01 Chaos
Land is not construction scale
By this point, the project contains several useful numbers. They are precise—but they are not interchangeable.
Separate the numbers ↓02 Illusion
“Both projects are on 1,200 sq ft plots, so they are roughly the same size.”
Not if one builds only the ground floor and the other builds Ground + 2.
Similar land can support very different amounts of constructed floor area, subject to the actual design and applicable controls.
Next · Calculate the floor area↓03 Shift
Multiplication works when the floor plates are approximately the same size. When they differ, add them instead.
Use a simple multiplication only when the working floor plates are approximately equal.
04 System
Built-up area begins to describe construction scale. It does not predict every quantity perfectly, and double the area does not automatically mean exactly double the final price.
Area changes scale. Layout, specification and complexity shape the final cost.
Concrete, reinforcement, formwork and structural labour somewhere in the system.
Masonry or blockwork, plaster and related wall finishes.
Electrical distribution and plumbing work, driven by actual rooms and service points.
Flooring, paint, tiles, ceilings and fittings across more spaces.
More total construction work, sequencing and coordination.
05 Craft
Always ask which area the number describes.
How much land exists inside the site boundary.
How much ground the building physically occupies.
How much constructed floor area exists across all levels.
06 Exercise
First use the relationship between floor area and constructed levels. Then identify what the result can—and cannot—tell you.
Built-up area is a scale number. It is not an exact price by itself.
Use the calculator, then choose the meaning of the result.