velocities at lower vibration frequencies than at higher ones. Without knowing both the maximum velocity and its frequency
distribution, any such statements cannot be verified.
Third, vibrations are only rarely monitored in construction settings, even though many, perhaps most, construction contracts require vibration monitoring explicitly. Often, people depend upon vibration propagation "calculations", which are regularly so inaccurate when compared to measurements that they are, at best, educated guesses, in absence of confirmation. When faced with such assertions about standards, the homeowner should ask to see ALL the supporting data. He may (not) be surprised to find there are few or none which actually support the "met standards" claim. Do Contractors Learn from Damage Incidents?One might hope that a construction company, and/or its sponsors, whose projects result in extensive damage would learn from that experience and become better at their jobs. However, that doesn't happen in some cases. One construction firm which created most of the damage to multiple homes discussed in the CVDG was recently given another project on a nearby street. As photos show, that new project has also created substantial damage, very similar in appearance and type to that caused in the previous job. The photos constitute well less than 10% of the damage visible from the sidewalk. They cover only about 1/3 of the length of one side of the street. Thus, a construction firm with a record of damage in its projects should be carefully monitored and controlled in any future projects so as to avoid repeating the same mistakes. Construction vibration damage is usually avoidable, if done properly. Look for Exterior Damage, TooPeople often think of construction vibration damage as involving only interior cracking, or, in extreme cases, cracks in concrete slabs and patios. However, exterior finishes are commonly affected, as well. The corner cracking in exterior stucco, shown in this photo, appeared in a home adjacent to, and about 25 feet from, a road reconstruction job in a suburban community. Such roughly diagonal cracking at wall penetration corners is a common characteristic of homes placed in shear (i.e. undergoing "racking" motions) by vibration. It is fairly common in homes with rigid exterior finishes like stucco to develop corresponding interior and exterior cracks as a result of heavy equipment vibration, leading to through-holes which must be fixed immediately to prevent water damage and heat loss.
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E-mail to drzeigler@vibrationdamage.com or send online questions or comments about Vibrationdamage.com.
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This photo shows all the major types of drywall cracking that are normally seen in construction vibration damage situations. It was taken in a child's
room, in a home which had been subjected to extremely high vibration velocities, caused by pounding on pavement with an excavator bucket less than 50 feet from the home. At the lower right, there is a diagonal crack running from a
door frame corner, due to shear forces caused by the vibration. The vertical crack at left is along a drywall sheet edge. The horizontal one and its diagonal extension is a through-sheet crack. This home was the one closest to this
incidence of pounding on pavement and suffered somewhat more extensive damage than most.
Diagonal cracks at the corners of window and door penetrations indicate that a home has been placed in shear ("twisted"), often by vibrations. Cracks
of this type spread over an entire home are frequently found in construction vibration damage. This photo shows what usually happens when you try to cover such cracks with paint and then sell the home quickly. The fresh coat of paint
initially covered the crack, but, because the home had not stopped adjusting to the stresses placed on it by the vibrations (in this case, from pounding on pavement with an excavator bucket), the crack re-opened. Thus, any attempt
to repair damage should only be made at least a year after the vibrations causing the damage have ceased.
Most construction jobs are not monitored for vibration, despite the very real potential for damage to nearby homes. Yet, many, if not most, construction
contracts require vibration monitoring as part of their boilerplate list of requirements (see graphic for an extract from a real IFB where the requirement for monitoring was ignored by the contractor, until damage was reported
nearly a month into the job). A vibration monitoring task may be found in the contract proper, the Request for Proposal (RFP), the Information for Bidders (IFB) document or in conditions provided by reference to other documents (e.g.
state DOT specifications). You may also want to pay some attention to requirements for pre-construction surveys (sometimes called "pre-condition surveys") and to traffic management. In this job, the contractor violated its own traffic
management rules during the project. If damage is done in a job near your home, get the contractual documents listed above and search them for a vibration monitoring requirement. It takes only a few minutes to find and search them
online ("vibration monitor") for most public projects. Any contractual violations you identify this way can significantly strengthen your hand in settlement negotiations or at trial.
"Safe distances" are easier to use and measure than ground vibration velocities (PPV's), which require a properly installed and configured seismograph
for meaningful determination. Safe distances are usually based on calculations of distances at which vibration velocities drop below a given standard PPV limit. Such calculations have considerable limitations.
If you see one of these around a construction job or blasting site, it likely means that vibration data are being recorded. This is one of the most common
types of blasting seismographs, the Instantel Blastmate III, used for vibration monitoring. The blue box is the computer and printer which record digital vibration velocity data from the transducer, connected by the visible cable
off the photo to the right. At the top of the screen is an alert light to tell the construction crews when they have exceeded limits put into the seismograph. Not all seismographs have blue boxes, but they will all look something
like this one. You will want to get copies of the RAW DATA they produce, NOT pre-digested reports prepared for the contractor, if you experience damage from construction work.
