How to Calculate Site Coverage on a New Zealand Site Plan

Site coverage measures how much of a property is covered by buildings when viewed from above. It is usually expressed as a percentage and is one of the main planning controls used to manage building bulk, open space, landscaping and the overall intensity of development.

Calculating site coverage on a New Zealand site plan looks simple: add the building footprints, divide that total by the relevant site area and multiply by 100. The tricky part is deciding exactly what counts as a building footprint and which land area should be used in the calculation.

Those definitions can vary between councils, zones and planning documents. A garage, covered patio, carport, large roof overhang or access leg may be treated differently depending on the rules applying to the property.

What Is Site Coverage?

Site coverage—also called building coverage in many district plans—is the proportion of a site covered by buildings or parts of buildings.

It is generally based on the horizontal footprint of the counted structures when viewed from directly above. It is not usually based on:

• The total internal floor area
• The combined area of every storey
• The number of bedrooms
• The usable floor space inside the building
• The volume or height of the building

A two-storey house with a 140m² ground-floor footprint will commonly contribute about 140m² to building coverage—not 280m²—unless another part of the building extends beyond the ground-floor outline.

Local definitions control the actual calculation. Auckland’s Unitary Plan, for example, defines building coverage as the part of the net site area covered by buildings and expressly includes accessory buildings, cantilevered portions and certain large eave or spouting projections.^[1]

Why Councils Limit Site Coverage

Site-coverage controls help manage the amount of development placed on residential land.

Depending on the zone, these controls can help preserve:

• Usable outdoor space
• Landscaped areas
• Separation between buildings
• Sunlight and outlook
• Space for trees and vegetation
• Stormwater infiltration
• Neighbourhood character
• Opportunities for future development

The permitted percentage varies. For example, Auckland’s Single House Zone has historically used a maximum building coverage of 35% of net site area, while other Auckland residential zones allow different percentages. Taupō District Council increased the permitted building coverage in most residential environments from 30% to 35%. These examples show why a percentage taken from another city—or even another zone in the same city—should not be applied to your property.^[2][3]

The Site Coverage Formula

The calculation involves three basic steps:

1. Add all building footprints that count under the applicable planning definition.
2. Confirm the correct site-area figure—often the net site area.
3. Divide the counted footprint by the site area and multiply by 100.

Worked Example From the Featured Image

The featured site plan uses the following example:

200 ÷ 650 × 100 = 30.77%

Rounded site coverage = 30.8%

If the relevant planning rule permitted a maximum of 35%, this example would sit 4.2 percentage points below that limit.

35% − 30.8% = 4.2 percentage points remaining

That does not necessarily mean another 4.2% can automatically be developed. Setbacks, recession planes, landscaped-area requirements, impervious-area limits, outdoor-living requirements, easements and drainage constraints may restrict further building.

Site Coverage Versus Floor Area

Site coverage and floor area measure different things.

Example

A two-storey dwelling could have:

• A ground-floor footprint of 120m²
• An upper floor of 90m²
• A gross floor area of approximately 210m²
• A building-coverage contribution of approximately 120m², plus any separately counted projections

Site Coverage Versus Impervious Area

These calculations are related but should not be confused.

A property can comply with the permitted building coverage while exceeding its maximum impervious area because of extensive concrete, paving or parking.

Site Coverage Versus Landscaped Area

Landscaped-area requirements usually identify the amount of the site that must remain in grass, plants, trees or another qualifying landscape treatment.

The three calculations may therefore operate together:

• Building coverage: how much land is covered by buildings
• Impervious area: how much land cannot readily absorb rainfall
• Landscaped area: how much qualifying planted or landscaped space remains

Do not assume that everything outside the building footprint automatically qualifies as landscaped area. Driveways, artificial surfaces, swimming pools, narrow strips and covered spaces may be excluded or treated differently.

What Usually Counts Toward Site Coverage?

The following structures commonly count, but the exact local definition must be checked.

1. Main House Footprint

The main house is normally the largest component of the calculation.

Use the footprint shown on the coordinated architectural or roof plan. Depending on the local definition, the counted area may include:

• External wall footprint
• Attached garage
• Covered entrance
• Verandahs
• Roofed outdoor living areas
• Cantilevered upper-floor areas
• Qualifying eave projections

Do not simply use the internal floor area from a real-estate listing or construction estimate. Internal area and planning footprint are not necessarily the same.

2. Attached and Detached Garages

Garages normally count because they are buildings or parts of buildings.

Include:

• An attached internal-access garage
• A detached garage
• A workshop incorporated into a garage
• Storage areas beneath the same roof
• Covered connections where included by the local definition

A detached garage should not be overlooked simply because it is separated from the dwelling.

3. Carports

A carport is roofed and supported by posts or another structural system. It will commonly count as a covered structure even though its sides are open.

Use the horizontal roofed area rather than merely the area between the posts when the roof extends beyond them.

4. Covered Patios and Verandahs

A roofed patio or verandah commonly contributes to building coverage because it occupies covered land.

Show:

• The complete roof projection
• Supporting posts
• Connection to the house
• Outside dimensions
• Total counted area

The featured image counts the 16m² covered patio. That is a reasonable educational example, but the final treatment must follow the applicable district-plan wording.

5. Pergolas

The treatment of pergolas can be less straightforward.

Factors that may affect the calculation include:

• Whether the overhead structure is open or solid
• The spacing of the rafters or battens
• Whether louvers can close
• Whether retractable roofing is installed
• Whether the structure meets the district-plan definition of a building
• Whether it is attached to another building

An open timber pergola may be excluded under one plan but counted under another definition. A louvered pergola that closes to form a weatherproof roof is more likely to be treated as covered.

6. Roof Overhangs and Eaves

Eaves are a classic source of mistakes because different plans can use different thresholds.

For example, Auckland’s current definition includes any part of the eaves or spouting that projects more than 750mm horizontally from the exterior wall. The amount counted is determined under that specific definition.^[1]

Do not apply Auckland’s 750mm threshold automatically in another district.

The site plan should show:

• The external wall line
• The roof or eave outline
• The projection dimension
• The portion included in the calculation

7. Cantilevered Upper Floors

An upper floor that extends beyond the ground-floor wall can cover additional land when viewed from above.

Examples include:

• An upper-storey bedroom projecting over a patio
• A cantilevered bay
• A room above an open parking space
• A building bridging over a pedestrian route

Where the definition includes overhanging or cantilevered building areas, the site-coverage outline should follow the outer projection rather than only the foundations.

8. Balconies and Elevated Decks

Balconies and elevated decks may be counted depending on whether they are covered, enclosed, cantilevered or included within the local definition of building coverage.

Show their complete outlines and identify:

• Whether the area below is open
• Whether there is a roof above
• Whether the deck is attached or freestanding
• The height above the ground
• The council definition used

9. Sheds and Other Accessory Structures

A small shed can still count even when it does not require building consent.

Building-consent exemptions and planning rules are separate. MBIE advises owners to check district-plan requirements such as maximum site coverage even where the building work itself is consent-exempt.^[4]

Include existing:

• Garden sheds
• Tool sheds
• Storage buildings
• Sleepouts
• Studios
• Detached workshops

10. Rainwater Tanks and Utility Structures

The treatment of tanks, plant enclosures and utility structures varies.

A large tank or enclosed pump house may be treated as an accessory building under some provisions, while smaller equipment may be excluded or specifically exempted.

Check both:

• The general building definition
• The building-coverage definition
• Any zone-specific exclusions
• Rules applying specifically to water tanks or infrastructure

What Usually Does Not Count?

The following items often do not count as building coverage when they are open and uncovered, but they may affect other calculations:

• Uncovered driveways
• Open parking spaces
• Uncovered paths
• Uncovered ground-level patios
• Garden and lawn areas
• Swimming-pool water surface
• Low open decks in some districts
• Fences and ordinary boundary walls
• Landscaping

What Is Net Site Area?

Many district plans calculate coverage against the net site area rather than the gross area shown on the record of title.

Net site area commonly means the usable portion of the site after excluding certain land. Possible exclusions can include:

• An access leg serving a rear site
• A right of way
• Land used for shared vehicle access
• Land subject to certain designations
• Land that belongs to another legal site
• Other areas specifically excluded by the district-plan definition

The definition varies. Never subtract an accessway or easement merely because it looks unusable. Some easement land remains part of the net site area, while particular access strips may be excluded under the applicable plan.

Gross Site Area Versus Net Site Area

Rear-site example

Suppose a property contains:

• Gross title area: 720m²
• Qualifying access leg excluded under the plan: 70m²
• Net site area: 650m²
• Total counted buildings: 200m²

720m² − 70m² = 650m² net site area

200 ÷ 650 × 100 = 30.8% coverage

Using the gross area instead would produce:

200 ÷ 720 × 100 = 27.8%

That three-percentage-point difference could incorrectly make a non-compliant proposal appear compliant.

How to Measure an Irregular Building Footprint

Most houses are not perfect rectangles. Divide the footprint into simple shapes and calculate each area separately.

For example, an L-shaped house could be divided into:

• Main rectangle: 12m × 10m = 120m²
• Side wing: 4m × 5m = 20m²
• Covered entrance: 2m × 3m = 6m²

120 + 20 + 6 = 146m²

Alternatively, calculate the large outside rectangle and subtract any open courtyard or notch:

Complete rectangle − open area = building footprint

Computer-aided drafting software can calculate irregular areas accurately, but the base dimensions and coverage boundary must still be correct.

How to Calculate Coverage for an Existing House Addition

An addition calculation must include the buildings already on the site—not only the proposed extension.

Example

• Existing house: 145m²
• Existing detached garage: 32m²
• Existing shed: 9m²
• Proposed house addition: 28m²
• Net site area: 600m²

145 + 32 + 9 + 28 = 214m²

214 ÷ 600 × 100 = 35.7%

If the permitted maximum were 35%, the proposal would exceed it by approximately 0.7 percentage points.

How to Calculate the Maximum Permitted Building Area

You can reverse the formula to estimate the maximum permitted building footprint.

Example

For a 650m² net site with a 35% maximum:

650 × 0.35 = 227.5m²

If existing counted buildings total 200m²:

227.5 − 200 = 27.5m² theoretical remaining coverage

The word theoretical is important. The remaining 27.5m² may not fit within the permitted setbacks, recession planes or usable part of the property.

Can You Round the Result?

Show enough precision to demonstrate compliance clearly.

A result of 34.96% should not casually be described as 35% when the permitted maximum is exactly 35%, especially if the dimensions are preliminary or rounded.

Good practice is to:

• Use accurate source dimensions
• Calculate areas without early rounding
• Show the final result to one or two decimal places
• Retain the full calculation in the working file
• Leave a reasonable design margin below the maximum where possible

Minor construction changes, thicker walls or revised eaves can move a project over the limit when it is designed exactly to the maximum.

How Site Coverage Should Be Shown on the Site Plan

A clear site plan should include both the graphic footprint and the calculation.

Show:

• The complete legal site boundary
• Any area excluded from the net site calculation
• Existing buildings
• Proposed buildings
• Structures to be removed
• The counted footprint of each structure
• A distinct hatch or colour for counted areas
• The net site area
• The total counted building area
• The calculated percentage
• The maximum percentage permitted by the relevant rule

Example Site Coverage Schedule

Existing Buildings Must Be Included

A new project is assessed together with the buildings already occupying the site.

Commonly overlooked existing structures include:

• Old sheds
• Detached garages
• Carports
• Sleepouts
• Covered decks
• Lean-to storage areas
• Pool houses
• Previous additions

Even unconsented or undocumented buildings may physically contribute to site coverage. Their legal and consent status may need to be investigated separately.

Structures to Be Demolished

A structure that will be removed as part of the proposal can generally be excluded from the proposed completed-site calculation, provided the drawings clearly show its demolition.

A useful schedule can distinguish:

• Existing coverage
• Coverage being removed
• New proposed coverage
• Final total coverage

Example

• Existing buildings: 210m²
• Shed to be removed: −18m²
• Proposed addition: +25m²
• Completed total: 217m²

Cross-Lease Properties

Coverage calculations on cross-lease properties can be confusing because an owner may use only part of the land while sharing the underlying legal site.

Depending on the applicable planning definition, the calculation may need to consider:

• The complete underlying site
• Every dwelling on the property
• All garages and accessory buildings
• Common areas
• Exclusive-use areas
• Any access land excluded from net site area

Do not calculate coverage using only one owner’s fenced garden unless the district plan expressly requires that approach.

Read Site Plan Requirements for Cross-Lease Properties in New Zealand.

Unit Titles and Multi-Unit Developments

For unit-title and multi-unit developments, the calculation can depend on whether the planning site comprises:

• The entire development
• A legally separate allotment
• A parent site before subdivision
• Several amalgamated titles
• A proposed future lot

The planning rules, subdivision status and consent conditions should be reviewed before choosing the denominator.

Subdivision and Proposed Lots

A new house may be designed for a proposed lot that does not yet have its own title.

In that case, the calculation should coordinate with:

• The approved or proposed subdivision plan
• Net lot area
• Access lots and rights of way
• Consent notices
• Building platforms
• Existing buildings to remain
• Any staged development conditions

Do not use the original parent-title area when the house will eventually occupy a smaller proposed lot.

Rural and Large-Lot Properties

Rural properties may have lower maximum coverage percentages even though the land area is much larger.

The calculation may need to include:

• Dwellings
• Garages
• Barns
• Farm sheds
• Covered yards
• Commercial or rural-industry buildings
• Other structures included by the zone definition

Some agricultural structures may have special rules or exclusions. Check the rural-zone provisions rather than applying a residential-zone definition automatically.

What Happens if the Proposal Exceeds the Limit?

Exceeding the permitted maximum can trigger resource consent unless another planning pathway or exemption applies.

Possible responses include:

• Reducing the house footprint
• Adding a second storey instead of expanding outward
• Removing an old shed or garage
• Reducing a covered patio
• Changing a solid-roofed structure to an open feature where appropriate
• Reducing large roof projections
• Reconfiguring accessory buildings
• Applying for resource consent

Whether resource consent is granted depends on the applicable plan, the activity status and the effects of the additional coverage.

Building Performance confirms that a project may require resource consent under the district or regional plan even where its building-consent position is otherwise straightforward.^[5]

Does a Building Consent Check Site Coverage?

Building consent and resource consent address different laws.

The building consent authority assesses the proposed work against the Building Code. The council’s planning process assesses matters such as:

• Site or building coverage
• Boundary setbacks
• Height
• Recession planes
• Landscaped area
• Impervious area
• Outdoor living space

The applications may be reviewed together administratively, but building consent does not override a planning-rule breach.

Common Site Coverage Calculation Mistakes

Using gross title area without checking net site area

An access leg or another area may need to be excluded under the district-plan definition.

Counting only the proposed building

Existing houses, garages, sheds and covered structures must also be assessed.

Using internal floor area

Coverage is generally based on horizontal building footprint, not usable room area.

Counting both storeys

Upper floors usually count only where they extend beyond the footprint already counted below.

Leaving out a detached garage

Accessory buildings commonly contribute to total coverage.

Ignoring covered patios and carports

Open-sided structures can still be buildings or covered areas under the plan.

Measuring between support posts

The counted footprint may follow the outer roof or building projection rather than the post centres.

Ignoring cantilevered areas

An upper floor or bay that projects over open ground may add coverage.

Applying another council’s eave rule

Projection thresholds and exclusions vary between plans.

Confusing coverage with impervious area

Driveways and uncovered patios may not be buildings but can still count as impervious surfaces.

Using outdated district-plan rules

Planning provisions and zone standards can change. Confirm the current legally relevant version.

Rounding too early

Rounding every individual area can distort the final result on a proposal close to the maximum.

Not identifying demolished buildings

Show clearly which structures are retained, removed and proposed.

Providing only a percentage

Include a schedule showing how the numerator and denominator were calculated.

Site Coverage Checklist

• Confirm the property address and legal description
• Identify the applicable zone and overlays
• Read the current building-coverage definition
• Read the current net-site-area definition
• Confirm the permitted maximum percentage
• Obtain accurate site dimensions
• Show the complete legal boundary
• Identify excluded access or other land where applicable
• Measure all existing buildings
• Measure all proposed buildings
• Include accessory buildings
• Check covered patios, verandahs and carports
• Check eaves and cantilevered areas
• Identify structures to be demolished
• Prepare a coverage schedule
• Calculate without early rounding
• Show the final percentage clearly
• Compare the result with the permitted maximum
• Check landscaped and impervious-area rules separately

Information to Gather Before Ordering a Site Coverage Plan

• Property address
• Record of title
• Lot and deposited-plan details
• Existing survey or site plan
• Legal site area
• Access-leg or right-of-way information
• Applicable zone
• Current district-plan coverage definition
• Existing house dimensions
• Garage, carport and shed dimensions
• Proposed floor plans
• Proposed roof plan
• Covered patio and verandah dimensions
• Eave and cantilever projections
• Structures proposed for demolition
• Driveway and paved-area dimensions
• Any council planning advice
• Previous resource-consent documents
• Photographs of the property

Order a Site Coverage Plan in New Zealand

NZ Site Plan can prepare a clear property drawing showing the legal boundaries, existing and proposed buildings, counted building footprints, net site area and a detailed site-coverage schedule.

Depending on the information supplied, the plan can show:

• The main dwelling footprint
• Garages, sheds and accessory buildings
• Carports and covered outdoor areas
• Roof and eave projections
• Existing, proposed and demolished structures
• Access legs and relevant site exclusions
• Total counted coverage area
• Net site area
• Calculated coverage percentage
• Impervious and landscaped areas where requested

The drawing can be prepared using an existing survey, record-of-title information, council mapping, architectural plans, measurements and photographs supplied by the property owner or designer.

Where exact legal boundaries, planning interpretation, cadastral certification, architectural design or resource-consent assessment is required, those services must be obtained from the appropriate surveyor, planner or other qualified professional.

Frequently Asked Questions

What is the formula for site coverage?

Add the building footprints that count under the applicable district plan, divide the total by the relevant site area and multiply by 100.

Is site coverage calculated using gross or net site area?

Many plans use net site area, but the applicable definition must be checked. Do not assume the gross title area is the correct denominator.

Does a garage count?

Yes, garages commonly count as buildings, whether attached or detached.

Does a carport count?

It commonly does because it is a roofed structure, but confirm the local definition.

Does a covered patio count?

Covered patios and verandahs commonly count. The exact treatment depends on the district plan.

Does an uncovered patio count?

It may not count as building coverage, but it can count toward impervious-area calculations.

Does a driveway count?

An uncovered driveway does not usually count as a building footprint. It may count as impervious area and affect stormwater or landscaped-area compliance.

Do eaves count?

That depends on the applicable definition and the projection distance. Auckland, for example, includes eaves or spouting projecting more than 750mm.

Does a pergola count?

It depends on its construction and the district-plan definition. Solid-roofed or closable pergolas are more likely to count than open overhead frameworks.

Does an upper storey count twice?

No. It generally adds coverage only where it projects beyond the footprint already counted beneath it.

Do small consent-exempt sheds count?

They can. Building-consent exemption does not automatically exempt a structure from planning controls such as site coverage.

What is the maximum permitted coverage?

There is no single nationwide percentage. The maximum depends on the council, property zone and applicable planning provisions.

What happens if I exceed the limit?

You may need to revise the proposal or apply for resource consent, depending on the activity status and applicable plan.

Can I calculate coverage from an aerial image?

An aerial image can help with preliminary planning, but it may not provide sufficiently accurate boundaries, roof outlines or dimensions for a final council calculation.

Can NZ Site Plan confirm the planning interpretation?

NZ Site Plan can prepare the drawing and calculation using the information and applicable requirements supplied. Formal planning interpretation or resource-consent advice should be obtained from the council or a qualified planner where needed.