DIN 277: floor areas in building construction

The types of area

• BGF – gross floor area. The sum of all floor areas of all plan levels, measured at the outer edges of the enclosure.
• KGF – construction floor area. The area taken up by walls, columns and shafts.
• NRF – net room area. BGF minus KGF. Since the 2016 edition it has been the main term; older documents speak of NGF, meaning the same thing.
• NUF – usable area. The part of the NRF that serves the purpose of the building.
• TF – services area. Areas for building services installations.
• VF – circulation area. Corridors, stairs, lift shafts.

The classification is hierarchical: BGF minus KGF gives NRF, and NRF divides into NUF, TF and VF. Anyone checking an area figure first recalculates this sum.

How the usable area is classified

The NUF breaks down into seven types of use. This classification is the reason DIN 277 is needed in operation at all: it turns a number of square metres into a statement about what the area is for.

• NUF 1 – Living and recreation
• NUF 2 – Office work
• NUF 3 – Production, manual and machine work, research
• NUF 4 – Storage, distribution, sales
• NUF 5 – Education, teaching, culture
• NUF 6 – Healing and care
• NUF 7 – Other uses

Space management that only knows the total can neither tender cleaning services nor allocate operating costs. It needs the assignment per room, and that is created during the survey, not afterwards.

Volume is part of it

DIN 277 governs not only areas but also the gross volume (BRI): the volume that the gross floor area occupies over its height. It is needed wherever calculations are based on volume – for heating load, ventilation and in early cost estimates.

Where the areas are used further

The figures rarely stay in the drawing. They flow on into:

• Cost estimating to DIN 276. The gross floor area is the usual reference value for benchmarks per square metre.
• Service charge accounting. Allocation keys are based on defined areas, not estimated ones.
• CAFM and space management. There the area is attached to the room polygon and linked to the room book via the room number.
• Cleaning and maintenance contracts. Payment is by area and floor finish – both details from the same CAFM data foundation.

Why the edition matters

Terms and assignments have shifted between editions. The most noticeable change is the renaming of the net floor area (Nettogrundfläche) as net room area (Netto-Raumfläche). An area figure that does not name the edition is therefore incomplete – in tenders and leases it can be challenged. We state the edition in every delivery.

Internationally, DIN 277 corresponds to DIN EN ISO 9836. The terms are not identical; anyone reporting to an owner abroad should agree beforehand which of the two applies.

Where area figures fail in practice

Three errors keep recurring, and all three only come to light when money depends on them.

• Measured off the old plan. The plan shows the designed state. Whatever has been altered since is not in it.
• Edition not stated. Two figures for the same building then cannot be compared, and neither of them can be defended.
• NGF and NRF mixed up. The same area under two names, side by side in one table – the classic route to a total that does not add up.

The remedy is unspectacular: calculate the area from a survey of the current state, state the edition alongside it, and carry the room number as the key.