Removing an old timber sleeper retaining wall is a job many Kiwi homeowners can tackle themselves — but it needs careful planning. The biggest risk isn't the wall itself; it's the soil behind it. Get that wrong and you could trigger a slip, damage neighbouring property, or undermine a structure. Here's how to do it safely.
Understand What You're Dealing With First
Before you lift a single sleeper, you need to understand what the wall is holding back. Retaining walls support retained soil, and removing that support — even temporarily — can cause the bank to slump or collapse.
Key questions to answer before you start:
- How high is the wall? Walls retaining more than 1.5 metres of soil generally require a building consent in New Zealand. Even if you're removing rather than building, check with your local council — some require consent for demolition of retaining walls above this height.
- Is there a structure, driveway, or boundary close to the top of the bank? If so, a geotechnical engineer's advice is strongly recommended.
- What are the sleepers made of? Older sleepers (pre-2000) may be treated with CCA (copper chrome arsenate), which contains arsenic. This is a health hazard and requires careful handling and proper disposal.
Always check with your local council before starting. You can find guidance on consent requirements at MBIE Building Performance.
Safety Gear and Hazardous Materials
Old railway sleepers and treated timber can contain hazardous chemicals. Before handling:
- Wear heavy-duty gloves, safety glasses, a P2 respirator mask, and long sleeves.
- Do not burn old treated sleepers — burning CCA-treated timber releases toxic fumes and is illegal in NZ.
- Contact your local council or a licensed waste contractor about disposal options for treated timber. It cannot go in a standard skip or green waste bin.
For health and safety guidance, refer to WorkSafe NZ.
Plan Your Soil Management Strategy
This is the most critical step. You must have a plan for the retained soil before you remove any sleepers.
- Bench or batter the bank — cut the bank back at a safe angle (typically 45° or less for most NZ soils, but this varies by soil type) before or as you remove the wall.
- Work in sections — never remove the entire wall at once. Take out a 1–2 metre section, manage the soil, then move along.
- Have fill or temporary support ready — in some cases, you may need to install a new retaining solution (timber, concrete block, or a planted batter) before fully removing the old wall.
- Check for drainage — old sleeper walls often have ag-pipe or weep holes behind them. Removing the wall can redirect water flow, so plan for this.
Tools and Equipment You'll Need
| Tool | Purpose |
|---|---|
| Reciprocating saw or chainsaw | Cutting through old sleepers and fixings |
| Wrecking bar / crowbar | Levering sleepers free |
| Sledgehammer | Breaking apart stubborn sections |
| Spade and mattock | Managing soil behind the wall |
| Wheelbarrow | Moving soil and debris |
| Excavator (hired) | Useful for larger walls — consider hiring |
You can hire tools and small excavators from Bunnings or Mitre 10, or through local hire companies.
Step-by-Step Removal Process
1. Mark services
Before any digging, call Dial Before You Dig (0800 248 344) to identify underground services — power, gas, water, and drainage lines are often buried near retaining walls.
2. Batter or bench the bank
Using a spade or small excavator, cut back the top of the bank to reduce the load on the wall before you start removing sleepers.
3. Remove the top course first
Always work top to bottom. Pry off the top sleeper, cut any tie-back rods or deadmen anchors (these run horizontally back into the bank), and work your way down course by course.
4. Cut and remove deadmen
Most sleeper walls have deadmen — horizontal sleepers buried into the bank to anchor the wall. Use a reciprocating saw to cut these flush, or dig them out if you need to reuse the space.
5. Manage soil as you go
As each course comes down, pull the soil back and re-batter the face. Don't let the bank overhang.
6. Dispose of materials responsibly
Stack clean untreated timber separately from treated timber. Treated timber must go to an approved disposal facility — check with your council.
Replacing the Wall
If you're putting up a new retaining wall, remember that walls over 1.5 metres typically require a building consent and may need to be designed by a Chartered Professional Engineer (CPEng). Walls under 1.5 metres may qualify as Schedule 1 exempt work under the Building Act — but always confirm this with your council first, as site-specific conditions (like proximity to boundaries or slopes) can change the rules.
When to Call a Professional
Call a licensed demolition contractor or builder if:
- The wall is over 1.5 metres high
- There are structures, fences, or a neighbouring property close to the top of the bank
- The soil is unstable, waterlogged, or has a history of movement
- You're unsure about the presence of CCA or other hazardous treatments
- The wall is near any underground services
A qualified geotechnical engineer should be consulted for any wall on a steep or unstable site. You can find experienced local demolition contractors and builders on tradedirectory.co.nz.
For guidance on licensed building work and what requires an LBP, visit Licensed Building Practitioners.
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