Extrusions have been having a hard time lately because their constant cross sections are uncool. I’d like to say a few words in their defence. For starters, many useful things are extrusions. PVC conduits are extrusions and their constant cross sections use a minimum of material to protect the cables within.
Extruded beams use metals less expensive than steel to achieve the same strength as rolled beams. This is more than just a matter of cost because additional functions can be designed into sections that are impossible to fabricate by rolling.
Extruded aluminum or PVC sections for window frames are incredibly complex, with small sectional changes permitting new functions and enabling new properties. Each tiny protrusion works with air gaps and insulation to use the minimum amount of material to bear load, prevent twisting and limit thermal bridging. It is a field of specialist research and design to which people devote careers.
Sausages aren’t extrusions because they assume their final shape after being stuffed into a mold rather than extruded from one.
Concrete columns aren’t extrusions either as they’re made by concrete being poured into a mold and allowed to harden.
Slip-form concrete structures may appear to grow but they’re not extrusions because concrete is set in a formwork mold in a dynamic process but it’s the mold that moves and not the concrete. It’s still a good way of producing concrete structures having constant cross sections useful for elevators, stairs and all manner of shafts. The structures may look the same top to bottom but that’s rarely the case within because stresses such as those caused by uneven wind loading mean the amount and placement of reinforcment is never uniform.
Page 39 of the structural analysis peer review report for 432 Park Avenue recommended the local addition of reinforcement to the northeast corners on levels 25 and 39 in order to handle uplift under certain wind conditions. [c.f. Moneymaking Machines #1 : 432 Park Avenue]
Yes, extrusions are great, but what I object to is people thinking them dull and unimaginative simply because they look the same top to bottom. The word extrusion has come to take on a derogatory meaning that derives from those 3D modelling functions that convert polygons into prisms of arbitrary length. The insinuation is that a building with a repeated floorplate is the result of a simple operation executed thoughlessly and without the input of “creativity”.
This isn’t saying much because all you have to do to not make your building look like an extrusion is change the plan every now and then to show your building can’t be constructed in the easiest way possible. Whether this is creative or not I don’t know. Some non-extrusions are better value than others but we don’t live in a world that’s ready to have architectural concepts rated in terms of aesthetic efficiency.
Until it ever is, it might be more useful to explore what can be done with extrusions. If they can’t embody creativity as it’s currently defined then it might still be possible for them to embody intelligence or even a certain kind of creative intelligence that doesn’t have to be kept a secret. [c.f. Architecture Myths #24: Beauty vs. Everything Else]
The following layout is of one of those Hong Kong apartment towers typically maligned as extrusions. It has differently-sized apartments arranged around a central core having access and services. All kitchens and bathrooms are naturally ventilated. It needs no ducts for apartment utilities. The only major fault is those living room windows adjacent at 90°.
With this next configuration, kitchens face into the internal corners and push living room windows away from each other but kitchen odours are more likely to reach them. The dining area has a rear window for cross-ventilation. As long as adjacent buildings aren’t connected, there remains a degree of turbulence that dries laundry on racks accessed from that rear window.
This next layout uses the same principles but separates the living rooms by 120° instead of 90° and places the kitchens inbetween and thus closer still to the living room windows.
This next layout takes the kitchens back away from the living room windows that are now mirrored and angled like the previous kitchen ones were. It’s the best solution. Concentric walls allow for various combinations of monolithic and prefabricated construction. As a configuration that integrates sightlines, ventilation, servicing, structure and construction with a functioning floorplan, it’s as close to perfect as anything you’ll ever see.
Towers having layouts like this are often laid out like at Whampoa Gardens Estate in Hong Kong [and yes, that is a decommissioned ship – I don’t know why]. Here and there you’ll see two buildings linked across one side of the service lightwells but this hasn’t become general practice. It’s easy to see how it would reduce air movement.
At the internal corners of these superblocks, adjacent living rooms face a gap where a fourth building would complete a habitable room light well. This is the principle of the following proposal.
Imagine a city of perimeter blocks where all habitable rooms now face the courtyards and streets are overbuilt apart from shafts servicing the non-habitable rooms. What we get is a building experienced around negative space. Instead of buildings interrupting space, we have space interrupting a building.
The Extruded Mat Building
1. Take a perfect layout.
2. Extrude 5-7 storeys. Repeat horizontally to make a mat building.
3. Elevate to activate access, airflow, and vegetation.
The elevated mat building makes its own context. It is not experienced as a building object in a landscape or city but from within apartments arranged around extruded shafts of airspace. This isn’t a new idea.
What is new is that those shafts are now 360° and the only views out are up to the sky and down to the ground. And it’s ok. Diagonally opposite living room windows face each other across a distance of about 26.6m which is about ten metres more than the distance at which subtle facial expressions are supposed to cease to be readable, thus ensuring emotional if not visual privacy. The distance between opposing bedroom windows is 20.9m which is almost five metres greater than the UK standards I’m familiar with. These distances aren’t setbacks or spacings liable to violation – they’re inbuilt and permanent.
The extruded mat building is its own view and its own streets and its own city irrespective of site and location. It exists already as shopping malls and might be a useful typology in a future in which the good sites are all taken and the good views all built out.
Having more storeys means the sky and ground become further away and though this will limit daylight penetration it may well enhance ventilation. The tradefoff is a no-brainer in the higher latitudes but, if we’re in the tropics, better ventilation is preferable to sunlight streaming through the windows.
According to Obrist and Koolhaas, architecture is A) a Western construct and B) about stylistic “movements” because C) Japanese Metabolism was the first time a non-Western movement “contributed” to Architecture. If one accepts A and B then C is true but it’s still one temperate-zone architecture contributing to another. A significant amount of the planet’s population lives between 23°26’22″S and 23°26’22″N where the sun passes directly overhead.
The tropics have their own truths that a Western, northern-hemisphere, higher-latitude centric architecture that values sunlight is insensitive to. Even a conception of architecture as masses brought together in light makes little sense in places where the sun shines straight down.