In Luxembourg, some works require building authorisation, others don’t. Getting it wrong can be costly: fines, demolition orders, even legal proceedings. This guide clarifies the rules in force in 2025.
The Basic Principle
The general rule is simple: any construction or modification to a building’s exterior appearance requires authorisation. But many exceptions exist for small works.
Building authorisation is issued by the mayor of your municipality. Deadlines and requirements may vary slightly from one municipality to another.
Works That Require a Permit
Here are the works that mandatorily require building authorisation in Luxembourg.
New construction includes any new house, building or structure, even an annexe or separate garage. Extensions over 10m² or modifying the façade also require a permit.
Façade modifications concern changing windows if dimensions or appearance change, modifying openings such as doors and bay windows, rendering with change of colour or material, and adding a balcony or conservatory.
Roof works include changing the shape or pitch of the roof, adding dormers or skylights, and modifying the building height.
External landscaping covers building an in-ground pool, boundary walls over 2 metres, and garden sheds over 10m².
Important: In protected zones or near listed monuments, requirements are stricter. Always consult your municipality before starting.
Works Exempt from Permits
Certain works can be carried out without authorisation, provided urban planning rules are respected.
Routine maintenance includes interior painting and replacement of coverings, like-for-like window replacement with same dimensions and appearance, like-for-like roof repair, and façade repairs without change of appearance.
Small external works include garden sheds under 10m² and under 3m high, fences under 2m high, ground-level uncovered terraces, and driveways and vehicle access.
Technical installations include solar panels integrated into the roof, heat pumps under certain conditions, satellite dishes not visible from the public road, and air conditioning without façade modification.
Interior works cover kitchen or bathroom renovation, removal of non-load-bearing partitions, electrical upgrades, and heating replacement.
The Authorisation Application Procedure
If your project requires a permit, here are the steps to follow.
The first step is preparing the file. You’ll need a cadastral plan of the plot, plans of existing and proposed by an approved architect for major projects, photos of the existing situation, a descriptive note of the works, and the municipal application form.
The second step is submission to the town hall. The complete file is submitted to your municipality’s planning department. A receipt is given to you.
The third step is file processing. The municipality examines the file and may request additional documents. For certain projects, the opinion of other services such as Sites and Monuments, Environment or Highways may be required.
The fourth step is the decision. The mayor grants authorisation, refuses or requests modifications. In case of refusal, you can lodge an appeal.
Average Timescales
Timescales vary according to project complexity and municipality.
For simple works like an extension or windows, allow 4 to 8 weeks. For new construction, plan for 3 to 6 months. For projects in protected zones, allow 6 to 12 months.
Advice: Submit your application as early as possible. A refusal or modification request can delay your project by several months.
Mistakes to Avoid
Starting works without authorisation is the worst mistake. You risk a site stoppage, a fine and an obligation to restore. Even if works are completed, the municipality can require demolition.
Submitting an incomplete file leads to requests for additional documents that extend timescales. Check the list of required documents with your municipality carefully.
Ignoring PAG rules - your municipality’s General Development Plan defines what’s buildable and how. A non-compliant project will be refused.
Not consulting neighbours - for certain projects near property boundaries can generate objections. Better to prevent and dialogue beforehand.
The Special Case of Co-ownerships
In a co-ownership, you need two authorisations: one from the municipality for planning aspects, and one from the co-owners’ general meeting for anything affecting common areas or external appearance.
Even for works exempt from municipal permit, like like-for-like window replacement, co-ownership regulations may impose constraints.
What to Do in Case of Refusal
If your application is refused, several options are available.
An amicable appeal asks the mayor to reconsider their decision by making modifications to your project.
A hierarchical appeal is addressed to the Minister of the Interior within 3 months of notification of refusal.
A legal appeal is made before the Administrative Court if other appeals have failed.
In all cases, help from an architect or specialist lawyer can be valuable.
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FAQ
Can I install a heat pump without a permit?
Generally yes, if the outdoor unit is not very visible and respects regulatory distances. But some municipalities require prior notification. Check with your municipal administration.
How much does a building permit application cost?
Fees vary by municipality and nature of project. Expect between €50 and several hundred euros for major projects, plus architect’s fees if necessary.
My neighbour is building without a permit, what should I do?
You can report the situation to your municipality’s planning department. If the construction causes you direct harm, you can also apply to the court.
Does authorisation have a validity period?
Yes, generally 2 years. If you haven’t started works within this period, the authorisation lapses and you must reapply.
