BruttoRaumanteil

BruttoRaumanteil (BRA) is a planning metric used in German-speaking architecture and real estate to describe the share of a building's floor area that is allocated to defined usable rooms relative to the building’s gross floor area. The exact definition of “Räume” varies by regulation or project, but it typically includes living-, working-, and service spaces intended for occupancy, while spaces such as corridors, stairwells, technical rooms, and other non-occupancy areas are excluded.

Calculation: BRA = (sum of floor areas defined as Räume) / (total Bruttofläche) × 100. The numerator and denominator are usually taken on a per-building or per-floor basis, and the result is a percentage. Some standards specify which spaces count as Räume and whether partial areas (e.g., mezzanines) are included.

Interpretation and use: A higher BRA indicates a greater share of the floor area is allocated to usable rooms, suggesting a more space-efficient layout for occupancies. A lower BRA reflects larger non-occupancy spaces or service areas relative to the total floor area. BRA is used in space planning, regulatory assessments, and market presentations, but it should be interpreted in the context of the counting rules applied.

Limitations and related terms: There is no universal definition; the term is regionally defined and may align with terms such as Bruttoraumfläche, Nutzfläche, or Nettoraumfläche in different standards. Always consult local planning guidelines for the exact method. BRA is distinct from volumetric measures like Bruttorauminhalt or Bruttoraumvolumen.