RICS Gross Internal Area (GIA) Measurement Rules
Under Regulation 9 of the CIL Regulations, chargeable development is measured according to RICS Code of Measuring Practice (6th Edition):
Included in GIA:
• Internal perimeter walls and partitions.
• Attics, basements, and loft rooms with headroom exceeding 1.5 metres.
• Integral private garages and internal refuse stores.
• Common stairwells, lift shafts, and entrance lobbies.
Excluded from GIA:
• External open balconies and unenclosed garden terraces.
• Perimeter external wall thickness and external cladding.
• Open covered parking bays (carports) with no perimeter enclosing walls.
Typical CIL Cost per m² Matrix Across Selected UK Authorities (2026 Indexed)
| Local Authority & Zone | Adopted Base Rate (£/m²) | Indexed Effective Rate (2026) | Cost on 150 m² House |
|---|---|---|---|
| Wandsworth (Zone 1 - High) | £575 / m² | £895 / m² | £134,250 |
| Oxford City (Residential) | £345 / m² | £538 / m² | £80,700 |
| Bristol City (Inner Zone) | £130 / m² | £208 / m² | £31,200 |
| Leeds City (Zone 1 Prime) | £90 / m² | £145 / m² | £21,750 |
| Manchester City (High Value Zone) | £65 / m² | £104 / m² | £15,600 |
| Durham County (Band C) | £0 / m² (Zero-rated) | £0 / m² | £0 (Exempt) |