About admin

I am a consulting professional engineer with 38 years civil and forensic engineering investigative experience. I have worked on civil engineering projects, and forensic and insurance cases, in eastern, western and northern Canada, offshore Nova Shore, the Beaufort Sea, and overseas in the Caribbean, the U.K. and Australia. Civil engineering alters and reshapes the natural environment to provide built environment to meet the needs of mankind. Civil engineering includes the planning, design, construction and maintenance of structures making up the built environment. Examples of these structures are industrial, commercial and residential low- and high-rise buildings, also bridges, roads, dams, drainage systems, earthworks, and hydraulic works. Included is the plant and equipment in the buildings and the infra-structure servicing the buildings. Forensic Engineering investigates the cause of problems and failures with these structures as well as the cause of traffic and industrial accidents that occur in the built environment. The technical data from an investigation is used by the judicial system in determining damages. I practiced as a provincial land surveyor on Prince Edward Island, Canada before studying and practicing civil and forensic engineering.

How do you carry out a forensic investigation during a pandemic?

Engineering experience plus data from a visual site assessment carries the day during a pandemic. More often than not engineers know the probable cause of a problem soon after they’re told about the problem.


I blogged in the past about the value of a simple visual site assessment. Simply going to the site of a failure or accident and visually examining what’s exposed at the surface. In a sense, walkin’ around and kickin’ the tires. (Ref. 1)

Never mind taking things apart and seeing what’s beneath the surface. No field testing. No laboratory testing. Nothing like that. Just look and see what’s exposed at the surface.

Then I realized it had to be a virtual visual site assessments when COVID-19 struck. Like in, ‘Stay the blazes home!’. I talked about how valuable these types of assessments are too. (Ref. 2)


Recently I was reminded about the value of simple engineering experience.

A few days ago after blogging about why the multi-story building collapsed in London, Ontario (Ref. 3) I was in touch with an experienced construction engineer in Ottawa, Ted Ruiter. Ted and I are UNB engineering classmates. He was quick to say, “while he hadn’t read my blog yet about the London building collapse”, the probable cause was hurried construction and inadequate support of the concrete floor forms.

Ted’s comment got me thinking about the chat I had earlier still with an experienced design engineer in Halifax, Jamie Yates. Jamie and I are friends. I chat with Jamie at times if a problem seems to have a structural element. We talked about the design of the temporary support of floor forms like those used in the London building. He was also quick to note inadequate support as a cause.

We also chatted about the problems that develop when construction is rushed.

So, the experience of two well-regarded engineers kicked in and quickly pointed the finger at inadequate support – sans virtual visual site assessments.

Of course, that’s not enough – just knowing based on experience – a client wants analysis and reasoning to a conclusion based on the evidence in the spirit of the scientific method. An experienced forensic engineer did that and I concluded inadequate support too.

Three experienced engineers and the same conclusion about inadequate support as the probable cause of the building collapse.


I’m not surprised at the value of plain old engineering experience – the theme of this blog.

I blogged a while ago about the failures that are everywhere in the built environment from the simple to the complex. (Ref. 4) Also the many 100s of ways different structures can fail. For example, 209 for a building alone. (Ref. 5) An experienced engineer knows about many of these and will pick out the probable cause from the many.

Add a visual site assessment to engineering experience and you’ve got a powerful forensic investigative tool.


You can get close to settling your insurance claim or assessing the merit of a case now – from your home office. Maybe even completely settling the claim or reliably assessing merit. You don’t need to wait for the second COVID-19 wave to pass.


  1. COVID-19 and an initial forensic task a.k.a. a visual site assessment, sans social distancing. Posted June 1, 2020
  2. What can you get from a virtual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020
  3. Why did the four story building collapse during construction in London, Ontario? Posted December 31, 2020
  4. You could be excused for thinking that everything is falling down. Posted July 23, 2020
  5. What’s in “…the built environment” and how many ways can it fail? Posted July 8, 2020


(Posted by Eric E. Jorden, M.Sc., P.Eng., Januray 8, 2021 consulting professional engineer, forensic engineer, Halifax, Nova Scotia, Canada ejorden@eastlink.ca)

Why did the four story building collapse during construction in London, Ontario?

The forensic engineer will guess – an initial hypothesis, based on a simple analysis of the virtual evidence – that the culprit was inadequate temporary support for the section of the 4th floor where concrete had been placed.


According to news reports the virtual evidence – the 4th floor collapsed on the morning of December 11 when a section of freshly poured concrete gave way crashing through the floors below. Note that it was a section of the floor not the entire floor, and the concrete was already in place.

The multi-story building is being constructed at 555 Teeple Terrace in the west end of London. Two workers were killed, one a new Dad in his early 20s, and four others injured.

Some background

A concrete floor in a multi-story buildings is constructed by placing a horizontal form of a material like plywood at the level of the underside of the floor – the 4th floor in this case. The form is supported by beams and jack posts resting on the completed floor below – the 3rd floor.

(Jack posts are simple steel posts whose length can be adjusted a little – jacked up or down)

Concrete from a large bucket is then placed on the form and smoothed off. The result is a floor – the 4th floor – when the concrete hardens.

The large bucket is filled with concrete from a truck parked on the ground below and lifted into place by a construction crane. These cranes can lift buckets of concrete many stories in multi-story building construction.

The 3rd floor below would have been constructed in a similar way a few days before and still supported by the form, beams and jack posts until the new concrete there is strong enough. And the 2nd floor below that, a few days earlier still.

Structural engineers design the size, strength and spacing of the form, beams and jack posts. They also determine when this temporary floor support system can be removed.

An analogy

Similar, are the vertical timber forms that were placed to construct the basement walls of your house. These forms were supported by diagonal bracing/posts resting on the ground beyond the basement wall. Simple vertical basement forms, adequately supported, like simple horizontal floor forms, adequately supported.

Some simple virtual analysis

Sometimes construction is moved right along – rushed a bit – to stay on schedule, and mistakes are made. (Refs 1 and 2) Christmas is coming and this floor, the 4th, is the last one.

Most of us can see several places where things can go wrong in multi-story building design and construction like the one in London:

  1. Too much heavy, wet concrete placed at one location on the form – sort of like a point load in engineering design – that was not provided for in design. Concrete is about 2.4 times as heavy as water
  2. Too much concrete placed too quickly at one location on the form – like a dynamic load in engineering design
  3. The bucket load of concrete was lowered too quickly or came loose and fell and hit the form – like a dynamic point load
  4. The temporary supporting beams and jack posts were not placed properly for the 4th floor. Either too few were placed or they were not spaced properly this time
  5. In general, construction was rushed in some way for the 4th floor, the last one – let’s get on with it, time is money and Christmas is coming

More simple virtual analysis

Construction workers reported seeing a section of the 4th floor collapse after concrete was placed, the debris fall to the floors below and take these out too. Photographs from people on scene and video from a drone above generally support this report.

The construction procedure is simple – support a form with beams and jack posts then place concrete. Not unlike a horizontal basement wall – sounds funny but the engineering principles are similar. The procedure worked for the other floors, and it was being followed on other construction sites in Canada at the time. Why not this site too?

Wet concrete placed on a surface, a form, flows a little like cold molasses – it has to so the workmen can spread and level it to form the smooth concrete floor. I can’t imagine it as much of point or dynamic load on the floor.

The concrete floor was in place according to reports. I can’t imagine the concrete bucket lowered too quickly and hitting the floor form and smashing it. The bucket was probably down at the truck on the ground or on it’s way.

I’ve done materials testing and inspection on multi-story building construction and that’s what happens – the bucket is lowered after unloading the concrete. It doesn’t hang around up there.

But, if the beams and posts supporting the 4th floor form were placed properly like for the 3rd and 2nd floors – which did not collapse during construction – then a section of the 4th floor would not have collapsed like it did.

My conclusion as to the culprit

That leaves inadequately placed beams and jack posts as the culprit, the cause of a section of the 4th floor collapsing at the multi-story building site in London.

That’s my initial hypothesis as to cause based on a simple analysis of virtual evidence and knowing something about how multi-story buildings are constructed. (Ref. 3)


  1. Thinking about the cause of “wavey”, sagging floors in a building and how Counsel benefits. Posted April 6, 2016
  2. Bridge failure in litigation due to inadequate bracing – City of Edmonton. But, inadequate for what? Posted March 15, 2016
  3. What can you get from a virtual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020

(Posted by Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Halifax, Nova Scotia, Canada December 31, 2020 ejorden@eastlink.ca)   

Using Google Earth photographs in forensic engineering investigation.

I continue to be impressed by how valuable aerial photographs are in forensic engineering investigation. Most recently by the high resolution of photographs of urban areas from Google Earth Pro. You’ll be impressed too when you get photographs from Google Earth of a site involved in a civil case or insurance claim, possibly even before you retain an expert.

However, the resolution is not so good of rural areas. You get a big picture but it has a blurry look when you zoom in low. It’s not so suitable for reliable terrain analysis and data collection.

I tested this a few days ago by comparing Google Earth resolution to that on video from a drone-mounted camera. The video was of a rural site with a problem that I had investigated earlier. The Google Earth photograph was certainly useful but found wanting for detailed, accurate analysis.

I’ve been taking video of accident and failure sites using drones for several years. It’s routine for me now during my forensic work. The video can be taken at any elevation from ground level up to 400 feet, whatever suits the investigation. I’ve told you about this in previous posts. (Ref. 1)

But it was a photograph sent by a client of an urban site in Ottawa taken from Google Earth Pro that opened my eyes. This was the scene of a retaining wall failure. I was able to get a lot of data from the photograph. (Ref. 2)

I also learned last evening over a glass of wine that a friend has been using photographs from Google Earth in traffic accident reconstruction for a long time.

He can draw an accident diagram on a Google Earth scene using a program like FARO BLITZ.  The program contains a file of vehicle dimensions so that vehicles placed on the diagram are automatically drawn to scale. 

Also in the program are the symbols, lines, curves, scales, etc. typical of a land surveyor’s plan. And these are placed on the accident diagram much quicker and cheaper than a surveyor could.

Finally, objects such as vehicles that happen to be in the Google photograph and not needed can be deleted.

A forensic engineering drawing quickly made to order using Google Earth while sitting at your desk.


This is what’s available from Google Earth Pro for an urban site:

  1. High resolution video from a sports utility vehicle, a SUV, on the road in front of the rural or urban site
  2. High resolution video from a satellite of a site in a built-up, urban area
  3. Video of sites in rural and built up areas that are okay from a satellite but get blurry when you zoom in

The mid range video, #2, in the above is not available from Google Earth Pro for a rural site. This video is taken with very sophisticated cameras on satellites way up high and is excellent for terrain analysis and data collection at a forensic site in an urban area. (Ref. 2)

The stepped procedure for doing this is straight forward:

  1. Open Google Earth
  2. Enter the civic address of the site into the Search box
  3. You are now looking at a high level Aerial View of the property of interest and its surroundings
  4. To switch to “Street View”, pull the little person icon from the “ghosted” controls on the top right to the place on the roadway you want to examine
  5. You can then rotate your view using those controls on the upper right and can use your mouse to choose to move right or left along the road by clicking on the arrows ( < or > ) which appear on the roadway itself
  6. To leave the Street View and return to the Aerial View, choose the “Exit Street View” on the top right of the screen
  7. To add a slider to the top left of the screen which shows earlier imagery, choose “Historical Imagery” from the “View” drop down menu at the top

Here is the most direct link to download Google Earth Pro using a PC. I’m not familiar with downloading to Mac, Apple desktop computers. The procedure is in a different part of the Google Earth website.



You have a wonderful tool at Google Earth Pro to get photographs of a site minutes after a client briefing about an accident or failure in the built environment. If you subsequently retain an expert to determine the cause of the problem you’ll be able to brief him or her in a more informed way. A picture is still worth a 1,000 words. I’m using it now and you can too – you don’t need to be a technical expert.


  1. A Bundle of Blogs: Aerial video of insurance and forensic sites taken with cameras mounted on drones. Posted October 31, 2019
  2. What can you get from a virtual visual site assessment about the cause of a leaning retaining wall? Posted November 13, 2020


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

What’s there to know about experience v. engineering in the neighborhood?

Is it important to know that a lot of the built environment has not been engineered but built on experience? Built on the basis of personal and first hand knowledge, observation and practice – that is, experience. Rather than on the application of science and mathematics – engineered. It is as I show in the following.

Some examples:

When was the last time you thought about the depth of a telephone pole in the ground and how this was determined – so it wouldn’t get pulled over by the power lines tugging at the top? And related, how the anchors for the pole’s guy-wires are figured out and constructed?

Not big issues you say? But note how some poles lean next time you’re driving around.

A leaning pole near where I live had a new anchor and guy-wire installed in the last couple of days, alongside the old anchor that didn’t work. Looking up you see lots of wires near the top tugging on one side but none on the other side. Was the new anchor engineered or experienced? Obviously, the old one wasn’t engineered because the pole leaned.

How about the foundations for your house and all the others on the street? For that matter, foundations for all kinds of structures.

We’re absolutely certain the foundations for a multistory building are designed by an engineer but what about a single story commercial building in an industrial park?

How about the foundations for the piers and buttresses of a bridge? I’m sure the foundations for the piers at a river crossing are engineered. But, what about those simple abutments?

When was the last time you wondered who built the drip loops on the power supply to a commercial building – an engineer or an experienced person? Then wondered what happens during heavy rain and strong, gusting winds out of the southeast?

(Drip loops are loops in the power lines from the street to a building. They are located near where the cable enters the building. Rain water on the lines drip off at the loop down rather than run along the cables and into the building. Except they don’t work well in heavy rain and strong winds with up-gusts as I determined recently – they fail in engineering terms)

What about the retaining walls along our streets and highways? And the paved bike paths in our green belts?

Also the soil slopes along our holidays? For example, see the highway slope failure near Exit 10 on Hwy 104 in Nova Scotia. It’s subtle but it’s there. Is that an engineering failure or an experience failure?

What about those large steel or concrete culverts carrying roads and streams beneath our highways. Are they engineered or experienced?

And those tall, slender propane tanks at service stations? For certain, the steel tanks have been engineered but what about the foundations to resist overturning of the tanks in strong winds?

I can give more examples but that’s enough; I’m sure you get the picture.


I thought of this as I was driving about recently – so much of what we see constructed is based on experience. There are no engineers involved.

Why take an interest if things are working most of the time, performing as they should? Regardless of whether they were engineered or built on experience.

How is this relevant to understanding forensic work, the objective of this blog site?

Here’s why it’s relevant and important to take an interest

Things do fail and also occasionally injure people.

For example, if a kid on a bike falls and is injured after hitting a pot hole on a bike path what happens during the forensic investigation? Lots of bike paths are built based on experience. But pot holes form because of well understood engineering principles.

Or an electric room in a commercial building floods in spite of the engineered or experienced drip loops? What happens during the forensic investigation?

Or a highway slope fails, a bridge collapses, or a telephone pole leans?

We can figure out why something failed – the easy part. But determining the standard of care and what a reasonable person would do is tougher when the thing was built based on experience.

Who should determine the standard? A planner, an architect, a design engineer, a construction engineer, another experienced person, the owner of the structure, someone else?

And if things work quite okay, should we, nevertheless, wonder if they’ve been engineered or experienced – particularly things used by the public!?

Things built on experience are sometimes overbuilt and cost more money than they should. And sometimes they’re under-built and cost more money when they fail and occasionally injure people.

It’s important to take an interest because lots of questions arise when something fails that was built on experience, not engineered.


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

What can you get from a virtual visual site assessment about the cause of a leaning retaining wall?

What can you get from a virtual visual site assessment? That’s easy, pretty much the same as from a real visual site assessment. Except the expert doesn’t go to the failure or accident site and look at everything up close in assessing cause.

The expert relies on what s/he can see in photographs and video, after a briefing by the client and reading documents. He may also ask for additional information from someone at the site as I did recently.

A visual site assessment examines what is exposed at the surface of a site. It’s a preliminary stage in a comprehensive forensic investigation that also examines what is exposed below the surface after taking things apart or probing with some device.

The following is a good, easily understood example of what you can learn from pictures – the data you can get and the conclusions you can draw. The data is in italics in the following:

The wall in general

A party called me from Ottawa about a concrete retaining wall that was leaning. He wanted to know why and if it was dangerous.

He briefed me on the situation. I asked for photographs which he sent and I studied. He also sent some measurements of the lean. I then asked for aerial video from a kid’s drone and I got that. A little later a Google Earth shot of the scene was sent to me which was revealing.

I saw that the wall was low, maybe 2′ near the ends, and about 6′ at the highest point. Not a big wall but still a problem – it will fall down in time but when is difficult to predict.

I got this data based on the height of cars that I could see in the scene. Also knowing the standard height of 8′ from the floor of a building to the ceiling. This was evident on the outside of buildings in the area by the distance from the bottom of the brick work to the eaves.

The lean was greater at the higher sections of the wall. This was clear in photographs along the length of the wall. No thinking and figuring was necessary. But, was it significant?

There also appeared to be a building behind the wall near the higher section, and a smooth area too – pavement? These apparent features were just visible beyond grass, shrubs and trees in back of the wall.

Hmmmm, a budding conclusion? Was there some association between the the higher section of the wall, the greater lean and a possible building behind this section of wall?

The face of the wall:

I saw in close-up pictures at least seven vertical cracks in the wall from top to bottom. Concrete retaining walls are not supposed to crack.

The concrete was stained white along the length of the cracks. Water running down concrete can stain it.

The concrete wall on one side of some cracks leaned farther out. This would not happen if there was horizontal reinforcing steel in the wall as is often the case in well designed retaining walls.

Conclusion? Properly designed and constructed walls do not lean a lot, crack at several locations, drain water from the cracks, and lean farther out on one side of a crack.

I did not see any holes in the face of the wall – possibly one or two – typical of drain holes that are often designed and constructed in a retaining wall.

The base of the wall:

Concrete retaining walls are supported on a concrete base that extends to the rear of the wall, called the heel, and a little to the front, the toe.

Close up pictures of the bottom of the wall where the soil was removed at one location showed the toe. The toe was a few inches wide and the top a few inches deep.

The toe of the base of a properly designed retaining wall is usually much wider than this and deeper – at least below the depth of frost penetration for the area. The size and depth of the toe was evident from maple leaves in the picture.

The rear of the wall:

Video from the camera on the kid’s drone, and screen grabs from the Google Earth video, particularly the latter, were quite revealing too. I was surprised at the excellent resolution of the screen grabs.

A house, driveway and garage could be seen behind the retaining wall in the aerial photographs. The garage was opposite the section of wall that was leaning the most. The near side of the garage was about 9.0 feet from the retaining wall. I got the distance from a scale on the Google Earth photograph.

The driveway was paved and ran from the street to the garage, and over to the side of the house.

I asked my client to check the distance from the wall to the side of the garage. He did this and got 8.5 to 10 feet and confirmed the approximate measurements I took from the Google Earth photograph. He also noted the garage roof did not have an eaves trough.

Conclusion? Some of the rain water falling on the driveway and the garage roof would seep into the ground at the rear of the retaining wall.

Conclusion about why the wall is leaning:

I concluded based on the data from my virtual site assessment that the retaining wall was inadequately designed and constructed and this was the cause of the lean.

For example, the rear of the wall was not well drained. I’m sure this is a significant cause of the lean. Water in the soil behind the wall expands on freezing in the winter and pushes against the wall, moving it a little each year.

This is like the frozen water in soil pushing against the underside of a house footing that has not been constructed below the depth of frost penetration – frost heave.

Also, the wall did not have an adequate foundation base, certainly not at the toe. This would contribute to the lean. The soil at the back of a retaining wall applies pressure on the wall trying to push it over – make it lean. A suitably wide base at the heel and the toe prevents this. This kind of pressure is in addition to the push from frozen rain water that has seeped into the ground.

The shallow depth of the base means it is susceptible to frost heave which might also contribute to the wall leaning.

The wall did not have horizontal reinforcing steel. This type of reinforcement stiffens the wall and helps prevent leaning.

Future Forensic Engineering Investigation:

Future investigation would consist of:

  1. A real visual site assessment to confirm the findings of the virtual visual site assessment.
  2. Collecting data from the site for design of a new retaining wall. Data like the nature of the foundation soils at the location of the wall.
  3. But, particularly, data on how to collect and remove rain water shed by the nearby driveway and the garage roof – for that matter, data on how to drain water from behind the wall in general.


I got all of the above from a simple virtual visual site assessment of the cause of the retaining wall’s lean – by studying pictures. The assessment took about an hour and a quarter of my time.

This type of assessment is possible for all failures and accidents. For certain, the amount of data got will vary depending on the incident. But, also for certain, you will be surprised at what you can get from a simple virtual visual site assessment by an experienced forensic engineering expert.


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

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.


  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 reliability 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.


  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, Canada 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.


  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)

Update: Principles governing the cost control of dispute resolution and claim settlement involving experts

I updated the Principles after being contacted by a Toronto firm about a slip and fall accident. The question came up about being retained on contingency. The contact said they do this when the injured party may have a claim but no money to pursue their rights. He also thought the claim would settle within a year. I told him I couldn’t do this.

The chap was pleasant but I thought later, after he remarked he was acting for a partner in the firm, that he may have been a more junior member of the firm and just didn’t know: Experts don’t take cases on contingency, and slip and fall cases typically take more than a year to settle.

Common law requires that experts: (Ref. 1)

  1. Be independent from the parties that retain them
  2. Provide objective, unbiased opinion evidence in relation only to matters within their expertise, and,
  3. Avoid assuming the role of advocate for the parties that retain them

These requirements are the same in all issues involving dispute resolution and claim settlement. The great majority of experts know that they serve the process, as found in a pilot study of 152 Canadian experts, not the party who retained them. (Ref. 2)

The requirements also mean that an expert must engage on a fee basis not on a contingency basis.

But, to be absolutely sure that there wasn’t another school of thought out there on experts and contingency I contacted the head of another Toronto law firm. I haven’t been answered – slammed would be more correct – as quickly as in this case: “Absolutely not!”.

After all this, I thought, I better update the Principles to be sure it’s clear when managing cost that experts are not retained on a contingency basis.

You can read the updated Principles at http://www.ericjorden.com/blog/2019/07/30/principles-governing-the-cost-control-of-dispute-resolution-and-claim-settlement-involving-experts/ as originally posted on July 30, 2019.


  1. Stockwood, Q.C., David, Civil Litigation, A Practical Handbook, 5th ed, 2004, Thompson Carswell
  2. Corbin, Ruth M., Chair, Corbin Partners Inc. and Adjunct Professor, Osgoode Hall School, Toronto, Breaking the Expert Evidence Logjam: Experts Weigh In, presented at Expert Witness Forum East, Toronto, February, 2018


  1. Jorden, Eric E., Consulting professional engineer; forensic engineer, Geotechnology Ltd., Halifax, Principles Governing the Cost Control of Dispute Resolution and Claim Settlement Involving Experts, presented at the Expert Witness Forum East, Toronto, February, 2018

(Updated September 23, 2020 by Eric E. Jorden, M.Sc., P.Eng, Halifax, N.S. Canada.  E: ejorden@eastlink.ca)

Get on site and do a forensic visual assessment before COVID-19 returns

There’s an argument for getting on site and doing a visual assessment before COVID-19 returns. There is talk of a second wave. I thought this when I was thinking of getting up to New Brunswick to visit friends before I get COVID-19-stayed in Halifax for the winter.

There’s no question about the value of virtual site assessments as I noted recently. (Refs 1, 2) Studying emailed documents and photographs of a site and getting a lot of data without leaving the office. Including the cause of a slip and fall accident that stared me in the face recently. (Ref. 1)

But, the worth of an on-scene visual assessment has been well understood for decades – if it can be done safely. Pre, second-wave COVID-19 would be safe. (Ref. 3)

Getting on site would give us:

  • additional photographs to those in the documents,
  • aerial video – pre-planned with a virtual drone flight (Ref. 4),
  • accurate measurements,
  • re-enactment of a slip and fall accident, if that’s the issue,
  • a forensic engineer calibrated to the site (Ref. 5), and,
  • more hard data for continued virtual site assessment back in the office.

In many cases, a forensic investigation unfolding in this conventional way – document study then an on-site visual assessment – often points to the cause of a problem and those responsible. And often, as well, to how an insurance claim might unfold or whether a civil case should be filed. Additional intrusive investigation at the scene is sometimes needed but not always.

So, what are we waiting for? If a second COVID-19 wave is in the wings ready to wash over us, and we quickly visit friends in the Atlantic bubble to get ahead of it, why aren’t we quickly doing an on-site visual assessment?


  1. What can you get from a virtual visual examination of an accident scene? Posted August 28, 2020 2.
  2. COVID-19 and forensic engineering investigation. Posted May 7, 2020
  3. COVID-19 and an initial forensic task a.k.a a visual site assessment, sans social distancing. Posted June 1, 2020
  4. It’s here, cost effective, efficient aerial video for forensic investigation! Posted October 8, 2019
  5. Can you “calibrate” a forensic expert? Posted June 23, 2020