10: Re-compaction with Aufstockungen

Livable Low-carbon City

Aufstockungen is the German term for vertical additions. These are rooftop additions common throughout European cities - where many structures were built with concrete, block, or stone.
Vertical additions offer a really interesting path towards re-compacting (densifying) existing neighborhoods in an incredibly sustainable manner.
They preserve more affordable, existing housing.
They reduce sprawl.
They allow the incorporation of new housing without sealing new surfaces - thereby reducing the urban heat island effect, and allowing more area for mitigating storm inundations and flooding.
It is also an approach that can be utilized to add to a number of different building types - not just housing, but schools, offices, institutions, etc.
Further reading...

Aufstockungen: Innovative Density, Mike Eliason's 2014 piece on vertical additions, via the Urbanist.
Viel ungenutztes Potenzial: Dachgeschoßwohnungen am Gemeindebau (Untapped potential: Attic apartments in municipal buildings), Der Standard article on the potential for vertical additions and attic housing in Vienna's municipal housing.
Wohnraumpotenziale in urbanen Lagen: Aufstockung und Umnutzungvon
Nichtwohngebäuden, (pdf) TU Darmstadt study on the potential for new housing via vertical additions and office conversions, in the cores of German cities

Sauerbruch + Hutton's mass timber addition to an existing DDR Plattenbau, for the Berlin Metropolitan school, via Baunetz.
AO Architekten's mass timber addition to the HTL in Graz, Austria, via Detail.
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