It is still way to early to know for sure, but some things are starting to emerge as far as the possible reasons for the collapse of the condo tower (Champlain Tower South) in Surfside City, Florida. The two best sites for getting an understanding of what may have happened are (1) the 2018 engineering report from Morabito (engineering) Consultants, who were hired to do a 40 year inspection of the building; and (2) the chat board of structural engineers in which they discuss the evidence and speculate on the significance. What seems most likely is what one engineer on that chat board wrote: “In big accidents like this, it’s rarely 1 single item that causes the failure; there are usually many contributing factors that all come together in the wrong way.”
Morabito Consultants Report
Morabito reveals several problems, some of which are not really structural, such as improperly flashed doors and windows. They also say that the windows and doors and the glazing are at the end of their useful life and all should be replaced.
“Main Issue: Flat Slab”
The biggest problem Morabito reports is the following: “The main issue with this building structure is that the entrance drive/pool deck/planter waterproofing is laid on a flat structure. Since the reinforced concrete slab is not sloped to drain, the water sits on the waterproofing until it evaporates. This is a major error in the development of the original contract documents…
“b. … the replacement of the existing deck waterproofing will be extremely expensive…. the installation of deck waterproofing on a flat structure is a systemic issue for this building structure”
Cracked and Spalled Concrete
Beneath the pool deck area, in the street level parking garage, Morabito reports “abundant cracking and spalling [cracking and chipping away of the cement] of various degrees… in the concrete columns, beams, and walls.” The condo owners association had evidently hired a contractor to try to repair this problem but Morabito reports on the “poor workmanship” of that contractor.
This leads to several conclusions: First is poor/cheap design. Second is shoddy construction itself. And third is poor maintenance.
One simple non-structural issue shows the mentality: Morabito reports that according to present OSHA standards, safety hooks are supposed to be installed throughout the exterior of the building for fall protection for window washers and others working on the exterior. That would have been a relatively simple issue to resolve, yet it seems the condo owners association did nothing about that. As one engineer in the chat board cited below wrote about condo boards in general, “These condos are full of cheapskate board members who think they’re engineers.”
Engineers Chat Board
The chat board is even more revealing:
One issue is cheap design: For example, the shear walls (walls that prevent a building from twisting or racking and also hold weight) were from cinder block not poured cement. Such walls are weaker and also heavier. They may also be a reason why there may be no survivors in the rubble. If the walls were poured in place cement, huge slabs of those walls would have fallen whole, possibly leaving spaces beneath them which could protect a person from being crushed. However, the cinder block walls simply crumbled totally.
Another engineer said that “the structure doesn’t [even] have enough shear walls”.
Another issue is placement of the load bearing columns in the parking garage. Normally, such columns are placed directly below the columns above them so that the weight bears down directly on the column as opposed to the deck itself. According to several commentators, in this case it seems that the columns on the second floor pool deck were not directly above those in the parking garage. Possibly this was because the latter columns were more spaced out to allow for more cars. Some of the engineers speculated on the possibility that the columns on the pool deck level simply punched through the deck. That could explain the phone call from Casssie Straton to her out-of-town husband just seconds before the building collapsed. A resident of the fourth floor of the building, she was standing on her balcony and called her husband in a panic saying “honey, the pool is caving in. The pool is sinking to the ground… the ground is shaking. Everything is shaking.” Her husband then heard a scream and the phone went dead.
The second is shoddy construction as the improperly flashed windows and doors show. The most serious question on this is the placement of the reinforcement steel (rebar) that is placed in poured concrete to reinforce it. Such rebar must be placed at least a couple of inches away from the surface of the cement. This both helps protect it from the weather
and prevents it from coming “unzipped” – in other words simply pulling out of the cement. On decks, the rebar mat is supposed to sit on wire “chairs” a couple of inches above the bottom. The engineers on the chat board point to evidence that the rebar in the deck was sitting right on the bottom of the deck rather than being placed on chairs. They point out the picture of the bottom of the deck and consider that evidence that the rebar may have come “unzipped”.
Another piece of evidence is how clean the rebar is, with no chunks of concrete adhering to it. (See photo.) The engineers also consider this to be evidence that the rebar may have come unzipped. As a retired carpenter who worked on plenty of jobs like this, it also raises another question for me: Before the rebar is placed, the wooden forms that hold the concrete and
the plywood deck on which the concrete is poured are sprayed with oil. This is to enable stripping the forms off after the concrete sets. This has to be done before the rebar is placed so that the oil doesn’t get on the rebar because if it does, then the concrete won’t attach/stick to the rebar. But if the rebar mat was simply sitting on the already-oiled plywood deck, it would get oil on its bottom side. Also, as workers continued working and walking on the deck, they would get oil on the soles of their boots and spread this to the top of the rebar. So if the rebar mats were placed right on the plywood deck on which the concrete was poured, in addition to that in and of itself weakening the structure, it seems very likely that the rebar would have oil on it.
Again, to emphasize: If this happened, then the cement wouldn’t stick to the rebar. The picture showing the clean rebar, with no bits and chunks of cement sticking to it, is a piece of evidence that this may have happened.
Where Were City Officials?
We don’t know that this was the case at this point. If it was, you would think that the inspector would have caught this in a second. It should have been a bright, flashing red light for any inspector. We don’t know for sure if the rebar was improperly placed, so we can’t say for sure about the inspection of it. What we do know is that the windows and doors were improperly flashed. That is something that a building inspector certainly should have caught, but evidently they did not. Why not?
One engineer commented regarding the lack of slope in the deck and driveway “this is not an engineering problem. It is a licensing and accountability problem.” In other words, why was this plan even approved by Surfside City building department? This makes one wonder if there was corruption involved in both the approval of those plans as well as in the inspection of the construction of the building as it proceeded. We don’t know, but it opens that question.
Condo Owners Association
These issues were exacerbated by the role of the condo owners association. Think of it from their point of view: What they must have been concerned with was protecting the value of their investment. That means that, yes, some maintenance is necessary, but keep it to a minimum. Something like tearing out the entire pool deck and driveway is too expensive. And as to seriously investigating the cause of the spalling in the parking garage: Best to cover it over with a cheap repair. After all, if it is seriously investigated, it might reveal some seriously expensive problems, and once you know about the problems, you are legally and financially liable if you do nothing about it and just cover them up. So just get the cheapest and most superficial repair possible and keep on trucking. Certainly, the idea of the entire building collapsing never occurred to them.
The Real, Underlying Issue: Salt Water Intrusion & Sea Level Rise
But the most serious issue was the location of the very building itself – and the buildings around it: One engineer cited an engineering study of “salt weathering”. The report says: “This occurs in concrete due to the capillary rise of water rich in [salts] through the soil and foundation structure. It is prevalent in the areas with the considerable concentration of chlorides in the soil, ground water and atmosphere, which is mostly the case in the coastal areas of the warm seas or in the structures where defrosting salt is often used.” In other words, the salt water is drawn up in the soil and into the concrete. The study says this is “particularly prominent in those cases when the structures are positioned near the warm seas…. The higher temperatures are the cause of the faster initial hydration of cement which leads to the increased porosity of concrete and facilitates capillary rise.” In other words, the warmer the temperature, the faster this process of salt water soaking into the cement happens. This would not only cause the rebar to corrode, it would weaken the cement itself.
That process would be accelerated by sea level rise, which is due to global warming. According to one report, the sea level in Florida rose eight inches from 1950-2016. The rate of rise in recent years has been at one inch every five years, so by now the total rise since 1950 has probably been about ten inches. And keep in mind that the parking garage was already built below sea level.
A report from Champlain Tower East Building – the sister building which is still standing – shows a picture of the same cracking and spalling of the columns in the parking garage.
Recent decades saw a massive building boom in Florida along with massive profits for the developers and contractors. They exercise a huge political influence, but the main point is that the entire process is part and parcel of an unplanned economy, one that operates based on short term private profit. Champlain Tower South is most likely only the canary in the coal mine. Already, similar spalling to columns in the parking garage of its sister building – Champlain Tower East – is reported. (See photo.) Despite that, residents of that building were not ordered to evacuate.
Federal Aid: For Who?
And how about the buildings all up and down this shoreline? What seems most likely is that what we saw was the chain breaking at its weakest link (poor design, shoddy construction, lousy maintenance). But the stress on the other links (salt water intrusion) will continue. This is a human (and economic) disaster waiting to happen. Meanwhile, Republican governor Ron de Santis is welcoming federal aid, while he and the rest of this type oppose any federal assistance to other human and economic disaster zones, such as the impoverished inner cities. But that is another story. Or is it?
Since this article was published, a few people commented on the fact that the building was built on land fill. None of the engineers seemed to feel that was a cause of the collapse. It seems the only that could have been a cause is if the building had subsided a lot in one direction, causing it to tip over. But the building didn’t tip over, it collapsed straight down – pancaked. Maybe the landfill was relevant in that the land might be more porous, meaning greater sea water infiltration. But that only means that the process already described, of the effect of salt on the concrete would be accelerated. Also, one engineer explicitly ruled out a sink hole as being a cause.
A few people have also asked whether residents in the other buildings of this project have been evacuated. The last news I heard was that it was “voluntary”, which means “no”. My guess is that if the residents were ordered to evacuate, then the owners of the project would have to compensate the residents for loss of use of their residence.
Two New Points There are two other issues: First, it may be that too much water was used in mixing the cement. That would make it weaker. Second, there was no expansion joint between the pool deck slab and the building. An expansion joint of a piece of felt-like material about a quarter of an inch thick that allows a concrete slab to expand and contract. It also separates two concrete pours. In this case, its absence meant that the pool deck was really bonded to the outer wall of the building. So, when the pool deck collapsed, it pulled hard on the wall of the building itself.