01Brief, survey and design
02Approvals, specification and agreed quotation
03Groundworks, structure and weather-tight shell
04Services, finishes, inspections and completion
Completion & handover
Agree a snagging record, handover information and the relevant completion documentation. Planning permission and building-regulations approval are separate matters; do not assume that permitted development removes building-control requirements.
Walk through the work together, list outstanding items and agree who will resolve them and when. Keep relevant care instructions, certificates and written warranty terms.
Planning Portal: extension approval ↗General homeowner guidance for England, checked October 2026. The correct specification and approvals depend on the property and work proposed; confirm these with the appropriate designer, installer or local authority.