Height in Relation to Boundary (HIRB) Calculator

Calculate the height available beneath a recession plane at a chosen point on your building. Enter the boundary and building ground levels using the same datum, horizontal setback, and the plane’s starting height and angle. Enter a proposed building height to compare it with the envelope.

Worked example: Boundary level 100 m, building level 101 m, setback 4 m, plane origin 2.5 m and angle 45° gives an envelope level of 106.5 m, allowing 5.5 m above ground at the building point.

This checks the geometry at one point. Confirm the applicable rule and assess the whole building, separate height controls, boundary exclusions and exceptions for your project.