Home extension: 6 mistakes to avoid

To achieve its objectives, the house extension must be perfectly suitable for needs having motivated it and in harmony with the part already built. The first mistake to avoid, before even thinking about the means to be implemented, is therefore to neglect the precise definition of family and environmental aspirations. To synthesize, you have to look for “why make an enlargement, avant to know if he isdoable and how“.

1 – Poorly defining your project: source of serious disappointment

Two motivations can be at the origin of an extension:

And simple concern for aesthetics, can push to adapt the house to its environment or to the personal tastes of the occupants. It is often the simplest option to manage, because to improve the style of the building, it is sometimes enough to modify the slope of a roof, to join a utility room, to build a courtyard, a veranda, a tower or a garage…).

Adapting the living environment to a new imperative, such as the arrival of a new occupant or a change of activity, by avoiding the inconvenience of a move, remain the most frequent motivation for extending houses. In this case, the integration of the new building must not only meet the aesthetic requirements, but also comply with the standards of comfort et of use considered. The administrative procedures may also be different.

In quality of master of workyou alone are responsible before the law and can define the principle orientation for the extension to be carried out. The architect, project manager and contractor, as competent and talented as they are, can only advise and help you on the appropriate techniques to achieve the set objective.

2 – Budget and neighborhood: details which, neglected, can make life unbearable

The costs of extending a house vary endlessly, depending on the type, surface area and materials used. Generally, horizontal extensions are less expensive than extensions. In this matter, only one rule: the budget must be defined precisely in advancein accordance with the expertise of professionals, and respected at each phase of the construction site.

Building modifications are a common source of conflict (including in court) with the neighborhood. It is important not to underestimate them. Explaining the project to those around you, or even asking for advice, is a reassuring approach that avoids frustration due to surprise. In any case, be sure to respect scrupulously national and local planning regulations.

3 – Non-compliance with town planning rules: no building permit

The town planning rules define, among other things, the permitted surface areas and habitable areas on your land, the indications or obligations in terms of colours, materials or elevation of buildings. It’s really the first administrative approach to undertake to find out the type of enlargement authorized. For example, a plot of 500 m², located in a zone, can admit a floor area of ​​800 m² (which supposes one floor), while at some distance, the building area is limited to 200 m² ( or less), for the same land area. This legal framework is defined by each municipalityin accordance with national regulations, depending on the local particularities of the territory and/or the political options of elected officials.

These rights and obligations are contained in the Local Urban Plan (PLU), which can be consulted in the town hall of the place of construction and sometimes online. Beyond the town planning regulations, the PLU lists all the municipal provisions, present or in the making, in terms of collective accommodation or the environment. You will also find, in the appendix, the diagrams of the water networks and a plan of the 4 types de zones (U, buildable, AU to urbanise, N green areas and A zone agricole).

This document, at first daunting, is truly worth the effort of reading. Also make sure you have special rules, if you are located less than 500 meters from a heritage site outstanding. Special rules are applied to protected areas regardless of the built-up area.

4 – Building without authorisation: financial and legal sanctions

The expansion works of less than 5 m² of surface floor and up to 12 m in height, do not require no authorization administrative (except in protected areas). Beyond that, the filing of a prior declaration of work or a building permit is required.

To from 1is January 2012the extensions located in urban areas subject to a PLU (or any other urban plan) and a floor area equal to or less than 40 m² are exempt from building permits.

Without urban plan2 regimes apply:

  • extensions included between 5 and 20 m² are subject to Statement
  • the extensions of more than 20 m² fall under building permit.

The “preliminary declaration of works”, accompanied by its appendices, must be submitted to the town planning department of the town hall concerned, by hand or by registered mail with AR. Municipalities of more than 3 500 habitantsallow digital filing.

The house extensions of more than 40 m² are all subject to the filing of a building permit.

Failure to comply with these procedures exposes you to administrative interruption of the works, fines (up to €6,000/m² of built surface area), prison sentences (in the event of a repeat offence) or final stage, demolition of the structure.

5 – Non-use of an architect: risk of refusal of the building permit

Since March 1, 1977, regulations have set 150 m²the “threshold for compulsory recourse to an architect for physical persons who build or modify buildings” (decree no. 2016-1738 of December 14, 2016). For house extensions, this threshold is understood to mean the total surface area after enlargement. For constructions for agricultural use, the limit is increased to 800 m² for buildings and 2,000 m² for greenhouses less than 4 m high.

Outside this framework, applications for building permits without the mark of an architectare simply not examined.

6 – Non-declaration of completion of work: administrative and tax penalties

The project owner is obliged to submit to the town hall, upon completion of the construction, a file in 3 copies, containing the forms and the legal documents proving the successful completion of the work in the rules of the art and according to the regulations. in force. This file is subject to the control of the town planning department of the municipality which has a 3m delayois to instruct him (or 5 months for the protected areas or close to historical monuments). After these deadlines, the file is deemed approved. So you can claim within two weeks, to the mayor, the Declaration attesting to the Completion and conformity of the Works(DAACT) by registered letter with acknowledgment of receipt.

Without prejudice to criminal and financial penalties, the absence of DAACT deprives you of:

  • of the faculty of sale your property as a habitable building,
  • ten-year and property damage insurance protection, the coverage period for which starts on the day it is obtained.

The non-conformity of the work suspends the instruction period and may lead to a formal notice of correction of failuresupon removal of a amending building permit or in extreme cases, destruction of the work.

And don’t forget: the owner has 90 daysafter obtaining the DAACT, to declare the end of the work to finance administration (art-1406 of the General Tax Code).

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