As we all know, there was a catastrophic collapse of part of a condominium building in Surfside, Florida on Thursday, June 24th. I saw the news that morning, and was horrified. I think just about every structural engineer thinks when something like that happens, “what if I was the engineer?”. It is the worst nightmare of any responsible engineer to make a mistake that causes a failure that kills or injures people. My second reaction was puzzlement. Normally buildings catastrophically collapse during or right after construction, or due to an outside event. You do also see old buildings collapse in time due to rot and corrosion, but normally that does not happen to an occupied and maintained building.

So, what happened? The short answer is I do not know, but I’m going to speculate. The first thing I noted in the pictures is the building pancaked. That is due to column failure, like what happened in the World Trade Center. Normally, we design buildings to be redundant. That is if a beam or column fail, other portions of the structure can kick in and hold the building up. The building will move and crack, but it will still stand and allow people to be evacuated. You want that in case a car smacks into a column in the basement, or other unforeseen event. This did not happen here, so I think multiple columns failed.

What would cause more than one column to fail at the same time? I was puzzled about that, but a hint comes out in the Washington Post today. In 2018, an engineer, Frank P. Morabito P.E., expressed concern about cracking in elevated slabs in the building, and water infiltration due to improper waterproofing. He called out concerns about concrete deterioration due to this happening. If you look at his photos that are in the article, you can see reinforcing bar with severe corrosion.

So, my guess is that there was cracking in the concrete, which lead to water infiltration that caused corrosion in the reinforcing. That may have weakened a few critical structural members, so that when one failed, it put too much load on the other members in their weakened state. That would have caused progressive collapse of the members. Since it appears that the issue was happening at the ground, or below the ground floor, that would take out the bottom support, and everything would pancake down – fast.

I would venture to say this was not so much a design error, because the building did stand for 40 years through the usual hurricanes Florida encounters, but a lack of proper maintenance. Also, there may have been an initial construction error with application of waterproofing, but that should have been corrected with normal maintenance and repair.

So, what's my ultimate take? First, I'll apply the Principle of Mediocrity, in that this building probably was no better or no worse than similiar buildings put up at the same time in the same area. That means if you have a condo or office in one of those buildings, you need to be very concerned. Should you hire an engineer to examine your condo/office? It won't help much at all, here's why:

Ultimately, if you do own a condo like this, I can say for sure that you are going to be assessed for some significant money for building modifications in the future. A number of buildings may need to be demolished. Otherwise, we could see more building collapses.