Decking Calculator for NZ Builders
Calculate the materials you need for any deck size — boards, joists, and fixings. Works for 90×19mm, 140×19mm, or any custom board size.
Common NZ Decking Board Sizes
| Size | Board Width | Typical Use |
|---|---|---|
| 90×19mm | 90mm | Smaller decks, less wastage |
| 140×19mm | 140mm | Standard residential |
| 140×28mm | 140mm | Heavier commercial use |
| 90×45mm H4 | 90mm | Structural framing |
Joist Spacing Rules (NZ)
- 19mm boards: max 450mm joist spacing
- 28mm boards: up to 600mm joist spacing
- Always check NZ Building Code B1 for structural requirements
Decking Timber Grades
In NZ, all ground-contact or external timber must be H3.2 treated (above ground, protected) or H4 treated (ground contact). Untreated timber will rot within 2–5 years.
What Does a Deck Cost?
See our deck building cost guide for typical NZ prices by city, or find a local builder.