In recent years, architects and designers have turned to a variety of ingenious solutions that make good use of existing — and not always obvious — space in Europe’s housing-strapped historic city centers. Urban population growth was even the focal point of the 2014 Solar Decathlon Europe in Versailles where many of the competition's 20 participating collegiate teams zeroed in on new modes of innovative and affordable housing geared not for the 'burbs but for busting-out-of-their-seams cities.

Adaptive reuse-minded architects in the vibrant Catalan capital of Barcelona have been particularly busy when it comes to transforming unused/unwanted/unclaimed/unconventional spaces into much-need housing. Most of it, not surprisingly, falls under the “micro” category. While previous schemes in the city have focused largely on attics, basements, garages and other once-undesireable nooks and crannies, Madrid-based developer La Casa por el Tejado (“House on the Roof”) has its sights decidedly set a bit higher ... to Barcelona’s vacant rooftops.

While rooftop urban infill projects aren’t exactly new, the approach is making waves in Barcelona’s bustling, art nouveau-heavy Eixample district where LCT has unveiled its vision of “Penthouse Flats:" prefabricated apartment units that are hoisted up and plunked down on available rooftops via crane. Essentially, LCT adds factory-built “extra floors” to existing Barcelona apartment buildings that havn’t quite reached their allowed height limits.

Reads the LCT website:

In most historical cities, extensions of the old city were developed through sprawling. This meant that the city expanded outward, not upward. In many cases, the projected buildable area of a project was never exhausted and, thus, remains today as potential buildable space right in the city center. We believe the city is a living being that constantly progresses and changes; naturally redesigning the urban center becomes an intrinsic part of this process. As such, we propose a more balanced and sustainable approach to traditional development by taking advantage of the possibilities at-hand.

As detailed in a freshly released video by faircompanies that includes a snazzy time-lapse view of the install process, LCT simultaneously tackles two distinct undertakings. After acquiring the “air rights” of an existing building that’s structurally fit for a couple of new floors, LCT rehabs and improves it by upgrading utilities, installing an elevator, redoing the façade, etc. These fixes not only prime the building for a rooftop addition but also make it all-around more livable for current residents. Any existing rooftop structures such as storage sheds are removed to allow for a “substitution of weight.”

Meanwhile, at an off-site production factory, LCT begins work on the custom-built modular rooftop additions. Flooring, plumbing and electrical components are all incorporated into the module(s) during the construction process. Furnishings, cabinetry and other fixtures are installed after the penthouse is mounted and secured in place atop its new home.

Joan Artés, manager of LCT, explains the myraid benefits of prefab building in the video: “It’s faster and easier to monitor and we can create more efficient buildings.” He adds: “It’s a totally new vision. We can continue sewing the fabric. We can continue building city on top of the city.”

After the existing building is prepped and the modular units are completed and ready to be loaded and trucked off, the new is fused with the old in an install process that takes little as one day. Voila! A once down-and-out Barcelona apartment building has been reborn with a fabulous new prefab penthouse up top.

Complete with a expansive rooftop terrace that offers stunning city views, one of the penthouses featured in the faircompanies video is composed of 11 individual modules and, in all, measures a palatial 600 square meters spread across two floors — not exactly a micro-apartment by any means. Other additions are much more modest in size including another featured in the video that’s composed of a single module. Whatever the size of the penthouses, the goal behind them is the same: to generate new, high-density housing by harnessing the space above exisiting buildings. This, in turn, avoids the need to build on undeveloped land and create the requisite infrastructure that comes along with new development. It's making do with what you've already got, basically.

Built with healthy, low-impact materials, the prefab penthouses themselves — a solution that boasts “lighter construction, minimal environmental impact and maximum respect for the surrounding area” — are energy-efficient and incorporate smart water management systems (greywater recycling, rainwater harvesting, etc.) along with an array of other sustainable bells and whistles. Perched above the city, the prefab flats obviously enjoy abundant natural daylighting.

And true to their module nature, the units can be moved from one rooftop and be reassembled on another rooftop if need be. Just think of that. Desperate for a change of scenery after a decade or so in the same spot but don’t necessarily want to leave the neighbhorhood entirely? No sweat as your entire apartment can be dissembled and mounted atop the vacant rooftop of another building several blocks away. No more moving houses, just moving rooftops.

Via [faircompanies]

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Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.