Hardie™ Gravis™ Panel Floor
Concrete underfoot. Framed upstairs. Ready for tiles tomorrow.
AAC floor panels that feel like a poured slab
Hardie™ Gravis™ Panel Floor is a 75mm tongue and groove AAC panel, reinforced with corrosion-protected steel, that lays over timber or steel joists. It gives a framed upper storey the solid, quiet feel of a concrete slab, without formwork, props or curing time.
Use it for first floors, suspended ground floors, bathrooms, decks and balconies. Once it's down and glued, the floor is ready for finishes within 24 hours, so your trades keep moving.
Use it for first floors, suspended ground floors, bathrooms, decks and balconies. Once it's down and glued, the floor is ready for finishes within 24 hours, so your trades keep moving.
Need advice regarding Hardie™ Gravis™ Panel Floor? Midstream Hardware is here to help.
Why build your upper floor with Gravis
WA two storey builds usually land on one of two options: a suspended concrete slab with all the formwork, propping and wait time that comes with it, or a sheet floor that can bounce and creak. Gravis sits in the sweet spot.
- Feels like concrete. No bounce, no squeak, and a solid base under any floor covering.
- Quieter between levels. With insulation and a plasterboard ceiling, systems reach Rw+Ctr 50 to 51 for airborne noise, up to 60 with a tiled topping slab.
- Fast on site. Panels screw and glue straight to the joists. Lay finishes within 24 hours.
- Pairs with Gravis walls. Run the same AAC system through your walls and floors from one supplier.
Where it works
Features & Benefits
Why choose Hardie™ Gravis™ Panel Floors for your next project? Like our other James Hardie products, it offers benefits such as:
-
Solid and stableDesigned for residential Category A1 loads: 2 kPa spread across the floor and 1.8 kN concentrated. - Fire resistantNon-combustible, FRL 90/90/90 from above, and up to 90/90/90 from below with 2 x 16mm fire rated plasterboard ceilings.
- Warmer in winter, cooler in summerTotal R-values around 3.0 with R2.0 ceiling insulation, ready for your energy rating.
- Termite resistantAAC won't feed termites, though your overall termite management still applies.
- Plays well with services
Penetrations up to 80mm need no extra support; go bigger with blocking either side.
Performance by floor finish
Timber joists at 600mm centres, R2.0 ceiling insulation and one layer of 13mm fire rated plasterboard below. Lower Lnw means less footfall noise downstairs.
Product specifications
All panels are 600mm wide with square edges and single mesh reinforcement. Weights are approximate at 35% moisture content.
Framing and layout essentials
- Joists: max. 600mm centres, nominal 45mm wide (40mm for narrow timber I-joists, 42mm for LVL). Steel joists 0.75 to 1.9mm BMT.
- Spans: every panel crosses at least three joists. Short edges sit on a joist or trimmer.
- Stagger: offset butt joints by at least one joist bay, with a minimum 450mm overlap.
- Control joints: max. 6m apart, plus over bearers, support walls and wherever joist direction changes.
- Fixing: a 5mm bead of adhesive on every joist, joints (2 to 3mm) fully filled with Gravis Adhesive, and two screws per panel at every joist, 100mm from the edge.
- Loadbearing walls: add a joist or solid blocking underneath.
- Notching: max. one quarter of the panel width, with blocking beside the notch.
Everything for the floor system, from one counter
Walk out with a complete, compliant system rather than chasing parts across town.
You'll also need: 14-10 x 100mm MP bugle head Type 17 screws for timber joists (or 95mm hex head self-tappers for steel), Class 3 or 4, plus construction adhesive, ceiling insulation, and a membrane for wet areas or balconies.
Finishing the floor
- TilesFlexible adhesive to ISO 13007.1 and AS 3958.1. When direct fixing, carry the 5mm panel control joints through the tiles. Start tiling from a control joint and work out.
- Timber, laminate and hybridAcclimatise boards first. If the panel reads over 6% moisture, lay a taped 200 micron poly sheet before flooring.
- VinylLevel minor imperfections, then use an AAC compatible adhesive.
- CarpetClean, dry, dust free surface, with AAC approved adhesive for direct stick.
- Don't sandDon't sand the panel. Patch it instead.
Hardie™ Gravis™ Panel Floor FAQs
Yes. It lays over timber or light gauge steel joists at up to 600mm centres and gives a framed upper storey a solid, concrete-like floor.
Within 24 hours of installation. In wet areas and outdoors, the membrane and finishes must go on within 3 months, and the panels kept dry in the meantime.
Yes, with a waterproof membrane installed to AS 3740. The electrician must also provide equipotential bonding in wet zones under AS/NZS 3000.
Yes. Apply a flexible external membrane that complies with AS 4654.1, installed by an accredited applicator, within 3 months of laying the panels.
It removes bounce and squeak because the panels are glued at every joint and to every joist. With insulation and a plasterboard ceiling, airborne sound ratings reach Rw+Ctr 50 to 60.
Each panel is 1800 x 600 x 75mm and weighs about 56kg. Carry them on edge and use panel lifters.
Yes, with an extra joist or solid blocking directly underneath to keep stress on the panel within limits.
Lay a floor that feels like it was poured
Bring your floor plan to 79 Pinjarra Road, Mandurah, or call (08) 9535 3000. We'll help you work out panel numbers, fixings and the right membrane before you order.
For more information about James Hardie's Hardie™ Gravis™ Panel Floor product specifications, accessories & tools, and technical resources, please see the James Hardie website.
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Reliable Site Delivery
Count on Midstream Hardware for efficient, reliable delivery when your schedule demands it. Our service area includes:
For larger orders or ongoing builder projects, we also service outer Metro areas and selected regional sites such as Bunbury.
If a project sits outside these areas, please get in touch with us - we can usually work something out.
Need a quote or immediate product specifications?
For dependable advice, product information sheets, or to place a large-volume order, contact Midstream Hardware directly on (08) 9535 3000.
- Mandurah
- The Peel Region
- Southern Perth Metropolitan Area
For larger orders or ongoing builder projects, we also service outer Metro areas and selected regional sites such as Bunbury.
If a project sits outside these areas, please get in touch with us - we can usually work something out.
Need a quote or immediate product specifications?
For dependable advice, product information sheets, or to place a large-volume order, contact Midstream Hardware directly on (08) 9535 3000.