Replacing window frames is one of the most common renovation jobs. In Brussels, whether you need a permit depends on exactly what the work involves.
Do you need a permit to replace your windows?
The answer depends on two factors:
- Is it a like-for-like replacement? (same materials, shapes, colours and profiles)
- Is the facade visible from the public space?
Like-for-like replacement (exempt)
Replacing window frames is exempt from planning permission if all the following conditions are met:
- The original shapes are kept (arches, visible divisions, opening and fixed sections)
- The material is kept (wood → wood, aluminium → aluminium)
- The colour is kept
- The width and moulding detail of the profiles are kept
- The architectural appearance of the building is not altered
- Any stained glass is kept
Important: replacing wooden frames with PVC (same shape, same colour) requires a permit, because the material changes.
Single or double glazing can be replaced with double or triple glazing without a permit.
Altering openings (with or without a permit)
Creating, removing or altering openings (windows, doors) is exempt from planning permission if:
- The openings are not visible from the public space
- The alteration does not involve structural work
- The facade is not in the protection zone of a protected heritage site
On the front facade or any visible facade, a permit is required for any alteration to an opening.
Do you need an architect?
Altering openings or window frames without any structural issue is exempt from the architect requirement, even if a permit is needed.
Grants for windows
Replacing window frames may qualify for Renolution grants:
- Grant for replacing window frames and fitting high-performance glazing
- The amount varies with income and the thermal performance achieved
- The glazing must reach a minimum Uw value set by the Region
Practical tips
- Take photos of the existing frames and check the legally permitted situation in the planning archives
- If in doubt about the material or appearance, ask your municipality’s planning department
- Stricter rules apply to protected heritage sites and to properties in a protection zone