Extending your house is a common project in Brussels, where space is limited. Whether it is a side extension, a rear annexe or an extra storey, a planning permit is almost always required.
Is a permit always required?
Yes, in almost every case. Any extension changes the built volume and therefore requires a planning permit under Article 98 of the CoBAT (Brussels Spatial Planning Code). There is no exemption for habitable extensions.
Common types of extension
- Rear extension: extending the ground floor into the garden (the most common in Brussels)
- Adding a storey: an extra floor, or converting the loft with a change in volume
- Side extension: possible if the plot is wide enough
- Annexe: an attached structure (summer kitchen, bathroom, extra bedroom)
RRU rules: depth, height, party walls
Title I of the RRU (Regional Urban Planning Regulation) sets out important rules:
- Building depth: do not go beyond the deepest neighbouring building (unless a derogation is granted)
- Height: respect the building envelope of the street and of the neighbouring buildings
- Party walls: stay within the 45° plane in relation to the party walls
- Permeable surface: keep at least 50% of the courtyard and garden area permeable
Any derogation from the RRU must be stated in the permit application and may trigger additional publicity measures (public inquiry, consultation committee).
Architect requirement
An architect is mandatory for any extension project. The architect is responsible for the design, the permit application and checking that the work complies.
EPB requirements
Any extension that adds heated floor space is subject to the Brussels EPB (energy performance of buildings, PEB in French) requirements. Depending on the floor area added, an EPB declaration or an EPB certificate may be required.
Steps to follow
- Consult your municipality’s planning department (preliminary opinion)
- Hire an architect
- Check compliance with the RRU, the RCU (municipal urban planning regulation) and any PPAS (special land-use plan)
- Prepare and submit the permit application
- Wait for the decision (75 to 160 days in general)
- Display the permit and start work within 3 years