Groundbreaking concepts showing how city buildings could be raised upwards through wooden extensions have been released online.

Wood manufacturer Metsä Wood has created the database, which showcases the 172 entries to its ‘City above the City competition.’

The company said that the world’s growing urban population and the rising demand of housing and interior spaces mean cities must start developing strategically and environmentally – which means looking to the skies.

Wood, it argued, can provide the answer, as it is lighter, can be stacked taller and is better for the planet.

Entrants had to design a wooden extension to an existing urban building from one of 69 cities.

Winners received awards in two categories: small-scale intervention and large-scale intervention. The total value of the prizes is €35,000.

First prize winners in the small-scale intervention category were Nile Greenberg (USA) for his design for New York and Alma Studio (Spain) for their design for Shanghai. The runners-up were Superspace (Turkey) with a design for Istanbul and Sigurd Larsen Design & Architecture (Germany) with a design for Berlin.

First prize winners in the large-scale intervention category were Lisa Voigtländer (Germany) and SungBok Song (Korea) for their design for Tampere, Finland. The runners-up were Basic Architects (Australia) with a design for Perth, L Arkkitehdit (Finland) with a design for Helsinki, Giuseppe De Marinis Gallo and Gianluca Gnisci (Italy) with a design for New York and Kim Min Jae Architects (Hong Kong) with a design for Hong Kong.

These, and all the other entries, can be viewed on the online database.

Frank Werling, head of Technical, Engineering and Design at Metsa Wood, told CLAD: "When you know the population increase in urban areas will grow so much over the next 35 years, how do we house these people? We need green spaces to breath. How much residual strength is there in existing buildings, and can we utilise that through wood, which is a green and strong material? The city above the city concept derived from that idea.

"We can work with some of these concepts straight away. Some of them you can see are already at the stage where they could go to tender. Others are really outlandish, but sometimes you have to think outside the box in order to get something new. They are examples of architecture at its best, with a focus on community and sustainability."

Michael Green from MGA Architects, who chaired the jury, said: “Construction must become sustainable and cities must stay liveable. I'm happy that so many architects share this view, especially the younger generation.

“The entries were innovative and added value to both the building and the community.”