Investigating a vibrating building

(This is not an East Coast ghost story)

(The following is one in a series of cases I have investigated that illustrate the different forensic engineering methods I use to investigate the cause of failures and accidents that result in civil litigation.  Knowledge of simple frost heave was important in this case)

The investigation of the vibrating building is reported under the following main headings with several sub-headings:

  • The case (A description of: 1. The building and the problem experienced by the owner; 2. The building’s foundations, and the problems with the building, 3. The legal/technical issues, and, 4. My client)
  • Forensic engineering investigation of the problem and the methods used
  • Findings of the investigation (conclusions with respect to the technical issues)
  • Resolution
  • Lessons learned

The case

Description of the building and the problem 

The building was a large, well appointed mobile home in the Halifax area that vibrated quite noticeably during the winter months.  The vibration occurred when the owner and his family walked the length of their home from one room to another.

The owner also wanted to know why the interior partitions at some locations were separating from the ceiling.

Legal/Technical Issues

The main issues were the cause of the vibration and the cause of the gaps at the tops of the partitions.


I was retained to investigate the problem by the company who placed the mobile home on the site.

Forensic engineering investigation

My forensic engineering investigation involved the following methods:

  1. Take a briefing on the problem from the owner.
  2. Visually examine the building and the site it was on.
  3. Examine and determine how the building was supported and the foundations constructed.
  4. Sample and determine the type of foundation soils underlying the building site and their physical properties.
  5. Analyse the data collected during these examinations.

Investigations and Findings

Briefing  The owner was quite clear in describing how the building vibrated in winter in walking from one end of his home to the other.  He also described the gaps at the top of the partitions.  The building did not vibrate during the summer.

I wasn’t on site during the winter but saw and measured gaps of about 1/4 to 1/2 inches during my visit.

Visual examination:  The home was on a sloping site with the length of the building aligned up the slope.

Examine foundations:  I crawled under the building and established that the mobile home was supported on two continuous steel beams running the length of the mobile home.  The beams were in turn supported by concrete block piers at regular intervals.  The piers were supported on the sloping ground a few inches below the surface.

Because of the sloping ground, the height of the piers and the home above the ground gradually increased from 1.5 feet at the upslope end to 3.5 feet at the downslope end.

Test foundation soils:  I took samples of the soils supporting the piers and had the samples tested in a laboratory.  I also researched the soil geology of the area – the surficial geology.

The tests and research established that the foundation soils comprised a dense, silty glacial till typical of the many drumlins in the area.

Drumlins are teardrop shaped glacial soil deposits.  The Citadel in Halifax is on a drumlin.

Analyse data: The fact that the mobile home vibrated in winter but not in summer was interesting, and took some reflection on my part.

The shallow depth of the pier foundations supporting the mobile home – a few inches, was not typical for foundations in this area.

We dig our foundations down typically about 3.5 to 4.0 feet in the Halifax area to get below the depth of frost penetration and the effects of frost heave.

A characteristic of the fine grained soils found beneath the piers is that they are very frost susceptible – water collects in the soils easily and freezes in winter.  The mixture of water and soil expands on freezing – frost heave to everyone.  The more soil freezes – the greater the depth of freezing, the greater the frost heave.

The pier foundations would have heaved in winter for certain considering they were only a few inches below the ground surface, not 3.5 to 4.0  feet..

The depth to which the soil freezes depends on the severity of the winter.  Deeper in cold winters, shallower in warmer winters.

A source of heat from an external source other than the weather can also affect the depth of frost penetration in the ground and the amount of frost heave.

Regardless of how well we typically insulate our homes, heat is lost in winter to the surrounding air.  The air is warmed in the process and in turn warms other surfaces in contact where it is protected from the wind.

That was the case at the upslope end of the mobile home where the building was closer to the ground – 1.5 feet.  The depth of frost penetration and heave could be expected to be less at this end of the building than at the downslope end where the home was 3.5 feet above the ground.  It was also exposed to the wind at this downslope location.

Frost was penetrating the ground to an increasing depth from the 1.5 foot end of the mobile home to the 3.5 foot end.

All the piers along the length of the home would heave due to frost action but not necessarily a proportionate amount.  This is because conditions at each pier could be expected to vary a little: Foundation soil conditions could vary, also heat loss from the mobile home, protection from the wind, etc.

The steel beams could be expected to be lifted off the piers completely at some locations – and “suspended” between adjacent piers, because of the disproportionate amount of heave at the adjacent piers.

Steel beams deflect between piers.  The greater the suspended distance between piers providing support to a mobile home the greater deflection.  Walking along a floor supported on such beams causes the floor and the beam to deflect and vibrate.  I think a good many of us have walked along wooden planks supported at each end and felt the deflection and vibration.


I concluded that the mobile home was vibrating as much as it was because it was not properly supported by the piers in the winter time.  Because of the magnitude of the vibration, I believed that the mobile home was only supported by the piers at the ends of the two beams.

The gaps formed at the top of the partitions because the joints between the tops of partitions and the ceiling are relatively weak and would separate when the supporting beams deflected.  I suspect that small gaps would have formed at the bottom of the partitions as well but went unnoticed.


I recommended digging and founding the piers deeper and below the depth of frost penetration and heave.

Lessons learned

  1. Always look at the weather conditions along different parts of a foundation when unusual problems are occurring in the structure above.






Experts on the wane?

I don’t think so..!!  

Certainly not in the forensic engineering field where ‘small-data’ is the rule and where there will always be a need for the subject-area expert – a well experienced, knowledgeable person in a particular field of study.

Someone who can gather engineering data and facts, for example, then bridge the gap between these facts and the formulation of an opinion on cause.  Finally, someone who can help civil litigation lawyers and the judge understand the technical cause of a failure or accident in the built environment (Ref. 1).

But, exciting things are happening in the Big-Data world

But, there does appear to be exciting things happening in the ‘big-data’ world as suggested in a recent item in the Globe and Mail. (Ref. 2)  The item – headed up ‘Experts on the wane?’, quotes the authors of a recent book (Ref. 3) who predict “Data-driven decisions are poised to augment or overrule human judgement”.  The new big-data way will “…let the data speak.”

(The book is a very good read – a study to some extent, with much insight on what can be learned from large amounts of data, and also how we are being monitored with today’s technology.  There is an extensive bibliography)

No excitement in the Small-Data world

That may be the case as far as big-data is concerned but there’s nothing new there in the ‘old’, small-data world.  Practitioners of forensic engineering investigation have been “letting the data speak” all along and following the evidence where it leads.

Definition of big-data with a good example

Big-data refers to the ability of society to harness huge amounts of data in novel ways with today’s computers, and analyse the data to produce useful insights on people, or goods and services of significant value. (Ref. 3)

For example, Amazon now regularly analyses tens of thousands of customers’ book purchases to predict what related topics any one us will be inclined to purchase next, and then offer it to us.  The experts who did this in the past were all laid off.

Engineers go outdoors and get dirty – fortunately for the justice system

In spite of this ability of today’s technology, it will still be necessary for an engineer to go on site and get his hands dirty and mud on his boots examining a foundation failure or measuring skid marks at the scene of a traffic, or slip and fall accident.  And crawling over the debris of a collapsed structure.

We engineers in North America are known overseas for our interest and willingness to go on site and get data firsthand.  And the justice system appreciates that hands-on approach.  The big-data way won’t cut it in the investigation of a failure in the built environment.

The justice system still wants to know the cause of a problem

As well, gathering large amounts of data and analysing the data with computers focuses on establishing correlations rather than causes.  Identifying the what of a problem rather than the why – the cause of a problem. (Ref. 3)  That would never do in forensic engineering where the cause of a problem must be determined before you can fix it, and before the justice system can determine damages.

The old, small-data way solves problems in the built environment

All the problems that I experience in my forensic engineering practice – requiring the gathering and analysis of small-data by an expert, or that I hear about from my colleagues in their practices, and see in the literature, are from the built environment.

Problems and failures in the built environment to do with the planning, design, construction, performance, and maintenance of structures like industrial, commercial, institutional, and residential low- and high-rise buildings.  Also civil engineering structures like bridges, roads, airport runways and taxiways, dams, drainage systems, earthworks, harbour works, and hydraulic works.

And included is the plant and equipment in these structures and the infra-structure.  Also the traffic, industrial, and slip and fall accidents that occur in and around these structures.

The big-data way can’t solve these problems because these problems in the built environment are not characterized by a gazillion amount of data.  There are a lot of data sometimes but not that much.  These problems are characterized by small amounts of data appropriate to the small-data way of an expert – who then applies his judgement to formulate an opinion as to cause.

Experts on the wane?  No, they’re not.  There will always be a need for experts as long as there are failures and accidents in the built environment.


  1. The Globe and Mail, Thursday April 11, 2013, page S8.  A relevant item, an obituary of a man, Martin B. Wilk, scientist, statistician, sage, who thought of statistics as a beautiful blend of science and art, bridging the gap between mathematical facts and human understanding.
  2. The Globe and Mail, March 6, 2013, page L10.  See ‘Experts on the wane?’
  3. Mayer-Schonberger, Victor and Cukier, Kenneth, Big Data: A Revolution That Will Transform How We Live, Work and Think, Houghton Mifflin Harcourt, New York, 2013.

Investigation of a fatal Bahamian aviation accident

(The following is one in a series of cases I have investigated that illustrate the different forensic engineering methods I use to investigate the cause of failures and accidents that result in civil litigation. 

This is a good case for illustrating how simple an engineering investigation can sometimes be, and how knowledge of the geology of an area can form the basis of informed comment.

The investigation of the fatal aviation accident is reported under the following main headings with several sub-headings:

  • The case (a description of the fatal aviation accident, the legal/technical issues, and my client)
  • Forensic engineering investigation of the failure and the methods used
  • Findings of the investigation (conclusions with respect to the technical issues)
  • Post mortem (resolution and lessons learned)

The case

Description of fatal aviation accident 

Ms. Jane Doe was killed when her plane crashed on take-off from an international airport on one of the family islands in the Bahamas.  The accident occurred near a runway where I had completed a geotechnical/foundation investigation prior to construction of the runway several years previously.

Legal/Technical Issues

The main issue was whether or not the propeller on the starboard side of the aircraft – the right side for landlubbers, could penetrate several inches into the ground at the crash scene, and this not occur on the port side – the left side.


I was retained by a U.S. aviation accident reconstruction expert on the advice of the Public Works Department in Nassau, Bahamas and a law firm practicing in Nassau.  Both were involved in the case.  The Department was my client for the earlier geotechnical investigation.  The law firm knew of my work as a professional engineer in the Bahamas.

Forensic engineering investigation

My forensic engineering investigation and advisory services involved the following methods:

  1. Taking a telephone briefing on the aviation accident by the U.S. reconstruction expert
  2. Studying photographs of the crash scene e-mailed as attachments
  3. Reviewing my geotechnical/foundation investigation report for the runway design and construction
  4. Briefing the U.S. expert on the geological processes on the Bahamian island and the degree of probability that the propeller on the starboard side penetrated the ground where the port propeller did not

You will note that this forensic engineering investigation was a simple document review and my knowledge of the published geology of this particular Bahamian island.  An extremely simple investigation.  There would have been no advantage to me flying to the island and examining conditions at the crash site because these would have changed since the accident.


I was able to advise the U.S. aviation expert with considerable certainty the degree of probability that the propeller penetrated the ground several inches on the starboard side.  I’m not at liberty to state that degree of probability.


The case may still be in litigation.

Lessons learned

  1. Do the most thorough and reliable engineering work possible every time because you never know how the data you collect will want to be used for a different purpose in the future.
  2. Worthwhile forensic engineering investigations of serious incidents, e.g., fatal aviation accidents, can be carried out at a distance based on a simple document review.  And sometimes that’s all that is possible, as in this case, because site conditions had changed since the accident.



Most influential business ethics blog; Chris MacDonald, Ph.D, Blogger

You might be interested in Chris MacDonald’s business ethics blog at  Particularly if you are in one of the professions and practice in a business-like manner.

Chris is an educator, speaker, and consultant in business ethics.  He teaches in a school of management at a university in Toronto and is associated with another in the U.S.  He is co-editor of the Business Ethics Journal Review.

Chris is a philosopher by training, a practical philosopher by inclination – this chap’s not stuffy by a long shot.  He’s seldom still.  An east coast guy that has done good and is influencing the business world in a big way.  And doing this in an area – business ethics, that is in desperate need of a good influence.

Philosophy means “love of wisdom”, from the ancient words philos (love) and Sophia (wisdom) (Ref. 1).  Think most of us in the professions are in that good place.

I met Chris when he taught a critical thinking course a few years ago at Saint Mary’s University in Halifax.  One of the best courses I’ve taken in my life by a good teacher, and a course that all professional engineers practicing forensic engineering should take.

Chris has twice been declared one of the “Top 100 thought leaders in trustworthy business behaviour”.  He has several times been named one of the “100 most influential people in business ethics”.

He has been blogging since November, 2005.  His blog is current, well designed, easy to navigate, and very readable – not cluttered and busy like so many.

He tells you about his blog much better than I could at his web address above.  I think a good, spirited summary of who he is and what he’s trying to do with links is at his page, ‘About’.  He warns you on this page that you will probably be irritated by his blog – but, I found, your thinking challenged in the process.

One of his recent postings lists five must-reads on business ethics at

I’ve been reading some of Chris’ material on ethics for several years now.  It’s well I should, considering that one-third of the content of a 140 page set of guidelines for forensic engineering practice – 46 pages, is on ‘ethics in forensic engineering’ (Ref. 2).  Another approximately one-third is on legal matters and business considerations.

One-fifth of another 200 page set of guidelines for forensic engineers is on legal matters and guidance for experts preparing for the civil litigation process (Ref. 3).  There is some emphasis on ethics in these guidelines too.

Also, I should read the business ethics blog if there’s anything to my comments on professional ethics and the tyranny of the bottom line, updated, a blog I posted October 11, 2012 (Ref. 4).

Those are enough reasons for a professional engineer to take an interest in Chris’ blog, as I have, but allow me one more reason.

Rule 55 in the Nova Scotia’s civil procedures rules is quite direct in informing experts that they are reporting to the court, and that they are to be objective – that’s all there is to it, with no qualifiers on objectivity.  And experts are to state the reliability of their opinions.  These charges to experts from the justice system are explicit and contain a clear ethical requirement.

It’s possible some of you might be interested in Chris’ blog.  I think he’s got something to say to all of us.


1. Mannion, James, Essentials of Philosophy, The Basic Concepts of the World’s Greatest Thinkers, Fall River Press, New York, 2002

2. Lewis, Gary L., Ed., ASCE (American Society of Civil Engineers), Guidelines for Forensic Engineering Practice, 2003

3. ASCE, Guidelines for Failure Investigation, 1989

4. Professional ethics and the tyranny of the bottom line. Updated.  Blog posted, October 11, 2012