By: Jari Lonka, Francesco Allaix & Lilja Mustila
Archigram's Plug-in city was a visionary manifesto of new megastructures on top of the existing city. Their trailblazing approach opened the doors to new way of thinking architecture and urban planning.
Fifty years later the PLUG-IN model is scaled down to the building level in a powerful yet realistic concept. New wooden structures are superimposed to existing buildings. The vertical connections (stairwells and HVAC shafts) are organized as independent new elements, hence the PLUG-IN buildings are fully independent structures, acting as benign parasites to the present city fabric.
The combination of 2 basic modules allows for multiple housing solutions to address contemporary multifaceted needs.
The modular housing units are organized so that one side is fully open towards the exterior (to maximize views, sitting on top of existing buildings), while the opposite side looks towards the inner courtyard or the walkway with shared facilities.
The basic boxy unit is formed by two prefab CLT bearing walls and two composite walls with MetsäWood LVL elements. The Kerto Ripa floor system is resting on the CLT walls. MetsäWood Kerto T LVL wall studs and plywood are used for interior partition walls.
Communal spaces (such as saunas, workshop room, shared living room, home-office area, etc.) are designed using the same hybrid CLT/LVL system.
The advantages of the hybrid system are that it allows for a fully open façade (unlikely in CLT elements) and uses the CLT and LVL elements at their best. LVL beams to and panels are used in shear walls, such as the façade towards the walkway. Kerto S LVL beams are used to support the glazed façade. CLT prefab elements, on the other hand, are used in load-bearing walls, on which to floor structure sits. Floor slab Kerto Ripa system is the chosen option, being light but sturdy, soundproof and fast in assembly (no on-site concrete casting).
Four case studies in Helsinki city centre are examined to show the rage of possible combinations.
The Ympyrätalo case study is developed more in detail, since it would be an interesting case study for increasing housing density in a central and lively neighborhood.
The building's location would allow for raising the volume without blocking any close-by building's view and the new apartments would have majestic long views.
Using the PLUG-IN model three independent entryways are set in the arcade in front of the existing office stairwells. In this way the new housing blocks have quick and independent vertical connections (staircases, elevators, new HVAC shafts) that do not alter the existing circulation system and respect the current fire regulations.
Four new floors are added on top of the existing volume. The existing top floor is a service floor and it would now include both old and new HVAC systems, as a buffering layer between the new and the old structure.
The apartment units and balconies are set on a continuous ring and multiple combinations are design using the prefab modular elements A and B, made out of CLT panels and MetsäWood products.