Can we stick affordable housing on the rooftops of cities?

Makka housing
© Stéphane Malka

Paris is a mid-rise city with very expensive housing. Architect Stéphane Malka has proposed a way of building new housing; he proposes a prefabricated system, "3box", where units are added to the rooftops of existing buildings. The architect says it would be economical to build because there is no land cost; the right to build is obtained in exchange for upgrading and renovating the existing building's common areas and services.

Then, we are able to propose a green housing 40% below the real estate market price, built without any nuisance in workshops, in extremely short time thanks to our patented panels and unique technique of prefabrication. These patents were achieved in collaboration with a team of engineers and specialists from “Les Toits du Monde

There is a lot to love about the idea. As the architect notes on his about page,

It is difficult to speak of “sustainable/environmentally friendly” architecture when the act of building in itself generates environmental degradation. The construction industry results in enormous pollutions of water, air, and land. In light of these social, economic, and ecologic urgencies, it is necessary to reconsider the city with the logic of transformation: through superposition, addition, and the extension of our built heritage more than through that of a univocal tabula rasa. This means reclaiming territory in the marginalized areas of our cities, with projects that bear insurrection and civic mobilization.

It makes a great deal of sense; as noted it preserves our existing built heritage, increases density, and there theoretically is no land cost, but there are other significant costs.

TreeHugger has shown a number of rooftop additions before, and until now they have all been very lavish and expensive structures, or the projects have stalled because of the other costs. As was noted in discussions about the Loftcube prefab, "fully half of the budget is taken up by purchasing air rights, contractor fees for installation and other charges." Then there are other additional costs:

  • Adding to the top of a building creates additional earthquake and wind loads, and the buildings often have to be braced accordingly;
  • Stairs and often elevators have to be extended;
  • Rooftop equipment has to be relocated
  • .
Malka appears to be proposing lightweight steel structures that are standing on legs above the buildings below, and those legs might well extend right down to grade, making many of these problems moot. But he makes it sound so easy; perhaps their system, with its legs and patented panels, has solved them. Because I know from personal experience how hard it is.

2 queen west© Lloyd Alter Architect

My last project as Lloyd Alter Architect involved adding lightweight steel boxes on top of an existing hundred year old building, and it was disastrously expensive and difficult.

Kensington Lofts© Lloyd Alter

My last project as a real estate developer involved adding lightweight steel structures to the roof of an existing school and the extra density added on top certainly paid for itself and more, but required reinforcement of columns throughout the entire building, enlargement of footings, and other modifications that we could do because the building below was empty.

addition to side© Stephane Malka

The idea of adding on top while people are in the building and coming out 40 percent less costly? I really wish him luck. It is all a wonderful idea but it is really hard to do.

Can we stick affordable housing on the rooftops of cities?
It's not so easy to build on rooftops, but it can be done. Whether it will be affordable is another matter.

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