Retrospective Certification & Performance Solutions for Unapproved Structures

Understanding Retrospective Building Certification in Queensland

Discovering that a building, extension, deck, shed, or conversion on your property was completed without prior council approval can cause major legal and financial stress. Unapproved building works frequently surface during property sales, conveyancing title searches, insurance claims after storm damage, or council compliance audits (Show Cause Notices). In Queensland, carrying out building work without approval is a breach of the Building Act 1975 and the Planning Act 2016.

Fortunately, you do not always need to demolish the structure. Retrospective Certification is the formal legal process where a licensed RPEQ (Registered Professional Engineer of Queensland) inspects the existing building, evaluates its structural adequacy against the National Construction Code (NCC) and Australian Standards, and provides the documentation required for a Private Building Certifier to grant retrospective approval.

How We Support Your Response to Council Show Cause & Enforcement Notices

If your local council (such as Brisbane City Council, City of Gold Coast, Logan City Council, or City of Moreton Bay) issues a Show Cause Notice, you typically have 20–30 business days to respond. Ostanes Engineering conducts urgent on-site structural inspections, performs engineering computations, and prepares an official Engineering Compliance & Rectification Report. We provide the engineering information that private certifiers and councils need to assess the work. Approval and enforcement decisions are made by the certifier and council, not by Ostanes Engineering.

Class 10a to Class 1a Dwelling Conversions

Converting a non-habitable garage, shed, or patio (Class 10a) into a habitable granny flat, studio, or extra bedroom (Class 1a) requires meeting building requirements that can include minimum ceiling height, slab moisture barrier (damp-proof membrane) provisions referenced in AS 2870, termite management, bracing and energy efficiency. Your certifier confirms which apply. We assess the structural aspects of the existing building and, where possible, look for options that avoid replacing concrete slabs or roof trusses.

Form 15 vs Form 12: What Certificates Do You Need?

Retrospective approval commonly involves two Queensland statutory documents, depending on your certifier’s requirements: Form 15 (Compliance Certificate for Building Design) certifying that the structural design and any required remediation work meet the NCC; and Form 12 (Aspect Inspection Certificate) issued following inspection of a specified aspect of the work, recording the engineer’s inspection findings for that aspect. It is not an approval for occupancy.

NCC Performance Solutions

When an existing structure cannot strictly meet “Deemed-to-Satisfy” (DTS) provisions of the Building Code (such as non-standard footing depths or boundary clearances), our Chartered Engineers develop custom Performance Solutions under the NCC. Through rigorous engineering calculations and risk analysis, we assess whether the structure can achieve equivalent safety and performance, to support your application to the certifier or council without assuming disruptive alterations are needed.