Mansard Roof, Parasite or Symbiont? Strategies for Increasing Urban Density at Roof Level

Roofs often play a significant role in the process of increasing urban densities. Building extensions at roof level provide extra space without accruing infrastructure costs, involved in developing empty plots of land. It is often the case that building space on top of existing constructions is in fact the only available alternative. The principles relating to subsequent construction on, or in, roof spaces can range as much as the desired usage, size and budget. While mansard roofs offer excellent opportunity for sensitively increased urban density within historic contexts, other temporary solutions known as “parasites” act rather as landmarks, calling attention to themselves and creating new impulses within the city quarter. The scale of roof extensions can range from mobile single-room hotel capsules – from the Swiss artist L/B – to the Elbe Philharmonic in the Hamburg Harbour City – from Herzog & de Meuron – with two concert halls, various apartments, car parking and a 220-room hotel. Roofs can be renovated to create new, high-quality living spaces; this is demonstrated by low-budget living rooms in angular timber cubes, and sculptural, highly-styled single family dwellings, perched 15 metres above the ground with refined aluminium skins. This article shows, with some outstanding examples, that the roof can be much more than just the fifth facade.