Arris Rails

What Is an Arris Rail For?

An arris rail gets its distinctive triangular shape from the way it is made - a 75x75mm square section timber post is cut diagonally in half, producing two identical triangular rails. This angled profile does two important jobs: it gives the rail the strength to carry the featheredge boards fixed to it, and the sloped top sheds rainwater quickly rather than letting it sit and soak into the timber.

Fixed horizontally between fence posts, arris rails run the full width of each bay and the featheredge boards are nailed directly onto them, creating a strong, solid fence face.

How Many Arris Rails Do You Need for a 1.8m (6ft) Fence?

The number of arris rails per bay depends on the height of your fence:

• Up to 1.2m (approximately 4ft) - two arris rails per bay
• Up to 1.8m (6ft) - three arris rails per bay, one near the top, one in the middle, and one above the gravel board
• Taller or more exposed fences - three rails as a minimum, with additional bracing considered for very exposed sites

Spacing the rails evenly across the height of the bay distributes the load and keeps the featheredge boards from bowing over time. For long runs, we recommend fitting a centre stump to support the bottom arris rail - this prevents sagging and adds stability, particularly in softer ground or exposed positions. We stock centre stumps, which can be found here.

Choosing the Right Arris Rails

The right type of arris rail for your project depends on the spacing of your posts and how you plan to fix everything together.

Sizes, Lengths and Shaped Ends

We stock arris rails in three lengths:

• 2.4m - green, square cut ends
• 3.0m - with a choice of square cut ends or shaped ends for morticed posts; straight-end arris rails are available in green or brown, 
• 3.6m - green, square cut ends

Square cut ends suit installation using arris rail brackets fixed to the post face - suitable for both timber and concrete posts and ideal for DIY projects and repairs.

Shaped ends are specifically designed for use with morticed timber fence posts, where the shaped end slots directly into the pre-cut mortice hole in the post for a neat, bracket-free finish. Please note shaped ends are available on the 3.0m length only.

Brown arris rails are available on the 3.0m length only, with shaped ends. Green is available across all three lengths.

Pressure-Treated Arris Rails for Fencing That Lasts Years

Fencing timber spends its life outdoors in constant contact with the elements. That is why our arris rails are pressure-treated to help guard the timber against rot, fungi and insects. The pressure treatment works with the rail's angled top that prevents water pooling, ensuring a strong, reliable structure that lasts far longer than untreated timber and requires less maintenance.

Arris Rail Installation, Brackets and Fencing Accessories

V-notched posts with straight cut rails (most popular)

The most common and popular method. The straight cut end of the rail sits directly into the V-notch cut into the post, holding it firmly in place and creating a continuous, uninterrupted fence line with no brackets or visible metalwork at the joint. Simple, neat, and the go-to choice for most closeboard fencing projects.

Arris rail brackets with straight cut rails

Metal arris rail brackets fix to the face of the post and the straight-cut rail slots in. This is a flexible method that works with both timber and concrete posts, and is particularly useful for repairs where you need to replace a rail without disturbing the rest of the fence. We stock 12-inch arris rail brackets as our most popular option, and also sell bolt-on pairs which use less metal for a cleaner finish.

Shaped end rails for morticed posts

The shaped end of the rail slots directly into the pre-cut mortice hole in a timber or concrete morticed post. No brackets or nails are needed at the post end, giving a clean, traditional appearance with no visible metalwork. Please note that shaped end rails are available on our 3.0m length only.

Order Your Arris Rails From Timberstore

Whether you are building a new fence or repairing an old one, you will find arris rails, brackets and matching fencing accessories to suit the job here at Timberstore. All our arris rails are made from quality timber and pressure-treated to ensure their longevity. 

You'll always get our best price when you order through the Timberstore website, but our team is always happy to help you work out exactly what your project needs, so don’t hesitate to contact us if you need advice regarding your order.

You can call us on 01494 671 921, or email sales@timberstore.co.uk if no agent is available on the online chat. We deliver across South East England using our own fleet, covering Buckinghamshire, Berkshire, Oxfordshire, Hertfordshire, Greater London, Surrey, West Sussex, and Hampshire. If you are outside our delivery area, you are welcome to click and collect from our yard in Beaconsfield, HP9 2RX. Not sure how many rails you need or which option is right for your project? Just get in touch and we'll be happy to help.

Arris Rails FAQs

What is an arris rail?

An arris rail is a horizontal triangular timber rail fixed between fence posts to support the vertical featheredge boards in a closeboard fence. The rails carry the weight of the boards and keep them straight and secure, forming the structural backbone of the fence.

How many arris rails do I need per bay?

For a standard 6ft (1.8m) fence, three arris rails per bay is the recommended number - one near the top, one in the middle, and one just above the gravel board. For fences up to around 4ft (1.2m), two rails per bay is usually sufficient.

What lengths do arris rails come in? 

We stock arris rails in 2.4m, 3.0m, and 3.6m lengths. The 3.0m length is our most popular and is available in both green and brown, with a choice of square cut or shaped ends. The 2.4m and 3.6m lengths are available in green with square-cut ends.

What is the difference between arris and cant rails?

Both support featheredge fencing, but they have different profiles. An arris rail has a triangular cross-section, produced by cutting a 75x75mm square section timber diagonally in half. A cant rail is rectangular with a chamfered top edge. Arris rails are the standard choice for closeboard fencing across most of South East England - cant rails are more commonly seen in certain regions further north. We stock arris rails only.

What is a scarfed arris rail?

A scarfed arris rail is another name for a shaped end rail - the end is nicely shaped rather than square so that it slots neatly into a morticed post, creating a strong, tidy joint where the rail meets the post.

Do arris rails need treating?

All our arris rails are pressure treated as standard, so no additional treatment is needed before installation. However, always apply an end grain preservative to any cut ends after trimming to length, as the pressure treatment only penetrates the outer layer and freshly cut ends are vulnerable to moisture.

How do I replace a broken arris rail?

You don't need to dismantle the whole fence to replace a damaged arris rail. Remove the broken rail carefully, fit a pair of arris rail brackets to the posts on either side, and slot a new rail into place. It is a quick, straightforward repair that leaves the rest of your fence untouched. We stock arris rail brackets alongside our rail range, including brackets for concrete posts, which make replacing arris rails easy.

Do I need centre stumps for arris rails?

Centre stumps are recommended for longer bays to support the bottom arris rail at mid-span and prevent sagging over time. They are particularly useful on softer ground or in exposed positions where the bottom rail takes more load.