Green Roof 1.0: The Seaweed Houses of Læsø, Denmark

Though green roofs are reemerging in the most advanced building designs around the world, for centuries, people constructed buildings out of materials immediately available to them in their surrounding environment. It is only a relatively recent luxury, for example, that people have easy access to roofing materials like asphalt shingles made hundreds, perhaps, thousands of miles away.

On the island of Læsø, Denmark there still stand a handful of buildings that are excellent examples of what communities would do with what was immediately available to them — if only they had any of it left.

In the Middle Ages the island of Læsø became famous for its salt industry. Hundreds of salt kilns were built, throughout the island, requiring constant fuel for the important final stage of commercial salt concentration. But on the island of Læsø—a community with a finite availability of natural resources—constantly feeding the hundreds of salt kilns eventually led to the island’s deforestation.

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Once the island’s vegetation disappeared, violent sandstorms buried entire villages. Læsø belongs to the Danish “desert belt” and during the summer months there is so little rain that streams and ponds partly dry up, as such, nothing grows back quickly. Soon after the villages were buried, salt extraction was banned. At that point, residents turned whatever was available to them to build houses thatch their roof - in this case it was seaweed (eelgrass) and driftwood from shipwrecks.

Because both the seaweed and timber had been impregnated with saltwater, the seaweed houses of Læsø have shown themselves to be remarkably impervious to the elements, standing virtually unaltered since the 1600s.

Images: seier+seier+seier

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