How the standard of care is determined when a failure or accident occurs in the built environment. Update

(See, How the standard of care is determined when a failure or accident occurs in the built environment. Posted June 28, 2014, updated October 30, 2020)

I updated the procedure for determining the Standard when a failure or accident occurs in an area that has not adopted the National Building Code. The intent of the Code is to detail the minimum provisions acceptable to maintain the safety of buildings. (Ref. 1) A forensic expert would consider what the Code says in assessing what a reasonable person would do in a given situation. Also what a reasonable person would do in an area that has not adopted the Code.

The need for this update occurred to me when I was contacted about a slip, trip and fall accident in an area that had not adopted the Code at the time. I was briefed and sent pictures of the scene of the accident. I knew how to investigate the cause as would any expert with similar experience. I thought to reflect this in the Standard as posted on June 28, 2014.

Reference

  1. National Building Code of Canada, relevant edition

Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada ejorden@eastlink.ca      

The reliability of an educated guess on the cause of a failure or accident

I thought to remind readers that some initial hypotheses by experts, educated guesses, on the cause of accidents or failures are very reliable – and others are less so. And there’s every gradation in between. This sometimes causes problems for client and expert alike.

A client decides to take a case or commit to settlement of an insurance claim and all’s good – additional forensic investigation supports the initial hypothesis.

But often enough the hypothesis must be modified a little or a lot – as per the scientific method – and on occasion – rarely – rejected completely. (Ref. 1) This can be difficult.

There’s also the hope – expert’s feel it as a subtle, unintended pressure – that the expert’s additional investigation will support the initial hypothesis. One colleague commented on this several years ago.

One solution is not to ask for or give an initial hypothesis. I’ve experienced that in the past, not often but on occasion – complete the forensic investigation then give us the findings.

Another might be to assign reliability to a hypothesis on a scale of 1 to 10 so a client has a feel for what s/he is getting. Or more simply: Is it probable or only possible? Maybe give the possibilities.

Still another solution, state clearly that in forensic work an initial hypothesis is an educated guess based on the available evidence. And additional investigation may change things as per the scientific method that is followed in forensic work. (Ref. 1) Evidence that an expert gets from:

  1. The client’s briefing on the problem – the accident or failure
  2. A document review (text, pictures, video)
  3. A visual site assessment – in person or virtually
  4. The expert’s past experience

***

All this came to mind when I saw a large barn on the verge of collapse during a drive in the New Brunswick countryside a few days ago. (Ref. 2) The ridge of the roof sagged an estimated 10 feet from where I was driving. It was something to see.

If an expert was retained to assess the cause of a collapsed structure and saw pictures of a structure like this then a very reliable initial hypothesis would jump off the page.

***

My thoughts about the reliability of hypotheses were reinforced when a party in Ottawa contacted me a few days ago about the cause of a leaning retaining wall. He sent me 23 pictures of the wall. (Ref. 3)

I studied them for an hour and the cause gradually presented based on:

  1. The nature of the cracks in the wall
  2. Water stains on the face of the wall, and their location
  3. What was not seen on the face of the wall
  4. Wall foundation construction as seen at one location
  5. The location of the lean with respect to a feature behind the wall, and
  6. Past experience with this type of retaining wall construction

On a scale of 1 to 10 – where 10 is like the relevance of a 10 foot sag in a barn roof – I would give the reliability of my assessment of the cause of the lean an 8.

To be really sure, I’ve asked for low level aerial photography of the site with a camera mounted on a kid’s drone – a few dollars of expense for what I’m certain will be clinching evidence.

***

Following are my assessments of the reliability of an educated guess, on a scale of 1 to 10, of the cause of accidents and failures I investigated in the past:

1. I’ve investigated the cause of slip, trip and fall accidents different times. If I had been asked about a slip and fall on one particular occasion, I would have given my assessment of cause a 9.

2. A trip and fall accident would have got an 8.

3. The cause of a nail gun accident would also have got an 8.

4. Sagging, sloping floors in a high rise would have got a 4 maybe a 5.

5. The cause of large cracks in the wall of a three story building would get a solid 6. I didn’t even see this wall, not even virtually. I was just told the type of wall and the size of the cracks – not hairline, which was significant – and, right away, I knew their configuration and cause.

6. The cause of the John Morris Rankine fatal motor vehicle accident would have got a 10, if I had been asked. No question. I drove the test vehicle during my re-enactment of the accident. I’m here to tell the tale which, if I could tell you more, would say a lot about the reliability of an initial hypothesis of cause in this case. Three dimensional video – video from three directions, including early drone-like video from above – was the clincher.

***

And so it goes, the up and down reliability of initial hypotheses, and the importance of realizing this. The expert must form an initial hypothesis, an educated guess, but, if possible, keep your distance from it till s/he is well into the forensic investigation and has a good understanding of where it’s heading.

References

  1. Google the scientific method and read all about it, in fairly jargon-free language
  2. Update: You could be excused for thinking that everything is falling down. Posted October 13, 2020
  3. Morry, C. J., Personal communication, October, 2020

Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia E: ejorden@eastlink.ca

Update: You could be excused for thinking that everything is falling down

I saw a catastrophic failure waiting to happen during a drive through New Brunswick a few days ago (September 26, 2020).  A barn roof that was sagging a good 10 feet in the middle.  For sure, a barn that was no longer in use because of the risk.

Of course I added it to the list of failures I posted last July 23 that are everywhere in the built environment. (Ref. 1)

It was the magnitude of the sagging ridge that caught my eye. Even at a distance it was easy to imagine, maybe just see the bulging eaves. The eaves of a roof bulge out when the ridge sags.

You see lots of large and small buildings in the country with roofs that are sagging a little or a lot.  Many are abandoned, but not all. And some are only a few years old, not gray with age and many decades old.

You can also see buildings in town – houses, for example – with sagging ridges. A tiny sag, a few inches at most, just enough to catch your eye from the street.

The large sags are probably due to inadequate design of the roof trusses or the rafters. Many of the tiny sags are design failures too.

But some tiny sags are due to green lumber shrinking as it drys after construction is complete. This is a planning failure because less suitable green lumber was accepted for building design and construction.

Reference

  1. You could be excused for thinking that everything is falling down. Posted July 23, 2020 (Scroll to July on the right of the blog page and see Item 9 in Section C. Large and Catastrophic Failures)

(Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia. ejorden@eastlink.ca)