Panelised vs Traditional Timber Granny Flats: What NZ Homeowners Should Know
With the introduction of the 70m² granny flat building consent exemption, more homeowners are exploring ways to add a second dwelling to their property. Alongside this growing interest has come an increase in different construction methods — particularly panelised or transportable systems versus traditional timber-framed builds.
Some nationwide providers, such as HouseMe, use prefabricated panel systems that are manufactured off-site and assembled on location. Others, including Buildmac, construct granny flats using conventional 90×45 timber framing, the same method used in most New Zealand homes.
So which approach is right for you?
This article explains the key differences, trade-offs, and long-term considerations — so you can make an informed decision based on your site, budget, and future plans.
What Is a Panelised Granny Flat?
Panelised or transportable dwellings are typically built using factory-manufactured wall, roof, and floor panels, often similar in concept to refrigeration or insulated panel systems.
These panels are:
Manufactured in a controlled factory environment
Transported to site
Assembled quickly to form the structure
This approach is commonly marketed as a fast and efficient building solution, particularly for repeatable designs.
Potential advantages
Faster on-site assembly
Factory-controlled production conditions
Predictable material specifications
Considerations
Less familiar to many local trades and inspectors
Future alterations can be more complex
Repair methods may differ from standard NZ housing
Buyer and insurer familiarity can vary
Panelised systems are a legitimate construction method, but they operate differently from conventional residential builds and may not suit every site or homeowner.
What Is Traditional Timber-Framed Construction?
Traditional timber framing uses 90×45 radiata pine framing, built on-site by licensed building practitioners. This method has been the backbone of New Zealand residential construction for decades.
At Buildmac, this is the same construction approach we use for:
New homes
Renovations
Extensions
Granny flats (including under the 70m² exemption)
Why this matters
Councils, banks, and insurers understand it well
Repairs and alterations are straightforward
Materials and skills are widely available nationwide
It feels, performs, and ages like a “normal home”
Side-by-Side Comparison: Panelised vs Timber-Framed Granny Flats
Transportable Granny Flat
| Feature | Transportable Granny Flat | On-Site Timber-Framed Granny Flat |
|---|---|---|
| Where it’s built | Fully built off-site in a factory | Built entirely on-site |
| Delivery method | Transported complete and craned into position | Constructed in place |
| Construction method | SIPs Panel (cool store refrigeration panel) | 90×45 timber framing |
| Site access needs | Truck and crane access required | Standard residential access |
| Traffic management | Often required | Rarely required |
| Design flexibility | More limited | Highly flexible |
| Future alterations | More complex | Straightforward |
| Maintenance & repairs | Specialty contractors | Standard NZ building methods |
| NZ Building Code compliance | Required | Required |
FAQ
Do transportable granny flats still need to meet the NZ Building Code?
Yes. All granny flats — including transportable homes — must fully comply with the New Zealand Building Code. The 70m² building consent exemption changes the consent pathway, not the construction standard. Licensed Building Practitioners must still be involved, and all required documentation must be provided.
Can a transportable granny flat be placed on a rear section?
Sometimes. Transportable granny flats require truck and crane access, which can be difficult on rear sections. In many cases, building on-site is more practical and avoids the need for complex logistics or traffic management plans.
Do transportable granny flats require traffic management plans?
They often do. Because transportable homes are delivered and craned into position, traffic management plans may be required depending on road access, traffic volumes, and council requirements.
Are timber-framed granny flats better for future alterations?
Generally, yes. Timber-framed granny flats are built using standard NZ construction methods, making future changes such as layout modifications, decks, or service upgrades easier to carry out.
Does Buildmac build transportable granny flats?
Yes. Buildmac builds transportable homes and granny flats using traditional timber framing. We also regularly build on-site, which often suits rear sections and properties with limited access.
70m² Granny Flats and Building Code Compliance
Regardless of whether a granny flat is built on-site or transported in, the rules remain the same.
Under the 70m² building consent exemption:
All work must comply with the New Zealand Building Code
Design and construction must be carried out or supervised by Licensed Building Practitioners (LBPs)
Certificates of Work (CoWs) and Records of Work (RoWs) are mandatory
A Project Information Memorandum (PIM) must be issued before construction begins
The exemption simplifies the consent process — not the standard of construction.
Under the 70m² building consent exemption, all granny flats must still comply with the New Zealand Building Code. A Project Information Memorandum (PIM) is required before work begins, and licensed building professionals must be involved throughout the design and construction process.
For homeowners in Hawke’s Bay, the Hastings District Council provides guidance on 70m² granny flats and minor residential units, including local planning and infrastructure requirements.
Long-Term Considerations for Homeowners
Maintenance and repairs
Because Buildmac uses standard timber framing for both on-site and transportable builds:
Repairs use familiar NZ materials
Any qualified builder can carry out maintenance
Long-term upkeep is straightforward
Future changes
On-site builds typically allow easier:
Layout changes
Deck or pergola additions
Service upgrades
Transportable homes can still be modified, but early planning is important.
Insurance, finance, and resale
Homes built using familiar construction methods tend to:
Be easier to insure
Attract fewer questions from lenders
Provide stronger buyer confidence in the future
Which Option Is Right for Your Property?
A transportable SIP’s granny flat may suit you if:
Your site has excellent access
Crane placement is straightforward
Minimal on-site build time is a priority
An on-site timber-framed granny flat may suit you if:
Your site is at the rear of the property
Access is limited
You want maximum design flexibility
You want to avoid traffic management complexity
Buildmac’s Approach
At Buildmac, we:
Build timber-framed granny flats
Offer both on-site and transportable solutions
Assess each site individually before recommending an approach
Our goal is not to force a system onto a site, but to choose the most practical, compliant, and durable solution for your property.
Thinking About a 70m² Granny Flat?
If you’re considering a granny flat under the building consent exemption and want advice based on real site conditions and NZ building experience, we’re happy to help.
👉 You may also find this useful:
Granny Flats Without Building Consent in Hawke’s Bay – The 70m² Guide