Sir, you are proof the "these days, people can't pay attention to anything long" is a dirty myth. We are not irritated by length. We are intolerant - of having our time wasted. Know your audience. Tell us what we want to know. And we'll listen - for hours. Because you provide valuable information. No filler. No clickbait. No BS. Just facts. Critical evidence. Clearly communicated. (And that's why we love you.) Thank you!

Another instance of my thoughts changing from, "How did this building fall?" to "How was this building standing?"

Don't apologize for going long. You do it to make sure we get it and it's a brilliant job.

I've been a carpenter contractor for 46 years, and have worked on many of these old brick buildings, so maybe I have a bit of an advantage when I say definitively that the engineer in charge of this project was a complete and total SCREAMING IDIOT. And his contractor wasn't far behind. I've had to challenge many, many drawings and "game plans" for similar reasons because sometimes what they draw will never work. This catastrophe could have been avoided through simple common sense. They didn't even have to be all that experienced....just smarter than your average bucket of bricks. It's an actual miracle that this thing didn't cave in on the contractors while they were working on it. I'd be willing to bet it was making strange popping sounds all day long...

The ability for brick masonry to shift load paths so far like that is impressive. And it gave so much warning before throwing in the trowel.

Literally the best engineering channel. Always excited for a fresh Building Integrity video.

That photograph of the deformed window from the inside is terrifying. I don't understand how that didn't trigger an evacuation, it seems so clear that the structure of the building is in major trouble.

it really is a testament to how strong that building actually is that it didn't just collapse as soon as they started tearing the structure apart at the base.

Your constraint is amazing. I was internally screaming watching this. I’ve had masonry tradespeople who would know what to do with this without any engineering input. I’ve seen them do such jobs. I know that their lead guy would go paper-white-faced upon seeing this. It’s so infuriatingly crazy what went on with all those “repairs”.

I toured the building two weeks before it collapsed, and would've been neighbors with one of the souls that died if I didn't get accepted at another apartment complex. We can't thank you enough for going into detail about this investigation. We can't let corruption slide.

It's a miracle the thing didn't collapse sooner given all the structural brick that had already failed (crumbling, pulverizing, falling, etc) and was no longer bearing loads above, forcing adjacent areas (which may not be in much better condition) to carry both loads, thus contributing to their failure, and repeat. There's only so much support that you can remove over time before gravity does its thing on everything above.

Just to add insult to injury GEICO has twice refused to honor the rental insurance of one of the tenants. The insurance adjuster told her she should have gone back into the building to get her stuff since her part of the building did not collapse. Story is on our local subreddit and a couple of local outlets.

Discovered your channel after Surfside. Your videos are amazing. Detailed and scientific, but explained well enough for anyone to understand. Thank you!

Ditto on everybody's "don't apologize for the long video", comments. I don't know of any other engineering channel able to keep me glued to the video screen until the end like this one does. Very educational. You make things make sense! Thanks!

No wonder the mayor wanted his buddy's apartment demolished right away. The investigation has clearly turned it from negligence to gross negligence, incompetence, and reckless disregard for human life, causing injury, death, and loss of home/possessions.

As a structural engineer I really love the longer format, detailed videos you produce. This was fascinating, I've heard about multiple-wythe brick construction but I've never dealt with it firsthand. Hopefully other engineers/contractors can watch part 1 & 2 to educate themselves about this method of construction and the dangers of modifying it, hopefully avoiding another similar unnecessary disaster.

Classic case of seeing what one wants to see, while overlooking things that should be obvious. Reminds me of years ago when I was presented a problem at my place of employment. There was a tool that, on occasion, when being dismantled, would break. This was costly, like about $10,000/time. All the people who had dealt with this for years attributed it to carelessness on behalf of those taking the tool apart. I investigated. The design engineer had made it virtually impossible to put ANY bending moment on the part being removed. That is what it would have taken, IF it was carelessness, as they thought. I could see that something else was in play. I looked at records of when the tool had been run. There were two conditions that both had to be met, before the tool was broken upon disassembly. High heat, and high pressure. One without the other was not sufficient. Clearly there was something else going on. Turns out an insulator material was not up to the task. It would deform when both high heat and pressure were there, but was strong enough when one or the other was not present. The deformation made it impossible to remove the tool without breakage.

I'm just an old woman with zero training. But as I watched your explanation I understood because you were special plain language and show what was happening. As I watched I began feeling physically ill because people were allowed to continue living there. By the end I was having to fight off going into hysteria over the lives lost. From the news at the time this was happening I remember a statement that this was low income housing and some homeless were given shelter to live there. Part of me now wonders if the people were allowed to continue living there because "they are poor ". It is clear that our society doesn't think the poor matter. I am old and sick but I'm trying to figure out out how to determine if the same sorts of situations could be developing in my own area. And also where to inquire about these things in my small town. I thank you for sharing your knowledge.

Whether or not a steel column is in the wall seems like a pretty important detail that the engineer should have been able to determine.

Don't apologize for long videos. I didn't even realize it was 50 minutes because I was so engaged in what you were explaining. Thank you!

There's a video from two months before this collapse of a facade coming away from the wall of an apartment building in New York. The building was immediately evacuated. I don't understand why this one wasn't also. The negligence from all parties is astounding.

We can criticize the way the building was originally constructed back in the 1900's, without steel columns...but it is impressive that the building actually did give PLENTY of warning before it collapsed. I can't believe it wasn't evacuated.

Future engineers need you as in instructor. I would take a whole semester with you just to go over engineering failures. A) how to spot the failures and B) what could have been done to prevent it. You're an amazing teacher, even if this is just what you do for work. Being smart doesn't always mean people can convey it to others. You do a phenomenal job of explaining it.

In short, due to a lack of proper shoring while doing the repair work. They took a structure that was designed to handle vertical loads. And made it take diagonal ones. Shearing the structural brick and causing to crumble

I hope the city officials, engineer, and owner, all of whom are responsible for this murderous idiocy, go to jail. No care for their craft, for their responsibilities, and for the human lives their decisions affect. Thank you for making these videos, you are amazing at explaining complex topics and breaking them down into understandable chunks. Still, no matter how good you are at explaining - it's disturbing how intuitive this structural problem here is. It should be obvious to any random person, that you cannot just assume a 100-years-old brick wall is supported by beams, and that you cannot just leave entire brick wall segments largely unsupported, and that the failure signs shown in the images are obvious indications of a major structural issue.

Creators have proven long form works if and only if they are good at being a great teacher or provide something interesting and worth listening to or learning about. You are an example of that. Take as long as you need.

This was amazing especially about the load shifting and I'll tell you why. I lived in an older building with a partially exposed underground parking structure held up by steel ibeams connected to brick walls. We got a blizzard that dumped 2' of snow. The garage roof had roughly 50' of it down the length covered in 8' of snow (drifts..etc), plus all the snow on the roof. During that storm three of the support steel pylons fell OFF their support due to the weight of the snow and the rust that had eaten them. The entire corner of the 2 story building fell about 4" when the supports fell. The apartment management company (truly shady operation) called out a structural engineer, I was there and heard him say: this needs to be addressed immediately. Was it? No. I left as soon as I could. Found out later the management company collected the insurance money and their fix was to put up 2 floor jacks. Nothing was said to the residents ever. Despite the concrete falling off the walls of the stairway that led to the underground parking garage.

I'm not an Engineer. Well I have some Firefighting Engineering Credentials. Including some classes and lots of training on inspecting a building, reading a building and knowing when to get the hell out of a building, or to not go in. I've spent some light duty time doing Code Enforcement and inspections. So by no means a Civil or Structural Engineer. But a fairly well educated layman. These pictures scare the hell out of me. And I think what scares me more is there would have been a real Engineer standing there telling me that I was worrying over nothing. One of the tricks I was always taught for fast assessment of a building when pulling up on a scene is to quickly look for the buildings lines. Find the corners, find the window frames and doors. Is everything still plum? At proper straight lines and perpendicular to each other. No Curves is a big one. Do all the windows line up as expected are door frames straight? This is just the quick 123 test you do as you are walking up to any unknown building on a fire call. And boy would this fail my quick test. Setting eyes on the interior face of the supporting walls. That's the point where you very gently get your crew to take careful babysteps to the nearest exit while you have the trucks start blowing the evacuate alarm. That stuff going on at 34:10 I would have spotted that, in the dark. And I'm a complete idiot with structures.

My experience in college was that 2/3rds of the people in my classes only passed because people who understood things helped them. They could never figure out anything on their own, yet they passed anyway.

Breaking down a complex situation for those of us that don’t have your qualifications, into something we can fully understand, is what makes these dissections so interesting. Thank you for your time and effort. Regards from OZ 🇦🇺

You should be teaching at a top engineering school. I'm an electrical engineer with an interest in civil and structural engineering. This video was a great "lesson" on load transfers and stress flows. Well done!

This was an excellent video. It’s like a case study happening almost in real time. And as a naval architect, it’s always interesting to learn about how structures on land work, especially because masonry structures behave so differently from steel. Thank you!

This video is giving me Hyatt Regency walkway vibes. Great work and a great explanation.

The engineer's failure to acknowledge what was happening is infuriating & incredible. How did he not understand the building at all?

Another fantastic video, Josh. Gripping. Am always excited when I get a heads-up you’ve posted something new. Don’t apologise for the length - I love your clarity and focus and your measured delivery. Thank you.

Wow you did it again! This presentation is like what you did for me with the Champlain Towers collapse. It made me see how complex and detailed analysis is needed BEFORE the building falls down in addition to after. Thanks.

Interesting that you and I reached the same conclusions. Having worked for a company that did sheeting, suring, pile driving and underpinning, I got to see the correct ways to consolidate loads without losing the structure or damaging it. As I see it the only way to accomplish the necessary work was to vacate all the apartements in the affected area so as to allow for installation of temporary support from the ground all the way up, then to replace existing support. In my mind there was a reluctance by the owner to do this correctly as it would have caused a loss of cash flow from those apartments where work was required. I don't see any other way to correct the decay without this procedure. And it might have entailed doing this along the entire perimeter of the building wherever support columns existed. Essentially, rebuilding the structure with new support, throughout. And at that point you have to ask yourself, as the owner, is it worth saving the building at all. But to allow occupancy until the demise occurred is criminal, in my mind. Don't know who paid the engineer who made recommendations but there seems a bias in his opinion or even worse, perhaps a lack of knowledge.

Dude, I *love* your long explanations. I know nothing about structural engineering, but as a mathy person who's fascinated by how things fail (and thus secondarily how they work at all in the first place), this, like all your videos, was awesome.

I always come away from Josh's videos so much smarter. You truly one of the best teachers I have ever witnessed and you have ignited my interest in engineering and desire to forensically analyze these building failures. Thank you Josh.

BUILDING INTEGRITY ! This is the kind of thing the internet should be doing ... sharing REAL information and cogent analysis of what went wrong so that WE THE PEOPLE can LEARN from mistakes and IMPROVE going forward. Sadly too much of the internet is cluttered with false and misleading babble.

I'm not an engineer or anything of the sort, but I find all this fascinating. Thanks for explaining it so an average person can understand.

The negligence/incompetence here is stunning

As a citizen of the United States, and of Davenport, Iowa, I just want to thank you for the time and effort that you put into this excellent presentation, particularly regarding the failure of providing adequate structural supports. A sixth lawsuit has recently been filed; I suspect it will not be the last. (The warnings, and shoddy workmanship have been noted.) Parts 1 & 2 have been shared to one of our local pages dedicated to the collapse and the corruption.

No apologies. The video was as long as it needed to be. No unnecessary filler. Absolutely clear analysis.

I didn't realize how complex this entire incident was. This was very eye opening.

I am an engineer and I love this channel. Brilliant, clear, and honest explanations of physical facts. What happened to the engineer that designed the repair that apparently lead to the subsequent colapse?

Makes me value my old 1903-1910 International Correspondent School books covering construction and wall design.

Really sad we will be seeing less of you in the next few months, but I'm super thankful for all the time you spent to put these together. Really makes a huge difference even as just a homeowner, I'm now constantly aware of structures I'm in and paying close attention to how my own house moves or shifts.

I m construction worker from Finland , and your channel have been a reason why I ve taken interest in building engineering.

Thank you so much for this video and all of your hard work producing the content on your channel. My construction is basically limited to decks and small projects. I’ve always tried to do the best job and give my clients a quality project. Your analysis of building failure is really helpful as you point out many factors that a lot of contractors might not see. Because I tend to slightly overbuild, I’ve never had any issues with anything I’ve built. Hopefully everyone in the construction trades can learn from these very educational videos. I’m looking forward to the next episode.

Thank you for taking time to share the analysis. It is too bad the contractor was not in a position to have more input into the design of the remodeling. I’ll bet the laborers on the job could easily look up and intuitively understand that several stories of unsupported layers of brick between the new CMU wall sections wasn’t going to stay floating there for long. This disaster shows that bilateral communication channels need to be built into projects like this so that oversights don’t become disasters.

Excellent as usual Josh. I have followed your KZfaq presentations for some time now, starting with the Surf side collapse. What I'm also looking forward to is any follow-up on the Milleniuim Tower in San Fransisco. As a retired consulting electrical and mechanical engineer I worked with several different structural engineers in the design and construction of commercial buildings. I remember during my early years I worked with a structural engineer in North Dakota. As a young inexperienced engineer I asked him if his design would "work". His answer was " I hope not". He patiently explained to me that work was force through distance, and he " didn't want anything to move". Keep up the good work.

I watched this video hair raised in my head first 30 minutes straight. Maybe this is why we got building tecnology history classes in our HVAC engineering classe (🇫🇮). It really looks like the design engineer here did not understand how 100 years old wall works. Cotractors were more alert, so I would not blame them. Most likely result here is, that the engineering design company is found 100% at fault in court. You should not pressure wash the brick walls (at least full speed and perpebdicular to the wall) as you saturate the bricks' cavities with water. And you should not paint the brick (at least with modern plastic based paints) as those are functioning as steam barrier and screws up hygroscopic operation of the wall. The collapse was so fast, that rhis was not factor for the collapse - but may of been cause of the earlier damage.

I learn more from your videos than I do from most Professional Engineer education videos. Thanks!

Thank you so much for these videos! My background is in engineering (BEng in IT & MSc in EE; structural and mechanical only by practice), however, I've spent most of my professional career so far in administrative and financial roles. Nothing wrong in them, I don't mean that, but this drive you show, the need to understand how things work, and how we may or may not make them work, really makes me to want to get back into my roots.

The engineer who was having the Building get away from him, he needed to ask other engineer friends to take a fresh look at the Building. He needed fresh sets of eyes to look at these escalating problems.

There was recently a partial building collapse in a neighboring county, and the building is constructed similar to this one, with the beams (wood, in this instance,) bearing directly on the brick wall, which collapsed. This is a fantastic video series about this incident in Iowa, and you've absolutely earned yourself another subscriber!

Josh, this was very engaging, and highly detailed and entertaining, I learned so much!! Please never apologize for length. When things are important, and great info, it is limitless and fascinating. I hope you submit this to the city, over there to take a look at it, because they seem to not have the capability in their local builders, inspectors, and contractors, to know what they are doing. this is everything that happened, that they need to know, and they did not need to tear the rest of that building down, like they did. This incident is horrific, as folks have died. so terrible.

Excellent content! I commented about your conretes worst enemy video earlier this year, and you replied. It was a pleasure to chat with you. I recommend your channel all the time, and have learned alot from you! Thank you.

Fantastic video, as always. Definitely one of my must-watch channels on KZfaq. Have a thought for a 'Part 3' in this series: At various points during the timeline leading up to the collapse, what would your recommendation have been to repair the building correctly? And at what point do you think the building passed the proverbial "point of no return?" And also at what point should the building have been evacuated?

Oh, those were STRUCTURAL bricks? (Sorry, I could not resist. Thanks for the wonderful video!)

You analyses are always so thorough and excellent. While I don't hope for disasters, I look forward to your analyses when there is a collapse.

It's exactly this sort of analysis that should have been done before starting work. This sort of half arsed approach is far more common than people realise. People often think they know more than they do. Great video

been waiting for this! can confirm it was worth it as well, detail is what makes this channel special :)

Info note, on west coast we'd use terms "unreinforced masonry" and "veneer brick." Seismic considerations would have put this project in front of a specialized engineer and had the full attention of building department. Likely the building would have a yellow tag (unsafe to enter, do not occupy, repair immediately) or red tag (demolish as matter of public safety) when eyes were laid on that rotten bearing wall. Florida wins most-cautious award, though, for the required periodic reinspection.

Your content shows the dire need of competent structural engineers, as they save lives!! It is sad with news of buildings falling over, that all of that could have been prevented. Very sad.

Incredible video. Thorough, not long, extremely informative and evidence based. It’s a shame that every municipality doesn’t have a building engineer like you on staff to catch these tragic oversights.

As always, a thorough and believable analysis of what went wrong in this collapsed building and in the professionals (private and city) responsible for this disaster. I just watched the short but detailed KZfaq video by Mike Bell and he was able to slow down the video of the building's final 9 minute slow-mo collapse. This showed two major things: 1) that second-by-second you could see the silly wooden "braces" were actually moving and zinging before the fall, and 2) that there were about 6 other noticeable puffs of dust indicating bricks as they turned into powder and the building load shifted to other bricks that then powdered and crushed. One news article I read on-llne indicated that the actual repair work on the building was done by a masonry company owned by the building's owner, Andrew Wold,. Wold is being sued by at least 6 parties for negligence...a real "bad actor" as you say Josh.

The psychological/political issues deserve some attention. An engineer is paid (sometimes) to write a report that suits the client. The paragraph the began "The main takeaway..." is a screaming code word for what the unsophisticated client demanded to hear. Integrity is corrupted by magical and complacent thinking. Paraphrasing: A man will believe anything if his paycheck depends on it.

prayers to anyone who lost their life here. relative to the construction, OMG, what crappy construction methods. looks like the best thing to happen to that building was for it to have collapsed. Thank you for taking the time to go through all the details. Your knowledge is fascinating. keep up the good work.

Another fine post Josh! Thank you so much. A few blocks away from me, the entire brick side of a masonry 2-story house peeled off last week; a similar situation where material was falling into the void between the structural block and the brick facade.

Josh, never apologize for going long on your videos, us less than knowledgeable folks love your in-depth explanations. This forensic investigation is some of your finest yet, Thank you.

On a much smaller scale, I called in some contractors to look at a house built around 1898 and got a quote for some work. The price wasn't too bad, but something didn't sit quite right with me. So I called out a retired contractor friend who'd done a lot of work on older houses. His estimate of repairs was triple what the original contractor's was and it wasn't because he was trying to be expensive. It's because his eyes saw things that needed fixing that the contractors who work on more modern houses didn't even notice or didn't know about.

Excellent analysis! I am shocked at the original repair design. I am an engineer from completely different field but I can follow the logic. I am also amazed by the lack of the attention by the repair design to the loads. My neighbour has his brick wall little two storey house modified and they put more attention to transferring the loads from the wall above while modifying the window opening. And here you have the huge, complicated building and design that doesn't take the wall thickness into account.

Incredible analysis. This kind of rigor and detail is what separates good content from "most everything else". I usually relax through 45+ minute videos, but this one had me on the edge of my seat, the *whole time*. Terrific video, thanks for doing this hard work.

Quote from the mason that warned people about the imminent collapse: ""Andrew contacted us to give them a bid on the back of the building to repair the exterior masonry that was crumbling and falling," Shaffer said. "Our bid was to support the building all the way up, replace the section of wall on the inside that was missing and then redo the façade of the brick on the outside." So it appears that the (higher bidding) trades were aware they needed to properly shore the whole load, it's bizarre to me that an engineer wouldn't understand or recognize that. Actually, I think if you took a random person off the street and explained that you wanted to cut away an entire section of a large building wall at the base, their first question would be "how do you support it so it doesn't fall down?"

Where's the followup on the "did I find a $100000000 mistake" video? What did they say when you reached out to them?

I don't know how I even landed here (thx yt algorithm?) but have been binging your videos for days now. Really awesome content: informative, understandable for a layman (not a native speaker, I've been learning loads of new words haha) and straight to the point. Very educational. Subscribed and looking forward to more!

I certainly miss your videos. I hope no one pressured u to stop. I also hope u can make money in this forum.

Well, what to say here. This looks like Amateur Night for Engineers. This is what happens when jobs are carried out to save cost. I`ve done many such refurbs in my time and I wouldn`t go near this without a custom made steel support structure to take all the floor loads away from the brickwork. Doesn`t need to cover the whole facade, it can be carried out in sections. Trying to do this with strongbacks and props tied together is possible if you know what you are doing and have a capable engineer on board. I`ve dropped the spine wall on a ten storey building but I relied on more than good will to hold it up till the new structure was in place. The photo with those lightweight props under the window heads tells me all I need to know. Thanks again for a very interesting two parter!

31:20 I'm not an engineer, but a designer, this is something new I learnt today, caught me by surprise of how these brick building works, it isn't like regular steel structure or re-enforced concrete structure, the loads aren't transferred point to point, but more of flowing around.

After viewing the first part of the investigation, I questioned why the original structural engineer didn't use a full steel frame as opposed to relying on a thick brick wall for load bearing. Then realizing the build lasted 106 years and didn't fall down until an improper repair was made makes the case for the brick load bearing wall. Perhaps this design was standard practice at the time it was built.

I love the long videos! Never apologize for the length Josh. Many of us want long form content vs short videos! You rock!

this continues to be one of the most thoughtful and well-researched channels I've ever found. thank you for making amazing videos!

The lack of awareness of the engineer of building techniques in the early 20th century seems bizarre to me - I am neither an engineer, nor in the construction business, but even I am aware that 100-120 years ago, it was common for buildings up to 10 storeys to be built with a load-bearing perimeter wall. I don't even know _how_ I know, but I had assumed it was common knowledge that that was how buildings were built back then.

Have you looked more deeply into the early history of the building? Because I suspect those bricked in windows on the west face were originally loading bay doors. The tall thin profile fits the shape of a turn of the last century horse-drawn cargo lorry. The location in the building, at the rear and immediately below the less desirable service quarters also fits. Then, as now, a loading dock area would have been noisy and smelly and not something you would have wanted around the guests. It would also explain why they, and none of the windows around them, were bricked in when the area went out of use. If this is the case, there could have been very old cumulative damage in the area from decades of minor collisions, and cargo and trash being hauled in and out.

I have worked with very well degreed engineers with very impressive resumes: mechanical, electrical and optical, who lacked basic common sense and any sense of urgency so unfortunately this situation doesn't surprise me. People have asked me why it is so hard to find a good contractor. People would often cite Norm and Bobby and the other contractors on This Old House as being what they expect. I tell them that for every Norm or Bobby, there are at least 100 numbskulls who don't have a clue working as contractors. The same goes for engineers. For every Josh Porter, there are probably 25 that are just passable at doing their job. I give that a lower ratio because to be an engineer, you have to at least be able to obtain a degree so that will weed out a bunch of people.

Geez. I guess it's a testament to how well the building was built that this collapse didn't drag down the rest of it. What little I know of structural engineering comes from your channel, Josh, but I have a feeling that a more modern building would still be standing after this. (Maybe CTS illustrated this?)

Fascinating!!! Never would I have imagined the problems with the single vs multi story shoring, it's excellent to be able to learn from an expert in the field. Thank you :)

Brilliant analysis and investigation sleuth. I'm in construction and this an amazing lesson from you. I learned a lot. If I ever see a droopy window I will run ada fast as I can. 👏👏👏👏

Missing your contributions to this KZfaq channel. Hope everything is going well for you.

Excellent and comprehensive as always. Thank you so much! It’s so frustrating that people were hurt and killed because the OBVIOUS signs of impending collapse were ignored. Even if the building/repairs done at first were poor, there’s no excuse for ignoring the cracking and slow collapse of the wall that happened afterwards. We had a patio door out in the back wall of our red brick house. The shoring was unbelievable, even if it was only there for a short while, and it took three huge lintels to transfer the loads. I’m no building engineer, but seeing the ‘repairs’ here it seems obvious that the load bearing hasn’t been considered at all by the original repair designers? Or did they believe the arched brick over the window would somehow magically hold everything up? It’s insanity. They just blocked up windows, no structural repairs at all!

It's a testament to the buildings original design that it held out for as long as it did despite the beating it went through.

We had same issue, when we were doing reno and adding floor to our building (built 1908). Young architect (early 30') thought he can remove about 2m (7')of brick for elevator where there were originaly narrow windows. Older structural engineer (architects can work only on 2 floor buildings without one here) had him fired on the spot. (There was host of other issues on top this one) Thing is, most younger people in industry have no idea on how bigger than small 1 or 2 floot brick buildings work. A lot of them thinks it is reinforced concrete skeleton infilled with bricks. And I know for fact, that on architecure course they mentioned these like on one short lesson (45min) from a friend. And there are a lot of these (several hundred) in city center here (built between middle ages up to 1940's) including some palaces built in 1200's and 1300's. Our office for preserving National historical (and cultural) artefacts, since added requirement of having done some knowledge test or experience working on these for architects and structural engineers to lower their workload. Building does not to be marked As of national historic importance (like palaces), it just needs to be on their list , pretty much everything bigger than family house built before 1914 and most up to 1950 is on the list. Office has their own engineers that need check and approve any permits for these including such minor things as replacing doors and windows as on most of these you need to keep visual appearance for example.

I know in accident investigations, groups like NTSB try to recreate the mindset of the people at the time of the incident. We know after the fact that the wall was much wider and designed as the primary conduit of structural load from analysis. I'm interested in how the engineer got this so wrong? Wouldn't they have gone into the building to look at the site from both sides? Wouldn't they have noticed the width of the wall? And isn't pulling the building's drawings on file with the city part of the process to come up with the repairs they were planning? Is there a situation where these wouldn't need to be done? While I think we can agree that the engineer may be inept and this isn't a work of malice, what would cause them to ignore things like building plans when they had basic questions about structure?

This rapid acceleration of collapse had to have made scary noises people in the building heard.

Thanks for making this video. I am always a fan of your videos. I learned many new things as a structural engineer. Just a quick opinion. From 31:15, what I understood was that replacing the old structural brick part with post shoring affects the loading path of the above floor. However, if we solely consider this loading path change, and set aside all other aspects of this building, if the post shorings on the first floor are sufficient to replace the demolished structural brick, the loading path above shouldn't change significantly. If you want to modify a corner column on the first floor of the 10-story building, you don't need to post shore all the way up the 10 stories, but rather provide enough shoring to the adjacent area of the column on the first floor during construction. I am happy to hear different opinions.

This was a really interesting analysis. I didn't really get why the loads for the upper parts of the building wouldn't transfer to the new CMU until you reviewed it a second time, and I realized that the structural load will ALWAYS be there (even when the CMU isn't), so just filling the remaining space with the new CMU will leave the building in the distorted condition (from when the CMU wasn't there), with the loads shifted.

I can't believe it -- despite all of its problems, this building was literally screaming the warning signs of its imminent collapse to anyone who bothered to listen. As a non-engineer, I don't feel like some failure events (such as Surfside) appear quite as obvious in terms of the warnings to a layperson. But in this case, you don't even need an engineering degree to see how dire the situation was. Can't believe they weren't closing the building up at least until they could get it stabilized.

Agreed right down the line... you've *got* to get the load off first. Well done as always, thanks again Josh.