Strata plan: the registered plan that creates lots and common property

TL;DR

A strata plan is the registered survey plan that legally creates individual lots inside a multi-dwelling building, together with the common property those lots share. Lot boundaries run off the physical structure (typically the inner face of walls and the floor/ceiling surfaces), not pegs in the ground, so a late structural change during construction moves a boundary. At defects time, whether a defect is the lot owner’s problem or the owners corporation’s problem depends entirely on where the strata plan puts the boundary; waterproofing membranes, the slab, and external walls are almost always common property. Pull the plan before quoting remedial work on any strata building.

What a strata plan is

A strata plan is a registered plan of subdivision that divides a single title (typically a block of land with one or more buildings on it) into two or more privately owned lots, plus any areas designated as common property. Each lot becomes a separate title. The common property is owned collectively by all the lot owners through a body called the owners corporation (NSW, VIC), body corporate (QLD), or strata company (WA). That collective body is created automatically when the plan is registered (verified 2026-06-11: NSW Strata Schemes Management Act 2015 s.8; Strata Titles Act 1985 (WA) as amended by the Strata Titles Amendment Act 2018, Landgate registration guidance).

Strata plans exist in all Australian states but under different names and legislation:

State	Legislation	Name for the plan
NSW	Strata Schemes Development Act 2015	Strata Plan (SP)
VIC	Subdivision Act 1988	Plan of Subdivision (PS) with owners corporation lots
QLD	Body Corporate and Community Management Act 1997	Community Title Plan (CTP)
WA	Strata Titles Act 1985 (as amended 2018)	Strata Plan
SA	Community Titles Act 1996	Community Plan
TAS	Strata Titles Act 1998	Strata Plan

Victoria is the one state without a separately named “strata plan”: the same Plan of Subdivision instrument handles both land subdivisions and building (strata-style) subdivisions, with owners corporation lots noted on the PS (verified 2026-06-11: Land Use Victoria, plans of subdivision guidance).

How lot boundaries are defined

This is where strata plans differ from ordinary land subdivisions. Standard freehold lots are bounded by survey pegs in the ground; boundaries run from peg to peg and project vertically. Strata lots are bounded by reference to the building structure itself.

NSW (Strata Schemes Development Act 2015): The lot boundary is typically the inner face of perimeter walls and the upper surface of floors and underside of ceilings. The wall structure, slab, and ceiling structure are common property. The lot is the cubic airspace and the internal finishes (verified 2026-06-11: NSW LRS/Registrar-General’s Guidelines for Strata Schemes).

Victoria: Plans of subdivision must state whether each boundary lies along the interior face, exterior face, or median of the relevant structural element. “Interior face” means the boundary sits at the inner paintwork surface; the entire wall structure is common property. “Median” places the boundary at the centreline of the wall; each side owns half. “Exterior face” gives the lot owner the full wall structure. These notations appear as text on the PS (verified 2026-06-11: Subdivision (Registrars Requirements) Regulations 2011 (Vic), confirmed via industry commentary at lookupstrata.com.au).

Queensland: The Body Corporate and Community Management Act 1997 distinguishes two plan types. A building format plan defines lots by floors, walls, and ceilings within a multi-storey building. Boundaries in a building format plan run to the midpoint (median) of those structural elements. A standard format plan, used for townhouse-style ground-level lots, uses surveyed ground boundaries extending vertically; owner maintenance responsibility is significantly broader under a standard format plan (verified 2026-06-11: Queensland Government, body corporate format plans guidance).

Western Australia: A strata plan defines lot boundaries by reference to the building shown on the plan. Lot heights and depths are limited by the plan. The WA equivalent for ground-level side-by-side dwellings is the survey-strata plan, where boundaries are surveyed on the ground (as on freehold land) and buildings are not shown on the plan at all (verified 2026-06-11: Landgate, Strata in WA).

The practical read: unless the plan’s boundary notations say otherwise, treat the slab, all external walls, the roof structure, and the floors and ceilings between units as common property and therefore outside any single lot owner’s authority to alter.

The as-built accuracy problem

A strata plan is drawn from the as-built structure, not from design drawings. The surveyor measures the finished building, draws the lot boundaries off the physical walls and slabs, and lodges the plan for registration. This has two consequences for builders.

First, the plan cannot be completed or registered until construction is substantially finished. Sales are legally “off the plan” until registration; individual titles do not exist yet. Any material structural change after the plan is lodged (or after approval of the strata plan) means the plan must be corrected or redrawn, which is a significant cost and delay. The discipline this creates is valuable: the building must be built as designed because the plan is drawn off the finished structure.

Second, setout accuracy matters more on a strata job than on a freehold lot. A wall that moves 50 mm during construction may move a lot boundary and reduce a lot’s area below the design intention. On high-density schemes with many lots, cumulative tolerance drift compounds across floors. A surveyor engaged at setout (or at critical stage) to check structural positions against the approved strata plan drawings is money well spent compared to the cost of replanning and re-registering.

Strata plans and defects

Understanding the strata plan boundary is essential before pricing or quoting remedial or defect-rectification work on any strata building.

Who claims what depends on where the boundary is. Defects inside a lot (cracked internal plaster, a faulty exhaust fan) are the lot owner’s claim under the statutory warranties. Defects in common property (structural cracking, external waterproofing failure, facade defects) are the owners corporation’s claim. The owners corporation can bring statutory warranty claims against the original builder and developer as a successive owner in title (verified 2026-06-11: Sourceable, “Addressing Building Defects in Strata Schemes”).

Waterproofing is almost always common property. Original waterproofing on floors and external walls (under showers, on balconies, in basement slabs) is common property and the owners corporation’s responsibility to repair and maintain. In NSW this is reinforced by the Strata Schemes Management Act 2015. The most common serious defect category in recently surveyed strata buildings is waterproofing, affecting around 23% of buildings (verified 2026-06-11: industry survey data via CPR Facade Upgrades). A builder doing remedial waterproofing works on behalf of a single lot owner rather than the owners corporation is likely working without authority.

Strict time limits apply. Statutory warranty claims on common property defects run from the first interim occupation certificate. In NSW the Home Building Act 1989 applies a six-year period for major defects and two years for other defects. Miss the limitation period and the owners corporation loses the claim against the original builder, regardless of fault. Builders on large strata contracts should be familiar with when the limitation clock starts.

Strata plan vs survey-strata plan (WA) vs land subdivision

Three distinct instruments that new practitioners sometimes confuse:

A strata plan (or community title plan, depending on state) divides a building into cubic lots defined by the structure. Common property exists. An owners corporation or body corporate is created automatically.

A survey-strata plan (WA only) divides land into lots with surveyed ground boundaries, like freehold land, but with shared facilities. Lot boundaries are on the ground, not tied to a building. No building appears on the plan. Used for side-by-side townhouses and villas, not for apartments stacked vertically (verified 2026-06-11: Landgate, strata in WA).

An ordinary land subdivision (deposited plan in NSW, standard plan of subdivision in VIC, standard format plan in QLD) creates freehold lots with surveyed ground boundaries. No inherent common property. No body corporate.

The distinction matters at engagement: the plan type determines maintenance obligations, authority to work, approval processes, and who the builder is contracting with or answerable to on defects.

What can go wrong

Misidentifying lot vs common property before quoting. Quoting a waterproofing repair as a lot-owner scope job when the membrane is common property means the wrong party has engaged you and the owners corporation may not be bound by the work. Get a copy of the strata plan and the by-laws before pricing any strata remedial job.

Building past the approved plan without notifying the surveyor. If a structural wall moves during construction, the as-built survey will not match the design drawings and the plan must be corrected before registration. The cost and delay to correct a multi-floor discrepancy can be significant. Engage the strata surveyor at key stages, not just at completion.

Assuming owners corporation approval is optional. Work affecting common property (structural alterations, facade penetrations, changes to shared services, balcony waterproofing) requires owners corporation approval under the relevant state legislation, in addition to any council or certifier approval. The lot owner’s written instruction is not sufficient authority by itself.

Missing the defects limitation period. On new strata buildings, the clock starts at first occupation certificate issue, not at practical completion or settlement. Large multi-tower projects may have staggered certificates. Keep a register of the date of each certificate per building and work backwards from it to set internal review and notification triggers.

References

NSW Strata Schemes Management Act 2015, s.8 (owners corporation constitution), via NSW Legislation (verified 2026-06-11)
NSW Strata Schemes Development Act 2015, via NSW Legislation (verified 2026-06-11)
Subdivision (Registrars Requirements) Regulations 2011 (Vic), boundary notation requirements (interior face/exterior face/median), via Victorian legislation (verified 2026-06-11)
Queensland Government, Body Corporate: Standard format plan maintenance, via qld.gov.au (verified 2026-06-11)
Landgate, Strata in WA (strata plan vs survey-strata plan), via landgate.wa.gov.au (verified 2026-06-11)