Class 2 - Residential
High-Rise Residential Towers
Approvals typically in ~35 days
Two dwellings. One certifier. One timeline.
"Our duplex DA sat with council for 14 months before we found out we qualified for CDC. No1 issued our CDC in 18 days. We had lost over a year for nothing."
A duplex on the right lot can be CDC-approved in NSW without council - but fire separation, acoustic compliance, and party wall design must all satisfy the NCC before we can sign off.
- Party wall fire separation reviewed to NCC Specification 9 in a single assessment
- Acoustic compliance to AS 3671 checked before certificate issue
- Both dwellings covered by one CDC - one fee, one timeline
Eligibility Check
Does your duplex block qualify for a fast CDC?
Select all that apply to your project.
You missed a few requirements.
Based on your selection, your project might require an alternative approval pathway (like a DA). You are missing:
- Located in New South Wales
- Lot size over 600sqm (SEPP Housing 2021 dual occupancy provisions)
- Lot is not in a heritage conservation area
- Both dwellings have separate vehicular access
- Building height under 8.5m
- Not in a flood-prone or high-hazard bush-fire zone
Don't worry, we've got you.
Our experts can counsel you on alternative pathways and guide you through the process. Call us immediately for a free consultation.
Call 0421 936 489Duplex certification.
Both units, one process.
Typical duplex CDC issued in 14–20 business days.
Day 1
Submit Plans
Architectural drawings, site plan, BASIX certificates (one per dwelling), and engineering.
Days 1–7
BCA & Fire Review
Party wall fire separation, NCC Volume One compliance, and acoustic report checked.
Days 7–14
Conditions Resolved
Any conditions addressed directly with you - no council intermediary.
Day 14–20
CDC Issued
Certificate covers both dwellings. Builders can mobilise on both simultaneously.
During Build
Stage Inspections
Pre-slab, frame (including party wall), waterproofing, and insulation on one schedule.
Completion
Occupation Certificate
Final inspection of both dwellings. OC issued for each. Legal occupancy begins.
Have a question about the process? Call us - we're happy to walk you through it.
Scope of Works
Residential Certification Services
Expert guidance and fast approvals to get your residential project out of the ground sooner.
Complying Development (CDC)
Bypass council DA delays. We assess and approve Complying Development Certificates rapidly.
Perfect for new homes, duplexes & granny flats
Approval typically in 10–15 business days
We handle all government portal lodgements
Free initial eligibility consultation
Independent expert assessmentGet a quote
Ready to get started?
Get a fast-tracked quote from a licensed NSW certifier. Most clients hear back within 2 hours.
Select your project type
See the exact documents needed. No guesswork, no endless lists.
Architectural Drawings (both units)
Floor plans, elevations, sections, party wall details
Site / Survey Plan
From your licensed surveyor
BASIX Certificate (Ã-2)
One per dwelling - mandatory for all NSW homes
Structural Engineering Report
Including party wall and footing design
Acoustic Report
Party wall acoustic compliance to AS 3671
Hydraulic / Drainage Plan
Separate drainage for each dwelling
Missing something? Don't worry — we can help source it.
Start your applicationWhere We Provide This Service
No.1 Building Services provides fast, unrestricted certification across the following regions. Explore our interactive coverage map.
South West SydneyGreater Western & North West SydneyCity & Inner WestParramatta & Central WestNorthern Beaches & North ShoreEastern SuburbsSt George & Sutherland ShireNewcastle & The Lower Hunter
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Unrestricted Authority
Our Certification Capabilities
Recent Duplexes & Dual Occupancy we've certified
Class 1 & 2 - Residential
Custom Luxury Homes & Duplexes
CDCs typically in ~14 days
Class 10b - Residential
Swimming Pools & Minor Structures
CDCs typically in ~5 days
Duplex certification - your questions answered.
Yes, if the land and design qualify for CDC. A CDC can avoid the full DA process, but portal, notification and other approvals may still apply.
It depends on the local planning controls. If no LEP minimum applies, the complying development code may apply a 600m2 minimum.
Yes. A duplex generally requires compliant fire separation between the two Class 1a dwellings under the applicable NCC requirements.
BASIX documentation must cover both dwellings and match the submitted plans. It may not always be one separate certificate per dwelling.
We typically aim to issue eligible duplex CDCs within 14-20 business days after receiving complete and compliant documents. A DA is usually slower.
Get in touch
Request a quote
We'll review your project details and get back to you within 24 hours.
Unrestricted certifiers
Your project is reviewed directly by NSW-accredited certifiers - no middlemen.