What is first fix carpentry?

First fix carpentry covers all the structural timber work done before plastering: wall plates, stud walls, floor joists, roof timbers, door linings, and window boards. It also includes noggings for plasterboard support and herringbone strutting between joists. First fix is done after the building is weather-tight but before internal finishes.

How many noggings do I need per stud wall bay?

One row of noggings at mid-height is standard for 2.4m walls (providing support for plasterboard and lateral bracing). For walls over 2.7m, use two rows. Noggings are cut to fit between studs at the specified centres. Stagger them slightly for easier nailing — offset by 25mm alternately each side of the centre line.

What is herringbone strutting?

Herringbone strutting consists of short diagonal timber pieces fitted in a cross pattern between floor joists. It prevents the joists from twisting and distributes loads between them. Use one row at mid-span for joists up to 2.5m, two rows for longer spans. Alternatives include solid timber blocking or proprietary metal struts.

When do I need joist hangers?

Joist hangers are used where joists meet walls or beams without bearing on a ledge. They are mandatory for timber-to-masonry connections and are recommended at all joist ends for secure fixing. Each joist needs one hanger. Use the correct size — hangers are matched to joist dimensions (e.g., 44×200mm for a 47×200mm joist).

What timber sizes are used for first fix?

Common first fix timber sizes: wall plates 100×50mm, studs 89×38mm or 100×50mm at 600mm centres, noggings same section as studs, floor joists 47×175mm to 47×250mm at 400mm centres, and herringbone strutting 47×47mm or 50×50mm. All structural timber must be C16 or C24 graded.

TradeCalculator.co.uk

First Fix Timber Calculator

Calculate wall plates, studs at centres, noggins per bay, joist hangers and herringbone strutting for first fix carpentry.

Wall Plate Run

Total wall plate length

Stud Wall Length

Total stud partition length

Wall Height

Floor to ceiling

Floor Area

For joist and strutting quantities

Include herringbone strutting

Cross-bracing between joists

Avg Price Per Metre (optional)

Average across all timber sections

How We Calculate This

This calculator tallies all first fix timber components: wall plates for roof bearing, stud wall framing, noggings, joist hangers and herringbone strutting.

The formula

Studs = (Wall length ÷ Centres) + 1
Noggings = (Studs - 1) × Rows per bay
Herringbone pieces = Rows × (Joists - 1) × 2
Total timber = Sum of all component lengths