Building Approval for Factory Projects

Chapter 2 of 10 · 10 min read

Classifying the building and each part of it

Assign NCC classes to the office, workshop, plant room and mezzanine, test the 10% rule with gross areas, and see what each class decision changes later.

Almost every Deemed-to-Satisfy Provision in Volume One starts by asking what class of building you are dealing with. Fire compartment limits, exit concessions, fire equipment, amenities and access requirements all branch on class. A wrong classification therefore does not produce one wrong answer. It produces a whole set of them, often in directions that are hard to spot.

This chapter classifies the running case building part by part, tests the 10% rule that sometimes lets a small part take the class of the rest of the storey, and maps where each classification decision shows up later in the book.

Classification follows purpose

Part A6 of NCC 2022 Volume One sets out the classes. Under A6G1, each part of a building is classified separately according to its purpose, and must comply with the requirements for that classification. The classes that matter for industrial projects are:

  • Class 5: an office building used for professional or commercial purposes (A6G6).
  • Class 6: a shop or other building for the sale of goods by retail or the direct supply of services to the public (A6G7).
  • Class 7: a storage-type building. Class 7a is a carpark; Class 7b is a building for storage, or for the display of goods for sale by wholesale (A6G8).
  • Class 8: a process-type building, such as a laboratory or a building in which goods are produced, assembled, altered, repaired, packed or cleaned for sale (A6G9).
  • Class 10: a non-habitable building or structure, such as a shed, carport, fence, mast or retaining wall (A6G11).

Residential classes (1 to 4) and public buildings (Class 9) appear in industrial projects less often, but a caretaker’s flat is Class 4 and a training room open to the public could raise Class 9b questions. Classification describes what the space is for, not what the owner calls it.

Figure 1Classes that commonly appear in an industrial building
Classes that commonly appear in an industrial building. Industrial building. Class 5: office, administration, drawing office. Class 6: trade counter or showroom selling to the public. Class 7b: warehouse, wholesale storage and display. Class 8: workshop, production, assembly, repair, laboratory. Class 4: a single caretaker's dwelling, if any. Class 10a: detached shed or carport Industrial building Class 5 office, administration, drawing office Class 6 trade counter or showroom selling to the public Class 7b warehouse, wholesale storage and display Class 8 workshop, production, assembly, repair, laboratory Class 4 a single caretaker's dwelling, if any Class 10a detached shed or carport
Based on NCC 2022 Volume One Part A6. Each part of a building is classified by its purpose; one building can hold several classes.

Rooms that borrow a class

Some spaces take their classification from what surrounds them rather than from their own purpose. Under A6G1(3), a plant room, machine room or similar room containing mechanical, thermal or electrical equipment takes the classification of the major part or principal use of the building or fire compartment in which it is located. Electricity network substations are treated separately.

In the running case, a 20 m² compressor room inside the workshop therefore takes Class 8. If the same compressor room were inside the office part, it would take the office’s class. This is an illustration, but it shows why classification is done on a marked-up plan, not in a list.

Occupiable outdoor areas follow a similar idea under A6G1(4): they generally take the class of the part of the building they serve. A covered outdoor smoko area beside the workshop would normally be classified with the workshop.

The 10% rule

A6G1 contains an exemption that matters to many small factories. Where a part of a storey is used for a different purpose and occupies 10% or less of the floor area of that storey, the classification of the rest of the storey may be applied to the whole storey. The exemption does not apply to a laboratory, to a Class 2, 3 or 4 part, or to a Class 9b early childhood centre.

The word “may” matters. The exemption lets you simplify; it does not force you to. And the test is against the floor area of the storey, which the NCC measures over the enclosing walls and includes mezzanines and built-in fixtures. Net usable areas do not count.

Figure 2Can a small part take the class of the rest of the storey?
Can a small part take the class of the rest of the storey?. Question: Is the part 10% or less of the storey's floor area, measured over the enclosing walls?. No: more than 10%, classify the part separately and apply both sets of requirements. Yes, but it is a laboratory, a Class 2, 3 or 4 part, or a Class 9b early childhood centre: exemption unavailable, classify separately. Yes, and none of the limitations apply: 10% or less, the rest of the storey's class may apply to the whole storey ? Is the part 10% or less of the storey's floor area, measured over the enclosing walls? No more than 10% classify the part separately and apply both sets of requirements Yes, but it is a laboratory, a Class 2, 3 or 4 part, or a Class 9b early childhood centre exemption unavailable classify separately Yes, and none of the limitations apply 10% or less the rest of the storey's class may apply to the whole storey
Based on the exemption in A6G1 of NCC 2022 Volume One. The limitation list must be checked before the area test is relied on.

Classifying the running case

This is an illustration. The owner’s plan has four kinds of space on the single storey, plus the mezzanine.

The office. The office is 10 m by 30 m at the east end of the building, so 300 m² measured over its walls. It holds administration, sales, a drawing office, a meeting room, a small kitchen and the office toilets. Its purpose is professional and commercial work, so on its own it is Class 5.

The storey’s floor area is 1,800 m². The office share is:

300 ÷ 1,800 = 0.167, or 16.7%.

That is more than 10%, so the office cannot take Class 8 under the exemption. The building has two classifications on one storey: a Class 5 part and a Class 8 part.

The workshop. Machining, fabrication and assembly of goods for sale are Class 8 uses under A6G9. The machine shop, the fabrication and assembly area, the workshop amenities and circulation are all part of the Class 8 workshop.

The compressor room and switch room. These take the class of the major use of the fire compartment they sit in, under A6G1(3). Both are in the workshop, so both are Class 8.

The metrology room. The owner wants a 25 m² temperature-controlled room for measuring parts. A laboratory is expressly a Class 8 use, and laboratories are excluded from the 10% exemption. Inside the Class 8 workshop that makes no difference, because the room is Class 8 either way. If the metrology room were placed inside the Class 5 office instead, it could not be absorbed into the office classification by the 10% rule, however small it was.

The mezzanine store. The mezzanine holds the workshop’s own tooling, fixtures and work in progress. The designer treats it as part of the Class 8 workshop because its purpose serves the production process. If the business later used it to hold goods for wholesale sale to other businesses, the question of a Class 7b part would reopen.

Storage inside a factory: Class 7b or Class 8?

Storage is where industrial classification most often becomes a judgement. Class 7b covers buildings for storage, and for display of goods for wholesale sale. Class 8 covers buildings where goods are produced, assembled, altered, repaired, packed or cleaned. Most factories do both: raw material arrives, waits, is processed, waits again and is despatched.

A useful way to think about it is to ask what the space is for in the business, not what sits in it on a given day:

  • A raw material rack beside the saws serves production. It is part of the Class 8 workshop.
  • A finished goods store where orders are picked and packed may still be Class 8, because packing is a Class 8 activity, or may lean to Class 7b if it is mainly a store.
  • A separate warehouse holding stock for wholesale distribution, with little or no processing, points to Class 7b.

Where the storage area is a separate part of a storey and large, the classification has real consequences, because Chapter 7 shows that some fire equipment triggers depend on storage height and volume of combustible goods. Where it is small and serves the workshop, it usually stays with the workshop. Either way, write down the reasoning, so that a later change in use can be compared with it.

Buying or leasing an existing building

Owners who buy or lease a building inherit its classification history. Before signing, obtain the existing approval documents: the last building approval and its stamped plans, the occupation certificate, any Performance Solutions with their conditions, and the fire safety schedule or list of essential safety measures. These show what the building was approved for and on what basis.

The running case building was approved as an empty warehouse, which suggests a Class 7b approval. The new owner’s use is a Class 8 workshop with a Class 5 office, so the classification changes and the change itself needs approval. If the vendor cannot produce the approval documents, the certifier may need more investigation of the existing building, which takes time and money. That is a due diligence question, and it is cheaper to ask before settlement than after.

A method for marking up the plan

Classification is easiest to get right on a drawing. A simple method that works for most small industrial projects:

  1. Print the floor plan of each storey at a known scale, including mezzanines.
  2. Outline each area with a distinct purpose, using the enclosing walls as the boundary. Where there is no wall, draw the boundary the business will actually use and note it.
  3. Measure each area over the enclosing walls and write it on the plan.
  4. Assign a class to each area by its purpose, with the A6 clause beside it.
  5. Mark plant rooms and outdoor areas that take the class of what they serve, citing A6G1(3) or A6G1(4).
  6. Calculate each part’s share of its storey and test any part at or near 10% against the exemption and its limitations.
  7. List the shared elements, such as stairs, corridors, toilets and services, that serve more than one class.

The finished plan becomes the first page of the compliance drawings. Later chapters add fire compartments, occupant numbers and exits to the same sheet.

What the classification changes later

Classifying the office as Class 5 rather than Class 8 changes several later answers. Some are more demanding and some less. The table collects the ones this book uses, all from NCC 2022 Volume One.

Figure 3Where the Class 5 and Class 8 decisions show up later
Where the Class 5 and Class 8 decisions show up later. Largest Type C fire compartment, C3D3 (Ch. 4): Class 5 office 3,000 m² and 18,000 m³; Class 8 workshop 2,000 m² and 12,000 m³. Single exit travel distance concession, D2D5(3)(b) (Ch. 6): Class 5 office up to 30 m in some cases; Class 8 workshop not available. Fire hose reels, E1D3 (Ch. 7): Class 5 office Class 5 buildings excluded; Class 8 workshop required in a fire compartment over 500 m². Class A extinguishers, E1D14 (Ch. 7): Class 5 office required for Class 5 buildings; Class 8 workshop required in some cases only. Sanitary table, F4D4 (Ch. 8): Class 5 office Table F4D4a; Class 8 workshop Table F4D4b. Washbasins per employees beyond the first band (Ch. 8): Class 5 office 1 per 30; Class 8 workshop 1 per 20 Class 5 office Class 8 workshop Largest Type C fire compartment, C3D3 (Ch. 4) 3,000 m² and 18,000 m³ 2,000 m² and 12,000 m³ Single exit travel distance concession, D2D5(3)(b) (Ch. 6) up to 30 m in some cases not available Fire hose reels, E1D3 (Ch. 7) Class 5 buildings excluded required in a fire compartment over 500 m² Class A extinguishers, E1D14 (Ch. 7) required for Class 5 buildings required in some cases only Sanitary table, F4D4 (Ch. 8) Table F4D4a Table F4D4b Washbasins per employees beyond the first band (Ch. 8) 1 per 30 1 per 20
Values from the NCC 2022 Volume One clauses named. Each is explained in the chapter shown in brackets.

Under A6G12, a part with more than one classification must meet the requirements of each, and where requirements conflict the more stringent applies. When the office and workshop share a fire compartment, a staircase or an amenities block, expect the certifier to ask which class’s requirement governs the shared element.

Where classification goes wrong

The running case had its own classification error. The designer’s first drawing classified the whole building as Class 8 by relying on the 10% rule. The calculation behind it used the office’s net carpet area, 180 m² after deducting the corridor, toilets, kitchen and wall thickness:

180 ÷ 1,800 = 0.10, or exactly 10%.

On that figure the exemption would have applied. The error was detected when the certifier’s pre-lodgement review asked for the floor area “measured over the enclosing walls”, which is how the NCC measures the floor area of a storey. The gross office area is 300 m², and the exemption fails at 16.7%.

The cost of the error, had it gone undetected, would have shown up in four places: the office toilets and basins, the extinguishers, the fire compartment test and the treatment of any fire separation between office and workshop. Correcting it on paper took a day. Correcting it after construction would have meant reworking a fit-out.

Two other errors are common in industrial buildings:

  • Classifying by the lease or the zoning. A building zoned “light industrial” or leased as a “warehouse” may contain a Class 6 trade counter, a Class 5 office and a Class 8 workshop. The class follows purpose, not paperwork.
  • Forgetting that classification can change after occupation. A storage area that becomes a packing line changes from Class 7b to Class 8. A meeting room hired out for public training sessions can raise Class 9b questions. Changes of purpose may need approval, so the classification should be recorded and reviewed whenever the business changes how it uses space.
Figure 4Classification record for the running case
Classification record for the running case. Done: Office, 300 m², Class 5, 16.7% of the storey, so the 10% exemption is unavailable. Done: Workshop, 1,500 m², Class 8. Done: Compressor and switch rooms, Class 8, by A6G1(3). Done: Metrology room, 25 m², Class 8 laboratory, inside the workshop. Open: Mezzanine store, Class 8 as the workshop's own store; to confirm with the certifier. Open: Shared amenities or services between parts, governing requirement to agree under A6G12 Office, 300 m² Class 5, 16.7% of the storey, so the 10% exemption is unavailable Workshop, 1,500 m² Class 8 Compressor and switch rooms Class 8, by A6G1(3) Metrology room, 25 m² Class 8 laboratory, inside the workshop ? Mezzanine store Class 8 as the workshop's own store; to confirm with the certifier ? Shared amenities or services between parts governing requirement to agree under A6G12
This is an illustration. Each line is marked on the floor plan with its area measured over the enclosing walls.

Questions to take to the certifier

  • Do you agree with the class of each marked area, and with our reasoning for the mezzanine store?
  • How will you measure the office’s share of the storey for the 10% test, and do you agree it fails at 16.7%?
  • Where the office and workshop share an element, such as a corridor, toilets or a switchboard, which class’s requirement will you apply under A6G12?
  • What did the existing approval classify the building as, and what does the change of use bring into the current code?
  • Which future changes of use would you expect us to bring back to you before we make them?

The answers turn a set of assumptions into a set of agreed positions. Record them with the date and the person who gave them.

Exercise: shrink the office or keep two classes?

The owner asks whether it would be simpler to reduce the office to 180 m² gross so that the whole storey can be Class 8. What is the area test, what would be gained or lost, and what else must be checked?

Worked answer. The storey is 1,800 m², so 10% is 0.10 × 1,800 = 180 m². An office of 180 m² or less, measured over its enclosing walls, satisfies the area test, and nothing in the limitation list applies to an office. The exemption could then be used, and the whole storey could be treated as Class 8.

Gains: one set of requirements instead of two, and no question about which class governs shared elements. Losses: the office would take Class 8 requirements, which includes the smaller Class 8 fire compartment limits, Class 8 sanitary washbasin ratios and the hose-reel rule for Class 8 compartments over 500 m². The owner would also lose 120 m² of office space for a business that needs it.

Before deciding, the owner should check what else on the storey is a different class. A metrology room placed in the office could not be absorbed because laboratories are excluded. The decision is about function first and simplification second; a building that is too small for the business is not a saving.