What types of retaining walls can I build in 2025?
- romybromley
- Mar 21, 2023
- 7 min read
Updated: Jul 10
A Complete Guide for Homeowners, Builders, and Architects
Retaining walls are a critical piece of infrastructure in places like Wellington, where steep slopes, heavy rainfall, and earthquakes meet. Whether you're stabilising a slope, protecting a boundary, or excavating for a new build, the right retaining wall can make or break your project (literally).
In this article, we’ll walk you through the types of engineered retaining walls suitable for common site conditions and height ranges—from small 1.0m walls to complex systems over 3.0m. We also highlight when you’ll need expert help, and what’s changed in 2025.
New in 2025: DTCE now offers full design services for retaining walls over 3.0m, including ground anchors, geogrids, sprayed concrete, and more.
Related posts in the Retaining Wall Series
Choose the right Retaining wall type
To assist building owners and architects in making an informed choice, we've compiled a list of common retaining wall types and their strengths and weaknesses. Additionally, we've included a brief overview of the construction process for each type, as well as recommendations for different slope heights.
For easier navigation, click one of the three heights below to be taken to the specific section:
1.0m Cut Height
These wall types are often used for landscaping, driveways, and low boundary walls, and can be constructed with minimal machinery.
Engineered timber pole wall
Suitable for: landscaping walls, boundary walls, driveways
Cut height limits: 2.0m depending on site conditions
Pros: Fast to build, minimal maintenance, materials easily handled on-site
Cons: Not ideal for wetter soils or highly seismic areas -less rigid than block options
When to choose: You want something quick, affordable, and practical for small slope or driveway
Estimated cost: $350-$550/m^2
Construction Process:
Auger holes
Engineer construction monitoring site visit
Place timber poles in holes
Pour concrete foundation
Install lagging & drainage
Engineer construction monitoring site visit
Back fill
Engineered block wall with toe footing
Suitable for: subfloor walls, foundation walls, landscaping walls, boundary walls, driveways
Cut height limits: 2.5 - 3.0 meters depending on site conditions
Pros: High durability, integrates with foundations, easier to construct than heel footing if space constrained
Cons: Larger excavation required for fitting, not ideal if fill is limited
When to choose You're building next to a house or need a sturdy subfloor wall that ties to the foundation
Estimated cost: $500-$800/m^2
Construction Process:
Excavate foundation
Place foundation reinforcing
Engineer construction monitoring site visit
Pour concrete foundation
Layer blocks with wall reinforcing and install drainage
Engineer construction monitoring site visit
Fill the wall core with grout
Backfill
Engineered block wall with heel footing - 1.0m
Suitable for: sites that require a lot of fill i.e cut to fill sites
Cut height limits: 2.5-3.0m depending on site conditions
Pros: Reduces overall excavation size, good for cut-to-fill sites, strong overturning resistance
Cons: Reliable fill required, careful staging during construction, can interfere with underground services
When to choose: You have a cut-to-fill site and want a stable, efficient footing layout with strong performance Estimated Cost: $500-$800/M^2
Construction Process:
Excavate foundation
Place foundation reinforcing
Engineer construction monitoring site visit
Pour concrete foundation
Layer blocks with wall reinforcing and install drainage
Engineer construction monitoring site visit
Fill the wall core with grout
Backfill
2.0m Cut Height
Engineered timber pole wall
Suitable for: landscaping walls, boundary walls, driveways
Cut height limits: 2.0 meters depending on site conditions
Pros: Simple and cost-effective, Minimal excavation, Fast construction with common tools
Cons: Limited stiffness under lateral load, Timber deterioration risk, May require closer pole spacing
When to choose Ideal for accessible sites with average soil, and no seismic surcharge
Estimated Cost $400-$650/m^2
Construction process:
Auger holes
Engineer construction monitoring site visit
Place timber poles in holes
Pour concrete foundation
Install lagging & drainage
Engineer construction monitoring site visit
Back fill
Engineered block wall with toe, heel, and shear key - 2.0m
For taller cut heights or restricted footing space, heel and shear key may be necessary.
Suitable for: Basement walls, garage walls, and walls integral to building
Cut height limits: 2.5-3.0m
Pros: High structural performance, ideal for driveways, garages, or under houses, long design life
Cons: Requires more excavation, time consuming to build, concrete & blockwork trades needed
When to choose: Best for buildings, basements, or confined boundaries needing long term structural support
Estimated cost: $600-$900/m^2
This wall type has a relatively straightforward construction process:
Excavate footing, heel and shear key
Place foundation reinforcing
Engineer construction monitoring site visit
Pour concrete foundation
Lay blocks with wall reinforcing and install drainage
Engineer construction monitoring site visit
Fill the wall core with grout
Backfill
Non-engineered spray concrete wall - 2.0m
This wall type does not retain soil but can reduce the chance of a slip by keeping soil as dry as possible
Suitable for: a relatively cheap non-retained solution for exposed soil banks
Cut height limits: 2.0m
Pros: Low material cost, helps reduce erosion visually, good for quick stabilisation
Cons: Not a structural wall, requires regular drainage maintenance, requires specialist contractor
When to choose: Suitable for non critical slopes, where full retention is not required
Estimated Cost: $250-$400/m^2
Construction process:
Clear vegetation and contour the soil bank
Place mesh reinforcing and drainage
Engineer construction monitoring site visit
Spray concrete
3.0m+ Cut Height
Engineered timber pole wall with ground anchors - 3.0m
Ground anchors are needed for taller cut heights to prevent the wall from overturning, but can result in shallower foundations. Anchors crossing boundary lines will require consent from neighboring properties.
Suitable for: landscaping walls, boundary walls, driveway walls
Cut height limits: 3.0 meters
Pros: Allows for shallower footing, good for tight access
Cons: Consent from neighbour for anchors may be required. Requires specialty install
When to choose: Great for property boundaries with no room for heel or slab
Estimated cost: $600-$950
Construction process:
Augur holes
Engineer construction monitoring site visit
Place timber poles in holes
Pour concrete foundation
Install anchors and walers
Install lagging and drainage
Engineer construction monitoring site visit
Backfill
Engineered timber pole wall with ground geogrid - 3.0m
Suitable for sites that require a lot of fill i.e cut to fill sites
Suitable for: landscaping walls and driveway walls
Cut height limits: 3.0 meters
Pros: efficient where backfill is planned, uses passive resistance
Cons: Needs careful staging and compaction, fill needs to be engineered
When to choose: Best for cut-to-fill subdivisions or rural slopes
Estimate cost: $550-$850/m^2
Construction process:
Augur holes
Engineer construction monitoring site visit
Place timber poles in holes
Pour concrete foundation
Install lagging and drainage
Partially backfill to geogrid level
Install geogrid and walers
Engineer construction monitoring site visit
Complete backfill
Engineered timber pole wall with deadman - 3.0m
Suitable for: landscaping walls, boundary walls, and driveway walls
Cut height limits: 3.0 meters
Pros: Boundary consent requirement less likely, uses compacted soil
Cons: Difficult to handle on-site due to size of timber poles, can be disruptive to back yard
When to choose: Ideal where fill is available, and you want to avoid boundary anchors
Estimate cost: $550-$900/m^2
Construction process:
Augur holes
Engineer construction monitoring site visit
Place timber poles in holes
Pour concrete foundation
Install lagging and drainage
Excavate deadman
Place reinforcing for deadman
Engineer construction monitoring site visit
Pour concrete deadman
install walers
Backfill and fill overtop of deadman
Engineered sprayed and anchored wall - 3.0m+
Sprayed and anchor walls are typically used for taller cut heights exceeding 3.0m. Anchors crossing boundary lines will require consent from neighbouring properties.
Suitable for: Boundary walls
Cut height limits: over 3 meters
Pros: Excellent in tight sites or steep slops, strong seismic resistance
Cons: Expensive, requires specialist contractor and exposed steel maintenance
When to use: When you must retain tall banks in constrained space
Estimated cost: $950-$1400/m^2
Complex construction process:
Clear vegetation and contour the soil bank
Install anchors and anchor heads
Place mesh reinforcing and drainage
Engineer construction monitoring site visit
Spray concrete
Engineered block wall with pilasters - 3.0m+
Pilasters (reinforced block columns) are typically used for taller block walls to add strength. A heel and shear key may also be necessary to prevent overturning and sliding.
Suitable for: basement walls, garage walls, and walls integral to the building
Cut height limits: over 3 meters
Pros: High capacity, good for structures or garages
Cons: Heavy construction - High material and labour cost
When to use: For integral structure walls, like basements or retaining against homes
Estimated cost: $800-$1200/m^2
Construction process:
Excavate footing, heel, and shear key
Place foundation reinforcing
Engineer construction monitoring site visit
Pour concrete foundation
Lay blocks with wall reinforcing and install drainage
Fill the wall core with grout
Engineer construction monitoring site visit
Backfill
Pinned block wall with concrete slab - 3.0m+
Connecting block walls to a concrete floor slab and the top can allow the wall to be used for taller cut heights
Suitable for: basement walls, garage walls, and walls integral to the building
Cut height limits: over 3 meters
Pros: Strong integration with buildings, braced by slab for taller walls
Cons: Requires building co-ordination, less suitable for stand-alone walls
When to use: Optimal when the slab is part of the design anyway (garage & basement)
Estimated Cost: $850-$1300/m^2
Construction process:
Excavate footing, heel, and shear key
Place foundation reinforcing
Engineer construction monitoring site visit
Pour concrete foundation
Lay blocks with wall reinforcing and install drainage
Engineer construction monitoring site visit
Fill the wall core with grout and backfill
Place reinforcing slab for above
Engineer construction monitoring site visit
Pour concrete slab
Over 3.0m High? We've got you covered
Once a retaining wall exceeds 3.0m, it must be custom-engineered for both seismic and geotechnical stability. Our experienced team can now handle the entire design process in-house or collaborate with geotechnical consultants to develop the right solution for your site.
We also help you:
Identify when anchors, geogrid, or heel footings are needed
Avoid boundary and property conflicts
Navigate Building Consent requirements with local councils
Ensure long-term performance under earthquake and storm events
Choosing the Right Retaining Wall in 2025
"What type of retaining wall should i build?" depends on your cut heigh, soil type, site access, project use, and council requirements.
Let our structural and geotechnical engineers help you make an informed choice.
Contact us today for tailored retaining wall design within Wellington, Kapiti Coast, Levin, and Wairarapa.
Frequently Asked Questions
Q: What retaining wall type is best for Wellington?
A: Timber pole and masonry block walls are most common, but suitability depends on your slope height, soil type, and space availability. DTCE engineers can help recommend the best option for your site.
Q: Do I need consent for a retaining wall over 1.5m?
A: Yes. Most councils, including Wellington City, require Building Consent for walls over 1.5m or walls supporting structures, driveways, or boundaries.
Q: Can I build a 3m+ retaining wall without a geotechnical engineer?
A: No. For 3.0m+ walls, you’ll need a structural design supported by geotechnical input. DTCE can now offer full design services in-house.
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