Why New Zealand Is Moving From Butyl Membranes to Modern TPO Systems

For many years, black butyl rubber membranes were treated as a default solution for low‑slope roofs, decks, and internal gutters in New Zealand. They were familiar, relatively inexpensive, and often the first choice for waterproofing tricky areas.

In practice, a large portion of those butyl installations—especially where fully exposed and installed over marginal falls—are now at or beyond their practical service life, often well ahead of what owners expected under NZBC B2 (Durability).

At the same time, there has been a marked shift toward heat‑welded TPO single‑ply systems, often in warm‑roof assemblies, as a more robust way to satisfy E2 (External Moisture) and B2 on low‑slope work.

This article looks at:

• the failure patterns of legacy butyl membranes in NZ conditions
• how modern TPO systems differ technically
• and the main replacement strategies available on real projects.

1. The butyl membrane problem in New Zealand

1.1 Typical applications

Butyl membranes were extensively used on:

• Balcony decks and terraces over habitable space
• Internal gutters behind parapets
• Low‑pitch roofs at or below the minimum falls for sheet materials
• Tiled decks on pedestals, with butyl as the sole waterproof layer

In many of these cases:

• falls were minimal or inconsistent
• outlet detailing was weak (single outlet, no overflow, minimal sumps)
• substrate movement (ply over joists, light steel framing) was not well managed

1.2 Common failure modes

Across the country, recurring patterns show up when older butyl roofs are opened up:

• UV degradation: crazing, cracking, and surface ageing under NZ’s high UV load
• Shrinkage: membrane pulling away from parapets, terminations, and outlets
• Lap failures: adhesive‑based laps opening under movement and trafficking
• Blistering: trapped moisture under the sheet, particularly over damp substrates

Dark colours and high surface temperatures exacerbate these issues, especially on exposed decks and roofs with limited ventilation.

Many of these installations now struggle to demonstrate ongoing compliance with E2 performance clauses and B2 durability expectations.

Image 1. Cracking through the membrane. Membrane system failed and is leaking

2. How TPO single‑ply systems differ

TPO is a heat‑weldable thermoplastic polyolefin membrane, generally installed as part of a documented system (substrate, fixings, accessories, insulation where applicable).

2.1 System‑based design

Modern TPO systems are specified as complete assemblies, not just a sheet:

• defined substrate requirements
• compatible fixings and accessories
• tested details for upstands, gutters, and transitions

From a design perspective, this supports a more robust B2 story: you are specifying a tested system rather than relying on a generic membrane over a marginal deck.

2.2 Welded laps and accessories

TPO seams are made by hot‑air welding, giving:

• homogeneous fusion across the lap
• the ability to test seams (probe, destructive test strips)
• repeatable details using pre‑formed corners, pipe boots, and outlets

Compared with adhesive‑based butyl laps, properly welded TPO seams are:

• less sensitive to on‑site glue application variation
• more tolerant of intermittent ponding (within system limits)
• easier to include in a formal QA process

2.3 Solar reflectance and surface temperature

Most TPO membranes in the NZ market are light‑coloured. This reduces surface temperature relative to black butyl, which helps:

• slow down ageing of the membrane
• reduce heat load into the structure
• support internal comfort and HVAC efficiency

2.4 Integration with warm‑roof assemblies

TPO is commonly installed over rigid insulation boards in warm‑roof configurations:

• vapour control layer over deck or metal substrate (where required)
• mechanically fixed or adhered rigid insulation
• TPO membrane as outer waterproof layer

This aligns with evolving expectations around H1 energy efficiency, reduces thermal bridging, and improves control of interstitial condensation—areas where older cold‑roof butyl builds often underperform.

3. Where butyl membranes were used – and why they’re failing now

3.1 Multi‑unit decks and balconies

On many townhouses and apartment blocks, butyl membranes were:

• installed over plywood decks
• covered with tiles on pedestals or direct‑fixed decking
• run into internal gutters with limited overflow provision

Failures now showing up include:

• moisture tracking under tiles and locating pinholes or lap defects
• edge shrinkage at door thresholds and parapets
• long‑term leakage into framing, leading to rot and structural repairs

3.2 Internal gutters and complex junctions

Internal gutters behind parapets, or between roof planes, often combined:

• minimal fall
• a single critical outlet, sometimes without overflow
• timber framing with movement and settlement

Legacy butyl laps and outlet transitions are now failing after decades of movement, UV exposure, and incomplete maintenance, with water escaping into wall assemblies and interiors.

3.3 Low‑pitch roofs near or below sheet minima

Some roofs were built at 1–2° and sheeted in butyl as the primary waterproofing. Others combined butyl with metal or other materials in complex junctions.

The combination of marginal falls, concentrated drainage, substrate movement, and ageing dark membranes is proving unsustainable under NZ conditions.

4. Replacement and upgrade options

Once a butyl installation moves past localised defects into systemic failure, the realistic options are:

• re‑sheet as a modern TPO system, with or without warm‑roof build‑up
• overlay with a TPO warm roof where geometry allows
• re‑waterproof with a silicone‑based liquid membrane system on suitable substrates

The right choice depends on structure, falls, thresholds, use, and budget.

Option 1: Strip‑and‑replace with a modern TPO system

This is often the most robust long‑term solution, particularly for decks over occupied space.

Typical sequence:

1. Remove tiles/toppings and the existing butyl.
2. Inspect substrate (ply, concrete, or metal) for decay, deflection, and cracking.
3. Rectify structural defects and, where possible, rationalise falls and drainage.
4. Install a TPO system to supplier details, including:
   • upstands and parapets
   • outlets and overflows
   • terminations and separation from incompatible materials

Design advantages:

• Full reset of the waterproofing system and critical junctions
• Opportunity to correct non‑compliant falls and add secondary overflows
• Clean documentation trail supporting E2/B2 via tested system literature

Option 2: TPO warm‑roof overlay (where structure and heights allow)

Where the existing substrate is structurally sound, and there is sufficient height at doors and parapets, a warm‑roof overlay can address both waterproofing and thermal performance.

Indicative build‑up:

• Existing deck (and, in some cases, retained membrane as part of the vapour control strategy if appropriate)
• Vapour control layer (as designed)
• Rigid insulation boards
• Overlay board if required (for example, over profiled metal)
• TPO membrane as outer waterproofing

Key checks for designers:

• Thresholds: Maintain compliant step‑downs and finished-floor-level relationships at doors.
• Parapet and balustrade heights: Adjust design to ensure safety and weathertightness are still met with the increased build‑up.
• Structural load: Confirm the structure can support additional dead load.

Warm‑roof overlays are particularly attractive for commercial roofs and some residential decks where there is scope to improve R‑value and reduce condensation risk in parallel with waterproofing renewal.

Option 3: Silicone‑based liquid membrane over suitable substrates

Silicone‑based liquid systems offer another route for certain refurbishment scenarios, particularly over concrete, sound metal, or well‑prepared existing membranes.

These systems are field‑applied and cure to form a continuous, joint‑free coating. When used as a primary membrane (rather than a cosmetic coating), the design needs to follow full system specifications for:

• primers
• reinforcement
• dry film thickness

Design and installation considerations:

1. Substrate condition
   • Substrate must be structurally sound and stable.
   • All loose, degraded coatings or membranes should be removed.
   • Moisture content needs to be controlled; trapped moisture below can cause blistering.

1. Falls and drainage
   • Liquid membrane is not a fix for inadequate falls.
   • Designers should address birdbaths through local regrading, new sumps, or re‑framing where practical.
   • Outlets and overflows must be detailed to meet E2 intent.

1. Reinforcement at critical details
   • Joints, cracks, transitions, and junctions should be reinforced with fabric/tape embedded in the liquid system.
   • Particular care is needed at internal gutters, scuppers, and parapet junctions.

1. System thickness and QA
   • Achieving the specified dry film thickness (DFT) is critical for durability.
   • On‑site QA should include wet-film gauges, coverage-rate checks, and visual inspections for pinholes and skips.

Where this option fits:

• As a refurbishment solution where full strip‑out is impractical, but the underlying structure is good, and falls are acceptable.
• On some existing concrete or metal roofs where a continuous coating can simplify detailing without major height changes.

It is not appropriate where:

• there is significant substrate movement or decay
• falls are fundamentally wrong and cannot be corrected
• there is persistent moisture trapped in the existing build‑up with no path to dry

In those cases, re‑building the substrate and moving to a full TPO (or other system) remains the responsible approach.

5. Selecting the right strategy

From a design and construction perspective, the key questions are:

• What does the structure look like once the toppings and membrane are removed?
• If there is significant rot, deflection, or poor framing layout, a simple overlay is unlikely to be adequate.
• Can we achieve compliant falls and drainage?
• Is there an opportunity to rationalise outlets, add secondary overflows, or re‑frame critical areas?
• What are the threshold and height constraints?
• Warm‑roof overlays and re‑sloping may affect door thresholds, parapet heights, and balustrade design.
• How is the space used?
• A high‑traffic balcony over habitable space demands a more conservative strategy than a service roof over non‑critical areas.

When those constraints are understood, TPO warm roofs, direct TPO re‑sheeting, or a properly specified silicone liquid system can each form part of a defensible design. The constant is that the solution should be documented as a coherent system with clear references to system literature, installation details, and maintenance requirements.

6. Implications for architects, builders, and councils

The legacy of ageing butyl membranes has underlined the need for:

• more rigorous attention to falls, drainage, and junctions at design stage
• specification of complete roofing systems, not just “a membrane”
• better coordination between structure, membrane choice, and floor levels

For architects and builders, moving to modern TPO systems and robust liquid solutions is an opportunity to:

• lift the performance and durability of low‑slope roofs and decks
• align more clearly with E2 and B2 performance expectations
• reduce the likelihood of early‑life failure and dispute work

The key is to treat membrane selection as a critical building‑envelope decision, not a last‑minute line in the specification. When the structural design, falls, thresholds, and membrane system are considered together, modern TPO and well‑designed liquid membranes offer a significantly more reliable path forward than another generation of stressed, exposed butyl.

Roofing Masters Limited is here to help you

If you’re dealing with ageing butyl membranes or planning a new low‑slope roof, it pays to involve membrane specialists early. Roofing Masters Limited focuses on membrane roofing and waterproofing across Nelson – Tasman – Marlborough – West Coast, and we work with home owners, architects, builders, and body corporates to design and install systems that actually perform over time. Contact us to review your project, discuss TPO, warm‑roof, or liquid options, and get practical, code‑aligned recommendations for your next roof or remediation job.

Check this Before and After Butyl membrane replacement done by Roofing Masters Limited in Riwaka.

Image 2. Painted Butyl membrane ready for replacement

Image 3. New TPO membrane 1.52 mm installed by Roofing Masters Limited, supplied by Viking Roofspec with 20 years warranty.

Many buildings in New Zealand were constructed with metal roofs installed at pitches lower than those allowed by the NZ Building Code today. Under NZBC Clause E2/AS1, the minimum pitch for profiled metal roofing is generally 3°, depending on the profile and manufacturer. However, older roofs were often installed at 1° to 1.5°, and over time this has led to ponding, backflow, capillary action, corrosion around fixings, and persistent leaks.

When a metal roof no longer meets modern pitch requirements and increasing the pitch is not practical, a membrane overlay system becomes one of the most effective long-term solutions. Instead of rebuilding the entire roof structure, a membrane system creates a continuous, watertight surface that performs reliably at very low falls, often down to 0.5°–1° depending on design and detailing.

Overview

This article outlines why low-pitch metal roofs commonly fail, why membrane overlays are often the better long-term solution, which roof types are suitable, and how insulation upgrades can improve overall building performance.

Why Low-Pitch Metal Roofs Commonly Fail

Low-pitch metal roofs experience several predictable problems:

• Ponding water due to insufficient fall
• Capillary ingress at laps and seam joints
• Corrosion around penetrations and fasteners
• Wind-driven rain forced into laps and joints
• Thermal expansion movement stressing flashings and junctions
• Multiple penetrations added over time, such as heat pumps and vents

On roofs installed decades ago, these issues compound as coatings wear away and fixings loosen. Once corrosion begins beneath the lap, water can travel long distances, making leak detection difficult and repairs increasingly unreliable.

When the underlying structure is still sound but the roofing surface is failing, replacing the metal system like-for-like is rarely the best long-term approach if the pitch still does not meet NZBC standards.

Why a Membrane Overlay System Performs Better

A membrane system creates a monolithic waterproof layer, removing reliance on laps, ribs, and capillary breaks.

Key advantages at low pitches

1. Suitable for falls below metal roofing limits

Since metal sheeting requires a minimum 3° pitch, low-slope roofs cannot remain code-compliant without redesign. Membranes perform reliably at very low falls and are widely used on the following building types:

• Commercial buildings
• Schools
• Supermarkets
• Apartment blocks
• Industrial structures

2. No exposed fixings or laps

Membranes are welded or bonded into a continuous sheet, eliminating many of the common failure points associated with metal roofing.

3. Strong UV and ponding resistance

Modern membranes are engineered to tolerate New Zealand’s high UV exposure and intermittent ponding, provided detailing and drainage follow best practice.

Compatibility With Existing Metal Roof Types

Overlaying a membrane onto an existing metal roof requires careful assessment of the roof profile and overall condition.

The following roof types are commonly suitable for membrane overlays:

1. Trapezoidal or ribbed metal roofing

These roofs are common on older commercial and light-industrial buildings.

Why this profile works well:

• Strong, predictable structural behaviour
• Easy to span with overlay boards
• Ribs can create airflow pathways beneath the new system

Preparation typically includes:

• Fastening down loose sheets
• Addressing corrosion spots
• Installing an overlay insulation system such as PIR

2. Tray or standing seam roofing

These systems are often installed at low slopes but can become prone to seam leakage over time.

Overlay benefits include:

• Eliminating reliance on folded seams
• Providing a stable surface that helps absorb thermal movement
• Reducing leakage risk at long tray lengths

3. Diamondek or Dimond-type profiled roofing

These profiles are widely used in commercial buildings.

Overlay suitability:

• Diamond-pattern ribs usually require a levelling board
• The structural steel often remains sound even after coating breakdown

After preparation, these roofs can provide an excellent base for a membrane system.

Insulation Benefits During the Overlay Process

One of the biggest advantages of moving from metal to a membrane overlay is the opportunity to add thermal insulation without major reconstruction.

How insulation is added

1. A rigid insulation board such as polyiso, PIR, or EPS is installed over the existing metal roof.
2. A compatible substrate board is installed over the insulation.
3. The membrane is installed on top.

This creates a warm-roof system, which performs significantly better than the cold-roof construction used in many older New Zealand buildings.

R-value improvements

A typical PIR insulation board has an R-value of approximately R2.7–R3.5 per 100 mm, depending on product and density.

Adding even a 50–75 mm insulation layer can:

• Lift the roof’s total R-value considerably
• Reduce heat loss in winter
• Reduce condensation risk inside the building
• Improve occupant comfort
• Reduce energy consumption for HVAC

For commercial buildings, this can result in substantial operational savings over the membrane’s lifespan.

Additional Benefits of a Warm-Roof Membrane Overlay

1. Condensation control

Warm roofs can significantly reduce interstitial condensation, which is a common issue in metal roofs with insufficient ventilation or insulation.

2. Acoustic improvement

Insulation layers help dampen rain noise, making a noticeable difference in the following environments:

• Classrooms
• Offices
• Residential apartments
• Commercial premises

3. Increased system durability

Because the membrane sits above insulation, thermal movement is reduced across the roofing assembly.

4. Reduced energy costs

A properly insulated overlay system can reduce energy use year-round in conditioned buildings.

When an Overlay System Is Not Suitable

An overlay is not the right option when:

• The metal roof has deep corrosion or structural weakening
• The framing beneath is compromised
• The substrate cannot support the new system
• Moisture is trapped under the metal with no way to ventilate

In these cases, a full roof reconstruction is the correct approach.

Conclusion

When a metal roof is installed at a pitch below the NZ Building Code minimum, simply replacing it with new metal will not solve the underlying problem. A membrane overlay system provides a durable, code-compliant solution that performs effectively on low-slope roofs, extends roof life, reduces leaks, and enables meaningful insulation upgrades.

For building owners, architects, and engineers, membrane overlays offer a practical way to transform aging, underperforming metal roofs into modern, high-performance warm-roof systems without tearing the building open.

Project Example

The images below show a recovery system completed by Roofing Masters Limited in Nelson, New Zealand, converting a trapezoidal-profile roof into a 110 mm insulated warm-roof system.

Contact Roofing Masters Limited

If you are dealing with a low-pitch metal roof that continues to leak, or you are planning a new project and want to get the roof design right from the start, our membrane roofing specialists can help. Contact Roofing Masters Limited for practical advice, detailed inspections, and TPO or torch-on warm-roof solutions tailored to your building.

By Mathias Alvarez  

The answer is simple: it affects the heart of the business—the workers. Any poor decision related to mental health will inevitably impact those on-site, working hard, moving rolls of membrane, welding laps for hours, waking up early, and putting in long hours to deliver a great final product.

As business owners, we are always searching for the “unicorn worker”—someone who can manage an entire site independently, who is reliable and technically exceptional. But the real question we must ask ourselves is: can we nurture that unicorn? This isn’t just about money; it’s where mental health comes into play. We may have a few unicorns on our team, but are we supporting them adequately to maximize their potential?

I had a transformative experience during my recent university thesis on maximising profit through mental health. I explored numerous tools to enhance profit while simultaneously improving arrangements for everyone, including fair salaries and benefits. This might sound unconventional to some managers, but it’s real. One of the most effective tools I discovered is a blend of Lean processes that I call “Know Your Number” and “Pick the Right Mindset.”

Know Your Number

The lifecycle of a project involves different stages, and during challenging times, knowing the numbers in every process is crucial for evaluating and reducing waste, making decision-making more manageable. In my view, reducing hours or withholding deserved pay raises are major red flags—these should be last resorts, hopefully never used.

So, how do we know our number? This is where the popular acronym KPI (Key Performance Indicators) comes into play. Keeping KPIs up to date for every aspect of the project will help us determine if we are compensating our workers fairly, quoting projects accurately, need more manpower, or can afford new machinery. A simple equation I found useful for every step on a business KPI is:

(Allowed/Spent)x100%

This can be applied to materials, hours, or any other item of value. For example, if we allowed 120 hours worth $9,600.00 and spent $12,300.00 on manpower hours, the KPI would be 78%. This prompts investigation: why is there a $2,700.00 difference? Is the pricing right? Was the work harder or more difficult than expected? Is the client challenging? What improvements can be made for future quotes for this client or type of roof?

When you can establish a KPI for every item of a project and overheads, you truly know your number. This concept is vast and challenging to explain briefly, but I will delve deeper into this topic in the next publication.

The Right Mindset

Complaining and cursing the trade is always the wrong mindset. If you’re a manager who constantly complains about workers, the environment, suppliers, or clients, it’s time to change your mindset and start small. For instance, if you’re spending more on materials than necessary, how can you manage to achieve a proper KPI in materials to improve future quoting? If workers complain about unfair pay rates, how can you create a KPI for each worker and consider it during future reviews?

We must remember that every decision directly affects our workforce—the heart of our business. When you cut budgets or benefits, everyone will talk about it, wasting precious time and delivering lower quality services because the mental health of everyone has been damaged by poor decisions, lowering our KPIs. Before making a decision that will impact your team’s mental health, ask yourself: do I know every number for every process? Is there any process that needs improvement before reducing workers’ benefits?

By Raf Dow     

Abstract 

This case study examines MBIE Determination 2024/072, which addresses the legal and practical requirements surrounding producer statements (PS3s), including PS3s for membrane roofing on residential buildings in New Zealand. Although it is commonly understood in the industry that a PS3 producer statement is required for membrane roofing compliance, the determination clarifies that councils cannot insist on a PS3 as the sole evidence of compliance when issuing a Code Compliance Certificate (CCC). The situation involved a homeowner being unable to provide certain producer statements, including a PS3 for the roof membrane, due to subcontractor changes and lost documentation. The council refused to issue a Code Compliance Certificate (CCC) on the grounds of missing producer statements—despite the roof’s proven performance and its passing inspections. The MBIE determination found this refusal unjustified, as the council did not consider other available evidence of compliance and there was no evidence of non-compliance with the building work. The paper highlights the importance of comprehensive record-keeping, particularly the role of Licensed Building Practitioner (LBP) Records of Work (ROWs), in ensuring traceability and compliance. The findings reinforce that while producer statements are valuable, they are not legally mandatory, and councils must consider all reasonable evidence of compliance. Practical recommendations are provided for roofing professionals to maintain robust documentation and clear communication with clients and authorities.  

Case Study: When Is a Producer   Statement (PS3) Really Required? Lessons from MBIE Determination 2024/072 

Producer statements (especially PS3s for membrane roofing) are a familiar part of the compliance process, but a recent Ministry of Business, Innovation & Employment (MBIE) determination shows that councils can’t always enforce their use as a strict requirement. Here’s what happened, and what it means for our industry. 

The Situation 

A homeowner in Auckland applied for a Code Compliance Certificate (CCC) for a property with a membrane roof. The local council (the Building Consent Authority, or BCA) refused to issue the CCC, citing missing paperwork—including a PS3 producer statement for the membrane roof. However, it’s important to note that the core issue in this case was not simply the absence of the membrane PS3. The council’s refusal was based on a combination of outstanding producer statements and documentation for several aspects of the build (including the membrane roof, solar water heating, and reinforced concrete piles), rather than any identified non-compliance with the actual building work. The roof had been installed by a sub-contractor, and after several years and staff changes, the required PS3 couldn’t be located. 

The Council’s Position 

The council insisted that without the PS3 (and some other producer statements), they could not issue the CCC—even though: 

· The membrane roof had passed physical inspections. 

· The roof had performed well for years, with no leaks or issues. 

· The building consent conditions required producer statements to “demonstrate compliance,” but didn’t make them the sole form of evidence. 

The Owner’s Response 

The owner pointed out that: 

· The roof was in good condition and performing as intended. 

· The inability to produce a PS3 was due to circumstances outside their control (staff changes, subcontractor not identified, lost paperwork). 

· Other evidence (inspections, performance history) supported compliance. 

MBIE’s Determination 

MBIE found that: 

· Producer statements (like PS3s) are helpful evidence, but not mandatory under the Building Act 2004. 

· Councils must consider all available evidence of compliance, not just paperwork. 

· If a PS3 can’t be provided, other proof—such as inspection records, site performance, or a manufacturer’s inspection—can be used. 

· Refusing a CCC solely because a PS3 is missing, without specific evidence of non-compliance, is insufficient. 

Key Quote from the Determination:
“A producer statement does not hold any particular status under the Building Act, and an authority cannot require that a producer statement (as the only outstanding matter) be provided for issuing a code compliance certificate.” 

Practical Lesson: The Value of   Good Record-Keeping 

While the main focus of the MBIE determination was on producer statements, the case also highlights the importance of robust documentation in roofing projects. For restricted building work (RBW) such as residential roofing, Licensed Building Practitioners (LBPs) are legally required to provide a Record of Work (ROW) to both the homeowner and the council. This document records who carried out or supervised the membrane installation, but it also ensures that, years down the track, the project team can always identify the responsible parties—even if staff or contractors have changed. 

In this particular case, the inability to identify the original membrane roofing subcontractor made it much harder for the owner to provide the paperwork the council wanted. Having a properly completed ROW on file would have included the LBP’s details and could have streamlined the compliance process. It’s also critical to apply for your CCC promptly after the final inspection. Delays can result in lost paperwork, unavailable contractors, and increased compliance challenges, as demonstrated by the difficulties faced in this case. 

Takeaway::Keep thorough records for every project—including Records of Work (ROWs), producer statements, QA documentation, and photos. Homeowners should be advised to apply for their Code Compliance Certificate (CCC) without unnecessary delay. It’s not just about ticking boxes—it’s about protecting your business, your clients, and the long-term integrity of the building. 

What This Means for Membrane & Waterproofing Pros 

· Do your paperwork, but don’t panic if a PS3 goes missing. If you can’t provide a PS3, make sure you have other evidence—inspection records, performance reports, or a manufacturer’s assessment. 

· Councils can’t enforce PS3s as the only route to compliance. They must consider all reasonable evidence that the membrane system meets the Building Code and consented plans. 

· Communication is key. If you’re missing documentation, talk to the council early and suggest alternatives (such as a site visit by the membrane supplier or engineer). 

· Keep clients informed. Let homeowners and builders know that while producer statements are best practice, they’re not the only way to prove compliance. 

References 

Building Performance. (n.d.). Producer statements: Guidance for building officials. https://www.building.govt.nz/building-officials/guides-for-building-officials/producer-statements/ 

Building Performance. (n.d.). MBIE determinations. https://www.building.govt.nz/resolving-problems/resolution-options/determinations/ 

Licensed Building Practitioners. (n.d.). Record of work – What you need to know. https://www.lbp.govt.nz/for-lbps/record-of-work/ 

Ministry of Business, Innovation & Employment. (n.d.). Building code and system insights. https://www.mbie.govt.nz/building-and-energy/building/building-system-insights-programme/building-code/