Joining two fence rails end to end is one of the most common challenges in fencing, and doing it properly makes the difference between a fence that stays solid for decades and one that sags or fails within a few years. The golden rule is simple: always make your join at a post, never mid-span. Here's how to do it right.
Why the Join Location Matters
A fence rail is only as strong as its weakest point. If you join two rails in the middle of a span — away from any support — that joint will flex every time the fence is loaded by wind, animals, or people leaning on it. Over time it will crack, split, or pull apart. By contrast, a join made directly over a post transfers load straight into the ground, keeping everything rigid and stable.
Before you start, check whether your fence requires a building consent. Most standard residential boundary fences under 2 metres high are exempt under Schedule 1 of the Building Act, but rules vary by council and site. Always confirm with your local council before you begin — MBIE Building Performance has useful guidance on what work is exempt.
Method 1: Butt Join Over a Post (Most Common)
This is the standard method used by professional fencers across New Zealand.
- Cut both rail ends square so they meet cleanly in the centre of the post face.
- Each rail end should sit on at least half the post width — ideally 45 mm or more on a 90 mm post.
- Fix each rail end independently with two galvanised or stainless steel nails or screws per rail end, driven at a slight angle (skew-nailed) for extra grip.
- For a cleaner finish, use a rail bracket or timber connector plate over the join.
Tip: In NZ's variable climate — from wet Northland winters to dry Canterbury summers — timber expands and contracts significantly. Leave a 2–3 mm gap between the two rail ends to allow for movement and prevent buckling.
Method 2: Scarf Joint
A scarf joint involves cutting both rail ends at a matching angle (typically 45°) so they overlap when joined. This gives a larger gluing and nailing surface than a straight butt join.
- Still make this join over a post for support.
- Apply a weatherproof exterior wood adhesive before nailing.
- Skew-nail through both faces with galvanised nails.
Scarf joints look neater and are slightly stronger than a plain butt join, but they take more time and skill to cut accurately. They're a good choice for feature fences where appearance matters.
Method 3: Rail Splice Brackets (Metal Rails)
If you're working with steel or aluminium rails — common in pool fencing, Colorsteel-style fences, and modern slat fences — purpose-made splice connectors or joiner sleeves are the correct solution.
- Slide the sleeve inside both hollow rail sections so it bridges the join.
- Secure with self-drilling screws or pop rivets as specified by the manufacturer.
- Again, position the join over a post wherever possible.
For pool fencing specifically, NZ pool fencing must comply with NZS 8500:2006 and the Building Code clause F9. Always check that any joinery method you use meets the relevant standard — your local council or a licensed fencer can advise.
Method 4: Timber Connector Plates
Galvanised timber connector plates (sometimes called mending plates or rail joiners) are flat or angled metal plates that strap across a butt join. They're quick to install and add mechanical strength.
- Position the plate so it spans equally across both rail ends.
- Fix with the specified nails or screws (usually supplied or specified by the manufacturer).
- These are widely available at Bunnings and Mitre 10.
Connector plates work best as a supplement to a well-positioned butt join, not as a substitute for joining over a post.
Choosing the Right Fixings
In New Zealand's coastal and high-rainfall areas, using the wrong fixings is a common and costly mistake. Always use:
| Situation | Recommended Fixing |
|---|---|
| Inland, sheltered | Hot-dipped galvanised nails or screws |
| Coastal (within 500 m of sea) | Stainless steel (Grade 316) nails or screws |
| Treated timber (H3.2 or above) | Stainless steel or specifically rated galvanised fixings |
| Metal rails | Manufacturer-specified self-drilling screws or rivets |
Using standard bright steel fixings in treated timber or coastal conditions will cause rapid corrosion and staining. Check the BRANZ website for detailed guidance on fixing selection for NZ conditions.
Timber Treatment and Rail Selection
For ground-level or near-ground rails, use timber rated at least H3.2 (above ground, exposed). Rails that are close to the ground or in contact with soil need H4 or higher. Pinus radiata treated to the correct hazard class is the most common choice in NZ. Check with your supplier at PlaceMakers or your local timber yard.
Tips for a Neat, Long-Lasting Join
- Pre-drill near rail ends to prevent splitting, especially in dry or aged timber.
- Seal cut ends with an end-grain timber preservative before fixing.
- Space joins along a fence run so they don't all land on the same post — stagger them for better overall strength.
- Check that posts are plumb and set at the correct spacing (typically 1.8 m centres for standard residential fencing) before fitting rails.
When to Call a Professional
Most homeowners can tackle a straightforward fence rail join as a DIY project. However, consider hiring a qualified fencer if:
- Your fence is on a boundary with a neighbour (the Fencing Act 1978 may apply to cost-sharing and design).
- You're building or repairing a pool fence — this must comply with NZS 8500 and may require a building consent and inspection.
- The fence is on a retaining structure or on a steep or unstable site.
- You're unsure about consent requirements.
A skilled local fencer will get the job done quickly and correctly. You can find qualified fencing tradespeople in your area at tradedirectory.co.nz.
