A well-planned renovation begins before the floor plan is drawn up. This guide to renovating an old building is based on a key principle: it is not about modernising everything, but about understanding what is worth preserving, what needs to be rectified, and how to incorporate new ways of living without erasing the property’s identity.

In Barcelona, many old buildings combine extraordinary proportions, natural light, fine materials and construction techniques that are no longer easily found. They may also conceal structural problems, outdated installations and layouts that no longer meet current requirements. The value lies precisely in addressing both aspects of the project with a comprehensive architectural approach.

Start with the assessment, not the style

The first mistake in the renovation of an old building is deciding on finishes before understanding the actual condition of the structure. A hydraulic tile, a Catalan vault or original joinery can influence the project just as much as the structure or building regulations. First, the building is studied; then the spatial language is defined.

The assessment must examine the structure, the roofs, the façades, the floor slabs, damp, ventilation and the condition of the water, electricity and drainage systems. It is also advisable to identify previous alterations. In many older homes, subsequent refurbishments have concealed features of interest or introduced partitions that hinder the entry of light and the flow of traffic.

In a block in the Eixample district, for example, it is common to find flats compartmentalised by renovations accumulated over decades. By removing non-load-bearing partitions, long sightlines, more proportionate rooms and high ceilings can be revealed. However, opening up a space is not always possible or advisable: if a wall serves a structural function, the solution requires structural analysis, reinforcement and precise execution.

What to preserve and what to transform

Preservation does not mean turning the building into a museum piece. It means recognising the elements that lend character, spatial quality or heritage value, and making them compatible with contemporary use.

A terrazzo floor can be restored and integrated into a modern kitchen. A solid timber door can be salvaged, its fittings upgraded, and it can coexist with new bespoke pieces. An exposed brick wall, if its condition allows, can add texture without the need to clutter the space with decorative elements.

The decision depends on three factors: the value of the element, its state of repair and its function within the whole. Restoring badly deteriorated joinery may be more expensive than replacing it, but replacing it with a generic solution may reduce the perceived quality of the property. There is no automatic answer. The project must establish clear priorities from the outset.

The structure and services determine the actual scope

In an old building, what is out of sight usually accounts for the bulk of the investment. Reinforcing a floor structure, resolving rising damp or upgrading a downpipe can have a greater impact than any choice of furniture. That is why the budget must set aside a realistic allocation for technical works and contingencies.

The building services require special attention. The electrical system must be adapted to meet current requirements for equipment, lighting and safety. Plumbing and drainage must be checked to prevent a newly completed refurbishment from inheriting leaks, noises or pressure problems. In buildings with stacked flats, coordinating the new systems with the communal areas is crucial.

Air conditioning presents another balancing act. An efficient system should not encroach on high ceilings, mouldings or distinctive features without a clear strategy. Sometimes it is advisable to concentrate installations in service areas, design solutions integrated into furniture or work with less visible systems. The aim is not to hide everything at any cost, but to ensure that the technical aspects do not compete with the architecture.

Renovating to improve comfort and efficiency

Energy-efficient refurbishment improves day-to-day wellbeing and protects the property’s value. However, applying standard solutions to an old building can cause condensation problems, alter a listed façade or change the natural behaviour of the walls.

Before taking action, it is essential to understand how the building ‘breathes’. A traditional masonry wall does not function in the same way as a contemporary building envelope. Adding internal insulation may be a good option in certain cases, but it requires an assessment of thermal bridges, ventilation and the risk of damp. In other cases, improvements involve restoring windows, fitting compatible double glazing or selectively improving airtightness.

Natural light also contributes to energy efficiency. Rearranging the layout of the home to bring light into areas used on a daily basis can reduce reliance on artificial lighting and completely transform the perception of space. In deep-plan homes, opening up connections between rooms, using interior glass partitions or situating secondary functions in the less well-lit areas usually yields better results than forcing a single open-plan room.

Regulations and the owners’ association: two constraints worth anticipating

The refurbishment of an old building is not confined solely to the property itself. The works may affect communal areas, façades, courtyards, roofs, the structure or general installations. They may also require planning permission, a technical project and authorisation from the owners’ association.

In Barcelona, heritage protection adds a layer of complexity to certain properties and surroundings. A façade, a staircase, a gallery or the joinery may be subject to specific criteria. Far from being an obstacle, this condition can guide a more rigorous project and enhance the distinctive value of the intervention. The key is to factor this in from the outset, both in terms of the timetable and the budget, rather than discovering it only when the works are ready to begin.

Accessibility deserves the same level of attention. In entire buildings, improving access points, circulation routes, lifts or communal areas can extend the property’s useful life and make it more attractive to residents, guests or commercial users. Feasibility depends on the existing layout, but it is worth analysing this as a long-term investment.

Designing a new life for the building

Once the technical foundations have been sorted out, the most visible part of the project begins: defining how the space will be lived in. In a home, this involves organising private and social areas, creating built-in storage, adapting the kitchen to actual use and designing bathrooms that do not feel like afterthoughts. In a hotel, restaurant or commercial premises, it involves creating an experience consistent with the brand whilst retaining the authenticity of the venue.

The layout must respond to the building, not impose itself upon it. A room with large balconies begs to be lived in; an interior space can be converted into a bedroom, dressing room, study or utility area depending on its ventilation and proportions. New elements – kitchen, lighting, built-in furniture, finishes – must provide functional clarity and engage with what already exists.

Contrast can be very effective if used sparingly. A contemporary, clean and precise intervention can enhance the presence of a vaulted ceiling, reclaimed flooring or an original wall. The problem arises when materials, colours and design references are piled on without any sense of hierarchy. An old building already carries its own history. The design must curate this history, not add clutter.

Budget, timelines and construction decisions

A renovation requires flexibility, but not improvisation. The budget must be broken down into construction, services, restoration, finishes, fittings and a contingency fund for unforeseen discoveries. The older or more altered the property is, the more important this contingency fund becomes.

It is also advisable to decide which items cannot be cut back on. The structure, waterproofing, services and the quality of workmanship are not areas where costs can be reduced without consequences. On the other hand, certain finishes or items of furniture can be adjusted without compromising the overall functionality. A well-managed project protects the investment by enabling a distinction to be made between what is urgent, what is strategic and what is merely desirable.

Renovating an old building means working with layers of history. When the assessment is accurate and every decision responds to the existing architecture, the result does not look like a refurbishment applied to an old shell: it looks like a place that always had the potential to be lived in this way.