Under DIN 277:2021-08 the net room area (NRF) is the floor area of all rooms of a building without the construction – measured in clear dimensions between the component surfaces. It splits into usable area, technical area and circulation area: NRF = NUF + TF + VF. Until the 2016 edition the same quantity was called Netto-Grundfläche (NGF).
In short
- The NRF is the area one can walk on in a building – rooms, corridors, plant rooms.
- It is determined room by room in clear dimensions and summed per floor level.
- NRF is not living area: the WoFlV counts floor areas only partly, by height and position.
Definition under DIN 277:2021-08
Measurement is taken at the top of the floor finish between the finished surfaces of the bounding components. Plaster and cladding belong to the construction, not to the room. Each room is allocated as a whole to the area type matching its predominant purpose – usable, technical or circulation area – and to category R (enclosed on all sides) or S (not enclosed on all sides). The sum over all rooms of a floor level is that level’s NRF, the sum over all levels the building’s NRF.
Distinction
| Quantity | What counts | Measuring rule | Rule set |
|---|---|---|---|
| NRF | all rooms, without construction | clear dimensions, top of the floor finish | DIN 277:2021-08 |
| NGF | the same quantity, old name | as NRF | DIN 277 until 2016 |
| Living area | floor areas of the dwelling, without ancillary rooms | § 3 WoFlV, counted by height and position (§ 4) | WoFlV (2004) |
In practice
In the floor plan, the NRF is the quantity directly visible: every room polygon between the wall lines is a net room area once the scale is known. Two things decide the last centimetres. First, the plan revision – a structural shell plan shows the walls without plaster, a fit-out plan with; the difference is a few centimetres per wall, but adds up noticeably in small rooms. Second, the allocation: whether a corridor counts as circulation area or, as part of an open-plan space, as usable area is a professional decision, not geometry.
For portfolio owners, the NRF is the room book’s total line and the basis for service charge keys, cleaning contracts and CAFM. Anyone needing living areas cannot get there from the NRF without the WoFlV’s counting rules.
Normraum relevance
The net room area is the area Normraum calculates per room from the as-built plan: the room polygon in clear dimensions, deterministic, with confidence and source reference in the check log. Whether the plan shows structural shell or fit-out dimensions decides centimetres – the check log names the plan source. Height-related counting and the allocation to NUF, TF and VF remain a professional sign-off.