When a licensed drainlayer completes work on your property in New Zealand, you should receive as-built drainage plans — accurate drawings that record exactly where your drains have been installed, at what depth, and how they connect to the wider network. These documents are a legal requirement under the Building Act 2004 and are essential for future maintenance, renovations, or property sales.
What Are As-Built Drainage Plans?
As-built plans (sometimes called "record drawings" or "as-constructed drawings") are scaled diagrams produced after the work is finished. Unlike the consented design drawings prepared before construction, as-builts reflect what was actually built — including any changes made on site during the job.
For drainage work, these plans typically show:
- The location of all pipes relative to boundaries, buildings, and fixed reference points
- Pipe sizes, materials, and grades (fall/slope)
- The depth of pipes below ground at key points
- The position of inspection chambers, manholes, and cleanouts
- Connection points to the public sewer or stormwater network
- Separation of wastewater (sewage) and stormwater drains where applicable
- Any on-site wastewater systems such as septic tanks or treatment units
Why Are They So Important?
As-built plans protect you as a homeowner in several practical ways:
- Future excavation work — builders, landscapers, or other tradespeople need to know where drains run to avoid damaging them
- Fault-finding and maintenance — a plumber or drainlayer can locate blockages or collapses much faster with accurate records
- Building consent applications — your council will often require existing drainage records before approving new work
- Property sale — buyers, solicitors, and LIM reports may reference drainage records
- Insurance claims — evidence of compliant, recorded drainage can support a claim
Who Is Responsible for Producing Them?
Under the Building Act and NZ Building Code, the licensed drainlayer who carried out the work is responsible for producing and supplying as-built documentation. Drainage work is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006, meaning it must be carried out by — or under the supervision of — a person registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB).
The drainlayer must also issue a Certificate of Compliance (CoC) confirming the work meets the Building Code. This certificate, along with the as-built plans, should be handed to you on completion.
What Format Should the Plans Be In?
As-built plans are commonly provided as:
- Printed paper drawings (at least A3 size for clarity)
- PDF files sent by email
- CAD or GIS files for larger or more complex jobs
Always ask for a digital copy so you can store it safely and share it easily. Keep a physical copy with your other property documents as well.
What Should You Check When You Receive the Plans?
When your drainlayer hands over the as-builts, take a few minutes to review them:
| Check | What to look for |
|---|---|
| Scale and orientation | Is there a north point and a scale bar? |
| Pipe details | Are sizes, materials, and grades noted? |
| Depths | Are invert levels or cover depths recorded at key points? |
| Reference points | Are drains located relative to boundaries or the house? |
| Signatures | Is the licensed drainlayer's name and registration number shown? |
| CoC attached | Is the Certificate of Compliance included? |
If anything looks incomplete or unclear, ask your drainlayer to clarify or update the drawings before you sign off on the job.
Do the Plans Go to Council?
In many cases, yes. If the drainage work required a building consent, the as-built plans form part of the code compliance certificate (CCC) process. Your council's building inspector will need to be satisfied the work matches the consented design (or that any variations are acceptable) before issuing the CCC.
Some minor drainage work may be exempt from building consent under Schedule 1 of the Building Act — but always confirm with your local council whether consent was required for your specific job. Even for exempt work, the drainlayer is still required to issue a CoC and provide as-built records.
Many territorial authorities (councils) also maintain their own drainage records and may request a copy of the as-builts for their files. Check with your council about their specific requirements, as these can vary around New Zealand.
When to Call a Professional
Drainage work — including laying, altering, or connecting drains — is legally restricted work in New Zealand. It must be carried out by a registered drainlayer. Homeowners are not permitted to do this work themselves (with very limited exceptions). If you are unsure whether your drainlayer has provided the correct documentation, or if you've purchased a property and cannot locate any drainage records, contact a licensed drainlayer or your local council for advice.
You can find qualified, local drainlayers in your area through tradedirectory.co.nz.
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