Retrospective Certification & Performance Solutions for Unapproved Structures
Bought, built, or modified a structure without council approval? Our Chartered RPEQ engineers inspect existing buildings, resolve council Show Cause notices, and issue certified Form 15 / Form 12 documentation for prompt legal compliance across Queensland.
Four Certification Pathways,
One Complete Solution
Unapproved Extensions & Renovations
Structural certification for unpermitted room additions, removed load-bearing walls, patio enclosures, second-storey extensions, and unauthorized internal alterations.
Class 10 to Class 1 Dwelling Conversions
Engineering certification to legally convert non-habitable garages, sheds, or outbuildings (Class 10a) into compliant habitable secondary dwellings / granny flats (Class 1a).
Council Show Cause Notice Resolution
Urgent RPEQ engineering inspection, structural remediation reports, and council-lodgement documentation to resolve compliance notices and prevent fines.
Form 15 & Form 12 Certification
Issuing RPEQ Form 15 (Design Compliance) and Form 12 (Aspect Inspection Certificate) verifying structural adequacy, footings, framing, and tie-downs for building certifiers.
Simple, Fast & Legally Compliant —
From Inspection to Council Sign-Off
1. On-Site Structural Assessment
An RPEQ engineer inspects the existing unapproved structure, measuring framing, footings, roof tie-downs, and boundary setbacks to identify compliance gaps.
2. Analysis & Remediation Plan
We perform load calculations (AS 1170) and develop a practical Performance Solution or minimal rectification plan, avoiding unnecessary demolition.
3. Form 15/12 Sign-Off & Approval
Receive certified structural drawings, compliance reports, and signed Form 15/Form 12 certificates ready for certifier sign-off and final council clearance.
Certified Retrospective Approvals Across Southeast Queensland
Ostanes Engineering resolves unauthorized building compliance issues and issues retrospective certifications across Brisbane, Gold Coast, Sunshine Coast, Logan, Moreton Bay, Ipswich, and Toowoomba. All engineering assessments strictly adhere to the National Construction Code (NCC) and Building Act 1975.
- RPEQ (Board of Professional Engineers QLD) & CPEng Registered
- Form 15 (Design) & Form 12 (Aspect Inspection) Certification
- NCC Performance Solutions & BCA Assessment Reports
- Fast assistance for property sales, conveyancing & insurance claims
What Clients Say
After Approval Is Granted
Everything you need to know about retrospective certification
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 Resolve Council Show Cause & Enforcement Notices
If your local council (such as Brisbane City Council, City of Gold Coast, Logan City Council, or Moreton Bay City Council) 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 work directly with private certifiers and council town planners to halt enforcement action while approval is processed.
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 stringent building standards: minimum ceiling height (2.4m for habitable rooms), slab waterproofing and damp-proof membranes (AS 2870), termite protection (AS 3660), wind bracing, and energy efficiency. We assess the existing structure and design cost-effective compliance strategies that avoid ripping up concrete slabs or replacing roof trusses.
Form 15 vs Form 12: What Certificates Do You Need?
Retrospective approval requires two critical Queensland statutory certificates: Form 15 (Compliance Certificate for Building Design) certifying that the structural design and any required remediation work meets the NCC; and Form 12 (Aspect Inspection Certificate) issued following inspection confirming that the existing structure or completed rectification work complies with engineering specifications and is safe 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 demonstrate that the structure achieves equivalent safety and performance, securing council sign-off without disruptive alterations.
Get In Touch
Need retrospective building approval? Speak with an RPEQ engineer today
Whether preparing for a property sale, securing insurance, or resolving council compliance notices, Ostanes Engineering makes retrospective approval fast and stress-free.
- (+61) 411 631 777
- info [at] ostanes-engineering [dot] com
- Sunnybank, QLD 4109
- Denham Court, NSW 2565
