KG 300 building fabric: structure and allocation

The ordering follows the construction sequence from the ground up: excavation, foundations, rising structure, floors, roof. That logic eases checking for completeness, because a missing item stands out within the sequence.

Groups 330 to 350 each carry the addition of vertical or horizontal elements. It stems from consolidation with civil engineering, where the terms wall and floor do not always fit.

Cost group 330 shows how finely the standard subdivides. The third level reaches the individual element.

Two points are notable. First, the standard separates loadbearing from non-loadbearing elements, which is sensible for cost determination because the two carry entirely different unit rates. Second, claddings appear separately for the external and internal face, which eases allocation in a facade refurbishment.

Position 334, openings in external walls, covers windows and external doors. They are therefore part of the fabric and not of the technical installations, even where motorised. The drive itself may belong to building automation.

Cost group 200 covers preparatory works, that is preparing the site and servicing it. It must be kept apart from cost group 300, because it is not chargeable.

The dividing line runs at the building. Full demolition of an existing building belongs to preparatory works. Partial demolition within a conversion, by contrast, belongs to cost group 300, and specifically to the group whose element it affects.

This rule applies expressly to repair, temporary support and dismantling in conversions and modernisations too: the costs are to be shown within the cost groups affected and form no group of their own. The element reference therefore governs in existing buildings as well.

In practice this means a cost determination in existing buildings carries strip-out costs distributed across the whole of cost group 300. Consolidating them into a single collective item instead loses comparability with new build benchmarks by element, which in existing buildings would be the most important test.

What governs is connection to the building. Roof, facade and interior planting belonging to the building count within cost group 300. External works outside the building and designed open spaces count within cost group 500.

The boundary is not always clear-cut at ground-level junctions. A canopy structurally part of the building belongs to cost group 300; a freestanding shelter in the external area to cost group 500. In such cases an explicit determination within the cost estimate is advisable, so that the allocation stays the same across every stage.

This is the most fee-relevant allocation question in the whole standard, because it governs application of the special rule for technical installations. It governs the level of the fee basis.

As a rule of thumb: cost group 400 covers the technical installations or parts of installations built into the structure, connected to it or permanently joined to it. Cost group 300 covers what is fabric.

Typical borderline cases:

The details and the system of technical installations are covered in the article on KG 400. It also sets out which installations belong to that group.

Like every cost group, 300 ends with a catch-all position, here 390 other measures for building fabric. It is not a collecting point for anything unclear.

It is intended for costs belonging to the fabric in substance but not attributable to any element group, such as overarching measures connected with the fabric. A high share in that position indicates an incomplete structure.

It is not intended as a repository for items whose allocation is troublesome. A conspicuously large position 390 is a warning sign: it makes the determination incomparable with benchmarks, since comparison proceeds by element group, and it is hard to explain to a client.

Every cost group has a reference unit in which quantities are measured. It is the quietest and simultaneously most effective part of the structure, because it governs whether an item is comparable at all.

The benefit shows when comparing two designs. A benchmark per square metre of gross floor area for the whole of cost group 300 does not reveal why one design costs more. Benchmarks per element area do: an articulated form carries more external wall area per square metre of usable area, and a design with long spans carries more expensive floors per square metre.

A recommendation follows for cost determination that costs little effort: alongside the amount per cost group, carry the corresponding quantity. Only then does a later deviation reveal whether quantity or unit rate was the cause.

The element structure of cost group 300 is why a target-actual comparison across the stages is possible at all. It stays identical through cost estimate, cost calculation and final cost statement while quantities and prices are refined.

That advantage is lost as soon as ordering by procurement package begins with the pre-tender estimate, because trades and element groups do not coincide. A drylining contractor works on internal walls, floors and fixtures simultaneously.

The workable solution is to retain the element structure as the leading one and carry the procurement packages as an additional allocation. The article on trade-oriented cost structure covers that variant.

• The cost groups of DIN 276 at a glance
• KG 400 building services: structure and allocation
• Trade-oriented cost structure by procurement package
• The version problem: DIN 276 of 2008 and of 2018
• Shell and fit-out cost shares