Planning Permission vs. Building Regulations
A common misconception is that obtaining planning permission means you are ready to build. In reality, while planning deals with the appearance and impact on the local area, Building Regulations are strict statutory requirements ensuring the structural integrity, safety, and energy efficiency of the building.
Part A: Structure
This covers the fundamental stability of the build. It dictates the depth of foundations, the thickness of walls, and the specification of structural steelwork required to support loads.
Part L: Conservation of Fuel and Power
Modern extensions must be highly energy efficient. This regulation dictates the maximum U-values (heat loss) for new walls, roofs, and glazing. Often, adding large amounts of glass (like bi-fold doors or roof lanterns) requires an energy calculation (SAP calculation) to prove the house won't lose excessive heat.
The Inspection Process
You cannot simply build and sign it off yourself. A local authority building control officer or an approved private inspector must visit the site at key stages (foundations, damp proofing, steelwork, insulation) to verify compliance before issuing the final completion certificate.