Do You Need a Permit to Build an ADU (Accessory Dwelling Unit)? in Nederland
Usually yes. Building an ADU — whether a detached backyard cottage, a garage conversion, or an internal addition — nearly always requires a building permit because it creates habitable living space with its own plumbing, electrical, and egress requirements. Most jurisdictions require full plan review, structural engineering, and multiple inspections covering foundation, framing, plumbing, electrical, insulation, and final occupancy.
Do you need a permit?
Usually yes
- Permitting authority
- Gemeente (Omgevingsloket)
- Typical fee
- €500–€5,000
What triggers a permit
- Any new habitable living space (bedroom, kitchen, bathroom) regardless of square footage
- New plumbing connections or separate utility meters for the ADU
- Structural work: new foundation, framing walls, roof structure
- Electrical service panel addition or sub-panel for the separate unit
- Creating separate ingress/egress (entrance, exit windows, parking)
Country-specific detail
In the Netherlands, building a separate zelfstandige woonruimte (independent dwelling space) nearly always requires an omgevingsvergunning under the Omgevingswet. The key distinction is between a mantelzorgwoning (care home for relatives) and a reguliere zelfstandige woning (independent residential unit). A mantelzorgwoning for a family member requiring verzorging (care) may be vergunningsvrij under certain conditions in the achtererfgebied — but the moment the care relationship ends, the building must lose its woonbestemming (residential designation). A self-contained unit with its own keuken (kitchen), badkamer (bathroom), and separate toegang (entrance) that could be rented out independently is a woning splitsing (dwelling split) and requires both an omgevingsvergunning and a splitsingsvergunning from the gemeente. Many gemeenten have additional rules under the Huisvestingsverordening that restrict kamerverhuur (room rental) and woningsplitsing to maintain housing stock balance.