Railway sleepers form the walls of this extension to a library in Azkoitia, Spain, which is located at the town's former railway station.

Designed by Spanish studio Estudio Beldarrain, the Aizkibel Library extension adjoins the old station building, which had already been converted into a library but was in need of more space.

The disused railway track had been cleared away from the site, leaving the old building out of context. So Estudio Beldarrain used recycled sleepers to create a contemporary extension that references the site's history.

The extension takes the form of a group of small tower blocks – a shape dictated by the design of the spaces within. Italian studio Gianluca Gelmini took a similar approach for a copper-clad stairwell to a library housed in a medieval tower.

"A sculpted box with an irregular shape, takes the new expansion of the library," said Estudio Beldarrain.

"Its heavy cover made of wooden railway sleepers evokes the history of the building, almost as if when the tracks were dismantled the old sleepers had been stacked near the station."

The extension's rough, dark appearance is at odds with the pale decorative stucco facade of the station house – an intentional contrast conceived so as not to compete with the traditional style of the old building.

A metal-framed entrance protrudes from the base of the extension, which leads into a lobby. The upper floors are occupied by toilets and a stairwell, freeing up the rest of the main building for library space.

Here, three 133-square-metre rooms are subdivided with partitions to provide shelving for different genres of books.

Windows and terraces to the south side of the extension overlook a long boulevard where the train tracks once stood.

"The use of the aged wood as the facade material allows the architecture and park to relate, precisely because of its natural condition," added the architects.

Photography is by Jon Cazenave.

Project credits:

Project: Estudio Beldarrain – Juan Beldarrain
Collaborating architects: Marta Badiola, Itziar Combarros, Iker Garmendia, Román Arrizabalaga
Developer: Council of Azkoitia
Executive management: Asier Arambarri
Installations: Inconor Ingenieros Consultores
Structure: Construbrik