Skyscraper Construction: Floors

Noah Body · Oct 19, 2010

In my current WIP, I have several folks trapped in a 27-story skyscraper in NYC's midtown. At some point, they'll have to blast through a floor (they have demolitions with them), but I'm not really sure what the floor would be made of... carpet and padding over concrete reinforced with rebar? The building would be a 1950s-vintage structure. Any idea what my characters could expect to encounter?

Thankees all around.

Xelebes · Oct 19, 2010

1950s? There would be two popular construction methods: Skeleton and Concrete-Core. Problem with skeleton is the thirst for asbestos during construction - blasting the floor would be a serious health risk. Concrete is not much better, but less asbestos was used. In the Skeleton, it is steel I-beam, steel corrugate, concrete, grout and tiling/carpet with a dashing of fire-retardant asbestos. In concrete, it is I-beam, steel rebar, concrete, grout and tile/carpet with a dashing of asbestos.

ChronicSelfEditor · Oct 19, 2010

I just asked one of the guys I work with (architect firm) and was told that you are correct. But one additional thing that he mentioned was that if the building was built in the 50s, there is going to be asbestos too. I thought that was only on walls and ceilings, but he said the floor would have it too. Not sure if that helps or not. Of course if the story has a more modern setting, it's likely that there has been abatement done on the building and the asbestos would then be a non-issue.

PeterL · Oct 19, 2010

Noah Body said:
In my current WIP, I have several folks trapped in a 27-story skyscraper in NYC's midtown. At some point, they'll have to blast through a floor (they have demolitions with them), but I'm not really sure what the floor would be made of... carpet and padding over concrete reinforced with rebar? The building would be a 1950s-vintage structure. Any idea what my characters could expect to encounter?

Thankees all around.

In adition to the asbestos that has been mentioned, they might run into a place that has multiplt layers of steel beams due to intersections of beams. The concrete might be pretty darned thick. In most places that concrete would be six to eight inches thick, but there would be places where it would encase an I-beam. There probaly would be beams on the perimeter and in a grid pattern through the building. They might be able to determine locations by pulling ceiling tiles, because the beams probably would be one above another.

Noah Body · Oct 19, 2010

Tough break with the asbestos, but being exposed to it versus the alternative makes blowing a hole through the floor the preferred option. Xelebes, how far apart would the I-beams be, and how thick would the steel corrugate be? I presume it would be layered between the concrete, right?

alleycat · Oct 19, 2010

I work for a major structural engineering firm (large projects throughout the US). If you haven't gotten the information you need already, let me know and I can provide any details you need.

PeterL · Oct 19, 2010

Noah Body said:
Tough break with the asbestos, but being exposed to it versus the alternative makes blowing a hole through the floor the preferred option. Xelebes, how far apart would the I-beams be, and how thick would the steel corrugate be? I presume it would be layered between the concrete, right?

The beams could be any distance apart; the distance is dictated by the design of the building, not the code 16" on center for joists in residential construction. Any corrogated steel would be at the bottom, and that is usually 1/4" or 3/8", so it would be easy to blast through.

Don't worry about the asbestos. It takes decades of exposure for most people to develop any medical condition from it.

Xelebes · Oct 19, 2010

Noah Body said:
Tough break with the asbestos, but being exposed to it versus the alternative makes blowing a hole through the floor the preferred option. Xelebes, how far apart would the I-beams be, and how thick would the steel corrugate be? I presume it would be layered between the concrete, right?

The corrugate is the base layer for a floor, sitting atop the I Beam. The concrete be enough to fill the groove and a bit more to firmen up the corrugate. Corrugate is used because it is lighter than the concrete method but not as sound proof. Corrugate ranges in depth and thickness, but remain relatively standardised over the decades, so what is offered today by the steel fabricators is still valid. Checking their sites for what is offered doesn't hurt.

Noah Body · Oct 19, 2010

Thank you, all!

RJK · Oct 19, 2010

I'm not sure if you have your heart set on blasting through the floor, but wouldn't your characters be better off finding an elevator shaft, pipe chase, or wiring chase, they could pass from floor to floor using using access panels rather than blasting through all that concrete and steel.

PeterL · Oct 19, 2010

RJK said:
I'm not sure if you have your heart set on blasting through the floor, but wouldn't your characters be better off finding an elevator shaft, pipe chase, or wiring chase, they could pass from floor to floor using using access panels rather than blasting through all that concrete and steel.

Think of how exciting it would be when they ran into a narrow place in the pipe chase after climbing down six floors. "Jeez, where'd those other pipes come from? I'll bet that even the rats have trouble getting through there."

Noah Body · Oct 19, 2010

RJK said:
I'm not sure if you have your heart set on blasting through the floor, but wouldn't your characters be better off finding an elevator shaft, pipe chase, or wiring chase, they could pass from floor to floor using using access panels rather than blasting through all that concrete and steel.

I have my reasons for not using the obvious. In this case, they're trapped in a specific part of the building.

Chase · Oct 19, 2010

RJK said:
pipe chase

Alleycat's avatar and your reference are infringements on my public persona, and I strongly resemble both.

Tsu Dho Nimh · Oct 20, 2010

Noah Body said:
Tough break with the asbestos, but being exposed to it versus the alternative makes blowing a hole through the floor the preferred option. Xelebes, how far apart would the I-beams be, and how thick would the steel corrugate be? I presume it would be layered between the concrete, right?

They can joke about it, or worry about it, but they aren't going to drop dead overnight of lung cancer because of it.

The danger from occasional exposure is minimal - to get mesothelioma almost always requires not only long-term work-related exposure to asbestos dust but also heavy smoking for years.

Skyscraper Construction: Floors

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