NZ SITE PLAN
A building consent site plan for a deck extension in New Zealand should show where the existing deck is, where the new deck extension will go, how high it will be above the ground, and how it relates to the house, boundaries, stairs, access, drainage, easements, and nearby structures.
A deck extension can look simple, especially if you are only adding more outdoor living space. But council may still need enough information to understand whether the deck needs building consent, whether barriers or handrails are required, how close the extension is to boundaries, and whether the work affects drainage, privacy, sunlight, access, or the existing house.
This guide explains what to show on a deck extension site plan in New Zealand and how to avoid common drawing mistakes that can slow down a building consent application.
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Order a clear New Zealand site plan showing your existing deck, proposed extension, deck dimensions, height above ground, setbacks, stairs, drainage, easements, nearby structures, north point, and scale.
Do You Need Building Consent for a Deck Extension in New Zealand?
It depends mainly on the fall height and the design. Building Performance explains that a building consent is not required for decks, platforms, bridges, boardwalks and similar structures where it is not possible to fall more than 1.5 metres. Building Performance
The Can I Build It deck tool also says that before starting work, the deck must not exceed 1.5 metres in height to fit that pathway. It also reminds homeowners that even if building consent is not required, the work must still comply with the Building Code. Can I Build It
If your deck extension is higher, complex, attached to the house in a structural way, close to a boundary, includes stairs or barriers, changes drainage, or affects other site features, it is worth checking with your local council before building.
Why a Site Plan Matters for a Deck Extension
A site plan helps council understand the deck extension in relation to the full property. It is not the same as a deck framing plan, joist layout, or construction detail. A site plan shows where the deck sits on the land.
For a deck extension, the site plan usually helps show:
- Where the existing deck is located
- Where the proposed deck extension will be added
- How large the new deck area will be
- How high the deck is above the ground
- How close the deck is to boundaries
- Where stairs, landings, and access points are located
- Whether barriers, handrails, or guards may be required
- Whether drainage, easements, or services are affected
If the plan does not show these items clearly, council may ask for more information before the application can continue.
What Council Usually Needs to See
Each council can have different forms, checklists, and application requirements. Still, most deck extension site plans should show the same core details.
The SIMPLI Guide to Building Consent Application says a site plan is normally used for external or structural work and should show boundary dimensions, north point, finished floor levels, ground contours or levels, site area, street name and number, lot and DP number, building outline, distances to boundaries, and wind zone. SIMPLI Guide to Building Consent Application
1. Property Boundaries
The site plan should show the full property outline. This helps council understand where the deck extension sits on the section and whether it is close to neighbouring properties.
What to Show
- Full lot outline
- Front, side, and rear boundaries
- Boundary dimensions where available
- Street frontage
- Street name and property address
- Lot and DP number if available
If the deck extension is close to a side or rear boundary, the distance should be labelled clearly on the drawing.
2. Existing House and Existing Deck
A deck extension site plan should show the existing house and the current deck. Council needs to see what is already there before assessing the proposed addition.
What to Show
- Existing residence
- Existing deck footprint
- Existing stairs or landings
- Existing doors opening onto the deck
- Existing patio, paving, or outdoor living areas
- Existing garage, shed, driveway, or structures nearby
- Existing retaining walls, fences, or landscaping if relevant
This is especially important when the deck extension connects to an existing deck, wraps around the house, changes stairs, or sits near a boundary.
3. Proposed Deck Extension Location
The proposed deck extension should be clearly labelled. Do not leave council guessing which part of the deck is existing and which part is new.
What to Show
- Proposed deck extension footprint
- Connection to the existing deck
- Connection to the existing house, if applicable
- Location of new posts or supports if relevant
- Relationship to stairs, doors, paths, and outdoor areas
- Relationship to boundaries and neighbouring properties
Use shading, hatching, or a dashed outline to separate the proposed deck extension from the existing deck. A simple label such as “Proposed Deck Extension” can prevent confusion.
4. Deck Extension Dimensions
The proposed deck extension should include clear dimensions. Council may need to know the length, width, total added area, and overall deck size after the extension.
What to Show
- Length of the new deck extension
- Width of the new deck extension
- Total new deck area if requested
- Overall deck size after the extension
- Distance from deck edge to nearby structures
- Dimensions that match the floor plan or construction details
If the site plan says the extension is 5.0m x 3.0m, the construction drawings and specifications should match that size.
5. Deck Height Above Ground
Deck height is one of the most important details. In New Zealand, the 1.5 metre fall height is a key building consent threshold for decks and platforms.
Building Performance also says decks and balconies more than 1.5 metres above the ground need a building consent, and they must be maintained throughout their life. Building Performance
What to Show
- Height of the existing deck above ground
- Height of the proposed deck extension above ground
- Maximum fall height
- Finished deck level
- Ground levels or contours if the land slopes
- Steps or level changes between the house, deck, and ground
If the deck height varies because the land slopes, show the highest fall point clearly.
6. Setbacks to Boundaries and Structures
Setbacks are the distances from the deck extension to property boundaries, buildings, easements, or other structures. Missing setbacks are a common reason councils ask for more information.
Setbacks to Show
- Distance from deck extension to side boundary
- Distance from deck extension to rear boundary
- Distance from deck extension to front boundary if relevant
- Distance from deck extension to garage, shed, retaining wall, or fence
- Distance from deck extension to easements or services if applicable
Setback rules can vary by council, zone, deck height, privacy effects, sunlight access, and district plan controls. Always check local requirements before submitting or building.
7. Stairs, Landings, and Access
If the deck extension includes new stairs, altered stairs, or a new landing, show them clearly on the site plan. Access points are important because they affect how people move between the house, deck, yard, driveway, and outdoor areas.
What to Show
- Existing stairs
- Proposed stairs
- Landings
- Doors opening onto the deck
- Paths to the yard or driveway
- Changes to access around the house
If the deck is high, steep, or complex, council may need separate stair details, sections, handrail details, and barrier information.
8. Barriers, Handrails, and Guards
Deck extensions may need barriers or guards depending on the fall height and layout. A site plan can show where barriers are located, but detailed barrier design may need separate drawings.
Building Performance’s barrier design guidance covers barriers to decks, stairs, landings, and other areas where a fall of one metre or more may occur. Building Performance
What to Show
- Barrier or handrail location
- Open edges of the deck
- Stair handrail location if relevant
- Guard line around raised deck areas
- Access gates if applicable
- Separate barrier details if required
If the deck is raised, do not leave open edges unclear. Council may need to confirm where fall protection is provided.
9. Posts, Footings, and Structural Support
A deck extension usually needs structural support. The site plan may not show every construction detail, but it should show the deck location clearly enough to connect with the structural drawings.
What to Show
- Post locations if required
- Footing locations if required
- Connection to existing deck framing if relevant
- Connection to the house if attached
- Relationship to drains, services, paving, or retaining walls
For higher, larger, or more complex deck extensions, council may ask for engineering details, bracing information, pile details, joist layout, bearers, fixings, and connection details.
10. Drainage and Stormwater
A deck extension can change how water moves around the house, especially if it covers ground, changes paving, connects near the house, or is built over drainage lines.
What to Show
- Drainage fall direction
- Stormwater pits if known
- Drainage lines if known
- Downpipes near the deck
- Surface water flow around the deck
- Drainage easements if applicable
- Clearance around existing drainage features
The SIMPLI guide lists plumbing and drainage drawings as a plan type for new or altered drainage, including drainage layout, stormwater indication, inspection bends, junctions, on-site drainage, and council mains. SIMPLI Guide to Building Consent Application
11. Easements and Services
If the property has easements or services, they should be shown on the deck extension site plan. Posts, footings, stairs, and framing can create issues if they are too close to drainage, sewer, stormwater, power, gas, water, or access easements.
What to Show
- Drainage easements
- Sewer or stormwater lines if known
- Water, gas, power, or fibre services if relevant
- Shared access areas
- Restricted building areas shown on title or council records
- Distance from deck posts or deck edge to easements and services
If the deck extension is close to an easement or underground service, council may ask for more information or a different layout.
12. Privacy, Sunlight, and Neighbour Effects
Decks can affect neighbours more than some other small projects because they create outdoor living space. A raised deck may overlook neighbouring yards, windows, or private outdoor areas.
What to Show if Relevant
- Deck height near boundaries
- Distance to neighbouring boundaries
- Privacy screens if proposed
- Stairs or platforms near neighbouring properties
- Existing fences or landscaping
- Orientation and north point
Christchurch City Council notes that decks require building consent where it is possible to fall more than 1.5 metres and recommends checking before starting work. Its residential activity guidance also points homeowners to planning/property checks where decks and fencing may be involved. Christchurch City Council
13. North Point, Scale, Labels, and Legend
A deck extension site plan should be clear and easy to read. The reviewer should not have to guess what each line, shaded area, 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 boundaries, proposed deck, existing deck, setbacks, drainage, and easements
- Drawing title and date
Good labels can prevent simple delays. Use labels such as “Existing Residence,” “Existing Deck,” “Proposed Deck Extension,” “Proposed Stairs,” “Boundary Line,” and “Drainage Fall.”
Other Drawings Commonly Needed for a Deck Extension
A site plan is important, but a deck extension may need more than a site plan. Council may request additional drawings depending on deck height, size, complexity, barriers, stairs, and structural connections.
Common supporting drawings include:
- Existing deck plan
- Proposed deck floor plan
- Deck elevations
- Sections through the deck
- Post and footing details
- Bearer and joist layout
- Connection details to the house or existing deck
- Stair details
- Barrier or handrail details
- Engineering details if required
The SIMPLI guide lists different plan types that may be required for building consent applications, including site plans, floor plans, elevations, sections, bracing plans, drainage plans, and other details depending on the project. SIMPLI Guide to Building Consent Application
Common Deck Extension Site Plan Mistakes
Deck extension applications can be delayed when important site details are missing or unclear.
Common mistakes include:
- Existing deck not shown clearly
- Proposed deck extension not labelled
- Deck extension dimensions missing
- Deck height above ground not shown
- Setbacks to boundaries missing
- Stairs, landings, or access points unclear
- Barriers or open edges not shown
- Drainage, services, or easements missing
- Existing structures not shown
- No north point or scale
- Site plan does not match deck construction drawings
Deck Extension Site Plan Checklist Before Submitting
Before submitting a deck extension site plan, check that it shows:
- Property boundaries
- Boundary dimensions where available
- Street name and frontage
- North point
- Scale or scale bar
- Existing house
- Existing deck
- Existing stairs, doors, and access points
- Proposed deck extension clearly labelled
- Deck extension length and width
- Deck height above ground
- Maximum fall height
- Setbacks to boundaries and structures
- Proposed stairs, landings, and access changes
- Barriers, guards, or handrails if relevant
- Post or footing locations if required
- Drainage and stormwater details if relevant
- Easements and services if applicable
- Clear labels, legend, and notes
When a Site Plan Alone Is Not Enough
A site plan shows where the deck extension sits on the property. It does not prove the deck structure, barriers, stairs, fixings, and foundations comply with the Building Code.
Council may also need information about:
- Structural framing
- Piles and footings
- Joists and bearers
- Deck bracing
- Connection to the existing house
- Barriers and handrails
- Stairs and landings
- Timber treatment and durability
- Drainage and ground clearance
- Engineering, if the deck is high, large, or complex
If council asks for engineering details, barrier design, sections, or structural drawings, a basic site plan will not replace those documents.
Final Thoughts
A building consent site plan for a deck extension in New Zealand should clearly show the existing deck, proposed deck extension, boundaries, setbacks, deck dimensions, deck height above ground, stairs, landings, access, barriers, drainage, easements, existing structures, north point, and scale.
The most important items are usually the deck height, fall risk, dimensions, setbacks, and connection to the existing house or deck. If it is possible to fall more than 1.5 metres from the deck, building consent is likely to be required. Even when consent is not required, the deck still needs to comply with the Building Code.
A clear site plan does not guarantee approval, but it helps council understand the proposal and can reduce requests for more information.
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