B2/AS1 Durability

• ●the element in this situation lasts not less than this long
• a note in place of a period: the element takes another's, or has none
• in mono under a row: E2/AS1 Table C.1.1.1A gives the zones its material lasts this long in
• ≠≠ and a number: the documents say different things here. They are set out under the table, in the same order on every durability table

1. Same durability as the tile covering it.
2. No durability requirement under the Building Code.
3. Same durability as the cladding covering it.

Figure 2.1.1.2 is a means of assessment, not a lookup; an element Table C.1.1.1 names has its row there.

Does the element have to satisfy another clause of the Building Code?

A decorative finish or trim that no clause asks anything of has no durability requirement. One that also serves a purpose a clause does (the impervious, easily cleaned surface of a wet area) has the durability of that purpose.

Durability, not less than

–

1. Durability periods Every building element that has to satisfy another clause of the Building Code continues to satisfy it for not less than 50 years where it provides structural stability, is difficult to access or replace, or would fail without anyone noticing in use or maintenance; 15 years where it is moderately difficult to access or replace, or its failure would show in normal maintenance; and 5 years where it is easy to access and replace and its failure would show in normal use, or for the building's specified intended life, where that is shorter.

   2.1.1.1, Figure 2.1.1.2, Figure 2.1.1.2 note (1)

2. Hidden elements An element hidden by another lasts at least as long as the element that hides it: brick ties behind a masonry veneer take the veneer's life, not the cladding period.

   C.1.1.1 COMMENT, NZBC B2.3.2

1. Concrete Concrete building elements to NZS 3101.1 Section 3. Its provisions in non-specific or unquantified terms (special studies, manufacturer's advice, methods that are appropriate, adequate, suitable or the like) are not part of the Acceptable Solution and are an alternative solution.

   3.1.1.1

2. Structural steel Steel structures and components to SNZ TS 3404, within its scope.

   3.2.1.1

3. Light steel framing Light steel framing to clause 3 of NASH Standard Part 2, within its scope, with its clause 3.1 replaced: steel framing, brackets and fixings for walls, roofs and mid floors are within a closed building envelope performing at least as well as one to E2/AS1, and eaves are lined.

   3.2.2.1

4. Timber treatment Timber and wood-based building elements treated to Building Product Specifications Subsection 3.5.1 where not less than 50 years is required and Subsection 3.5.2 where 15 years is required, or to NZS 3604 with NZS 3602 and NZS 3640 as those two subsections modify them.

   3.3.1.1

5. Untreated Douglas fir framing Preservative-free solid Douglas fir only for roof members and wall framing protected from the weather, and floor members protected from the weather and ground atmosphere, in a stand-alone single household unit of no more than 2 storeys to NZS 3604; in a wind zone no higher than high; with envelope complexity no higher than medium risk and deck design no higher than low risk, and a risk matrix score of no more than 6 on every external wall face, all to E2/AS1; drained and vented cavities to E2/AS1 behind every cladding; roof and wall cladding systems and details to E2/AS1; a simple pitched roof draining straight to external gutters, with no internal, secret or concealed gutters and no roof element ending inside the external walls; a roof slope of at least 10°; corrugated iron, or concrete, metal or clay tiles on a skillion roof; and eaves of at least 450 mm on a single storey house and 600 mm on a two storey house.

   3.3.2.1

6. Solid plastering Cement plaster for walls, ceilings and soffits to NZS 4251.1, within its scope.

   3.4.1.1

7. Earth buildings Earth buildings to NZS 4297 and NZS 4299, within their scope.

   3.4.2.1

8. Insulating glass units Insulating glass units to NZS 4223.2, with its clause 5.3 replaced: each unit permanently and clearly marked with the manufacturer's or supplier's name or trademark, the year of manufacture at least, and “Complies with NZS 4223.2:2016”; visible once installed, legible and durable for the unit's life; etched or laser marked, never an adhesive label.

   3.4.3.1

9. Normal maintenance The specifier of each element states its normal maintenance, which includes following the manufacturer's recommendations, washing down exterior surfaces exposed to wind-driven salt spray, recoating protective finishes, replacing sealants, seals and gaskets, replacing valves, washers and similar parts, cleaning and replacing filters, servicing plant and emergency equipment, and keeping access, escape and hazard signs, with periodic inspection of spaces not seen without effort.

   2.2.1.2, 2.2.1.3

Building elementAppendix B

Any structural or non-structural component or assembly incorporated into or associated with a building: fixtures, services, drains, permanent mechanical installations for access, glazing, partitions, ceilings and temporary supports included.

Specified intended lifeAppendix B, Building Act 2004 s 113(3)

The period, stated in the application for building consent or in the consent, for which the building is proposed to be used for its intended use. No element has to outlast it.

Normal maintenance2.2.1.1

The work generally recognised as necessary for an element to achieve its expected durability, depending on the material or system, where the building is and where the element is in it; it can include replacing parts that wear fast. It does not include upgrading to new technology or new expectations.

Scheduled maintenance2.2.2.1

The inspection, maintenance and reporting of the elements on a compliance schedule under section 100 of the Building Act. Those elements are in effect required to last the life of the building, because they must perform as designed at all times; their maintenance may include replacing them.

Hidden, exposed, shelteredE2/AS1 Table C.1.1.1A note (3)

E2/AS1's words for where a material is, not B2's: hidden is concealed behind another element with no part visible; exposed has surfaces washed by rain; sheltered is visible but not rain-washed, and an element that is both is sheltered. B2/AS1 has no such division; its rows say what an element does and how hard it is to replace.

Primary and secondary elementAppendix B

A primary element provides the structure's basic loadbearing capacity, and its failure in a fire may start instability or collapse; a secondary element does not, and its failure will not.

Two questions, two tablesE2/AS1 2.1.1.1, E2/AS1 C.1.1.1, Table C.1.1.1

E2/AS1 2.1.1.1 asks three separate things of the building envelope: a) that it meets B2, b) that its materials suit their end use, location and environment by Table C.1.1.1A, and c) that they are compatible. B2/AS1 Table C.1.1.1 answers how long; E2/AS1 Table C.1.1.1A answers what a cladding, flashing or fixing may be made of to last that long in the site's exposure zone. B2 names no material; E2 names no period of its own.

Protective coatings agreeTable C.1.1.1, E2/AS1 9.4.9.2 COMMENT

A paint system easy to access and replace is 5 years in B2's table, and E2/AS1 9.4.9.2's COMMENT states the same minimum for protective coatings.

E2 sends timber to B23.3.1.1, E2/AS1 6.1.1.4, E2/AS1 7.1.2.1, E2/AS1 9.1.7.8 d), E2/AS1 9.1.9.4

E2/AS1 asks parapet framing and packers, deck timber and pergolas, cavity battens and jamb battens to comply with B2/AS1, and B2/AS1 3.3.1.1 hands the treatment to the Building Product Specifications by period. So a cavity batten's treatment follows the cladding's period: 15 years behind a non-structural cladding, 50 behind one that braces.

Masonry veneerTable C.1.1.1, E2/AS1 Table 9.2.7.1A, E2/AS1 Table 9.2.9.4A

Brick ties and their fixings, and steel lintels over veneer openings, are 50 years in every situation. E2/AS1 Tables 9.2.7.1A and 9.2.9.4A then give the durability class of tie and lintel by exposure zone, which E2's Claddings face reads.

B2 reads E2's risk matrix3.3.2.1 c), 3.3.2.1 f), E2/AS1 Table 3.1.3.1

3.3.2.1 is the only place B2/AS1 uses E2/AS1's scores: untreated Douglas fir framing needs envelope complexity and deck design low enough, and no external wall face scoring more than 6. E2's Risk matrix face scores each face and can be saved elevation by elevation.

No exposure zone in B2E2/AS1 Table C.1.1.1A note (1), NZS 3604:2011 Section 4

B2/AS1's periods do not change with the site. The site enters through E2/AS1 Table C.1.1.1A, whose zones are NZS 3604 Section 4's with E2's own Zone E added, and through NZS 3604's fixing tables.

The table, then the figure2.1.1.2, 2.1.1.3

2.1.1.2 offers Figure 2.1.1.2 as a means of assessing a period and 2.1.1.3 says Table C.1.1.1 can be used to establish one for the elements it names. Neither says which governs where they differ. This tool shows the table's period for a named element and uses the figure only for an element the table does not name.

Insulation in an accessible roof spaceTable C.1.1.1, 2.1.1.1 b), 2.1.1.1 d), Figure 2.1.1.2 Step 4

The table asks 50 years of insulation in every situation, an accessible ceiling or roof space included. By the figure's steps an element easy to reach, whose failure a maintenance inspection would find, stops at 15 years; 2.1.1.1 d) gives insulation as an example only in a skillion roof. The table's row stands.

Concealed electrical fittingsTable C.1.1.1, 2.1.1.1 b)

Electrical fittings “concealed and moderately difficult to access or replace” are ticked at 50 years, where 2.1.1.1 b) gives moderately difficult access 15. The figure reaches the longer period only through Step 4 a), failure nobody would notice, which the row's word “concealed” may be taken to say. The table's row stands.

A barrier's posts, balusters and boltsTable C.1.1.1, Definitions, F4/AS1 1.2.1, F4/AS1 Figures 1 and 2

A safety barrier's support posts and handrails are ticked at 50 years and its balusters at 15, and the bolts fixing structural parts of a barrier at 50. The Definitions make a baluster a post that supports the top and bottom rails, which is what a support post does, so the words do not settle which member the 15-year row means. F4/AS1's Figures 1 and 2 draw the pieces between the rails as infill rather than as posts, and a barrier detailed to them has members the table does not name.

A note in place of a tickTable C.1.1.1 notes (1)–(3)

4 rows carry a note number in all three columns instead of a tick. A damp-proof membrane behind tiles and a lining behind a tiled shower take the tile's period, vermin proofing at a drained ventilated cavity takes the cladding's, and tiling that is a decorative finish only has no durability requirement under the Building Code.

Empty cellsTable C.1.1.1

Roof framing and window hardware have no situation printed; tiling's decorative finish row has no component printed and is read under Walls and floors, the one above it. Balustrade and Framing have no period of their own and send the reader to Safety barriers, and to Wall framing or Roof framing.

Materials, components and what serves two purposes1.1.1.1, 1.1.1.1 COMMENT

B2/AS1 applies to materials and components required to meet another clause. An element no clause asks anything of (a decorative coating, trim) has no durability requirement; one serving two purposes has the durability of the one a clause requires.

Outside the Acceptable Solution1.1.2.1, 1.1.3.2

An element used outside the scope a referenced document gives it, or a design that cannot follow B2/AS1 in full, is verified by B2/VM1 or shown by an alternative solution.

Specified systems2.2.2.1

Elements on a compliance schedule are in effect deemed to last the life of the building, because their inspection and maintenance keep them performing at all times, replacement included. Table C.1.1.1's periods are not what governs them.

Douglas fir is for houses3.3.2.1 COMMENT

3.3.2.1 is offered for people who do not want chemically treated timber in their home. For commercial and other buildings, untreated Douglas fir is outside the Acceptable Solution and considered case by case.