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Why Is the Floor of the Oculus Already Crumbling?

Photo: Christopher Bonanos

Look up when you walk through the World Trade Center Oculus, and you can forgive almost everything. Yes, the cost topped $4 billion, a significant portion of that going for a pretty entranceway*, as the rest of the transit system starved. Yes, the central skylight was supposed to open every September 11 but doesn’t because the gasket tore the second time they tried it. (The solution, for a while, was Flex Tape.) Yes, the mall is underperforming, and in the middle of the concourse, there are too many dumpy little kiosks selling souvenirs. But you enter that hall, and it does what Santiago Calatrava said it would. Your eye is drawn up the Italian-marble walls and the glowing white ribs, and you are reminded of the nave of a great cathedral. You can experience, as a commuter, a moment’s uplift.

Cast your eye downward, though, and you’re back in busted-up New York.

The white stone slabs making up the floor of the concourse are chipped and flaked at the edges. Corners are broken, and thousands of scuffing soles have ground dirt into the rough spots, blackening them and making them highly visible against the honed surface. You can also see where a scattering of slabs has been replaced, because the new slabs are whiter and shinier than the others. The building opened barely seven years ago, in March 2016, and the rest of it still looks crisp and new. The floor does not. Grand Central Terminal will be 110 years old in a week, and its Tennessee marble floor shows gentle waves of wear from billions of feet but comparatively few cracks and chips. It’s arguably in better shape.

I asked the Port Authority of New York and New Jersey about the replacement work, some of which I saw going on last year. Its representatives offered a statement: “As part of the agency’s ongoing facility maintenance program, normal wear and tear of the Oculus floor is being addressed by systematically repairing and/or replacing damaged tiles,” adding that it had stopped for the holidays and “will resume later this year.” I asked Calatrava’s office as well, and his representatives declined to comment. Neither would talk in any detail about the beat-up floor.

The easiest guess, though not necessarily the correct one, is to blame the stone. It’s known as Lasa marble, quarried in Italy and brought in by a Vermont importer. It has little visible veining, and it’s fine-grained and extremely uniform in color, pure and lightly translucent. On the Mohs scale, which you may remember from Earth-science classes, it’s about a 3 or a 4: soft but not too soft. (Granite is about a 6 or a 7.) The slabs are one and three-16ths inches thick. Monuments all over Europe are made of Lasa marble, and so are about 90,000 American soldiers’ grave markers.

Raffie Samach, an architect who worked with Calatrava early in the project (and remains an admirer, calling the architect and the building “extraordinary”), offered this: “I was surprised by the choice of material. It isn’t what I would use in a public space — though we all have to concede that it’s beautiful.” However, he was quick to add, “I can also say that, whatever materials were proposed, they were vetted by the Port Authority — and they were very picky about durability.” Civic agencies, I suggested, tend to be conservative about choices like that. “Obsessively so.”

I decided to do a little comparative test, so I got my hands on one sample from the Oculus’s floor and another from Grand Central’s. (Never mind how.) They’re about the same thickness, and the texture of the grain seems similar. When I rubbed the rough sides against one another, though, the difference became obvious. The beige stone from Grand Central remained intact. The white Lasa marble shed crystalline crumbs that looked like sugar all over my desk. It’s clearly more fragile.

That tells you something but not everything. Remember that, despite appearances, it’s still stone, not a piece of pastry. The smooth top surface of my sample doesn’t chip when you knock anything against it. Certainly, it should be able to deal with Louboutins and wheelie bags, no?

Some of the problem is simply that we can see every little chip. The New York Public Library is also marble, albeit from Vermont, and it’s a little melty around the edges after a century of urban wear and tear and acid rain. It looks good all the same, mostly because it’s a Beaux-Arts building, full of filigree and detail. The weathering is part of its appeal. Calatrava’s designs, being geometrically pure, show even small dings not as patina but as damage, and your eye goes right to every one.

But that’s not all that’s going on here. Matthew Crawford, superintendent at a company called Gem Construction and Waterproofing, oversaw a lot of the floor’s installation and maintenance, and when I called him, he knew what I was asking about right away. He mostly brushed aside my suggestion that the choice of stone was the fundamental problem, though he agreed that it’s “not the most resilient. There are millions of little hammers, every single day, pounding on that floor. I’d see a woman with stiletto heels running there, and I’d cringe.” The deeper problem, he explained, is that there’s a radiant-heating system underneath of the type you see in a lot of premium construction these days. Thin pipes snake around, back and forth, atop a layer of insulation, and they’re filled with a glycol solution that is warmed up and pumped around. Radiant heat has many advantages — evenness, silence, no vents to collect dirt or blow dust around — and a warmish stone floor is pleasant during the cold months. As it warms up, the stone (like all materials, though less than some) expands. The edges press on one another, harder and harder, and eventually they shatter.

Engineers usually accommodate that movement with an expansion joint — a small gap that can stretch and shrink as needed — and there are indeed some on the floor here. “We recommended one-eighth inch between the joints with caulking,” Crawford says. The Calatrava–Port Authority team rejected that idea, he says; adding wider gaps would have changed the alignment of the stones, after which “the seams wouldn’t line up with the joints on the walls,” as the architects had specified. Instead, he said, the engineers stuck by their plan for relatively few relief joints, widely spaced. “There’s one every ten-by-ten stones, pretty much.” I walked the floor a couple of days ago, looking for them, and that approximation seems about right. They are just a hair wider than the grouted joints, and if you kneel down and press your fingernail against one of them, the filling is rubbery.

But, I suggest to Crawford, couldn’t they have trimmed a sliver from all the edges of each stone slab and thus preserved the alignment? “Yes, but that would have added cost.” Could the stone have been set more firmly, so it moved less? “Yes — with a thicker setting bed,” the mortar underneath would have limited its movement, “but that wouldn’t give them the R-value they wanted” — that is, less heat would come through the floor, compromising the building’s LEED goals. As an aside, he also mentioned that there have been glycol leaks in the heating system and you can see brown stains on the floor here and there. “I don’t want to get anyone in trouble,” Crawford says ruefully, “but we told them.”

There exists, in the Oculus, a proof of concept. The floors on the upper levels are made of the same material but don’t have the heating system underneath, and they’re in much better shape. (Admittedly, they are somewhat less heavily trodden, so that may also account for some of the difference.) More than that, though, Crawford’s company also got permission to re-lay one section of floor, one that lacked heating pipes, with a thick bed of mortar, as he’d recommended. It’s in front of a freight elevator at the northeast corner, where seasonal displays and heavy equipment are brought into the building. It’s probably the most heavily trafficked area in the place, he says, and “I go by and check on it every time I’m in there.” The other day I did the same. It remains nearly undamaged.

The Port Authority appears to have taken some of this advice belatedly. I did that same fingernail test around a few of the newly laid replacement stones, and most of them seem to have have been caulked in rather than grouted. This is a costly set of repairs, though, and until the whole floor is re-honed — a multistep process akin to sanding down a hardwood floor — it will look a little patchy and uneven. Re-honing an expanse this size will likely cost more than a million dollars a shot, and if the PA has to do it every year or two, as damaged stone continues to be replaced, that starts to run into real money.

Did the authority indeed brush away some real-world concerns in the service of Calatrava’s aesthetic? Neither the PA nor Calatrava’s firm is talking. But speaking to Samach reminded me of the mood surrounding this site in the first years after 9/11. New York (not to mention the nation as a whole) was in agony, feeling wounded and desperate to get its sense of its power back. The instinct, during the planning of the Oculus, was that almost no expense was too great, that no detail was too much to ask. We were going to have something perfect there, the very best in the world. And although that intensity of feeling faced a lot of practical concerns and cost overruns and political fights and a gradual understanding that maybe this project wasn’t going to do everything we were hanging on it, the core spirit lingered: It was going to be beautiful, and maybe, this one time, we could let practicality slip aside. But to accept that today, you have to avert your eyes. Just … look up.

*Clarification, February 2: This sentence has been altered to note that the $4 billion cost covered the entire transit hub, not only the headhouse.

Why Is the Floor of the Oculus Already Crumbling?