2018 inspection found "abundant" cracking and spalling of concrete in collapsed Miami tower's garage

boing
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True, I assumed this was something beyond the typical reserve fund, which tend not to be nearly enough to cover these sort of “This could cause the building to collapse” assessments.

In some ways, what is required may be more in the line of catastrophic building insurance, in which everyone has a tax levied, but it is paid out only to those who have these sorts of assessments.

Of course, cue the usually sort of complaints about moral hazard, some of which have a kernel of reality about them.

The truth is, no matter how well implemented, saving people from these small risk events is expensive. But if we value human life the way we claim to, then we need to be prepared to pay for it and more importantly persuade the rest of the populace that it’s worth paying for as well.

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In a well-built condo complex or building with a well-managed reserve fund, you’re probably still looking at a $10-15k special assessment once a decade. It sucks, but it’s manageable and can be planned for.

In this case of shoddy build quality and long-term neglect, I expect that no-one wanted to face the real issue back in 2018: the assessment to remediate the deficiency would be far beyond the means of most unit owners. So, without the city stepping in more aggressively, “roll the dice and hope for the best” was the response.

Or stricter regulations, including penalties to developers and HOAs for not addressing serious engineering and construction deficiencies like this one. America’s “market-based” approach to these matters, as expressed in de-regulation, underfunding of inspection departments, and the inclination to “financialise” everything, is very poorly suited to deal with problems like this (amongst others: see the response to COVID).

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Looks like troughs for drains to me, this would match the roof plan (page 193 of 336 in the PDF with all the plans) showing plumbing.
Looks like the floor/roof above the garage has a similar setup.
Which makes sense and should work (if done right).
Question is, did they actually build it that way, all the way, and properly?
The Morabito report can be read as indicating otherwise, but then it is barely scratching the surface. And who knows what kind of repairs/modifications have been made over the last 40 years.

Too soon to say anything yet, really.

Except maybe that the pool doesn’t look like it was part of the problem to me, not close enough to the starting point of the collapse.

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The way it works in Japan is that it is supposed to cover the cost of repairs without the need for assessments. As such, the amount that unit owners pay per month fluctuates based on the anticipated need for repairs in the future. For brand new buildings, it’s often less than 100 USD per month, while for buildings over the age of 40, it can go as high as 300 USD per month. (Note: That is still no guarantee that there will be no assessments later on, but they do their best to avoid it.)

Ultimately, the building will be torn down and completely rebuilt. (I was told to expect this after the building reached the age of 60. The building is now 25.) This is something that will happen, as a matter of course. The question of when it happens will depend on the condition of the building, but the tearing down and rebuilding is just how things are done in Japan. By then, unit owners will have been putting in money for decades, so it should be enough to cover it. The realtor even explained to me that, if the fund has enough to spare, it will even pay for temporary housing for residents while the building is being rebuilt. I, as the unit owner, will then have a brand-new unit that I can move back into or sell for more than I could have before the rebuilding. Win-win-win.

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It’s free, no paywall.

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actually what the drawing is showing is drainage to internal roof drains at the center of those "x"s abbreviated as RD preceded by the diameter of the drain pipe. You can see also these are surrounded by arrows indicating that the roof surface is draining towards the drain.

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the NYT article has an enlargement of the surveillance video that captured the collapse. You can see where the failure begins and how it spreads. I think the foundations or columns under this starting point will be found to be the critical failure.

basement_diagram-Artboard_1
basement_diagram-Artboard_11800×1216 219 KB

plan from NYT article notated by me

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It is a flat roof, with each section having a modest slope towards roof drains. You can see at least some of the drains in Google Maps, though some are hidden under the myriad condensing units jumbled up there. I doubt the roof was the culprit.

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I’m starting to lean towards the “construction error that has survived for 40 years” explanation.
Possibly something like a gravel nest in one (or more) of the reinforced concrete pilings. Because there is practically no way to notice there is one - it’s underground.
This can also happen in a column, of course, but that’s above ground, you can see the concrete surface after removing the formwork. Even if you can’t see the gravel nest directly, there are usually clues you can see. Which should be noticed and acted upon.

Reinforced concrete pilings and reinforced concrete columns are basically the same thing.
Pilings are built underground. You drill a hole into the ground, inside a steel pipe that is lowered together with the drill. The steel pipe keeps the dirt out of the hole and acts as temporary formwork for the concrete. The pipe stays in the ground when the drill is pulled out. You stick a preassembled rebar cage in it, and pour concrete in it. While the concrete is poured, the pipe is pulled out. This is the tricky bit. You don’t want the rebar cage to shift from its position, you don’t want bits of concrete sticking to the pipe and being pulled up with the pipe. Problem is, you can’t see what is happening, everything is going on in a pit filled with concrete. Experienced operators might sense something is amiss, but there is little to be done at that stage except giving it a bit more time with the vibrating cylinder when compacting the concrete.
When there are indications that a pile won’t work as intended, you can redesign the foundations a bit and put in more piles. Rebuilding a faulty pile usually isn’t an option. Pilings are usually overengineered to be on the safe side.

Columns are built above ground, so a gravel nest can be noticed and repaired. Or you tear down the column and pour a new one.
Of course, instead of properly repairing a gravel nest you can just do some cosmetic patching. And if it’s an element that later vanishes under rendering or cladding or whatever…

Concrete is a composite material made from cement, sand and gravel. The Romans called it liquid stone, and that’s just what it is and that’s why it is so practical in construction.
The cement is the glue that keeps everything together, the so-called matrix. The gravel (ideally pebbles) supplies the compression resistance. You want to end up with something as uniform and monolithic as possible, so the gaps between the larger pebbles are filled with smaller pebbles and so on all the way down to sand. The very little gaps that remain are filled with cement.

A gravel nest is basically a hole where there isn’t one supposed to be.
Usually a section where the gaps between the large pebbles are not filled by anything but air.

In a reinforced pile or column this means that the compressive force which should be borne by the concrete ends up in the vertical rebar which is not designed to do that.
Design: big hunk of concrete that does what it does best, taking a load of compressive force.
Reality: a handful of vertical steel pins, each maybe an inch or so in diameter, without any lateral support, having to perform a function they were never intended to.
You see the problem.
As steel can deal with compressive force just as well as tensile force, this point of failure won’t fail right away but much, much later. Either when the load piled up gets too heavy, or when the steel has rusted away somewhat, or both - or never, when you’re lucky.

 
It is also possible that some of the pilings failed because something happened with the ground they’re in.
I’ve seen it with a building that had been standing for 90+ years when it suddenly developed massive cracks within hours. You could literally see the cracks forming.
The experts later agreed that there probably had been a patch of clay somewhere under the foundations, and some sort of void somewhere under that. Not uncommon in this particular area, which is also a bit hilly. A couple of months before the cracks formed, a water main broke uphill. The water probably seeped downhill, liquefied the clay, and the clay poured into the void.

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I didn’t mean to suggest in my original post (way back now!) that this incident was caused by the flat roof. But I meant to say that, down here where there’s so much heavy rain, flat roofs lead to leaks which lead to structural problems. (Not to mention another big health and safety issue, mold.)

Yet these buildings are still the most common commercial structures, because they’re cheaper to build in terms of design and materials.

I suspect this building had a lot of problems. And I bet its neighbors do too. I think, as others have said here, that the problem goes back to the political/regulatory climate as much as the salt, heat, humidity, wind, waves, and all that.

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The owners of this building recently approved an assessment cost for each unit of $80k per bedroom to pay for the nearly $10mill in needed structural repairs.

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Then my off-the-top-of-the-head math wasn’t far off. But again, it’s tough to get condo buildings to approve those kinds of things and this time it was several years too late.

There are a lot of causes here but if that report had been more frank about the risks and the problems (instead of leading with problems with flashing around windows and leaving the most critical problems until the very end, and categorizing the issues found by level of danger) maybe that special assessment would have been approved when the report was issued.

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80K per bedroom is a mighty steep assessment for your average retiree condo owner to deal with. In many cases, it may be much cheaper to just walk away. (I’m assuming that they would have a difficult time selling it if prospective buyers hear they will need to immediately pay 80-240K (depending on condo size) in addition to the purchase costs) How much did the condo units sell for in the first place?

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That’s what I figured: beyond the means of most of the residents. It’s also almost an all-or-nothing situation, so if 10% of the owners have no way of paying other options have to be considered by the condo association and/or the municipality. That’s especially true of a 40-year-old building.

From what I’ve been reading, it sounds like the boards in previous years dropped the ball when it came to inspecting and maintaining the waterproofing and drainage around the pool deck and the garage. That was compounded by various failures on the part of several other parties (Surfside’s chief building official, the engineers who downplayed the urgency of the problem, a neighbouring development project, etc.).

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The wall street journal wants to paywall this, but it leaked through Safari’s “Reader View”

The tower’s rooftop apartments would have added significant weight but they were accounted for in the revised design, said Roberto Leon, a professor of construction engineering at Virginia Polytechnic Institute and State University, who reviewed the building plans.

The structural plans show that the size of the columns and reinforcements would have been typical for that time, and the roof would have had limited ability to redistribute the building’s load if one of the columns were to fail, he said.

That could mean a failure in one column could bring down an entire structure, which could have been what occurred with this building, Mr. Leon said.

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