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Streets In The Sky

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This last post for 2018 brings some closure to a train of thought that began in April 2016 when I became aware how the default apartment building configuration regards the corridor as nothing more than a means of physical access. [c.f. Plan B] The private space of apartments may be visually connected to the world outside but accessing it requires passing through shared space that’s as small as possible and with no redeeming features. This is the status quo and, despite those corridors being perceived as functional and impersonal, the typology is stable and there is little appetite or incentive to improve upon it.

Apartments are living units that are stacked and repeated and how to access them is one of those recurring architectural problems people have tackled over the years but most intensely in the 1920s. [c.f. The Types Study].

The Type A

Two apartments per landing is one of those architectural inventions that simply can’t be improved upon. It combines vertical and horizontal access into a single minimal unit and permits dual-aspect apartments. The configuration arises naturally because staircases occupy less volume (and thus require less building resources) than corridors. If elevators hadn’t been invented, this is how all apartments would still be. We may thank Chicago and New York for elevators and the skyscraper but not for enclosed stairs, impersonal corridors and single-aspect apartments.

The configuration has been invented many times around the world but, in accordance with the nomenclature adopted by Mosei Ginzburg’s Stroykom team, this blog has always referred to it as the Type A, most recently in the March 2017 post The Domino’s House when I tried to make a case for its continuing relevance.

The July 2017 post The Landscape Within mirrored the Type A into a tower with triple-height elevator lobbies that may not have been as picturesque as the internal spaces of Ricardo Bofill’s Walden 7 but nevertheless aspired to a similar two-way awareness of inner activity.

It was successful in that people coming and going in the triple height lobbies animated them for people overlooking them, and signs of activity in the apartments (such as lights being turned on and off) animated the building for the people coming and going in the lobby. One disadvantage was that all apartments had the same two-bedroom layout due, at least in part, to my reluctance to compromise what I imagined would be shear walls.

A proposal in the April 2018 The Inflexible Apartments post enabled apartment of varying sizes but using the same plan components. These apartments had corridor access but also had internal staircases linking access floors with those above and below. Apartments with the same plan could have a different number of bedrooms.

This proposal reversed the conventional “public-to-private” sequence by having entry into lobbies associated with the private spaces (as with hotel rooms) and to staircases accessing shared living space. The plans above show how, from left to right, a studio apartment, a three-bedroom apartment, a two-bedroom apartment and a one-bedroom apartment can be configured from the same layout. This ‘inflexible’ configuration can accommodate diverse types of household, including informal and temporary ones – a property that seems more suited to how residential space is used these days.

Even though the living areas are open in plan, much area is used for circulation only, such as that along the length of the kitchens. The one-, two- and three-bedroom apartments have the same amount of living space but, because the three-bedroom apartment has two internal staircases, the apartment that perhaps needs the most has the least.

This contradiction was eliminated in the proposal in the September 2018 post The Uncompleted Apartment that had the staircases as an optional part of the apartment layout. By blocking or unblocking the internal corridor in different positions, it was possible to access either one, two or three of the bedrooms from one or more apartments on the level above, below or to the sides. The inherent problem of this configuration was that there could only ever be one bathroom per apartment regardless of its number of bedrooms.

Putting the staircase on the outside wall cleared some space for a second bathroom to be associated with bedrooms accessed via the staircase.

  • In apartments A, the internal corridor is partitioned so one living area can appropriate the two available bedrooms while the other living area becomes a studio apartment.
  • The internal corridor for apartments B is differently partitioned to create two one-bedroom apartments from the same plan.
  • The (green) Apartment C, accesses an internal staircase allowing to connect to one of the bedrooms of the floor (and below).
  • With Apartments D, there is one studio apartment, one one-bedroom apartment and the second bedroom is accessed from a different floor, as with C above.
  • Apartments C and D apartments have, in addition to the bathroom connected to the living area, an additional bathroom on the stair landing for use by at least one bedroom, depending on how the other apartments are configured.

The additional bathroom was a plus but it was achieved by using external wall for the staircase. This next configuration returned the staircase to the inside wall and introduced bathrooms on either side. This proposal in a September post called The Universal Apartment solved the problem of the potential inequality of bathrooms and still allowed apartments having an arbitrary number of bedrooms.

This was all achieved by blocking or not blocking corridors and by creating or not creating door openings in the layout core. This core piece is a good candidate for prefabrication if prefabrication is to ever be a useful reality and not just a good idea.

Although apartments having a arbitrary number of bedrooms can be configured easily and with a minimum of construction variation, the resultant apartments are still the conventional arrangement having access to bedrooms via the living space and, as already mentioned, this arrangement is no longer suited to as many households as it once might have been. The new goal became a configuration having the advantages of The Inflexible Apartment and the advantages of The Universal Apartment. This was my first try.

External access is Type A with a unit of enclosed space on each side of the landing, but internal access is also Type A in principle as the internal staircases allows each unit of space to expand vertically to create (what are essentially) stacked terrace houses of arbitrary size.

  • The space enclosed could be office space or residential space that could be shared living space or private space.
  • The potential uses of that space are determined by whether there is bathroom and/or kitchen are provided within it.
  • An internal staircase allows those units of space to link to other units of space to configure larger apartments with a greater separation of functions. More affluent occupants,. for example, could have one unit for living and another for cooking-dining with some arbitrary number of bedrooms up- and/or downstairs. 

This is one direction Universal Apartment II could take but the visual connection between the apartments and the shared circulation space is lost because there is no longer sufficient shared wall surface to enable it. Moreover, the corridor spaces between lobbies becomes a utilitarian service space lined by bathroom windows, kitchen exhausts and service risers and this can only be solved by moving the kitchens and bathrooms away from the central corridor. Flipping the staircase so it’s now against the inner wall means its window can no longer receive daylight and sound from outside but it can give light and sound to the corridor inside. It is also possible to have small balconies but the big problem with this configuration is the position of the front door.

There aren’t many places left for the bathrooms and kitchens to go, so, to the outer wall it is! I wouldn’t have thought about it if it hadn’t been for Yves Lion’s 1984 Domus Demain project “Study for a habitat at the beginning of XXI Century” that had its bathrooms and kitchens on the facade [and I wouldn’t have known about that if it hadn’t been for Iago in Mexico City – thanks again Iago!] [c.f. The Open Bathroom]

The arrangement below seems to work. The former position for the front door creates a shorter path between the door to the external stair and the door to the internal one. Splitting the space into two corners for furniture groupings is something Josef Frank would have done. [c.f. Architecture Misfit #33: Josef FrankThe variation on the right, below, was my first thought but the one on the left might be a better compromise though the dimensions still need some tweaking.

The top line of this next image shows some variations, with equivalent layouts below. Four spaces could configure a two-bedroom apartment of 130 sq.m excluding stairs. Living room-only could have either an internal balcony or guest bathroom most likely accessed from the stairwell. Access lobbies are now overlooked by windows from the hallways, living rooms and internal stairwells and, equally importantly, these windows and the signs of life on the other side of them are seen from the access lobbies.

It seems close to being part of a perfect layout. It still needs to be combined into a larger building and one with about 72 apartments seems right for two elevators, one each end. The sole reason for the central corridor is to connect those two elevators and enable linear buildings. To bridge the corridor at middle and upper levels would completely kill it as a space but narrow projecting bay windows overlooking it would heighten its experience as the social spine of the building. The living areas of these apartments may receive daylight through openings in their outwards-facing walls, but they overlook – and thus give to and benefit from – the shared internal access.

What’s left is to sort out the construction, servicing, and planning of the ends of the building but that’s for another year. It’s more important to think about what it all means. If this were a house it would be a very introverted one, looking back in on itself as it does and though I have an idea of the benefits this can bring the occupants, I can’t say what it would mean for the greater city. Or even if it’s worthwhile thinking about. Half-landing bridges could always link buildings to form some Holl-Constructivist hybrid but I can’t see what additional benefits that would bring either occupants or city.

The configuration as it stands may well be all it’s ever meant to be. With its apartments oriented towards shared access and circulation, its streets in the sky are already far more than Smithsonian “streets in the sky” ever were. I think we’re done.

All that remains is to thank everyone who, over the course of 2018, kindly contributed some comment or thought that made this blog richer and more fun than it would have been had it been solely my own work Thank you.


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  • I have recently been looking at moving into a classic point block and it’s very telling how well 2 flats + access scales up; pair them and that works, make a cross-shaped block with 8 per floor and that works very well too.