Self-builders deal with building control more directly than developers, using either the local authority or a registered building control approver (formerly an approved inspector). This page explains how Part L 2026 affects that relationship.
Full plans or building notice
For most self-builds a full plans application is the safer route: building control reviews the design and the SAP calculation before work starts. A building notice lets work begin sooner but leaves compliance issues to be found mid-build, which is riskier on an FHS-spec home. Registered building control approvers use an initial notice instead.
The SAP compliance documents
The PV also has to meet the general rules on solar panels and building regulations, from roof loading to electrical safety. For Part L, building control needs the SAP 10.3 design-stage calculation showing the dwelling meets its Part L targets, details of the PV array, the ventilation strategy (Approved Document F), the overheating assessment (Approved Document O) and the fabric specification for walls, floor, roof, windows and doors.
Inspections
Typical inspections cover foundations, damp-proof course, drainage, pre-plaster and completion. On an FHS build, also plan for the roof structure before tiling (where in-roof PV is fitted), the air permeability test, ventilation commissioning and PV commissioning. Agree the schedule with building control early.
EPC and completion certificate
At completion the as-built SAP calculation is produced and the EPC issued. The building control completion certificate is usually needed to finish the mortgage drawdown, and warranty providers ask for it too.
Where things go wrong
Two common problems: an air permeability result above the design value, usually a detailing issue at penetrations or eaves that is fixed by sealing and retesting; and PV not commissioned before the final inspection, which is avoided by scheduling commissioning ahead of it.