Note: this guideline is issued by the Surveyor-General under section 7(1)(ga) of the Cadastral Survey Act 2002 about the Rules for Cadastral Survey 2010 and is not legally binding.

The following information relates to the use of a stratum boundary to define the vertical extent of a parcel, the requirements for witnessing and referencing a stratum boundary, and the definition of height covenants including where the height restriction is defined in a legal document.

A stratum boundary may be a surface that is:

  • mathematically defined, or 
  • defined by the surface of a water body or by the bed of a water body (eg the bed of Lake Taupo).

Ground level not a stratum boundary

Ground level is not an appropriate description for a stratum boundary.

Mathematical description of a stratum boundary

A stratum boundary that is mathematically described must have at least one point with a reduced level [r 6.8(a)].

The boundary must be unambiguously defined [r9.6.15(a)]; for example, reduced levels must not conflict with declinations or elevations or, in the case of unit developments, be confused with permanent structure boundaries.

Figure 1: A stratum boundary with a mathematical description
Diagram showing stratum boundaries with reduced levels
Figure 2: Stratum boundaries with reduced levels

Stratum boundaries - witness marks and PRMs

For all mathematically defined stratum boundaries:

  • all new stratum boundary points must be witnessed [r 7.3.1].  There must be a minimum of three witness marks for class A and four witness marks for class B [r 7.3.2(c)],
  • at least one witness mark must have a reduced level [r 7.3.4], and
  • there must be at least two PRMs with reduced levels [r 7.4.1 and r 7.4.3(d)].

Height covenants

A parcel to be subject to a height restriction is required to be depicted as non-primary parcel. This parcel must be defined in the horizontal sense, but is not required to be defined in the vertical sense, ie. not include a stratum boundary. It is presumed that the instrument creating the restriction will define the height of the restriction in the manner determined by the parties.

A CSD may define the height of a restriction by stratum boundary, but if it does, the CSD must comply with the rules for defining stratum parcels (refer to 'Stratum boundaries -witness marks and PRMs' above).

Alternatively, where it is intended that registered documents define the height of the covenant (ie. the CSD is not intended to define a stratum boundary), the CSD may include information about the height of a restriction as supporting information (eg reduced levels on marks, datum information, or the survey report expressing an intention to restrict a right).

In this case, the Diagram of Survey, the Diagram of Parcels and supporting information must not depict a stratum boundary in any form or show annotations that seek to describe the height restriction.

An existing covenant stratum boundary may be adopted except where the boundary is a class A parcel less than 0.4ha [r 6.2(a)(iv)].

Where the boundary is adopted, the information on the source CSD that defines the extent of the boundary must be included in the new CSD and related diagrams. This includes the height origin, level and source [r 8.1(f)], bench marks, heights and heighted boundary marks [r 9.6.10].

Last Updated: 30 March 2017
Authority: Surveyor-General - Section 7(1)(ga) of the Cadastral Survey Act 2002
LINZ OP G : 00031