Durability and compatibility
The treatment each timber part of a house needs, the steel that fixes it in the site's exposure zone, and which materials may touch or drain onto each other.
- B2/AS13rd Edition28 Jul 2025
- Building Product Specifications1st Edition Amendment 12 Apr 2026
- NZS 3602:2003
- NZS 3604:2011
- E2/AS14th Edition28 Jul 2025
- DBH Timber Treatment (2007)
This site's exposure zone
Read from NZS 3604's map, Section 4.2. Chosen here, it is the project's, and every tool that reads the zone takes it.
Timber treatment and fixings
Each part of a timber-framed house: how long it has to last, the treatment its timber needs and the steel that fixes it.
- Structural fixings, sheltered
- Set the zone
- NZS 3604:2011 Table 4.1
Treatment
- H1.2 boron, dyed pink
- H1.2 solvent-borne, dyed blue
- H3.1 no added colour, or a green of its own
- H3.2 · H4 · H5 copper, natural green-brown
| # | Part | Lasts | Treatment | Fixings, zones B and C | Fixings, zones D and E |
|---|---|---|---|---|---|
| 1 | PilesIn the ground; fixed near it | 50 yr | H5NZS 3602 Table 1, 1A.1 | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3, Table 4.3 note (7) | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3, Table 4.3 note (7) |
| 2 | Deck postsSet in the ground, carrying the deck | 50 yr | H5NZS 3602 Table 1, 1A.4 | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3, Table 4.3 note (7) | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3, Table 4.3 note (7) |
| 3 | Bearers and joistsUnder the floor, out of the weather | 50 yr | H1.2BPS Table 1C.1 | Connectors: hot-dip galvanised where the subfloor vents 7000 mm² or less, 304 stainless steel where it vents more Nails and screws: galvanised steel NZS 3604 Table 4.1, Table 4.3 | Connectors: 304 stainless steel Nails and screws: galvanised steel NZS 3604 Table 4.1, Table 4.3 |
| 4 | Ground floor boardsTimber flooring over the subfloor | 50 yr | H1.2BPS Table 1C.3 | Nails and screws: mild steel NZS 3604 Table 4.3 | Nails and screws: mild steel NZS 3604 Table 4.3 |
| 5 | Exterior wallsClosed, inside the wall | 50 yr | H1.2BPS Table 1D.14 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 |
| 6 | Internal wallsClosed | 50 yr | H1.2BPS Table 1E.5 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 |
| 7 | Cavity battensIn the wall cavity | 50 yr | H3.1BPS Table 1D.10 | Held by the cladding's nails E2/AS1 Table C.3.1.1 note (3) | Held by the cladding's nails E2/AS1 Table C.3.1.1 note (3) |
| 8 | Weatherboards, radiata pineExposed, painted | 15 yr | H3.1NZS 3602 Table 2, 2A.1 | Nails and screws: galvanised steel NZS 3604 Table 4.3; E2/AS1 Table C.1.1.1A (6) | Nails and screws: galvanised steel, punched, puttied and painted NZS 3604 Table 4.3; E2/AS1 Table C.1.1.1A (6) |
| 9 | Upper floor joistsInside, under the upper room | 50 yr | H1.2BPS Table 1E.2 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 |
| 10 | Upper floor boardsTimber flooring, inside | 50 yr | H1.2BPS Table 1E.7 | Nails and screws: mild steel NZS 3604 Table 4.3 | Nails and screws: mild steel NZS 3604 Table 4.3 |
| 11 | Balcony joists, cantileveredUnder the enclosed balcony, past the wall below | 50 yr | H3.2BPS Table 1D.7 | Nail plates: hot-dip galvanised Connectors: hot-dip galvanised Nails and screws: hot-dip galvanised NZS 3604 Table 4.1, 4.4.4 (b), Table 4.3 | Nail plates: hot-dip galvanised Connectors: hot-dip galvanised Nails and screws: hot-dip galvanised NZS 3604 Table 4.1, 4.4.4 (b), Table 4.3 |
| 12 | Parapet framingAround the balcony, within and beneath the parapet | 50 yr | H1.2BPS Table 1D.5 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 |
| 13 | Skillion roof framingLined underneath, over the single storey | 50 yr | H1.2BPS Table 1D.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 | Nail plates: continuously coated galvanised Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.3 |
| 14 | Roof trusses and framingRoof space | 50 yr | H1.2BPS Table 1E.1 | Nail plates: continuously coated galvanised, Z275 Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.2, Table 4.3 | Nail plates: continuously coated galvanised, Z275 Connectors: mild steel Nails and screws: mild steel NZS 3604 Table 4.1, Table 4.2, Table 4.3 |
| 15 | Open deck bearers and joistsExposed, open deck | 50 yr | H3.2NZS 3602 Table 1, 1B.3 | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3 | Connectors: 304 stainless steel Nails and screws: 304 stainless or better NZS 3604 Table 4.1, 4.4.4 (a), Table 4.3 |
| 16 | Decking boardsExposed, no roof over it | 15 yr | H3.2NZS 3602 Table 2, 2A.7 | Nails and screws: 304 stainless or better NZS 3604 Table 4.3, 4.4.4 (a) | Nails and screws: 304 stainless or better NZS 3604 Table 4.3, 4.4.4 (a) |
- Sheltered or exposed Closed is inside the wall or roof; sheltered is open to salt air but kept out of the rain, above a 45° line down from the edge of a floor, deck or roof; exposed is below it, or out in the rain.
NZS 3604:2011 Table 4.1 note (4), Figure 4.3
- Copper-treated timber Timber treated with copper, H3.2 and up, takes Type 304 stainless steel fixings wherever it is sheltered or exposed, in every zone.
NZS 3604:2011 4.4.4
- Piles near the ground Fixings and nails into a pile within 600 mm of the ground are stainless steel.
NZS 3604:2011 Table 4.1, Table 4.3 note (7)
- Type 304 or 316 Type 304 stainless steel meets the Building Code, though it can show surface rust. Type 316 goes beyond what the Code asks and is for where the look matters.
NZS 3604:2011 Table 4.3 note (9)
- Flooring Plywood and particleboard flooring need no treatment. In a wet area where an impervious coating cannot be kept up, timber or plywood flooring is H3.1 at least.
NZS 3602:2003 Table 1, 1C.3, 1E.7, note (7)
- Drained subfloor A subfloor holding steel fixings is drained so that it does not pond.
NZS 3604:2011 4.4.1 (a)
Other parts
Parts of a house the drawing does not show, and the treatment each needs.
| Part | Treatment | Lasts |
|---|---|---|
| Timber or plywood frame foundationsNZS 3602 Table 1, 1A.2 | H5 | 50 yr |
| Retaining wall uprightsNZS 3602 Table 1, 1A.6 | H5 | 50 yr |
| Retaining wall rails and boardsNZS 3602 Table 1, 1A.7 | H4 | 50 yr |
| Verandah posts above the ground, exposed rafters and beamsNZS 3602 Table 1, 1B.3 | H3.2 | 50 yr |
| Laminated beams out in the weatherNZS 3602 Table 1, 1B.1 | H3 | 50 yr |
| Laminated posts out in the weatherNZS 3602 Table 1, 1B.2 | H3 | 50 yr |
| Plywood cladding that bracesNZS 3602 Table 1, 1B.4 | H3 | 50 yr |
| Sarking and roof framing behind shingles or shakesBPS Table 1D.1 | H1.2 | 50 yr |
| Enclosed flat roof framingBPS Table 1D.2 | H1.2 | 50 yr |
| Wall framing within an enclosed balconyBPS Table 1D.6 | H1.2 | 50 yr |
| Plywood fascias, barges and cover boardsNZS 3602 Table 2, 2A.3 | H3 | 15 yr |
| Plywood sheet cladding that does not braceNZS 3602 Table 2, 2A.4 | H3 | 15 yr |
| Exterior joinery: window and door frames, sills and doorsNZS 3602 Table 2, 2A.5 | H3 | 15 yr |
| Flooring in a wet area whose coating cannot be kept upNZS 3602 Table 1 note (7) | H3.1 | 50 yr |
Metals that can be used in each exposure zone
Each bar runs from inland to the zone nearest the sea where the metal still lasts 15 years.
Bands are drawn equal and are not distances: the zone is the project's, read from NZS 3604's map and the site.
uPVC and butyl rubber may be used in every zone, exposed or sheltered. Bitumen is for hidden places only. E2/AS1 Table C.1.1.1A, 4.2.11.2
Key
- Exposed
- Out in the rain. Rain washes the salt off.E2/AS1 Table C.1.1.1A note (3)
- Sheltered
- In view but kept dry, such as under eaves. Salt stays on it, so its bar stops sooner. A part that is both counts as sheltered.E2/AS1 Table C.1.1.1A note (3)
- Hidden
- Behind another element, out of view. Not drawn here: E2/AS1's note (3) gives a hidden part 50 years, not 15, so the table judges it over a different period. TBCE2/AS1 Table C.1.1.1A note (3)
- Type 4, Type 6
- Grades of factory painted steel, under AS/NZS 2728. Type 6 may go nearer the sea.E2/AS1 Table C.1.1.1A
- Class 3, Class 4
- Corrosion grades of galvanised screws, under AS 3566.2. Class 4 is needed where a screw is exposed or sheltered.E2/AS1 Table C.1.1.1A, C.3.1.3
- Z450, AZ150, AM100
- The steel's metal coating and its weight in grams per square metre, under AS 1397.E2/AS1 Table C.1.1.1A
- Stainless fixings in coated steel
- Not advised near breaking surf or in industrial air: they can damage the coating.E2/AS1 Table C.1.1.1A note (11)
E2/AS1 Table C.1.1.1A, read for 15 years. Zones as NZS 3604 Section 4.2.
How thin each material may be
Roofs
| Pressed metal tiles, steel | 0.39 mm BMT | E2/AS1 8.3.2.2 |
| Pressed metal tiles, aluminium | 0.7 mm BMT | E2/AS1 8.3.2.4 |
| Profiled steel roofing | 0.4 mm BMT | E2/AS1 8.4.2.2 |
| Profiled aluminium roofing, 5000 series | 0.7 mm BMT | E2/AS1 8.4.2.3 |
| Butyl rubber or EPDM membrane | 1 mm | E2/AS1 8.5.2.2 |
Walls
| Profiled steel wall cladding | 0.4 mm BMT | E2/AS1 9.6.2.2 |
| Profiled aluminium wall cladding, 5000 series | 0.7 mm BMT | E2/AS1 9.6.2.3 |
Flashings
| uPVC | 0.75 mm | E2/AS1 4.2.2.1 |
| Aluminium, 5000 series | 0.7 mm | E2/AS1 4.2.3.1 |
| Galvanised steel | 0.55 mm BMT | E2/AS1 4.2.4.1 |
| Zinc-aluminium-magnesium coated steel | 0.55 mm BMT | E2/AS1 4.2.5.1 |
| Stainless steel, 304 or 316 | 0.45 mm | E2/AS1 4.2.6.1 |
| Copper | 0.5 mm | E2/AS1 4.2.7.1 |
| Lead sheet | 17 kg/m² | E2/AS1 4.2.8.1 |
| Zinc sheet | 0.7 mm | E2/AS1 4.2.9.2 |
| Butyl rubber or EPDM | 1 mm | E2/AS1 4.2.10.2 |
E2/AS1 4.2, 8.3.2, 8.4.2, 8.5.2 and 9.6.2. BMT is the base metal's thickness, before any coating. Lead is given by weight per square metre.
Which materials may touch or drain onto each other
Rows are the material on top, which water runs off; columns the one below, which it runs onto. Point at a square to see the pair; press one to keep it.
| Material below → Material above ↓ | Aluminium, anodised or mill | Aluminium, coated | Butyl, EPDM | Copper-treated timber | Cedar | Cement plaster | Ceramic tiles | Clay bricks | Concrete, old | Concrete, green | Copper, brass | Glass | Glazed roof tiles | Lead | Plastics | Stainless steel | Galvanised steel, coated | Galvanised steel | Zinc | Zinc-aluminium-magnesium, coated | Zinc-aluminium-magnesium, bare |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Aluminium, anodised or mill | |||||||||||||||||||||
| Aluminium, coated | |||||||||||||||||||||
| Butyl, EPDM | |||||||||||||||||||||
| Copper-treated timber | |||||||||||||||||||||
| Cedar | |||||||||||||||||||||
| Cement plaster | |||||||||||||||||||||
| Ceramic tiles | |||||||||||||||||||||
| Clay bricks | |||||||||||||||||||||
| Concrete, old | |||||||||||||||||||||
| Concrete, green | |||||||||||||||||||||
| Copper, brass | |||||||||||||||||||||
| Glass | |||||||||||||||||||||
| Glazed roof tiles | |||||||||||||||||||||
| Lead | |||||||||||||||||||||
| Plastics | |||||||||||||||||||||
| Stainless steel | |||||||||||||||||||||
| Galvanised steel, coated | |||||||||||||||||||||
| Galvanised steel | |||||||||||||||||||||
| Zinc | |||||||||||||||||||||
| Zinc-aluminium-magnesium, coated | |||||||||||||||||||||
| Zinc-aluminium-magnesium, bare |
Contact · E2/AS1 Table C.1.1.1BMust not touch. Keep them 5 mm apart.
Run-off · E2/AS1 Table C.1.1.1CWater must not run off the upper onto the lower.
Copper-treated timber is H3.2 and up: the piles, deck framing and decking on the Schedule face.
- May not touch
- May not touch in zones D and E
- Water may not run onto the one below
- Run-off may etch or stain glass
Appendix C Material tables, pp.181–189: Tables C.1.1.1A, C.1.1.1B, C.1.1.1C and C.3.1.1