Plasterboard | Chalkline

TL;DR

Internal wall and ceiling lining. Pick the grade for the location, fix to the right substrate at the right spacing per AS/NZS 2589, then set and jointed.

What it is

Plasterboard, also called Gyprock or drywall. Gypsum core, paper faces, fixed to timber or steel framing.

Properties

Property	Standard options
Width	1200mm
Length	2400, 2700, 3000, 3600, 4200, 4800, 6000mm
Thickness	10mm (ceilings), 13mm (walls), 16mm (fire / impact), 25mm (shaftliner)
Edge profile	Recessed (RE) for jointed finish. Square (SE) behind cornice or tile.

Sheet weight (manual handling)

Sheet	Approx weight
10mm 1200x4800	30 to 35 kg
13mm 1200x3600	35 to 40 kg
16mm fire-rated 1200x3600	50+ kg

Two-person lift or sheet trolley above 25 kg.

Grades

Grade	Where to use
Standard (white)	Dry walls and ceilings
Water-resistant (green / aqua)	Splash zones outside the shower. Not a tile substrate inside showers.
Fire-rated (pink)	Garage-to-house wall, between dwellings, service shafts. Use the tested system.
Impact-resistant	High-traffic walls, hallways, kids’ rooms
Acoustic	Bedroom walls, party walls, media rooms
Sag-resistant	Insulated ceilings or 600mm joist centres
Foil-backed	Where vapour barrier is required

Where to use

Internal walls and ceilings on framed construction
Behind cornices or square-set details
Splash zones (water-resistant grade, not in showers)
Garage / dwelling separation walls (fire-rated tested system)
Acoustic separation between bedrooms or party walls (acoustic grade in tested system)

Where NOT to use

As a tile substrate inside a shower enclosure. Use cement sheet or certified tile-backer per AS 3740.
Externally. Even water-resistant grade is internal-use only.
In place of fire-rated grade where NCC requires one.
Bridged across structural movement joints. Cracks guaranteed.
Over green or wet timber framing. Screw pops and joint cracking will follow.
As a structural member. Bracing comes from the frame, not the lining.

Fixing

Screw type by substrate

Substrate	Thread	Length (13mm sheet)	Tip
Timber stud / joist	Coarse	30 to 32mm	Bugle head
Steel stud	Fine	25 to 30mm	Drill-point or self-piercing

Coarse on softwood pine, fine on steel. Wrong thread strips or fails to hold.

Screw spacing (per AS/NZS 2589)

Location	General	At sheet ends
Walls (to studs)	300mm	200mm
Ceilings (to joists)	230mm	150mm

Fire-rated and acoustic systems: follow the tested system spec, not the general rule.

Sheet orientation

Walls: long edge perpendicular to studs (horizontal)
Stagger end joints by at least one stud bay
Recessed edges run perpendicular to studs/joists for jointing

Install sequence

Frame check. Studs and joists straight, plumb, square, at correct centres.
Mark up service penetrations from frame plan.
Hang ceilings first, then walls.
Cut by score-snap-cut. Rasp the cut edge.
Fix with the correct screw at correct spacing. Heads just below paper, no breakthrough.
Set and jointed by plasterer: tape coat, fill coat, finish coat. Sand between.
Cornice or square-set last.

Full procedure: AS/NZS 2589:2017. Manufacturer literature: CSR Gyprock Red Book, Knauf Australia tech docs.

Tolerances and acceptance

What “good” looks like in the finished state, before paint and at handover.

Numerical

Item	Limit	Source
Surface flatness, paint-grade walls	AS 2589 Level 4 finish (typical residential paint)	AS/NZS 2589:2017
Surface flatness, gloss / critical light	AS 2589 Level 5 finish (full skim coat)	AS/NZS 2589:2017
Wall plumb	Per current HIA Guide and state Guide to Standards and Tolerances. Pending HIA member access. [HIA-001]	HIA Guide / state guide
Wall straightness under a long straightedge	Per current HIA Guide and state guide. Pending HIA member access. [HIA-002]	HIA Guide / state guide
Joint ridge / depression	Not visible from the AS 2589 viewing distance under normal light	AS/NZS 2589:2017
Screw set	Heads just below paper face, no breakthrough, no protrusion	AS/NZS 2589:2017
Cornice line	Straight, no obvious dips, mitres tight (per HIA Guide qualitative criteria, exact wording pending). [HIA-003]	HIA Guide

Visual acceptance

Viewing distance: per AS/NZS 2589:2017 finish-level inspection requirements, with normal indoor lighting. Numerical viewing distance pending verification against the current AS clause. [HIA-004]
Lighting condition: ambient indoor light at the time of inspection. Don’t judge under raking low-angle light unless that’s the room’s actual day-to-day condition.
Critical-light walls (large windows, gloss paint, downlight wash) need Level 5 finish, not Level 4.

Defects typical at PCI

Screw pops (frame moisture moved after lining)
Joint ridges visible under raking light
Hairline cracks at door corners, architrave junctions
Patches showing through paint (different sheen)
Cornice gaps at mitres
Set joints showing through skim where Level 5 was specified but not delivered

For finish-level disagreements at PCI, AS 2589 Levels 1 to 5 is the arbiter. Specify the level in the contract or scope.

Working with other trades

Before lining (first fix)

Plumber: rough-in pipework and waste runs in. No retrofitting wet-area linings.
Sparky: cabling, conduits, mounting boxes set to depth.
HVAC: ducts run, register positions marked.
Comms / data: cables pulled and terminated.
Insulation: batts or board installed per energy report.
Pad-out blocks / noggings: marked on frame plan during framing for vanity, benchtop bracket, TV mount, wall-hung WC, grab rails.

During lining

Site clean, dry, and warm enough for compound to cure.
Sheet plan confirmed against frame layout before cutting.

After lining (second fix)

Sparky returns for fittings (downlights, GPOs). Hole saws can shred fresh joints. Penalty clauses help.
Plumber returns for fixtures.
Painter primes and finishes.
Tiler in wet areas only over correct substrate. If grade is wrong, build stops.

See first fix / second fix sequence for the full choreography.

Health & safety

Silica dust: cutting and sanding generates RCS and gypsum dust. Workplace exposure standard for RCS is 0.05 mg/m3 (8-hour TWA). Use M-class or H-class shadow-vac sanders or wet sand. P2 mask minimum.
Manual handling: two-person lift above 25 kg, or use sheet trolley. Sheets are awkward, not just heavy.
Sharp edges: paper cuts on edges, metal banding cuts when uncrating.
Asbestos lookalike: pre-1985 buildings may have asbestos-containing linings (Tilux, Wunderlich Fibrolite). Modern plasterboard contains no asbestos but old fibre-cement linings can. Test before disturbing.
Joint compound: skin and eye irritant. Standard PPE.

Suppliers

CSR Gyprock: largest market share. The Red Book is the install bible.
Knauf Australia: full grade range, strong on fire-rated and acoustic systems.
Siniat (Etex): full range.
USG Boral: now part of Knauf.

Trade pickup: building merchants, Bunnings Trade, plasterboard wholesalers (Plasterboard Wholesalers, Wright Forbes, others by region).

[Sponsor / preferred installer slot. ACCC disclosure required.]

What can go wrong

Screw pops: wrong screw type, wrong length, green frame, or too few screws.
Joint cracking: no tape, rushed coats, frame movement, or hairline cracks at door corners.
Ceiling sag: insulation overweight for grade, screws too few, joists at wrong centres.
Wet area damage: wrong grade in shower or behind splashback. Rip-out, not patch.
Failed fire-rated system: wrong screw spacing, missing layer, unsealed penetration. Re-test required.
Sound rating compromised: downlights cutting both leaves of a sound wall, services bridging.
Edge chip / damaged corners: over-sanded edges, impact damage. Patchable, obvious in raking light.
Compound shrinkage / ghost joints: too thick a coat, not enough cure between coats.

References

AS/NZS 2589:2017, Gypsum linings, Application and finishing (Standards Australia) (verified 2026-05-02)
AS 3740-2021, Waterproofing of domestic wet areas (Standards Australia) (verified 2026-05-02)
NCC 2022 Volume Two, Class 1 and 10 buildings (residential), ABCB (verified 2026-05-02)
HIA Guide to Materials and Workmanship (national, Housing Industry Association) (verified 2026-05-02)
State workmanship guides: VBA (VIC), NSW Fair Trading, QBCC (QLD), CBS (SA), BSA (WA)
CSR Gyprock Red Book (CSR), Knauf Australia tech docs (Knauf), Siniat docs
WHS Codes of Practice (state-by-state) for silica dust and manual handling