In Porto's Campo Alegre, Openbook Architecture has transformed a 1982 office building into a contemporary multi-tenant workplace of 10,000 sqm.
A new curtain wall with vertical and horizontal fins calibrated to each orientation, a daylit courtyard where escalators once stood and a rooftop terrace over the Douro reshape the building without erasing its identity.
The Mutual Building stands on the corner of Rua Gonçalo Sampaio and Rua do Campo Alegre, in the Lordelo do Ouro district of Porto. Designed in 1982 by the architects José Pulido Valente, Nicolau Brandão and Ricardo Figueiredo, it was occupied for decades by the insurance company AXA/Ageas. Acquired by Osborne+Co Portugal, it has now been transformed by Openbook Architecture into a contemporary office building of 10,000 sqm, seven floors above ground and two below, on a plot with three street frontages: Rua do Campo Alegre to the south, Rua Gonçalo Sampaio to the east and Rua João Martins Branco to the north.
The intervention worked along three lines: a complete renewal of the façades, a reorganisation of the internal circulation, and the optimisation of usable, lettable space. Underneath all three sits a single criterion, the relationship with the existing building.
Reconfigure Without Erasing
The building was in reasonable condition, but badly out of step with what a workplace now requires. Its façades had no strategy for solar exposure, its internal circulation worked poorly, and the shopping gallery on its lower floors had long lost its reason to exist. The response was to reconfigure without erasing. The identity of the building was preserved where it made sense and transformed where it was necessary, and its structure and volume were kept. One decision makes the approach tangible: an existing mural by a renowned artist of the period was restored and given prominence in the lobby, holding a line of continuity between what the building was and what it is today.
A Façade Calibrated to the Sun
The renewal of the façades is the most structuring gesture of the intervention. The original envelope was replaced by a curtain wall with external solar shading, a system of vertical and horizontal fins calibrated to the orientation of each elevation. They are denser to the south, where solar incidence is greatest, and more permeable to the north, where the aim is to bring in as much daylight as possible. New glazing with low thermal transmittance completes the response.
The result is a façade that is at once identity and performance. Its depth, rhythm and variation are not decorative. They are the visible trace of how each side of the building meets the sun, and they improve its thermal and energy behaviour through passive means.
At the base, the existing terraces were regularised into linear platforms that mark the horizontality on which the upper volume rests. This hierarchy between podium and tower gives the whole a formal coherence and strengthens its presence in the urban setting of Campo Alegre.
Light at the Centre
Inside, access and vertical circulation were reorganised across all seven floors, and the former shopping gallery was converted into office space. Where escalators once stood, the project introduces an open-air courtyard that brings natural light into the central areas furthest from the façade. It is the clearest example of how the intervention works: a space the old building no longer needed becomes the one that makes the new building work.
The main entrance, on Rua Gonçalo Sampaio, leads into a new reception, contemporary and minimal, set in a bright, double height space. Above it, the floors are designed around a flexible multi-tenant model, with layouts that can be repeated floor by floor and adapted as the market changes, so that the building can accommodate different occupiers over time without losing its coherence.
At the top, a rooftop terrace closes the programme with views over Porto and the Douro River.
Built for Performance
Below ground, the project provides parking, bicycle storage, changing facilities, electric vehicle charging and new technical areas, as a direct response to the LEED and WELL certification processes under going, and photovoltaic panels produce renewable energy for its own consumption.
The choice to rehabilitate rather than rebuild is itself part of this performance. Keeping the existing structure avoided demolition, the waste it produces and the resources a new building would consume.
The green frontage to the south, along Rua do Campo Alegre, received careful landscape treatment. All existing protected species were kept, and new native, low maintenance planting was added.
The Mutual is not born of a break with the past. It comes from the conviction that a building with a history can also be a building for the future.
