Design
What does a retaining wall design actually cover?
A design is the difference between a wall that was calculated and a wall that was guessed. It is also the thing Auckland Council assesses when a wall needs consent, so it is worth understanding what one contains before anyone starts digging.
Understand what a wall design covers and when one applies. SRW Auckland manages the whole project from the first site visit to the finished wall.
Source-led guidance
Published August 2026
Factual statements on this page are drawn from Auckland Council and MBIE published guidance. Neither organisation endorses SRW Auckland.
Before you read on. This page describes what a retaining wall design covers in general. It is not structural or geotechnical advice, and nothing here determines what any specific wall requires. That comes from a qualified engineer looking at the site.
01 / The short answer
A retaining wall design establishes what the wall must resist, and what has to be built to resist it.
A retaining wall design is the engineering work that turns a site into a buildable structure. It establishes the loads acting on the wall, selects a system capable of carrying them, and specifies the members, embedment, reinforcement and drainage needed to do it. It is produced by a qualified engineer.
The visible output is a set of drawings and calculations. The useful output is a wall that behaves the way it was assumed to behave, on the specific ground it sits on.
Design is also what makes consent possible. Where a wall requires building consent, Auckland Council is assessing a design, not an intention.
02 / Design inputs
What a retaining wall design has to account for.
Retained height, surcharge, ground conditions, groundwater, the slope above and below the wall, seismic demand, and what the wall is founded on. Change any one of these and the structure changes with it.
- Retained height
- The depth of ground being held back. Load rises faster than height does, so embedment, member sizes and reinforcement all increase disproportionately as a wall gets taller.
- Surcharge
- Any additional load on the ground behind the wall: a driveway, vehicle, pool, building or a second wall above. Surcharge adds to the design load and is invisible in a photograph.
- Ground conditions
- Bearing capacity, soil type, depth of undocumented fill and the presence of rock. This is what a geotechnical investigation establishes, and it is the input most often assumed rather than measured.
- Groundwater
- Water behind a wall generates pressure the structure has to carry. Design assumes the drainage works, which is why the drainage detail is part of the design rather than an accessory to it.
- Slope above and below
- Ground that keeps rising behind the wall increases load. Ground falling away in front reduces the passive resistance the embedded section relies on.
- Seismic demand
- New Zealand walls are designed for earthquake actions as well as static soil pressure. The demand depends on height, importance and the ground it sits on.
- Boundaries and services
- Where the wall sits relative to a boundary, and what is buried in the wall line, can constrain the form of the structure before any calculation begins.
03 / Design outputs
What a completed retaining wall design produces.
Drawings, structural calculations, a specification, and on a consented project a producer statement. Together these tell the builder what to build and tell Auckland Council why it works.
- Drawings
- Plan, elevation and section showing geometry, member sizes, spacings, embedment depth, reinforcement and the drainage detail.
- Calculations
- The structural check behind the drawings: loads, stability, member capacity and the assumptions each of those rests on.
- Specification
- Materials and workmanship, including timber treatment level, concrete strength, reinforcement grade, aggregate and geotextile.
- PS1, design
- A producer statement from the design engineer, provided where consent requires one. It is the engineer's statement about their own design work.
- Producer statements during construction
- Where required, further statements cover construction and construction review. These come from the parties who did that work, not from the designer.
04 / By wall system
How the design changes with the wall system.
A cantilever pole wall, a block wall, a poured concrete wall and a reinforced soil wall resist load in different ways, so the design work and the critical dimensions differ for each.
- Timber pole cantilever
- Poles embedded in concrete act as cantilevers. Embedment depth and pole spacing are the governing dimensions, and both come from the design rather than from a standard detail.
- H-beam and infill
- Steel beams embedded in concrete with timber or concrete infill spanning between. Beam size, spacing and embedment are the design outputs.
- Reinforced concrete block
- Blocks laid over a reinforced footing with vertical reinforcement and grout. Footing size, bar size and spacing govern.
- Poured concrete cantilever
- A reinforced stem on a footing, where the footing geometry does the stability work. Common where height or surcharge rules out simpler systems.
- Reinforced soil
- Geogrid layers build a reinforced block of soil behind a facing. Grid length, strength and vertical spacing are the design, and they extend well back behind the visible face.
05 / When it applies
When a retaining wall needs a design.
Design input is commonly relevant where a wall retains more than the exempt depth of ground, where it carries a surcharge, where ground conditions are poor or unknown, where it sits near a boundary or an existing structure, or where Council asks for it as part of a consent.
A commonly referenced exemption covers walls holding back no more than 1.5 metres depth of ground where there is no surcharge or additional load above. That is a starting point for the question, not an answer for a particular property.
Exemption from consent is also not exemption from building the wall properly. A wall that does not need consent still has to comply with the Building Code, and still fails if the drainage or the embedment is wrong.
Auckland Council makes the regulatory decision on every consent question. SRW engages and briefs the engineer, works the design through with them, and lodges the application.
Tell us about the site and what sits above the wall.
Share the address and what is happening. We work out the pathway, engage whoever the project needs, and deal with Auckland Council where consent applies.
06 / COMMON QUESTIONS
Common questions about design in Auckland.
Who produces the retaining wall design?
An independent qualified engineer. Engineering services are provided by independent qualified engineers, and SRW does not present itself as the engineer. SRW engages the engineer, briefs them on the site and the intended outcome, and works the design through to something buildable.
Do I have to find an engineer myself?
No. Where a project needs structural or geotechnical input, SRW engages and manages that relationship as part of the project, so you are not coordinating separate parties yourself.
Does a wall under 1.5 metres need a design?
Height alone does not settle it. A wall well under 1.5 metres can still need design input where it carries a driveway, a vehicle, a building or a steeper slope above it. The surcharge changes the question, which is why two walls of identical height can be treated differently.
What is a PS1?
A producer statement covering design. The design engineer provides it to state that the design work was carried out by them, and it is commonly submitted as part of a building consent application where the wall is engineered.
Can the design change once work starts?
It can, and the usual reason is that the ground differs from what was assumed. Undocumented fill and unexpected groundwater are the two that most often send a design back for revision.
How long is a design valid for?
A design is specific to a site, a wall geometry and a set of assumed conditions. Change the height, move the wall line, or add a driveway above it, and the design has to be revisited rather than reused.
A clear place to start
Tell us about the site and what sits above the wall.
Share the address, the situation and a short description. You do not need to know the wall system, consent pathway or engineering requirements.
Two short steps. We reply by email or phone.