Reconversion of existing buildings as a sustainable solution – Some legal considerations

The real estate sector must balance growing societal demands for office spaces, housing, and green areas with the need to reduce carbon emissions. Sustainability, particularly circularity, is becoming increasingly important. Developers are opting more frequently for reconversion of existing buildings instead of new constructions, offering both economic and environmental benefits.

Several reconversion projects illustrate this trend. The Antwerp Tower and Leopold Views in Evere have successfully transformed former office buildings into mixed-use spaces and residential apartments. Ongoing projects, such as the reconversion of the Boerentoren in Antwerp into a multifunctional building with apartments, museum, public and restaurant/café facilities, and Patrizia’s investment of 75 million EUR in converting office buildings into 1,000 affordable apartments, highlight the increasing importance of reconversion. In 2024 alone, nearly 180,000 square meters of office space have already been converted into residential units in the Brussels-Capital Region.

Legal considerations in reconversion

While reconversion offers many benefits, there are also important legal considerations to take into account. Below, we outline some key legal urban planning and zoning implications.

• Zoning compliance

The zoning regulations determine whether reconversion is possible. Office or administrative zones usually don’t allow residential use, requiring a prior zoning review. In Flanders, if the residential functions are not allowed, the zoning designation must be modified through a Spatial Implementation Plan (Ruimtelijk uitvoeringsplan, RUP), which can be a lengthy process. 

A new instrument, the Environmental Decision (Omgevingsbesluit, Flemish Decree of 17 May 2024), is expected in 2026 and combines the processes for adopting a spatial implementation plan and obtaining a building permit into one integrated decision. The Environmental Decision will be used for so-called ‘spatial impact projects’, which are projects that enhance spatial efficiency and quality, thereby increasing societal use. However, an annulment appeal is currently challenging the Decree of 17 May 2024 before the Constitutional Court of Belgium.

In the Brussels-Capital Region, the regional zoning plan determines the designation of an area. A Special Zoning Plan (Bijzondere bestemmingsplannen, BBP) at the municipal level can further refine the designation in the regional zoning plan. The regional zoning plan already allows for administrative zones (where office buildings are often located) to also include residential buildings, facilitating reconversion projects.

• Requirement of a building permit

Several aspects of a reconversion project will trigger the necessity of a building permit. This means that most reconversion projects will require proper preparation in order to submit a sound permit request (including an assessment of the environmental impact and mobility impact of the project, compliance with fire safety standards, etc.).

• Building permit – Change of function

Converting an office building into housing entails modifying the function of the initial building, for which a building permit is required both in the Flemish Region and in the Brussels-Capital Region. 

Even if the zoning designation allows for reconversion, a building permit is still required to modify the building’s function from ‘office’ to ‘housing’.

• Building permit – Renovation works

When converting office buildings into residential units, the building will undergo significant renovation works, often impacting the building’s stability. Such works generally require a building permit both in the Flemish Region and in the Brussels-Capital Region. In some cases, a notification can be done instead of a building permit, or smaller works could be exempted from a building permit. This must be assessed on a case-by-case basis.

• Housing standards and energy efficiency standards 

When converting office buildings into residential units, the new units must comply with applicable housing standards, such as minimum surfaces, minimum free height, and minimum natural light entry. These requirements can be challenging to meet in existing office buildings, which often have lower ceilings than residential units or greater depth, making natural light entry more difficult.  

In the Flemish Region, these standards are established in the Flemish Housing Codex of 2021. In the Brussels-Capital Region, the housing standards are established in the Brussels Housing Code of 2003 (revised in 2013). Additionally, specific urban planning regulations of the relevant municipality may impose further requirements, which can vary by municipality and are outlined in urban planning regulations.

On the other hand, converting office buildings into residential buildings means that developers must comply with the applicable EPC and EPB standards for housing instead of offices, ensuring compliance with energy efficiency standards.

• Parking standards

Another challenging aspect of the conversion process is compliance with the parking standards applicable to housing. 

In both the Flemish Region and Brussels-Capital Region, these standards are generally imposed in Spatial Implementation Plans (in Flanders) or Special Zoning Plans (in Brussels), or through the urban planning regulations of the respective Regions and/or municipalities. These parking standards require a certain number of parking spaces on site. Sometimes, paying a contribution or deviation from the parking standards can be allowed to compensate for the missing parking spaces, but this varies by municipality.

Some office buildings might not be suitable for reconversion, as it would be difficult to comply with the applicable parking standards, which are still quite high in many municipalities. On the other hand, a surplus of parking spaces might also negatively impact reconversion projects. Older office buildings often have too many parking spaces, which are not needed when converting the building into a residential building. Such surplus can directly affect the project’s profitability, as they are often hard to sell.