There is no longer any strict definition regarding what is considered to be "working at heights"; the onus is now on both workers and supervisors to minimise the likelihood of a fall from any height.
In Western Australia, it was previously the case that a person was considered to be working at heights in accordance with WA Occupational Safety and Health Regulations 1996, Part 3, Division 5, 3.55 and the WorkSafe WA code of Practice: The Prevention of Falls at Workplaces.
Regardless, certain obligations remain. Firstly, contractors must supply a Job Safety Analysis (JSA) to the responsible officer before any works start.
Further, all work at heights that requires use of a harness must be performed by someone with a current Work Safely at Heights certificate, and two or more people must be present. Scaffolds and scaffolding equipment must meet AS/NZS 1576 and the WA Occupational Safety & Health Regulation 1996 / Section 3.72 Inspection and marking of certain scaffolds. As well:
All ladders must comply with relevant Australian Standards and be positioned and used as described in the WorkSafe WA Code of Practice: The Prevention of Falls at Workplaces.
For example:
All necessary precautions must be taken by the contractor to protect people and property from falling objects, debris and tools before overhead work starts and at all times during work.