Building Construction Types (For Fire)
This is spun off from today’s article http://erictb.wordpress.com/2014/03/15/the-other-side-of-the-puer-the-senex which is framed around the East Harlem explosion, and was basically too long a tangent (even to make into an inset).
Two years ago, when sent for a Transit refresher course, which included “Fire School”, an interest was sparked in the different methods of construction in relation to fire. I had asked the fireman teaching the class why New Jersey buildings that looked so much like NYC buildings burned so much worse, even if made of brick. He told me it was something called “balloon construction”, which is where the floor beams meet wall beams without forming a complete horizontal seal.
A big wood beam box, the “balloon”, is constructed, and the floors are supported from this. Spaces between the beams allow a fire to rapidly spread from one floor to the other, and will engulf the whole side of the building, and then spread across the roof and cock-loft, and take out possibly the entire building. (On the news, you see just smoke out of a few windows, with the fire department already on the scene fighting it, but then a few moments later, the other news stories are interrupted for raging flames, and every break it gets worse and worse).
This has happened in NYC, but the buildings, even wood frame ones are usually better at containing a normal fire to one apartment. (The biggest problem with the wood frame is the fire spreading on the outside, and the whole frame compromised). The NJ construction was apparently banned in the city, with its stricter fire codes.
In both brick and even wood frame buildings, the floor decks are built over the top of the vertical beams or “studs” for each floor, and in addition to that, there are also “fire stops”, which are horizontal pieces of wood placed periodically between two studs.
Brick buildings basically have the floor beams (joists) implanted in the exterior wall.
So then I was looking up all of this, and also saw the five construction types of the International Bulding Code (IBC).
They run from less flammable to more flammable (called a heavier “fire load”):
Type 1 Steel frame with concrete poured over sheet metal decks. Universal high rise construction, but now, a lot of low rise residential buildings are using it.
The two buildings adjacent to the Harlem blast were new type 1’s and hence survived “structurally sound”, with only a few bricks removed (the bricks are not really integral to the frame).
Type 2 “non-combustible” brick or metal with metal roof without poured concrete. Often [newer] one story commercial buildings. Roof may be covered with tar and tar paper, so it’s not as fireproof as type 1.
Building that survived the Seaside fire (despite being right at its “ground zero”) looks like a type 2 (which would be common for beachside structures not made of wood). Obviously some sort of light “frame” construction, but none of the structure burned, (other than the siding melting).
The other commercial buildings alongside the main road were also apparently type 2 (concrete block walls with steel supported metal roofs without concrete protection), and held out for a long, long time, with the fire consuming the boardwalk and nearby wooden structures right at the front walls. But they were one story, and the roofs thus closer to where the fire was coming from, and were covered with flammable material (tar, etc), so once they and the stuff inside the buildings began burning, they were quickly gutted as well.
Type 3 The common brick, often pre-war “unreinforced masonry” (URM) building with wooden floor beams (joists) supported by the brick exterior walls (most interior walls are made of wood slats with plaster).
The roof often isn’t even a deck, but rather just two levels of joists forming a “cock-loft”, with the upper level having the tar paper (“membrane” roof) laid over it, and the lower one being the ceiling of the top floor.
This construction may be good to keep sun heat out of the top floor, but allows fire to travel across quickly (call it a “horizontal balloon construction”); especially with the highly flammable tar or “plastic roof cement”.
I’ve seen that this is the “achilles heel” of even the sound NYC apt. buildings, even brick ones, if the fire is on or under the roof. You usually lose the entire top floor, and possibly more when things begin collapsing.
This is the construction of the buildings that collapsed in Harlem. One building even takes out half of the other.
These are the worse things to be in not only in explosions, but also in an earthquake. The brick walls crumble, and the joists are only implanted in rectangular holes (you often see these holes left over in a wall when a building has been demolished, including at this site until they chipped the walls off the sides of the adjacent buildings), and the support is probably only a few inches deep.
While in NYC, the flooring and plaster is fire rated to be good at keeping fire contained (unlike the “balloon construction” of NJ), when a fire does burn through, it doesn’t take much to lose the support and collapse. (They even make “fire cuts” in the joists, so that they will break away instead of prying at the wall when they collapse from the other end being burned through, but the wall still ends up weakened when enough of them are broken or burned away).
What I grew up in was a fancier prewar building using Type 3 construction with a Type 1 basement. The ceilings in the basement were concrete (you can see wood grain, which was from the wooden mold the concrete was poured on), and then they build regular type 3 on top of the concrete deck.
Type 4: a “heavy timber” industrial (e.g. “mill”) version of type 3. Used a lot in old factories, warehouses and churches.
I think of the Fairway in Red Hook and the Amish market in the Atlas Mall (which was previously a Fairway. In both cases, the old warehouse creates the retro “old market“ theme the chain uses). You see the rugged bare wood floors and ceilings with thick beams and even the support columns (posts). “No wonder these buildings burn so fiercely” I thought.
The thick heavy duty wood is stronger and takes longer to burn, but once it does burn, it provides a lot of fuel (the heavier “fire load”), and is hard to put out. You often will lose the whole structure —which usually ends up collapsing from all the heat and the wood connected to it being burned away, as in all these old warehouses in the northeast that burn to the ground literally (watched a bunch of them in videos the other night researching for this article).
Churches too (even though you would think with all the open space, there wouldn’t be much to burn. Aside from the pews, nearly all the fuel or fire load is in the roof).
Hence really being more flammable than a type 3, and thus placed further down the list.
I’ve seen old one story stores being dismantled, and the cockloft is filled with thick wooden trusses. I wanted to take a picture of one along the J line three years ago, when I was mulling starting this blog (might have been my first article), but the entire roof was removed by the time I finally got over there when I was off. (I think most of the wood is still stacked up in the back of the lot left in its place).
Again; NO WONDER these things burn like that!
What were they thinking?
Type 5 is simply wood frame construction (even if clad over with a facade of bricks or concrete, like all those new suburban developments that burn to the ground whenever there’s a fire).
What I live in, I’m not sure which type it falls under. It seems like a sort of new version of type 3, with light steel frame walls paneled with plasterboard, on which the preassembled wooden beam floor deck is laid, and then the next walls constructed on top of that, and so on. Front is clad with brick, and rear with siding. It might be considered type 5, but the frame is not wood or otherwise “combustible”. (I said I would not live in a type 5, seeing the way they burn so much).
No cockloft, however, and it is the hottest place in the summer with the sun beating down.
Some of the new little townhouses in the area are a more solid version of type 1, using “hollow core concrete planks” for the floors and roof, instead of poured concrete. Would love to be in one of those. An earthquake probably wouldn’t even shake it!
The old brick “balloon” buildings in NJ might be considered type 5 as well. They are just clad with the bricks.
I got a sense of this, when accompanying my wife when she was in the process of becoming an NCCA counselor, and her supervisor in that organization was administering the APS to her. This was near New Dorp, Staten Island (And architecture there looks more like New Jersey), and a building in the SIRT station square had a prewar brick façade (which looks solid, compared to newer buildings which often have other wall materials along with the bricks), but they were repairing it, and you could see it was really a wooden plank wall underneath. In NYC, it’s a solid three layers of bricks, then the plastering from the inside. Except for a bunch of buildings in Bushwick, which were wood frame that had brick fronts added (sometimes with several yards of side wall added to meet the front of the adjacent building). You have to see it from above, or if the building next to it is torn down.
I think the balloon construction should probably have its own sub-type, like maybe 3b or 5b or something. It does make a significant difference in what’s called “fire behavior” that firefighters are taught to consider in each building.
You wonder why they didn’t just go with type 1 all along, and I’m starting to feel almost like I wish they would just demolish all the type 3’s and get it over with already, and put up type 1’s. (I heard LA once considered something like this, due to the earthquakes, for everything three stories and higher.
Both corrugated sheet metal and heavy steel frame construction began in the 1800’s, so Type 1 existed when nearly all of the old bildings that remain in tthe city were built, but it only took hold, for highrise commercial buildings first, at the end of the century.
If you say it was cost, then why can they all afford it now, especially when that was the industry that crashed the economy!)
Edit: more detailed definitions of types
QS_BuildingConstruction.pdf (File Download)
It seems there is an A and B designation for some of the types, which determines whether the exterior is “protected” or not. So the frame buildings with exterior bricks are 5A.