Internal linings overview: plasterboard, fibre cement, and timber boards

TL;DR

Standard 10mm plasterboard on ceilings and 13mm on walls covers most of the job. Pick the correct grade for the location: moisture-resistant (Aquachek / Aquacheck) for splash zones, fire-rated (Fyrchek / Firestop) for garage-to-dwelling separation and party walls per NCC 2022 Housing Provisions Part 9.3, and acoustic grade for separating walls between dwellings (Rw + Ctr not less than 50 per NCC Housing Provisions Part 10.7.1, verified 2026-05-10). Wrong grade in the wrong location fails inspection, and ripping out finished linings to rectify is a two-week delay with full plaster, paint and trade callbacks. Fibre cement is mandatory as the tile substrate in wet areas (showers, baths, laundries) where a waterproofing membrane per AS 3740-2021 is required. Timber board lining is a finish product only, not a structural or acoustic system.

Body

What internal linings do

Internal linings close the frame, provide the surface for paint and tile, contribute to acoustic and fire separation where specified, and form the substrate for cornice, skirting, and joinery. The lining trade (plasterer) typically drives the sequence: frame and pre-lining inspection, linings hung, set and jointed, then paint before second-fix trades return. See first-fix and second-fix sequence for the full trade order.

The main lining types in Australian residential construction are:

Standard plasterboard (gypsum-core sheet)
Specialty plasterboard: moisture-resistant, fire-rated, acoustic, impact-resistant
Fibre cement sheet (used as tile substrate in wet areas)
Timber board lining (VJ / tongue-and-groove: decorative finish product)

1. Standard plasterboard

Standard plasterboard is a gypsum-core, paper-faced sheet installed per AS/NZS 2589:2017 (Gypsum linings: Application and finishing, incorporating Amendment 1:2018 and Amendment 2:2021, verified 2026-05-10). It is the default lining for dry internal walls and ceilings.

Common thicknesses:

Thickness	Primary use
10mm	Ceilings at standard 450mm joist centres. Use sag-resistant grade (e.g. Gyprock Supaceil) at 600mm centres.
13mm	Walls. Standard residential.
16mm	Fire-rated and impact-resistant applications (see specialty grades below).

Sheet width is typically 1200mm or 1350mm. Sheet lengths range from 2400mm to 6000mm depending on product and supplier. Gyprock Plus 10mm (CSR Gyprock, verified 2026-05-10 from gyprock.com.au) is a common lightweight ceiling option for residential use.

Orientation and fixing:

Walls: long edge perpendicular to studs (horizontal), end joints staggered by at least one stud bay
Ceilings: hang first, walls second
Screw spacing per AS/NZS 2589: walls to studs 300mm general, 200mm at sheet ends; ceilings to joists 230mm general, 150mm at sheet ends
Fire-rated and acoustic systems: follow the tested system specification, not the general rule

Finish levels:

AS/NZS 2589:2017 defines finish levels 1 to 5. Level 4 is the standard for residential paint-grade walls. Level 5 (full skim coat) is required for gloss paint, critical-light walls (large windows, downlight wash), or feature walls under raking light. Nominate the finish level in the specification before the plasterer quotes. Retrofitting Level 5 after Level 4 is set and jointed is a cost adder that causes disputes. See AS/NZS 2589 finish levels and raking light.

Tolerances:

Workmanship tolerances for installed plasterboard (plumb, flat, joint ridge) are specified in the HIA Guide to Materials and Workmanship and the relevant state Guide to Standards and Tolerances. HIA member access is pending; current values are placeholder below.

Item	Tolerance	Source
Wall plumb	Per current HIA Guide and state Guide. Pending HIA member access. [HIA-095]	HIA Guide / state guide
Surface flatness (general)	AS/NZS 2589 Level 4 finish requirements	AS/NZS 2589:2017
Joint ridge or depression	Not visible under normal indoor light at AS/NZS 2589 inspection distance	AS/NZS 2589:2017
Screw set	Heads just below paper face, no breakthrough, no protrusion	AS/NZS 2589:2017

2. Specialty plasterboard grades

Select the grade to match the location and NCC requirement. Using standard plasterboard where specialty is needed fails the fire, acoustic, or moisture performance required by the NCC.

Moisture-resistant (Aquachek / water-resistant grade)

Identifiable by blue face paper (Gyprock Aquachek). Core, face and back are treated for moisture resistance. Gyprock Aquachek 10mm is rated Group 1 (non-combustible) and weighs approximately 7.1 kg/m2 (verified 2026-05-10 from gyprock.com.au).

Use moisture-resistant grade in:

Bathrooms, ensuites, laundries, and toilets: walls and ceilings outside the direct wet zone
Kitchen splash zones: walls above bench, not behind sink or on external wall without vapour control

Do NOT use moisture-resistant plasterboard as the tile substrate inside shower enclosures. The tiling wet zone (shower base, bath surround) requires a substrate classified under AS 3740-2021 as capable of supporting a waterproofing membrane. Fibre cement sheet (see section 3 below) and approved tile-backer boards are the correct substrate for tiled wet zones. Standard or moisture-resistant plasterboard behind tiles in a shower will swell, delaminate, and void the waterproofing warranty.

Knauf Aquaboard is the Knauf equivalent for moisture-resistant residential applications.

Fire-rated (Fyrchek / Firestop)

Identifiable by pink face paper (Gyprock Fyrchek). Glass fibre-reinforced gypsum core slows heat and flame transfer. Available in 13mm and 16mm (verified 2026-05-10 from gyprock.com.au).

Fire-rated plasterboard is required (as part of a tested system) where the NCC specifies an FRL (Fire Resistance Level). Key residential trigger points:

Separating walls between dwellings: must achieve FRL 60/60/60 per NCC 2022 Housing Provisions Part 9.3.1 (verified 2026-05-10 from ncc.abcb.gov.au), or be masonry not less than 90mm thick
Garage-to-dwelling separation: wall must achieve FRL 60/60/60 tested from the garage side per NCC 2022 Housing Provisions Part 9.4 (verified 2026-05-10 from ncc.abcb.gov.au), or masonry not less than 90mm. Floor system above a garage must achieve resistance to incipient fire spread of not less than 60 minutes, or FRL 30/30/30 from the underside

Always use a tested fire-rated system specification: the plasterboard product alone does not make up the FRL, it is the complete wall or ceiling assembly (framing, fasteners, insulation, sheet thickness and layer count, joint detailing) that is tested. Failing to follow the tested system (e.g. wrong screw spacing, skipped sheet layer) voids the fire rating.

Knauf Firestop is the Knauf equivalent fire-rated product.

Acoustic (Soundchek / Soundshield)

Used in separating walls and floor/ceiling assemblies between dwellings where the NCC sound insulation requirement applies.

NCC 2022 Housing Provisions Part 10.7.1: separating walls between Class 1 dwellings must achieve an Rw + Ctr (airborne) of not less than 50 (verified 2026-05-10 from ncc.abcb.gov.au). This requirement applies to walls common to adjoining Class 1 buildings. Wet area separation walls (bathroom or laundry abutting a habitable room in an adjacent dwelling) require discontinuous construction to further limit impact path transmission.

Gyprock Soundchek 13mm is primarily specified for commercial inter-tenancy walls, hotel bedrooms, and multi-residential separating walls. Knauf Soundshield Plus is available in 12.5mm and 15mm for higher acoustic performance (verified 2026-05-10 from onlineinsulation-sales.com). For residential detached dwellings (single Class 1 on its own lot) acoustic grade is typically not required unless specified by the designer or local planning control.

Impact-resistant

High-density core and heavy-duty liner paper. Used in high-traffic areas: hallways, stairwells, children’s rooms, garages. Gyprock HD and Knauf Impact are common products. Not a substitute for fire-rated grade in fire-separation locations.

3. Fibre cement sheet (wet-area tile substrate)

Fibre cement sheet (Villaboard by James Hardie, HardieFlex, generic compressed sheet) is the standard tile substrate in wet zones: shower enclosures, bath surrounds, laundry floors. It is classified as Type B internal sheeting under AS/NZS 2908.2:2000 (verified 2026-05-10) and is moisture-resistant but not waterproof.

Sequence in wet zones:

Fix fibre cement sheet to frame
Apply waterproofing membrane compliant with AS 3740-2021 over the sheet and all junctions (verified 2026-05-10)
Tile over the membrane using a water-resistant adhesive and grout

Minimum sheet thickness for tiled wet areas is 6mm per manufacturer specifications. 9mm is common for better rigidity and screw-hold. See cement sheet for fixing specifications, screw types, and silica dust controls. See Villaboard for James Hardie product-specific details.

Key rule: waterproofing membrane is mandatory between the sheet and the tiles in wet zones. Plasterboard (standard or moisture-resistant grade) behind tiles in a shower does not meet AS 3740 substrate requirements and will fail.

4. Timber board lining

Timber board lining (VJ board, tongue-and-groove, shiplap, beaded-board) is a decorative finish product. Common applications:

Feature walls in living areas, bedrooms, or outdoor-covered areas
Ceiling lining in verandahs or alfresco areas (check fire-resistance if near boundary)
Rumpus rooms, mudrooms, and feature ceilings where a warm, textured finish is preferred

Timber linings are fixed over plasterboard or direct to framing. When fixed over plasterboard, the plasterboard provides the fire and acoustic performance; the timber is a finish layer only. When fixed direct to framing, confirm the assembly still meets any fire separation requirement for the location.

Common species and products: Tasmanian Oak, Blackbutt, Baltic Pine (solid), and engineered products with veneer faces (Bord Touchwood). Widths typically 85mm to 185mm, thicknesses 10mm to 19mm. Suppliers include Australian Timber Ceilings, Nationwide Timber, Modinex, JBM Timber, and Bunnings for off-the-shelf MDF and PVC profiles.

MDF and PVC board profiles are available as low-cost alternatives. MDF is not moisture-tolerant. PVC is used in wet areas but is not a tile substrate; it is a finished wall cladding system.

Timber lining does not provide sound or fire rating on its own. Never substitute timber board for a code-required rated lining.

Decision matrix: which lining for which location

Location	Correct lining	Not permitted
Dry walls (bedrooms, living, hallways)	Standard plasterboard 13mm	Fibre cement (unnecessary, heavy)
Ceilings (standard 450mm centres)	Standard or lightweight 10mm	Fibre cement, timber direct (usually)
Bathroom walls outside wet zone	Moisture-resistant plasterboard	Standard plasterboard
Shower walls / bath surround (tiled)	Fibre cement sheet + membrane	Plasterboard of any grade
Shower walls (non-tiled wet wall)	Waterproofed fibre cement or compliant FRC panel	Plasterboard
Garage-to-dwelling wall	Fire-rated plasterboard in tested system (FRL 60/60/60) or masonry 90mm	Standard plasterboard
Dwelling separating wall	Fire-rated in tested system (FRL 60/60/60) + acoustic requirement (Rw+Ctr 50)	Standard plasterboard
Feature wall (decorative)	Timber board over plasterboard, or direct if no rating req.	None (aesthetic choice)

What can go wrong

Wrong plasterboard in a wet area. Standard or moisture-resistant plasterboard used as a tile substrate in a shower will delaminate. Water behind tiles migrates through any small grout crack, saturates the gypsum core, and the board blows. The tiler’s insurance will argue it is a substrate failure, not a tiling defect. Rectification means stripping tiles, board, membrane, and relining.
Fire-rated system not followed. Specifying Fyrchek or Firestop as a product without following the tested system specification for that FRL does not deliver the rating. Common failures: wrong screw spacing, missing second layer, joints not staggered, penetrations not fire-stopped. A certifier or fire engineer checking the assembly will identify the non-compliance.
Acoustic requirement missed. Separating walls between attached dwellings (duplexes, terraces) require Rw + Ctr of at least 50 per NCC Housing Provisions Part 10.7.1. Builders sometimes supply standard double-stud walls without tested acoustic board or insulation. Post-handover acoustic complaints are among the most common PCI and defects-period issues in attached residential. The fix is framing and lining removal and rebuild.
Finish level not agreed upfront. Nominating Level 4 in the contract then having the client expect Level 5 (full skim, critical-light ready) generates disputes at PCI. Specifying AS/NZS 2589 finish level explicitly in the scope of works is cheaper than arguing about it at handover.
Timber lining used as fire or acoustic substitute. Timber boards over direct framing in a party wall or garage separation provide no compliant fire or acoustic rating. The lining must be the rated assembly, with timber as an optional additional finish layer on top.
Frame moisture at lining. Plasterboard fixed over wet or green framing leads to screw pops and joint cracking within 6 to 12 months. Frame moisture checks before the lining trade is called up save callbacks.

References

AS/NZS 2589:2017 Gypsum linings: Application and finishing (incorporating Amendments 1 and 2, verified 2026-05-10)
AS 3740:2021 Waterproofing of domestic wet areas (verified 2026-05-10)
NCC 2022 Housing Provisions Part 9.3: Fire protection of separating walls and floors (verified 2026-05-10)
NCC 2022 Housing Provisions Part 9.4: Fire protection of garage top dwellings (verified 2026-05-10)
NCC 2022 Housing Provisions Part 10.7: Sound insulation (verified 2026-05-10)
Gyprock Aquachek 10mm product page, CSR (verified 2026-05-10)
Gyprock Fyrchek product page, CSR (verified 2026-05-10)
Gyprock Plus 10mm product page, CSR (verified 2026-05-10)
AS/NZS 2908.2:2000 Fibre cement products, Standards Australia (verified 2026-05-10)