Building Consent Site Plan for a Shed Extension in New Zealand

A building consent site plan for a shed extension in New Zealand should show the existing shed, the proposed extension, the total shed size after the extension, and how the structure relates to boundaries, the house, drainage, stormwater, easements, services, access, north point, and scale.

A shed extension can seem like a small backyard project. But once you add more floor area, change the roof, move closer to a boundary, add services, or change the use of the shed, council may need clearer information. A site plan helps show what exists now, what is being added, and whether the completed shed still fits the relevant consent or exemption pathway.

This guide explains what to show on a shed extension site plan in New Zealand and how to avoid common drawing mistakes that can delay council review.

Do You Need Building Consent for a Shed Extension in New Zealand?

It depends on the total shed size after the extension, the shed design, the intended use, the height, the floor level, the location, and whether the work meets an exemption under the Building Act.

Building Performance explains that a building consent is not required for a single-storey detached building between 10 and 30 square metres where the design or construction work is carried out or supervised by a Licensed Building Practitioner. It also says that if an existing single-storey detached building is being extended, the maximum total net floor area cannot exceed 30 square metres for that exemption. Building Performance

Can I Build It also lists common shed conditions, including that the shed must not exceed 30 square metres in floor area, must be one storey, must not exceed 3.5 metres above the floor level, and must not contain plumbing or facilities for storing drinking water. Can I Build It

The simple rule for homeowners is this: do not only measure the new extension. Measure the existing shed plus the proposed extension together. The completed shed size is what matters.

Why a Shed Extension Site Plan Matters

A shed extension site plan shows where the shed sits on the property and how the proposed extension changes the site layout.

The site plan is different from a shed floor plan or elevation. A floor plan shows the internal layout, doors, windows, wall layout, and dimensions. An elevation shows the side view, roof pitch, height, cladding, doors, and windows. A site plan shows where the shed and extension are located on the land.

For a shed extension, the site plan usually helps council understand:

• Where the existing shed is located
• Where the proposed extension will be added
• The total shed footprint after the extension
• How close the shed is to property boundaries
• Whether roofwater, drainage, or stormwater will change
• Whether easements or underground services are nearby
• Whether the shed remains a simple shed or is being used differently

What Council Usually Needs to See

Each council may have its own forms, checklists, and district plan rules. Still, most shed extension site plans should include the same core information.

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 existing shed and proposed extension sit on the section.

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 shed extension is close to a side or rear boundary, show the distance clearly. Boundary setbacks are one of the first things reviewers look for.

2. Existing Shed and Existing Site Layout

A shed extension site plan should show the existing shed, not only the new extension. Council needs to see what is already there before reviewing what will change.

What to Show

• Existing shed footprint
• Existing house
• Existing garage, carport, deck, patio, or other structures
• Existing driveway and access route
• Existing fences or retaining walls if relevant
• Existing trees or landscaping if relevant
• Existing stormwater pits, drains, or service locations if known

This is especially important if the shed extension is near the house, another outbuilding, a boundary, a driveway, or underground services.

3. Proposed Shed Extension Location

The proposed shed extension should be clearly labelled. Council should be able to tell the difference between the existing shed and the new extension immediately.

What to Show

• Proposed shed extension footprint
• Connection to the existing shed
• Extension length and width
• New roof outline if relevant
• New doors or windows if relevant
• Relationship to boundaries, the house, access, and drainage

Use shading, hatching, or a dashed outline to separate the proposed extension from the existing shed. A clear label such as “Proposed Shed Extension” helps avoid confusion.

4. Existing Shed Size, Extension Size, and Total Floor Area

For a shed extension, the total floor area after the extension is critical. Do not only show the size of the new addition. Show the size of the existing shed and the completed shed.

What to Show

• Existing shed length and width
• Proposed extension length and width
• Existing floor area
• New extension floor area
• Total shed floor area after extension

Building Performance says the net floor area of a single-storey detached building is limited to a maximum of 30 square metres for the relevant exemption, and if an existing building is extended, the maximum total net floor area cannot exceed 30 square metres. Building Performance

If the completed shed will exceed 30 square metres, building consent is more likely to be required.

5. Shed Height and Floor Level

Shed height can affect both building consent and planning checks. The floor level can also matter, especially if the shed is on sloping ground, raised piles, or a platform.

What to Show

• Existing shed height if known
• Proposed extension height
• Maximum height above floor level
• Finished floor level if available
• Ground levels or contours if the land slopes
• Any step-down or level change between existing and proposed areas

Can I Build It says a shed must be one storey, not exceed 3.5 metres above the floor level, and have a floor level not exceeding 1 metre off the supporting ground for the listed shed pathway. Can I Build It

6. Setbacks to Boundaries and Other Structures

Setbacks are the distances from the shed extension to property boundaries, the house, other buildings, easements, and services. Missing setbacks are a common reason for council requests for more information.

Setbacks to Show

• Distance from shed extension to side boundary
• Distance from shed extension to rear boundary
• Distance from shed extension to front boundary if relevant
• Distance from shed extension to the house
• Distance from shed extension to other structures
• Distance from shed extension to easements or services if applicable

LBP guidance on the newer building consent exemptions says single-storey detached buildings up to 30 square metres can be affected by boundary setback rules, and LBPs must still check local district plans and Resource Management Act requirements. Licensed Building Practitioners

7. District Plan Setbacks and Planning Rules

Building consent and planning rules are not the same thing. A shed extension may be exempt from building consent but still need to comply with local district plan rules.

Building Performance says homeowners should check with the local council for district or regional planning implications, including site coverage, yard or setback requirements, daylight access planes, and permitted activities. It also notes that resource consent may be required and should be obtained before starting work. Building Performance

Dunedin City Council’s planning checklist for simple residential buildings says the site plan should show the entire site, including legal property boundaries, site area, north point, underground services, easements, and District Plan yard setbacks. Dunedin City Council

8. Intended Use of the Shed

The use of the shed matters. A garden shed, storage shed, workshop, machinery shed, sleepout, office, or hobby room can trigger different questions.

Uses to Label Clearly

• Garden storage
• Tool shed
• Workshop
• Storage room
• Sleepout
• Home office
• Machinery shed
• Pool equipment shed

Building Performance says buildings that include bathroom and kitchen facilities cannot be built using the small detached building exemptions, and any buildings that include plumbing require building consent. Building Performance

If the shed extension changes the use of the building, be clear in the application. A storage shed extension is usually different from a sleepout, office, or building with plumbing.

9. Doors, Windows, and Access

The site plan should show important access details, especially if the shed extension changes how people enter the shed or move around the property.

What to Show

• Existing shed door location
• New door location if relevant
• Window locations if relevant
• Access path from the house or driveway
• Vehicle access if the shed stores equipment or machinery
• Clearance around the shed extension

If the shed extension is used as a workshop, sleepout, office, or storage area with frequent access, council may need more detail than for a simple garden shed.

10. Roof Area, Roofwater, and Stormwater

A shed extension usually adds roof area. That means roofwater and stormwater should be considered before submitting.

What to Show

• Existing shed roof outline
• Proposed roof extension outline
• Roof fall direction
• Gutters and downpipes if applicable
• Stormwater pits if known
• Stormwater connection points
• Drainage fall direction
• Drainage easements if applicable

Building Performance says homeowners need to consider Building Code requirements for disposal of stormwater from the roof, seek professional guidance and council approval, and use an authorised drainlayer for new drains. Building Performance

11. Easements, Services, and Underground Pipes

If the property has easements or underground services, they should be shown on the shed extension site plan. Posts, slabs, foundations, roofwater pipes, and drainage work can affect underground services.

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 shed extension to easements and services

Building Performance says homeowners need to confirm the location of underground services that could affect the build, including drains, electricity, gas, and telecommunications. Building Performance

12. Levels, Contours, Cut, Fill, and Foundations

Some shed extensions are built on simple flat ground. Others are built on sloping sites, near retaining walls, or over areas that need cut and fill.

What to Show if Relevant

• Existing ground levels
• Proposed finished floor level
• Contours if available
• Areas of cut or fill
• Retaining walls near the shed
• Foundation or slab location
• Drainage fall around the shed

SIMPLI says site-specific information is required if the building envelope is being extended, and asks whether land has been cut or filled or whether cut/fill is proposed. SIMPLI Guide to Building Consent Application

13. Existing and Proposed Plans

For a shed extension, it is helpful to show both the existing layout and the proposed layout. This makes the change clear.

Existing Site Plan Should Show

• Existing house
• Existing shed
• Existing driveway and access
• Existing structures
• Existing drainage, easements, and services where relevant
• Boundaries, north point, scale, and street frontage

Proposed Site Plan Should Show

• Everything important from the existing site plan
• Proposed shed extension clearly labelled
• Extension dimensions
• Total shed floor area after extension
• Setbacks to boundaries and structures
• Roofwater, drainage, access, and service changes where relevant

This is where many homeowners make mistakes. They submit only the proposed shed extension and leave out the existing shed, total size, boundaries, and setbacks.

14. North Point, Scale, Labels, and Legend

A shed extension site plan should be 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, setbacks, drainage, easements, and proposed extension
• Drawing title and date
• Revision number if the plan has been updated

Good labels can prevent simple delays. Use labels such as “Existing Residence,” “Existing Shed,” “Proposed Shed Extension,” “Stormwater Pit,” “Drainage Fall,” “Boundary Line,” and “Easement.”

Other Drawings Commonly Needed for a Shed Extension

A site plan is important, but it may not be the only drawing needed. Depending on the shed size, use, location, structure, roof, and services, council may request extra drawings or supporting documents.

Common supporting documents include:

• Existing shed plan
• Proposed shed floor plan
• Elevations
• Sections
• Roof plan
• Foundation or slab details
• Door and window details if relevant
• Drainage or stormwater plan
• Engineering details if required
• Product specifications for kitset or prefabricated sheds
• LBP or engineer documentation if relying on a specific exemption pathway

The SIMPLI guide lists different plan types that may be required for building consent applications, including site plans, floor plans, elevations, sections, drainage drawings, and other details depending on the project. SIMPLI Guide to Building Consent Application

Common Shed Extension Site Plan Mistakes

Shed extension applications can be delayed when the plan is unclear or incomplete.

Common mistakes include:

• Existing shed not shown clearly
• Proposed shed extension not labelled
• Only the extension area is shown, not the total shed area
• Shed dimensions are missing
• Setbacks to boundaries are missing
• Height or floor level is not shown where relevant
• Roofwater and stormwater are not shown
• Easements or services are missing
• Use of the shed is unclear
• Doors, windows, or access points are missing
• No north point or scale
• Site plan does not match the floor plan, elevations, or kitset drawings

Shed Extension Site Plan Checklist Before Submitting

Before submitting a shed 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 and structures
• Existing shed clearly labelled
• Proposed shed extension clearly labelled
• Existing shed size
• Extension size
• Total shed floor area after extension
• Shed height and floor level if relevant
• Setbacks to boundaries and structures
• Doors, windows, and access points if relevant
• Drainage and stormwater details
• Easements and services if applicable
• Levels, contours, cut, fill, or retaining walls if relevant
• Clear labels, legend, and notes
• Plans match all supporting documents

When a Site Plan Alone Is Not Enough

A site plan shows where the shed extension sits on the property. It does not prove every structural, drainage, fire, durability, or Building Code detail.

Council may also need information about:

• Foundations or slab design
• Wall and roof framing
• Wind zone and bracing
• Roof cladding and roof pitch
• Connections to the existing shed
• Fire spread near boundaries
• Durability of materials
• Stormwater disposal
• Use of the shed as storage, workshop, sleepout, or office
• Professional design, LBP supervision, or engineering

If council asks for engineering, specifications, product documents, or drainage design, a basic site plan will not replace those documents.

Final Thoughts

A building consent site plan for a shed extension in New Zealand should clearly show the existing shed, proposed extension, total shed area after extension, boundaries, setbacks, dimensions, height, floor level, access, roofwater, drainage, stormwater, easements, services, north point, and scale.

The most important details are usually the completed shed size, distance to boundaries, intended use, roofwater disposal, and whether the extension still fits a building consent exemption. If the total shed area exceeds 30 square metres, if plumbing is added, if the use changes, or if the shed is close to boundaries or services, council may need more information.

A clear site plan does not guarantee approval, but it makes the proposal easier to understand and can reduce requests for more information.

References

• Can I Build It – Shed
• Building Performance – Check if you need consents
• Building Performance – Single-storey detached buildings not exceeding 30 square metres
• Building Performance – Notes for single-storey detached buildings
• Licensed Building Practitioners – New building consent exemptions
• Dunedin City Council – Planning information checklist for simple residential buildings
• SIMPLI – Guide to Building Consent Application