Millboard Exterior Decking System

Millboard holds its shape, colour and finish through every season. Resistant to impact, rot and algae, it is engineered to withstand the elements without compromise. The result is enduring performance with minimal upkeep.

Engineered from the same robust mineral core as Envello Cladding, Millboard Decking resists warping, rotting and algae, ensuring it won't degrade over time. Extensive UV and weathering tests confirm its suitability for New Zealand's environment, while its low-maintenance Lastane® surface offers enduring performance with minimal effort.

Why Use Millboard Decking
Scope & Limitations of Use

Millboard Decking is engineered for performance across New Zealand's demanding conditions, suitable for use in all exposure zones as defined in NZS 3604:2011. Designed for external decking on residential and commercial projects, the system suits both timber framing and the Outdure QwickBuild aluminium subframe system, making it as suitable for ground-level decks as it is for rooftop terraces and balconies. Installation must follow the conditions set out in NZS 3604:2011 to ensure long-term structural performance and compliance.

Key specification points:

  • Suitable in all exposure zones as defined in NZS 3604:2011 (contact Forté for microclimatic conditions)

  • Compatible with timber framing or the Outdure QwickBuild aluminium subframe system

  • Timber framing must have a minimum design load of 2kPa or be subject to specific engineering design

  • Joist spacing at a maximum of 400mm centres (residential) or 300mm centres (commercial)

  • Stainless steel Durafix® fixings required throughout (4.5 x 60mm for timber subframe, 4.5 x 45mm for aluminium subframe)

  • Single board spans up to 3600mm

Full scope, limitations and technical detailing are set out in the Millboard Exterior Decking System Design Guide.

Download the Millboard Decking Design Guide

Additional Applications

Millboard Decking offers exceptional strength and versatility, adapting effortlessly to a variety of architectural styles and complex detailing, enabling a seamless, durable and visually striking finish across a range of applications.

Pool Edges and Spas

Millboard can be installed flush to the pool edge and continued down the vertical face, offering a clean, modern look ideal for residential applications. The same approach frames spas and hot tubs, with the structure planned to carry their added weight from the outset — supporting both deck-mounted and recessed installations to suit the project.

Stairs & Planters

Bullnose boards provide a refined, radiused tread edge, while Reveal boards complete the riser detail for a seamless vertical finish. Accurate calculation of tread and riser dimensions ensures a safe, durable and visually considered stair installation.

Decking and reveal boards can also frame raised planter boxes, drawing on the same resin mineral composite core that resists rot and moisture absorption elsewhere in the system.

Curves

Using the Flexible Square Edge profile, Millboard can be formed to a 1.2m radius, allowing curves and circles to define spaces, levels and texture — giving projects the freedom to move beyond straight lines without compromising on finish.

Decking to Interior Flooring Detailing

Carry the same oak character and single material language from your interior floor straight through to your exterior deck, creating a seamless flow between spaces.

Decking to Cladding Detailing

Create a seamless transition that flows between horizontal and vertical planes, with complementary tones and profiles. With decking and cladding available in coordinated finishes, Millboard makes it easy to carry a consistent material palette throughout a project. Alternatively, contrasting tones can be used to highlight form and elevate detailing.

Ramps

With a refined timber grain and dependable slip resistance, Millboard Enhanced Grain is well suited to ramp design where accessibility and aesthetics both matter, allowing for a seamless continuation of decking across sloped and level surfaces.

Millboard Decking Specifications

Available in Enhanced Grain and Weathered Oak profiles, Millboard's resin mineral construction delivers consistent Prime grade quality across every board. Finished with a durable Lastane® surface and engineered from a polymer resin core, each profile is built for reliable, long-lasting performance.

Specifications

Enhanced Grain 126 W

Enhanced Grain

Weathered Oak

Grade

Prime

Prime

Rustic

Construction

Resin Mineral Board

Resin Mineral Board

Resin Mineral Board

Core

Polymer Resin Core

Polymer Resin Core

Polymer Resin Core

Thickness

32mm

32mm

32mm

Width

126mm

176mm

200mm

Length

3600mm

3600mm

3600mm

Surface Finish

Lastane® Surface

Lastane® Surface

Lastane® Surface

Specifying Millboard Decking

The Millboard Exterior Decking System Design Guide is the reference point for specifying and detailing Millboard with confidence. It covers the full system — from timber and aluminium subframe requirements through to fixing methods, board setout, pool and spa detailing, ramps, stairs and curved features — giving specifiers the technical grounding needed to design a compliant, long-lasting deck from the ground up.

Detailed technical drawings accompany each junction and condition, providing the dimensional accuracy and construction detail required to translate the guide directly into working drawings.

Compliance is demonstrated under the Millboard Product Assurance Supplier Statement (PASS #19239), addressing NZBC clauses for structure, durability, access routes and hazardous building materials. Every detail in the guide — from subframe setout to pool edges, ramps and stairs — is drawn from tested, documented practice, ensuring the system performs as intended across the full range of design conditions it's built for.

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Compliance & Testing

NZ Building Code Clause

Compliance Pathway

Demonstrated by

B1 STRUCTURE B1.3.1, B1.3.2, B1.3.3 (a, b, c, e, f, j, m, q)

Alternative Solution

Tested to ASTM D7032-17 for creep-recovery, fastener holding, bending stiffness and bending strength [element, 17/10/22]

B2 DURABILITY B2.3.1(b)

Alternative Solution

Tested to ASTM D7032-17 for elevated temperature, moisture and freeze-thaw; tested for UV/accelerated ageing [element, 17/10/22; Q-Lab, 11/11/22]

D1 ACCESS ROUTES D1.3.3(d)

Alternative Solution

Tested to BS 7976-2:2002, cited in AS/NZS 4586:2004. Classified as low slip potential [SATRA Technology Centre]

F2 HAZARDOUS BUILDING MATERIALS F3.2.1

Alternative Solution

Manufactured material is inert; use in accordance with supplier's safety information

A Sustainable Choice

Millboard is a low-carbon material that has been rigorously tested to ensure our production has minimal impact on the environment. While most composite decking boards are thermoplastic (melted plastic mixed with wood), the structural core of Millboard is a blend of natural minerals bonded in a polymer resin — such composite materials are designed to provide mechanical strength, chemical resistance and durability.

Get in Touch with Us

Every detail, one point of contact. Speak to a Forté specification consultant and get the technical support, documentation, and product knowledge you need to specify Millboard Decking with confidence.