RAB™ Board
Close the Building In. Keep the Programme Moving
One of the more frustrating realities of commercial construction is the programme dependency on external cladding completion before internal trades can properly start. The building has to be weathertight. On a project with complex cladding systems, long lead times or constrained site access, that dependency can cost weeks.
RAB™ Board breaks that dependency. It’s a rigid air barrier board, a fibre cement sheet fixed to the structural frame ahead of external cladding installation, that makes the building weathertight before the cladding goes on. Internal trades can begin. The programme moves forward. The cladding goes on later, in its own sequence, without holding up everything else inside. It’s a straightforward product that solves a real construction programme problem.
Technical Specifications
Material
Fibre cement – rigid, non-tearing air barrier
Wind pressure rating
Withstands up to 7 kPa wind load – won’t tear in high wind conditions
Vapour permeability
Class 4 Vapour Permeable Membrane – allows vapour to escape without trapping moisture
Climate zone suitability
NCC 2022 Climate Zones 2–8 (standard) – suitable for most Australian building locations
Sealing technology
CoreShield™ penetrating sealer – helps prevent moisture ingress through the board
Frame compatibility
Timber and light gauge steel framing – residential and commercial
Cutting
Lightweight and easy to cut – score and snap with Villaboard™ Knife
Fixing
Screw or nail to frame – joints simply taped to complete the air barrier line
Fire classification
Non-combustible – suitable for non-combustible wall construction
Bushfire suitability
Suitable for use in bushfire-prone areas (low flammability index per AS 1530.2)
Hardie™ certified use
James Hardie certified for use with ExoTec™ and other Hardie™ external cladding systems
What RAB™ Board Actually Does
RAB™ Board serves two functions simultaneously in the wall assembly. First, it creates a weathertight building envelope, protecting the structural frame and internal construction from weather exposure while cladding is installed. Second, it acts as an air barrier, reducing uncontrolled air infiltration through the wall assembly in the completed building, which improves thermal performance and reduces energy load.
Unlike flexible weather-resistant barriers (wraps), RAB™ Board is rigid; it’s a fibre cement sheet that stays in place under construction conditions without tearing, lifting or requiring restraint against wind uplift during the cladding installation phase.
The Construction Programme Case
The specific programme advantage of RAB™ Board comes from its ability to separate the weatherproofing milestone from the cladding completion milestone, two things that are often treated as the same event.
Internal trades can start earlier
Once RAB™ Board is installed and joints are taped, the building is weathertight. Plumbing, electrical, framing and internal linings can begin regardless of where the external cladding installation is up to, eliminating the sequential dependency that causes programme delays.
Weather doesn't hold up the programme
On a building with a flexible weather-resistant barrier, wind events can lift or tear the wrap, requiring re-fixing and re-inspection before internal trades can enter. RAB™ Board's rigidity means wind and rain don't interrupt the construction sequence.
Complex or long-lead cladding isn't a bottleneck
When the external cladding system has long lead times, complex installation requirements or phased delivery, RAB™ Board allows internal construction to proceed at full pace while cladding proceeds in parallel, not in sequence.
Programme savings are cost savings
Every week saved on programme is a week of site overhead, crane costs, scaffolding costs and financing costs that doesn't need to be paid. On a large commercial project, the programme benefit of the RAB™ Board can justify its cost many times over.
Why Rigid Matters
Won't tear under wind load
RAB™ Board withstands up to 7 kPa wind pressure, significantly higher than flexible barrier wraps that can lift, tear and fail under strong construction-site wind conditions, particularly on taller buildings.
Maintains the air barrier line
A rigid board maintains a consistent, flat air barrier surface even when the frame deflects slightly under load, flexible wraps can sag between fixing points, creating air pathways that compromise the thermal performance of the completed wall.
CoreShield™ moisture protection
The CoreShield™ penetrating sealer technology in RAB™ Board helps prevent moisture ingress through the board body, complementing the tape at joints to create a continuous barrier against liquid water while allowing water vapour to escape.
Class 4 vapour permeability
Classified as a Class 4 Vapour Permeable Membrane under NCC 2022, RAB™ Board is suitable for Australian Climate Zones 2 to 8. In hot humid zones (Zone 1), the designer must confirm vapour-permeability suitability.
Featured Projects with RAB™ Board
Frequently Asked Questions
What is the difference between RAB™ Board and a standard weather-resistant barrier wrap?
RAB™ Board is a rigid fibre cement sheet, it is a structural panel, not a flexible wrap. This rigidity means it won’t tear or lift in wind conditions up to 7 kPa, maintains a consistent air barrier surface regardless of frame deflection and can be left in place for extended periods during the construction programme without the issues that affect flexible wraps in high-wind or wet conditions. It also carries the CoreShield™ penetrating sealer technology that helps resist moisture ingress through the board body.
Is RAB™ Board suitable for all Australian climate zones?
RAB™ Board is suitable for NCC 2022 Climate Zones 2 to 8 as a Class 4 Vapour Permeable Membrane. For Climate Zone 1 (hot humid, tropical north Queensland and Darwin), the designer must assess whether a Class 4 vapour permeable membrane is appropriate for the specific wall assembly. If an alternative product is used instead of RAB™ Board in any climate zone, the designer must confirm it meets the applicable AS/NZS 4200.1 classification.
Can RAB™ Board be used behind ExoTec™ Facade Panels?
Yes. RAB™ Board is James Hardie’s specified and tested weather barrier for use with the ExoTec™ Facade Panel and System. The ExoTec™ installation guide identifies RAB™ Board and Hardie™ Wrap Weather Barrier as the two products James Hardie has tested and certified for use with ExoTec™ in Climate Zones 2–8. Using an alternative weather barrier product behind ExoTec™ requires the designer to confirm its classification and performance independently.
How is RAB™ Board installed?
RAB™ Board is screwed or nailed to the structural frame, timber or light gauge steel, and is easy to cut on site using a Villaboard™ Score and Snap Knife, which minimises dust. Joints between boards are taped to complete the continuous air barrier line. The ExoTec™ top-hat system or other cladding fixing system is then installed over the RAB™ Board.