GEA (Gross External Area)
A building's total floor area, measured to the outside face of its walls.
Quick Answer
Gross External Area (GEA) is the total floor area of a building measured to the outside face of its perimeter walls on every floor. It includes wall thickness, internal walls, stairs and plant rooms. It comes from RICS cost-planning practice, and US estimators usually call the closest equivalent gross floor area or gross square footage.
The Full Picture
GEA is one of a family of area measures. Gross External Area is measured to the outside face of the perimeter walls, so the thickness of the exterior wall is inside the number. Gross Internal Area (GIA) is measured to the inside face of those walls, and Net Internal Area (NIA) is the usable area left after circulation, structure and services are taken out. The set comes from RICS measuring practice, which the RICS Code of Measuring Practice publishes, and it is common in UK and international cost planning.
The detail matters when two people quote the same building. Under UK valuation guidance, GEA includes perimeter wall thickness and external projections, internal walls and partitions, columns, stairwells and lift wells, and plant rooms. It leaves out open balconies, open fire escapes, open-sided covered ways, and open parking areas and terraces, and those excluded areas are normally reported separately. Party walls are measured to their centre lines.
In US practice the nearest term is gross floor area or gross square footage, and the definition changes with the audience. The building code, a lease standard and an owner's program can each count a floor slightly differently, for example in how they treat shafts, parking and exterior walls. An estimator should therefore never assume that a gross figure on a drawing, in a proforma and in a unit-cost database all follow one rule. Ask which edition and which definition was used before applying a cost per square foot.
GEA matters in precon because early estimates are often built as cost per square foot of gross area. A figure benchmarked on GEA and applied to a GIA quantity will come out low, because the walls are missing, and the gap grows on thick-wall or multi-story buildings. A detailed takeoff does not price GEA directly, since walls, slabs and finishes are measured by their own units, but the gross area is the sanity check against which the detailed number is compared.
Real Examples
Common Misconceptions
People assume: GEA and gross square footage are the same number everywhere.
Actually: They are close, but each standard or owner program defines inclusions differently. Under the UK valuation guidance for GEA, open balconies and terraces are excluded, while other documents may count them. Confirm the definition before comparing.
People assume: Gross external area is what a tenant can use.
Actually: GEA includes walls, stairs, shafts and plant rooms. Usable space is measured by net area (NIA in RICS terms), which is always smaller. Using GEA as lettable space overstates it.
Does MeltPlan Solve This?
Partially — adjacentGEA is an area measure taken from plans, and MeltPlan's takeoff service covers the measuring work behind it: AI pulls quantities from plans and US-based experienced estimators review and adjust them. Choosing which area definition a benchmark or owner requires is still a judgment your estimating team makes.
Get building areas measured from your plans →Frequently Asked Questions
What does GEA stand for in construction?
GEA stands for Gross External Area. It is the total floor area of a building measured to the outside face of the perimeter walls on each floor, used in RICS-style cost planning and by cost consultants outside the US.
What is the difference between GEA and GIA?
GEA is measured to the outside face of the external walls, so wall thickness is included. GIA is measured to the inside face, so it is smaller. On the same building, GEA is always the larger figure.
What is the US equivalent of GEA?
Estimators usually say gross floor area or gross square footage. The two are similar but not identical, because the code, lease standards and owner programs each define what is counted. Always confirm the definition in use.
Does GEA include balconies and parking?
Under the VOA rating guidance for GEA, open balconies and open parking areas are excluded and shown separately, while enclosed plant rooms and stairwells are included. Other documents can differ, so check the stated basis.