How should plasterboard be laid on a ceiling?

Plasterboard should be fixed perpendicular to the ceiling joists (i.e. the long edge of the board crosses the joists). This ensures maximum support along the board length. The long tapered edges should run perpendicular to the joists, making them easier to tape and joint. Stagger end joints between rows by at least 600mm to avoid a continuous joint line.

What screws should I use for a plasterboard ceiling?

Use 32mm drywall screws for 12.5mm boards, or 38mm for 15mm boards. Screws should be at 150mm centres around the board perimeter and 300mm centres in the field (where boards cross intermediate joists). Screws must penetrate at least 10mm into the timber joist. Set screws just below the surface without breaking the paper face.

Do I need noggings for a plasterboard ceiling?

Yes, noggings (timber cross-pieces between joists) are needed wherever board edges meet that are not supported by a joist. This occurs at the short edges of boards — the end joints that run parallel to joists. Noggings should be 50×50mm or the same depth as the joists, nailed or screwed between joists to provide a fixing point for the board edges.

What is the maximum weight a plasterboard ceiling can hold?

A single layer of 12.5mm plasterboard fixed to joists at 400mm centres can support approximately 25 kg/m² of imposed load (e.g. insulation above). For heavier loads or wider joist spacing, use 15mm board or double-board. Light fittings up to 3kg can be fixed directly to the board. Heavier items must be fixed to joists or use specialist plasterboard fixings rated for the load.

Should I use 12.5mm or 15mm board on a ceiling?

12.5mm is standard for domestic ceilings with joists at 400mm centres. Use 15mm board for joists at 600mm centres, where additional fire resistance is needed, or where heavy insulation will be placed above. 15mm board is heavier (approximately 12 kg per 2400×1200mm sheet vs 10 kg for 12.5mm) so requires two people to handle on ceilings.

TradeCalculator

Plasterboard Ceiling Calculator — Boards, Noggings & Screws

Calculate plasterboard sheets, noggings at joints, and screw quantities for ceiling installations with optimised board layout.

Room Length

Along the board direction

Room Width

Perpendicular to joists

Board Size

2400×1200mm is standard

Board Price (optional)

Per plasterboard sheet

Screw Price (optional)

Per individual screw

Nogging Timber Price (optional)

Per nogging cut to fit

How We Calculate This

This calculator optimises the board layout for minimum waste, determines nogging positions at unsupported joints, and calculates screw quantities at the correct centres.

The formula

Boards = (Boards across width × Boards along length) × (1 + Waste %)

Screws = Perimeter ÷ 150mm + Field joists × Board length ÷ 300mm

For a 4m × 3m room with 2400×1200mm boards: across = 3, along = 2 = 6 boards. With 10% waste = 7 boards. Noggings at 1 cross-joint × 5 bays = 5.

Screw centres

Perimeter: 150mm centres around all board edges
Field: 300mm centres where boards cross intermediate joists
Set depth: Just below paper surface without breaking through
Edge distance: Minimum 10mm from board edge

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.