How to get retrospective approval for building works on French home after completion

Extensions, conservatories, garages, conversions of existing garages into new rooms and some swimming pools, fences and entrances are among improvements that can need planning approval.

In general, only very small construction projects limited to a few square metres require no formalities. 

Above that, works of up to 20m2 typically require a simple déclaration préalable to your mairie. Above 20m2, work needs planning permission.

The local administration has the option to refuse the work within one month of receipt of a déclaration.

Even simple work such as installing a roof-light window requires a déclaration because it is regarded as an change to the appearance of the building’s exterior.

If that new window is part of the construction of a new room that is greater than 20m2 you need planning permission.

The rules are, naturally, stricter for properties in conservation areas, or for listed buildings. 

In such cases, before starting any work you should discuss your plans with the local council.

Not obtaining the required consent for home improvement work could lead to later applications for permission for other works being turned down.

However, work that did not meet planning approval requirements (for example, building a 25m2 extension rather than a 22m2 one that was subject to permissions received) is unlikely to face mairie opposition after 10 years of completion

In serious cases, not getting approval can lead to sizeable fines – a film director was fined €5m in 2010 for carrying out significant unauthorised work on a chateau near Nice.

But do not panic if you have had work done that you later realise should have required permission. 

Getting approval after work

It is possible to submit a planning application and obtain consent retrospectively, provided the work complies with local and national regulations.

If not, authorities can require you to return the property to its original condition.

The process for obtaining ‘regularisation’ (effectively, formal recognition) of previously unapproved property work is similar to the process for applying for appropriate permission in the first place.

A standard planning application needs to be made, with all the usual attachments – plans, ‘before and after’ drawings, and photographs.

Read more: I did not get permission for veranda at French home - what do I risk?

It must show that the work has already been carried out, and that the application is to formally recognise this fact, and request approval.

If a buyer, or notaire acting on behalf of a buyer, discovers work has been carried out without the necessary approvals, they may pull out of the deal – or demand that planning permission is obtained before continuing.

Be warned: the wheels of French bureaucracy grind slowly with applications for post-work approval, so expect a wait after the file has been submitted.

If you are unsure whether your work should have had planning permission, the service technique in your mairie should be able to advise you.

Most mairies will have a PLU (plan local d’urbanisme) and a POS (plan d’occupation des sols) which will include details of any rules, such as maximum heights of building and facade colours. 

In the absence of these, the national code de l’urbanisme sets the standard.

Note that any increase in the size or upgrade to your home, such as a swimming pool, is likely to impact the level of your local property taxes.

Declaration or permit?

Not all building work on your property requires planning permission – some work simply requires you to declare it to your mairie to ensure it complies with local planning regulations.

The mairie has 30 days to reply if they have an objection – or to ask more information.

After that you must put up a copy of the déclaration showing a stamp from the mairie outside your property.

Neighbours then have two months in which to object.

It is recommended to have a Commissaire de justice note that the notice is on show to avoid possible issues later.

Read more: How to settle neighbourhood disputes in France

The rule particularly applies to building work that creates a structure of between 5m² and 20m². The declaration - a déclaration préalable de travaux – is made on a simplified form (cerfa 13703*06).

Examples of when this can be used include:

• A conservatory or greenhouse if the height is more than 1.8m but less than 4m high and if the surface area does not exceed 2,000m2
• Installation of in-ground swimming pool of between 10m2 and 100m2 with a cover which is either fixed or moveable but less than 1.8m high.