What is the standard picket fence gap width?

The traditional UK picket fence gap equals the picket width — typically 70mm pickets with 70mm gaps. For a more closed appearance, reduce the gap to 50mm. For child safety, ensure gaps do not exceed 100mm to prevent small children from getting through. Consistent spacing is key to a professional-looking finish.

How tall should a picket fence be?

Standard UK picket fences are 900mm (3ft) to 1.2m (4ft) tall. Front garden picket fences are typically 900mm-1m. Taller pickets of 1.2m provide more privacy while still maintaining the traditional look. Picket fences over 1m at the front boundary adjacent to a highway may need planning permission.

How many arris rails per bay of picket fencing?

Use 2 arris rails per bay for picket fences up to 1.2m tall, and 3 rails for fences taller than 1.2m. The top rail should be positioned about 150mm from the picket top, and the bottom rail about 150mm from the bottom. A third rail goes in the centre for taller fences. Use 75×50mm or 75×38mm treated softwood rails.

What timber should I use for picket fencing?

Use pressure-treated (tanalised) softwood for durability. Pickets are typically 70×19mm or 75×22mm. Posts should be 75×75mm or 100×100mm, set at least 450mm deep in concrete. For a premium finish, use hardwood such as oak — though this costs significantly more. Always use UC4 treated timber for ground contact elements.

How do I calculate picket spacing accurately?

The formula is: Number of pickets = Total length ÷ (Picket width + Gap width). For example, a 10m fence with 70mm pickets and 70mm gaps: 10,000 ÷ 140 = 71.4, rounded up to 72 pickets. To get even spacing, divide the total length by the number of pickets, then subtract the picket width to find the exact gap.

TradeCalculator

Picket Fence Calculator

Calculate pickets, arris rails, posts and fixings for your picket fence. Adjustable picket width and gap spacing.

Total Fence Length

Total run of picket fencing

Fence Height

Standard: 900mm (3ft)

Picket Width

Standard: 70mm

Gap Between Pickets

Traditionally equals picket width

Picket Top Style

Pointed is traditional

Include post caps

Protects post tops from rain ingress

Price Per Picket (optional)

Price Per Post (optional)

Price Per Rail (optional)

How We Calculate This

This calculator determines the number of pickets, posts, arris rails and fixings for your picket fence based on the total length and your chosen picket width and gap.

The formula

Pickets = Fence length ÷ (Picket width + Gap width)
Posts = (Fence length ÷ Post spacing) + 1
Rails = Number of bays × Rails per bay (2 or 3)

For a 10m fence with 70mm pickets and 70mm gaps at 1.8m post spacing: 72 pickets, 7 posts, and 12 arris rails (2 per bay).

Building tips

Use a spacer block cut to the gap width for consistent spacing
Pre-drill pickets to prevent splitting near the ends
Leave a 50mm gap between ground and picket bottom for drainage
Use stainless steel or galvanised nails/screws to avoid rust stains

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.