Gross external area GEA
The area of a building can be measured in a number of different ways:
- Gross external area (GEA).
- Gross internal area (GIA).
- Net internal area (NIA).
It is very important to be clear about which measure is being used, for example in property sales, planning applications, building regulations applications, lease negotiations, rating valuations and so on.
The UK government’s Valuation Office Agency (VOA) Code of measuring practice: definitions for rating purposes suggests that ‘gross external area’ refers to the whole area of a building taking each floor into account, including perimeter walls. This includes:
- Perimeter wall thickness and external projections.
- Areas occupied by internal walls (whether structural or not) and partitions.
- Atria and entrance halls, with clear height above, measured at base level only.
- Columns, piers, chimney breasts, stairwells, lift wells, and so on.
- Lift rooms, plant rooms, tank rooms, fuel stores, whether or not above roof level.
- Any area with a headroom of less than 1.5m.
Gross external area excludes:
- Open balconies.
- Open fire escapes.
- Open sided covered ways.
- Open vehicle parking areas, terraces and so on.
- Canopies
- Voids over or under structural, raked or stepped floors
- Greenhouses, garden stores, fuel stores, and the like in residential property
- Any area under the control of service or other external authorities
It suggests that party walls should be measured to their centre lines.
According to NRM1: Order of cost estimating and cost planning for capital building work, the gross external area is '...the area of a building measured externally (i.e. to the external face of the perimeter walls) at each floor level.The rules of measurement of gross external floor area are defined in the latest edition of the RICS Code of Measuring Practice.'
The VOA Code of measuring practice is in general agreement with RICS Guidance Note, A guide for Property Professionals, 6th Edition Code of measuring practice 2007, other than, areas with a headroom of less than 1.5m which are excluded from the VOA measurement.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Do you take the lead in a circular construction economy?
Help us develop and expand this wiki as a resource for academia and industry alike.
Warm Homes Plan Workforce Taskforce
Risks of undermining UK’s energy transition due to lack of electrotechnical industry representation, says ECA.
Cost Optimal Domestic Electrification CODE
Modelling retrofits only on costs that directly impact the consumer: upfront cost of equipment, energy costs and maintenance costs.
The Warm Homes Plan details released
What's new and what is not, with industry reactions.
Could AI and VR cause an increase the value of heritage?
The Orange book: 2026 Amendment 4 to BS 7671:2018
ECA welcomes IET and BSI content sign off.
How neural technologies could transform the design future
Enhancing legacy parametric engines, offering novel ways to explore solutions and generate geometry.
Key AI related terms to be aware of
With explanations from the UK government and other bodies.
From QS to further education teacher
Applying real world skills with the next generation.
A guide on how children can use LEGO to mirror real engineering processes.
Data infrastructure for next-generation materials science
Research Data Express to automate data processing and create AI-ready datasets for materials research.
Wired for the Future with ECA; powering skills and progress
ECA South Wales Business Day 2025, a day to remember.
AI for the conservation professional
A level of sophistication previously reserved for science fiction.
Biomass harvested in cycles of less than ten years.
An interview with the new CIAT President
Usman Yaqub BSc (Hons) PCIAT MFPWS.
Cost benefit model report of building safety regime in Wales
Proposed policy option costs for design and construction stage of the new building safety regime in Wales.
Do you receive our free biweekly newsletter?
If not you can sign up to receive it in your mailbox here.