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Based on the following masonry construction standards, NZS 3604, NZS 4210, AS/NZ 2699. This appraisal covers the performance criteria for the Hydestone Schist Wall Cladding System when attached to a timber frame. The above mentioned Standards are specific about requiring a cavity of 40mm, this provides structural separation between the rigid masonry and the flexible timber frame.

A point to note is that the cavity battens and fibre cement backer board must be able to move independently of the wall frame. Any system that fixes the wall tie directly to either the timber wall framing or cavity battens that are securely fixed to the wall frame is inviting significant structural failure in an earthquake.

Weathertightness is provided by a minimum 40 mm cavity which is vented and drained at the bottom of the cavity and vented at the top with a minimum ventilation top and bottom are equivalent to 1000mm2 per lineal metre of wall.
This is very different to the requirements within NZBC Acceptable Solution E2/ AS1 for 20 mm cavities for fibre cement sheet. These 20mm cavities are designed to remain dry and handle incidental water only in the event of a weather tightness failure. In order to verify that Alternative Solution cladding systems incorporating a 20mm drained cavities meet the performance criteria of NZBC Clause E2, the system must be tested to the external moisture verification method E2/VM1. Masonry and stone veneer systems that meet the performance requirements of NZS 3604 and NZS 4210, ie incorporate a 40mm drained vented
cavity are not required to be subjected to this weathertightness verification testing.

Summary
Hydestone Schist Wall Cladding System meets the following performance criteria for stone veneer wall claddings.
There must be a minimum 40mm deep cavity for the masonry wall ties to perform their function
There must be a minimum of 40mm of flexible wall tie leg behind the veneer( ie the wall tie cannot be fixed a cavity batten.
There must be a minimum 40mm drained and ventilated ( NZS 3604) cavity which will manage weathertightness
Specific design must be carried out for the timber frame supporting walls where the veneer exceeds 220kg/m2