A lot can change in four decades. In its comprehensive renovation of the relatively young Renaud-Barrault Library in Avignon, Jakob + MacFarlane’s (J+M) task was not only to repair degraded building fabric and adapt to new reading habits, but also redefine an institution in response to developments in the city beyond.

Avignon, located 50 miles from the south coast of France, has an ancient and picturesque heart, but the library stands in a low-income suburb some way outside the city’s medieval ramparts, on a corner of a heavily trafficked highway, Rocade Charles de Gaulle. Designed in response to the fragmented landscape of 1970s housing projects, the 1985 building was composed as an asymmetric, village-like cluster. Facades of some upper stories incline inward, where the concrete structure was clad in blue metal. Single-glazed windows had a dense cross-hatching of bright green bars.

Standing outside the 27,000-square-foot library with Ali Elghouze, who acted as the city’s representative for the renovation, he recalls its technical failings: leaks, lack of insulation, traffic noise, and little protection from the fierce summer sun. Equally significant was a decline in visitor numbers. In an area with a variety of social problems, the city believed that local people needed more encouragement to engage with the library. To do that, the building needed a more emphatic presence and welcoming expression.

Together with a detailed program, those objectives formed the brief for a design competition. Alongside city officials, the jury included original architects Béatrice Douine and Jacques Prunis, now retired but still residing nearby. Their presence heightened awareness for Paris-based J+M that the proper approach to renewal should combine bold reinvention with respect. “The project needed to breathe new life into their building, but couldn’t simply be a restoration,” says Brendan MacFarlane, J+M cofounder with Dominique Jakob. “How could we work with some of the building’s characteristics and achieve a true renaissance?”

His response was a symbolic sheltering tree—a metaphoric allusion to the simplest places for congregation and sharing knowledge, and a practical answer to many of the building’s defects. As J+M’s principal addition, the timber “tree” has a symbiotic relationship to the original concrete structure. Its trunk is a fluid honeycomb of plywood bookshelves that rises through the building from the full-height entrance foyer, wrapping around a retained elevator shaft. Its canopy is made of cross-laminated timber—an age-old material in contemporary form—and appears almost to float above the building’s roof, touching lightly on the eaves despite its considerable size and weight. No additional reinforcement of the existing building was required. One advantage of working with older buildings, notes MacFarlane, is that they’re often over-engineered, with inherent capacity for adaptation as well as proportions that would be harder to achieve today. Projecting up to 26 feet outward on all sides, the slender canopy shades windows and the sidewalk below. Plants and photovoltaics on top contribute to improved environmental performance.

On approach, this eye-catching crown is the most evident sign of transformation, and its orthogonal outline lends a more ordered appearance to the informal jumble below. This reframing also allowed the architects to see the existing building in a more sympathetic light. “Finding a relationship with it took a while,” says MacFarlane, “but when we conceived the roof as an organizing element for the whole site, the project took off.”

Another consideration was that the building must now address a different urban context. A tramway is strengthening connections between the Rocade district and the city center, bringing new vitality, and a museum is planned on the site of a gas station across the street. The straight-edged part of the crown provides a useful foil for the museum’s future architect and begins to frame a new neighborhood gateway.

Externally, the fussy windows were replaced with larger panes of double-glazing, and cladding was stripped from facades to expose the structure. While the areas always intended to be visible are carefully ribbed or boardmarked béton brut, newly revealed concrete is more workaday. Enjoying the contrast, J+M was determined to keep necessary insulation to the inner face of the walls. The single facade material now gives the library a calmer, more civic character. One might even see a similarity to the monolithic limestone buildings of the city center, from the Papal palace to the Pont d’Avignon.

Concrete has also been exposed throughout the interiors, which were previously lined or painted. Here, again, scarred surfaces are preserved, with only limited repair after sandblasting—“Not so little that it would look bad,” says MacFarlane, “but not so much that it would look precious.” Such imperfections lend a distinctive identity, but they were a hard sell. “Citizens want to see where the investment has gone,” says Elghouze. “We had a lot of discussions before Brendan convinced us.”

Its stark character is further celebrated in the selection of complementary finishes that nevertheless introduce a sense of comfort. A foamy gray acoustic treatment has been applied to ceilings, while floors are covered in gray carpet patterned to resemble concrete.

More warmth comes from the amorphous plywood matrix of the “tree trunk,” which acts as book storage and is visible from most parts of the library. The material has an economy demanded by the $8.25 million budget, and its use adds a vital dose of delight. “You need some surprise or magic to get people into a building and wanting to spend time there,” says MacFarlane. “Simply sandblasting old concrete wasn’t going to do that.”

Plywood also forms freestanding custom-made bookcases. Books take center stage on every floor, but the remodeled library also has facilities intended to draw in diverse audiences. A wood-lined auditorium can be accessed independently of the library for after-hours events. A mezzanine overlooking the foyer invites passersby to stop for a coffee. Small kitchens encourage community gatherings. On the upper levels, rooms for computer use and video games are separated from the stacks by glass screens.

Arrangement of the loose furniture within the open-plan spaces was debated at length and tested at one-to-one scale using projected light in a local warehouse. J+M designed everything, from a kids’ playhouse to large, soft chairs in warm yellow and zesty green and orange. The bright colors recur in the architects’ work but here represent the leaves of the tree through the seasons. Throughout the building, these elements are recomposed to form subtly different spaces tailored to suit a spectrum of users, from adults to preschoolers or teenagers dropping in with homework.

Walking through the library, long views made possible by removal of partitions allow all of this activity to be taken in at once, along with once-hidden qualities of the building—a state of happy coexistence in an environment that is both relaxed and monumental. “A month after reopening, there are plenty of people coming in,” says Elghouze. The tree is already bearing fruit.