Write the programme and its connection to the house
Describe new uses, circulation, access and the parts of the existing building affected. Gather plans, site information and previous work records. Distinguish essential needs from options. The extension changes more than its new floor area: openings, levels, services and access to the existing home also need a place in the programme.
Investigate the site and existing structure
Ask which surveys, soil information and structural investigations are needed for the proposal. Include the junction between new and existing work. Record what remains an assumption. A similar extension next door does not establish the conditions under this building. Have technical feasibility assessed before using an indicative construction price as a confirmed budget.
Check permissions and property matters separately
Describe the proposed surfaces, appearance and uses to the competent planning service and consult the relevant official references. Identify property and neighbouring constraints separately from the planning process. This page does not choose an authorisation from a universal area threshold. Confirm the requirements for the actual site and project before committing to irreversible work.
Coordinate design, services and the work sequence
Confirm levels, openings, structure, envelope and service routes on consistent documents. Assign the junctions and temporary protection while the house is opened. If it remains occupied, discuss access and service interruptions. Agree the design decisions needed before quotations and orders so that contractors are not pricing different versions of the extension.
Compare the complete project and close the work
Include studies, site preparation, connections, reinstatement and finishes alongside the new construction. Keep conditions, exclusions and payment timing explicit. Schedule checks before concealment and handover with the appropriate records. Where administrative completion steps apply, confirm the procedure through the competent service rather than assuming that final payment closes every obligation.
Your preparation checklist
- Programme and existing-house effects described.
- Site and structure investigated.
- Permissions and property matters distinguished.
- Junctions and temporary protection assigned.
- Complete budget and sequence prepared.
- Handover and applicable completion steps confirmed.
Questions before you commit
Does an indicative price establish feasibility?
No. Keep investigations, design assumptions and relevant permissions separate from the provisional price.
Does planning approval assess every technical detail?
Technical design and other applicable constraints still require their own assessment.
Sources and the scope of this guide
This English guide covers the same project need as its French counterpart, with an editorial explanation in English. It is not a professional survey or a translation of foreign rules to France. Check current official requirements and the documents applying to your building and contract.
French reference: ANIL : préparer une extension de maison
French reference: ANIL : autorisations d’urbanisme
French reference: Service-Public.fr : déclaration d’achèvement et de conformité