GIA (Gross Internal Area) is the total floor area of a property measured from the inside of the external walls — including circulation space (hallways, stairs), internal walls, and built-in storage, but excluding voids, external walls, and unenclosed external balconies.
Also known as: Gross Internal Area, GIA measurement
GIA is one of the standard UK property measurement methods, codified by RICS (Royal Institution of Chartered Surveyors) in the RICS Property Measurement standard. It is the default measurement used in UK EPC assessments, residential valuations, and HMO licensing — and is broadly equivalent to the international standard "Internal Gross" measurement.
GIA differs from other measurements: *Gross External Area (GEA) measures from the outside of the external walls and is larger; Net Internal Area (NIA)* excludes circulation, internal walls and storage, and is smaller. Commercial property typically uses NIA; residential typically uses GIA.
For EPC assessments under RdSAP, the DEA needs GIA per habitable room plus a total GIA for the property. For HMO licensing, GIA per bedroom validates that the room meets minimum size requirements (typically 6.51 sqm for a single occupant, 10.22 sqm for two).
VizCraft delivers this work for UK estate agents, photographers and developers — typically within 6–12 hours.