Installing a fence on a boundary with a significant height drop is more involved than a flat-ground job, but it's very achievable with the right approach. The two main methods — stepped fencing and raked (or raked-panel) fencing — each suit different situations, and your choice will affect how the fence looks, how much material you need, and how complex the build is.
Understand Your Site First
Before you buy a single post, walk the boundary and measure the total height drop over the fence run. Use a builder's level or a laser level and a tape measure to find the gradient. This tells you:
- How many steps you'll need (for a stepped fence)
- The angle of rake (for a raked fence)
- Whether retaining is required at any point
- How deep your posts need to be set
Also check for underground services — water, gas, and power lines can run close to boundaries. Call Dial Before You Dig (0800 248 344) before any digging.
Stepped vs Raked Fencing
| Feature | Stepped Fence | Raked Fence |
|---|---|---|
| Appearance | Horizontal panels, staircase look | Panels follow the slope |
| Gaps | Triangular gaps under each step | Minimal ground gaps |
| Complexity | Moderate | Moderate to higher |
| Best for | Timber palings, lapped boards | Timber, some metal systems |
| Pet/stock containment | Gaps need infilling | Better ground coverage |
Stepped fencing is the most common DIY approach in NZ. Each panel is set level, and the fence drops in increments — typically matching one or two paling widths per step. The triangular gap at the base of each step can be filled with a cut timber kick board or extra palings.
Raked fencing has the top and bottom rails cut or set at an angle to follow the slope. This works well with some timber styles and many steel/aluminium systems, but requires more precise cutting and framing.
Post Spacing and Depth on a Slope
On sloping ground, post spacing is measured horizontally, not along the slope. Standard spacing is 1.8 m to 2.4 m between posts, but reduce this on steep sections for extra strength.
Post depth is critical — a general NZ trade rule of thumb is to bury one-third of the total post length in the ground, with a minimum of 600 mm. On a slope, the downhill post is under more lateral load, so consider going deeper (750 mm or more) or using a concrete collar. Always use H4 or H5 treated timber for in-ground posts to meet NZ durability requirements and resist rot in our damp conditions.
Setting Posts on a Slope
- Mark post positions with pegs and string line along the boundary.
- Dig holes with a post-hole borer or manual bar and spade.
- Set each post plumb (vertically level) — not perpendicular to the slope.
- Backfill with concrete (a dry-mix concrete is fine for most residential fences) and allow to cure for at least 24–48 hours before attaching rails.
Rails and Infill
For a stepped fence, rails are set level between each pair of posts. For a raked fence, rails are cut at the slope angle. Use H3.2 treated timber for rails above ground.
Attach rails with galvanised or stainless steel fixings — never use untreated steel fasteners outdoors in NZ's coastal or high-humidity areas, as they'll rust and stain your timber quickly. Brands like Mitre 10 and Bunnings stock a good range of treated timber and appropriate fixings.
For palings or boards, work from the bottom up on each panel, keeping them plumb even if the rails are raked.
Retaining Considerations
If the height drop is significant — say, more than 300–400 mm over a short distance — you may need a retaining wall at the base of the fence rather than relying on the fence posts to hold back soil. Retaining walls over 1.5 m high generally require a building consent in NZ. Check with your local council, as requirements vary. MBIE Building Performance has guidance on when consents are required under Schedule 1 exemptions.
Never use a standard fence post as a retaining structure — they're not designed for that lateral earth load.
Boundary and Neighbour Rules
In NZ, the Fencing Act 1978 governs boundary fences shared with neighbours. Both parties generally share the cost of a sufficient fence, and you should give written notice before starting work. If there's a dispute, the Disputes Tribunal can help.
Check your local council's district plan for height limits — many residential zones limit boundary fences to 1.8 m or 2.0 m above the ground level on either side. On a sloping boundary, this can get complicated, so confirm with your council planner before you build. Some councils measure fence height from the higher ground level, others from the lower — this matters a lot on a steep site.
When to Call a Professional
Consider hiring a qualified fencer if:
- The height drop is more than 1 m over the fence run
- Retaining is needed alongside the fence
- The boundary is disputed or complex
- You're unsure about consent requirements
- The ground is rocky, unstable, or has poor drainage
A professional fencer will have the right equipment (post-hole borers, laser levels) and experience to handle tricky slopes efficiently. You can find qualified local fencers on tradedirectory.co.nz.
Safety note: Always wear appropriate PPE when digging and handling treated timber — gloves, safety glasses, and a dust mask when cutting H4/H5 timber. Check WorkSafe NZ for guidance on safe handling of treated timber products.
