Yes, you can use landscape ties instead of sleepers for a retaining wall — but whether you should depends on the height of the wall, the load it needs to hold, and the materials involved. Both options have their place, and understanding the differences will help you make the right call for your project.
What Are Landscape Ties and How Do They Differ from Sleepers?
Landscape ties are typically smaller-dimensioned treated timber sections (often around 75 mm × 125 mm or similar), sold specifically for garden and landscaping use. Sleepers are heavier, larger-section timbers — traditionally railway sleepers, but now commonly new-sawn or recycled hardwood or treated pine in sizes like 200 mm × 75 mm or 200 mm × 100 mm.
The key differences come down to:
| Feature | Landscape Ties | Sleepers |
|---|---|---|
| Typical size | Smaller section (e.g. 75×125 mm) | Larger section (e.g. 200×75 mm or bigger) |
| Strength | Lower load capacity | Higher load capacity |
| Durability | Moderate (depends on treatment) | Generally longer-lasting |
| Cost | Usually cheaper | More expensive |
| Best use | Low garden edging walls | Taller or load-bearing walls |
When Landscape Ties Are a Suitable Choice
Landscape ties work well for low retaining walls — generally up to around 400–600 mm in retained height — where the wall is primarily holding back garden soil with no surcharge loading (no vehicles, structures, or heavy loads above). They're a practical, cost-effective option for garden terracing, raised garden beds, and gentle slope management.
For these modest applications, landscape ties are:
When Sleepers Are the Better Option
For walls retaining more than about 600 mm of soil, or where there is any surcharge loading (a driveway, building, or slope above), sleepers are generally the more appropriate choice due to their greater cross-sectional strength and durability. The larger timber section resists bending forces more effectively.
If you're building a wall that needs to handle significant lateral earth pressure, the lighter profile of landscape ties may not provide enough structural integrity over time.
NZ Building Consent — What You Need to Know
This is critical: in New Zealand, retaining walls over 1.5 metres in height require a building consent under the Building Act 2004. Walls under 1.5 m may be exempt under Schedule 1, but this exemption has conditions — for example, the wall must not be near a boundary, and it must not support any additional load such as a building or vehicle traffic area.
Always check with your local council before starting, as exemption conditions vary and some councils apply additional rules. You can find guidance on consent requirements at MBIE Building Performance.
For walls requiring consent, the design may need to be carried out or reviewed by a structural engineer, and construction may involve restricted building work requiring an LBP. Check with your council for the specific requirements. Find out more about LBPs at Licensed Building Practitioners.
Timber Treatment — Don't Cut Corners
Whether you use landscape ties or sleepers, the timber must be appropriately treated for ground contact. In New Zealand, timber in contact with soil must meet the relevant hazard class — typically H4 or H5 for ground contact situations, as per NZS 3640 (the standard for chemical preservation of round and sawn timber — confirm the current applicable standard with your timber supplier).
Using under-treated timber will lead to premature rot, structural failure, and potential safety hazards. Always check the treatment stamp on any timber you buy, and ask your supplier if you're unsure. PlaceMakers and other timber merchants can advise on the correct hazard class for your application.
Drainage Is Non-Negotiable
Regardless of whether you use landscape ties or sleepers, proper drainage behind the wall is essential. Without it, water pressure builds up in the retained soil (called hydrostatic pressure) and can push the wall over — often suddenly. A well-built timber retaining wall should include:
- A layer of free-draining aggregate (e.g. AP20 chip) behind the wall
- Weep holes or drainage gaps at the base
- Geotextile fabric to prevent soil migration into the drainage layer
For guidance on drainage and moisture management, BRANZ is an excellent NZ resource.
Installation Tips for Landscape Tie Walls
- Deadman anchors: For walls more than two or three courses high, install horizontal tie-backs (deadmen) running back into the slope to resist overturning.
- Stagger the joints: Like brickwork, offset each course so vertical joints don't line up.
- Secure each course: Use galvanised spikes or rebar to pin courses together.
- Set the first course below ground: Bury the base course to provide a stable footing.
When to Call a Professional
You should engage a qualified retaining wall builder or structural engineer if:
- The wall will retain more than 1.5 metres of soil
- There is any surcharge loading above the wall (driveway, building, slope)
- The ground is unstable, clay-heavy, or waterlogged
- You're unsure whether building consent is required
- The wall is near a boundary or public space
A professional will ensure the wall is designed and built to comply with the NZ Building Code and relevant standards, protecting both your property and your neighbours. You can find qualified local retaining wall builders on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
