Building Consent Site Plan for a Retaining Wall in New Zealand

A building consent site plan for a retaining wall in New Zealand needs to show where the wall will be built, how high it will be, what ground it will retain, how drainage will work, and whether the wall is close to boundaries, buildings, driveways, slopes, easements, or services.

Retaining walls are different from many simple backyard projects because they hold back soil. That means council may need to understand more than just the wall location. The site plan should help show the wall position, retained height, ground levels, nearby structures, drainage paths, and any loads above or behind the wall.

This guide explains what to show on a retaining wall site plan for building consent in New Zealand, when consent may be needed, and which details commonly cause council requests for more information.

Do You Need Building Consent for a Retaining Wall in New Zealand?

Sometimes yes, sometimes no. The answer depends on the wall height, retained ground, surcharge loads, site location, design, and whether the wall meets an exemption under the Building Act.

Building Performance explains that a building consent is generally not needed for a retaining wall that retains no more than 1.5 metres depth of ground and does not support any surcharge or additional load, such as vehicles. The same guidance says this exemption does not apply when the wall supports extra load, including vehicle driveways, parking spaces, swimming pools, buildings, other retaining walls, or sloping ground above the wall. Building Performance

The Can I Build It retaining wall tool also reminds homeowners that even if a project does not need building consent, it still must comply with the Building Code. Can I Build It

Because retaining walls can affect safety, drainage, neighbouring properties, and site stability, it is smart to check with council or a qualified professional before building.

What Is a Retaining Wall Site Plan?

A retaining wall site plan is a top-down drawing of your property showing the proposed wall location and the surrounding site details.

The site plan is not the same as a structural design. A structural or engineering drawing may show posts, footings, reinforcement, drainage behind the wall, wall section details, and calculations. A site plan shows where the wall sits on the property and how it relates to boundaries, slopes, drainage, buildings, driveways, easements, and access.

For a retaining wall, a site plan usually helps council understand:

• Where the proposed wall will be built
• How long the wall is
• How high the retained ground will be
• Whether the wall is near boundaries or structures
• Whether a driveway, building, pool, fence, or slope creates surcharge
• How water will drain behind or around the wall
• Whether easements, services, or stormwater features are affected

What Council Usually Needs to See

Each council can have its own building consent forms and drawing expectations, but retaining wall site plans usually need more detail than a basic sketch.

The SIMPLI Guide to Building Consent Application lists retaining wall details as an example of information that may be required, including the wall type, height of retained ground, relationship to the boundary, waterproof membrane, and proposed drainage. SIMPLI Guide to Building Consent Application

1. Property Boundaries and Dimensions

The site plan should show the full property outline, including the front, rear, and side boundaries. This helps council understand where the retaining wall sits on the section.

Boundaries are especially important if the wall is near a neighbouring property, a fence, a driveway, a shared accessway, or an easement.

What to Show

• Full lot outline
• Front, rear, and side boundaries
• Boundary dimensions where available
• Street frontage
• Lot and DP number if available
• Street name and property address

If the wall is close to a boundary, show the distance from the proposed wall to that boundary clearly.

2. Existing House and Structures

A retaining wall site plan should show the existing site layout, not only the wall. Council needs to see what is already on the property and what the wall may affect.

What to Show

• Existing house
• Existing garage, shed, sleepout, or carport
• Existing driveway and accessway
• Existing decks, patios, fences, or pools if relevant
• Existing retaining walls if any
• Existing trees or landscaping if relevant
• Existing stormwater pits, drains, or services if known

This helps council check whether the new wall will support or be affected by nearby structures or site features.

3. Proposed Retaining Wall Location

The proposed wall should be clearly labelled on the site plan. Do not show it as an unclear line without explanation.

Use a clear label such as “Proposed Retaining Wall.” If there are multiple wall sections, label each wall section separately.

What to Show

• Wall location
• Wall length
• Wall type or material, if known
• Whether the wall is timber, concrete, block, stone, gabion, or another system
• Whether the wall is straight, curved, stepped, or terraced
• Relationship to the house, driveway, fence, slope, or other structures

For example, the site plan might label the wall as “Proposed Timber Retaining Wall, 8.0m long, max retained height 1.5m.”

4. Wall Height and Retained Ground

Wall height is one of the most important retaining wall details. In New Zealand, the 1.5 metre threshold is important, but the height alone is not the only issue. Surcharge and site conditions matter too.

Building Performance gives examples where a retaining wall that exceeds 1.5 metres, or a wall that supports surcharge from a driveway, requires building consent. Building Performance

What to Show

• Maximum retained height
• Wall height along each section if it varies
• Existing ground level
• Proposed finished ground level
• Top and bottom of wall levels if available
• Where the wall steps up or down

If the wall height changes across the site, show the maximum height and label the different sections clearly.

5. Surcharge and Loads Above the Wall

A surcharge is an extra load above or behind the wall. This can make a retaining wall more complex and may mean a consent or engineering design is needed even if the wall is not very tall.

Common surcharge examples include:

• Driveways
• Parking areas
• Vehicles
• Buildings
• Swimming pools
• Other retaining walls
• Steep or sloping ground above the wall
• Large fences or structures on top of the wall

Building Performance says the 1.5 metre retaining wall exemption does not apply where the wall supports any surcharge or additional load, including vehicle driveways, parking spaces, swimming pools, buildings, other retaining walls, or sloping ground above the wall. Building Performance

What to Show

• Driveway or parking area above the wall
• Buildings or structures near the top of the wall
• Sloping ground behind the wall
• Fences on top of or near the wall
• Other walls above or below the proposed wall
• Distance from the wall to any surcharge load

If there is any chance of surcharge, it is safer to show the nearby feature clearly and ask council or an engineer whether extra design information is required.

6. Levels, Contours, and Slope

Retaining walls are usually built because the site has a level change. That means levels and contours can be very important.

A simple flat-site wall may need fewer level details. A wall on steep land, near a driveway, beside a house, or close to another wall may need more information.

What to Show

• Existing ground levels
• Proposed finished levels
• Contours if available
• Direction of slope
• Top and bottom of wall levels
• Height change across the wall
• Cut and fill areas if relevant

If council asks for a contour survey, levels plan, geotechnical report, or engineering design, a basic site plan may not be enough by itself.

7. Drainage Behind the Wall

Drainage is critical for retaining walls. Water pressure behind a wall can create serious structural problems if it is not managed properly.

The site plan should show where water will go and how drainage will be handled. More detailed retaining wall drawings may also be needed to show waterproofing, drainage metal, perforated drains, weep holes, outlet points, or stormwater connections.

What to Show

• Drainage fall direction
• Stormwater pits
• Drainage outlet or discharge point
• Drainage easements
• Overland flow paths if known
• Drainage behind the wall if shown on supporting details
• Connection to stormwater system if applicable

The SIMPLI guide specifically lists proposed drainage as part of retaining wall details that may be required for building consent. SIMPLI Guide to Building Consent Application

8. Easements, Services, and Restricted Areas

If the property has easements or services, they should be shown on the retaining wall site plan. Walls near underground services, drainage easements, or shared access areas can trigger extra review.

What to Show

• Drainage easements
• Sewer or stormwater lines
• Water, gas, or power services if relevant
• Shared access areas
• Restricted building areas shown on title or council records
• Distance from the wall to easements or services

If the wall crosses or sits near an easement, council may ask for more information or approval from the relevant authority.

9. Access for Construction and Maintenance

Retaining walls often need excavation, material delivery, drainage work, and sometimes heavy equipment. Access may matter, especially on narrow, steep, or rear-yard sites.

What to Show

• Existing driveway
• Construction access route if relevant
• Shared driveway or right of way if applicable
• Nearby parking or manoeuvring areas
• Access to the wall for future maintenance
• Street frontage and vehicle crossing if relevant

If construction access affects neighbouring land or a shared accessway, check what permissions or additional information may be needed.

10. North Point, Scale, Labels, and Legend

A retaining wall site plan should be clean and easy to read. The assessor should not have to guess what each line or symbol means.

What to Include

• North arrow or north point
• Scale or scale bar
• Street name
• Clear labels for existing and proposed work
• Legend for contours, wall line, drainage, easements, and boundaries
• Drawing title and date if useful

Simple labels such as “Existing Residence,” “Proposed Retaining Wall,” “Drainage Fall,” “Stormwater Pit,” and “Existing Driveway” make the drawing easier to review.

Other Drawings Commonly Needed for a Retaining Wall Consent

A site plan is important, but retaining walls often need more than a site plan. Depending on the wall height, surcharge, location, drainage, and soil conditions, council may request additional drawings or reports.

Common supporting documents include:

• Retaining wall elevations
• Wall sections
• Structural details
• Foundation or post details
• Drainage plan
• Engineering drawings
• Producer statement if required
• Geotechnical information if required
• Survey or contour plan
• Construction methodology if relevant

Building Performance’s guidance on retaining walls up to 3 metres in rural zones also shows that some larger retaining walls may involve Chartered Professional Engineer design or review, and certain location rules still apply. Building Performance

Common Retaining Wall Site Plan Mistakes

Retaining wall applications can be delayed when important site details are missing.

Common mistakes include:

• Wall location not clearly labelled
• Wall length not shown
• Wall height or retained height missing
• No levels or contours on a sloping site
• Surcharge from driveway, building, pool, or slope not shown
• Drainage behind the wall not explained
• Easements or services missing
• Boundary distances missing
• Existing structures not shown
• No north point or scale
• Site plan does not match engineering or wall detail drawings

Retaining Wall Site Plan Checklist Before Submitting

Before submitting a retaining wall site plan for building consent, check that it shows:

• Property boundaries
• Boundary dimensions where available
• Street name and frontage
• North point
• Scale or scale bar
• Existing house and structures
• Existing driveway and access
• Proposed retaining wall clearly labelled
• Wall length
• Wall height or retained ground height
• Wall type or material if known
• Setbacks to boundaries and structures
• Contours, levels, or slope direction if relevant
• Drainage behind or near the wall
• Stormwater discharge or connection point if relevant
• Easements and services if applicable
• Driveways, buildings, pools, fences, or slopes that may create surcharge
• Clear labels, legend, and drawing notes

Final Thoughts

A building consent site plan for a retaining wall in New Zealand should clearly show the proposed wall location, length, height, boundaries, setbacks, levels, contours, drainage, stormwater, easements, existing structures, access, north point, and scale.

The wall still needs to meet the Building Code and any applicable consent or local planning requirements. A clear site plan does not guarantee approval, but it helps council understand the proposal and can reduce requests for more information.

References

• Building Performance – Retaining walls up to 1.5 metres depth of ground
• Building Performance – Retaining walls up to 3 metres depth of ground
• Can I Build It – Retaining wall up to 1.5 metres
• Can I Build It – Retaining wall in a rural zone
• Building Performance – Check if you need consents
• SIMPLI – Guide to Building Consent Application