By Steven Van Rhoon, Director

Quality assurance is a critical part of any building process, and it is no different when it comes to waterproofing roofs.

It is common knowledge that when developing a new building about 2-3% of the cost are related to waterproofing and 80% of construction issues either during or after construction are related to water ingress.

It is hard to understand why people think that by saving money on waterproofing, they’re making a smart long term financial decision.

Quality assurance typically adds about 2% on top of the standard waterproofing cost. On larger roofs, that percentage drops even lower. We’re talking about a small fraction of the total build cost to guarantee that the work you complete will last beyond the standard 20-year product warranty requirements.

For decades in New Zealand, we appear to have ignored this reality. In our opinion, the construction industry is fixated on just passing the minimum 10-year legal liability requirements. There’s a critical Quality Assurance difference between avoiding legal liability and actually delivering on a minimum 20-year product warranty and satisfying building owners long term expectations.

Where Things Actually Go Wrong

While there’s better information on how to detail roof membranes and better training available through suppliers and manufacturers in New Zealand, historically these suppliers tended not to get involved with the quality assurance installation side. From their perspective at the time, the materials left their yards in good quality and that’s where most of their quality assurance stopped.We have noticed a significant increase in supplier and manufacturer involvement on-site in the last few years, with engineers, architects and main contractors actively requesting their participation — and Sansom has welcomed this development with open arms.

Having been involved in troubleshooting and fixing problems for over half a century, Sansom learned early on what goes wrong with membranes when they’re not installed correctly or when minimum detail requirements fail within the required warranty periods.

The actual durability of roof membrane sheets could last for decades if installed correctly, but nine times out of 10, problems occur at membrane upstands and termination detailing. Think of walls, skylights, parapets and membrane penetrations such as service penetrations, scuppers, outlets and overflows for example. In addition, other building elements such as joinery units, windows, cladding and (cap) flashings are known to contribute to water ingress and require the correct membrane detailing or termination in these locations.

This is why, at Sansom, we don’t just think about the five or 10 years that the workmanship warranty covers. We think about the next 20+ years, taking a conservative belt and braces approach.

For example, if you have a membrane upstand termination detail, you can limit this detail with a termination bar only as per the suppliers’ requirements. Although a termination bar is better than nothing, the superior long-term solution is to install an over flashing in addition to a termination bar. You get what you pay for.

A Shift in Industry Expectations

There has been a recent change where clients and consultants are insisting that suppliers come onsite and participate in quality assurance. As previously stated,10 or 20 years ago, that wasn’t the case at all.

When EFVM (Electric Field Vector Mapping) testing became available in 2009, we were the first company to adopt it in New Zealand, to this day we test all of our EFVM capable membrane installations. In other parts of the world due to insurance companies’ pressure for accountability, manufacturers even provide the full system warranties with EVFM testing being mandatory because it’s treated like a warrant of fitness upon completion of the membrane works.

In addition, we have seen the introduction of Quality Assurance systems such as CONQA introduced in 2015, and Sansom were early adopters of this QA software system still using it on all our projects every day, this QA system has been an invaluable tool to share our onsite Quality Assurance with our clients, architects, consultants and suppliers/manufacturers though a live online platform. Unfortunately, in our industry waterproofers are often guilty until proven innocent with any water ingress issues and CONQA has been an honesty tool for our company for many years now. 

Why EFVM Testing is Superior to Flood Testing

EFVM creates an electrical potential difference between the non-conductive membrane surface and the conductive substrate beneath, which is earthed or grounded. Water is applied to the membrane surface as a conductive medium, creating an electric field. 

If the membrane is watertight, the electricity cannot find a ground earth connection. However, if there’s a breach in the membrane, the electricity makes a ground connection and is pulled towards the positive pole. Technicians read the electric flow travelling across the membrane, enabling breaches to be mapped with pinpoint accuracy.

In Auckland, on consented projects, you must confirm either an electric field testing or flood testing. Most waterproofers are ignorant of the liability inferred by signing their PS3’s without this box ticked. It’s mandatory by Auckland council standards, and we believe it should be mandatory around New Zealand.

The term “flood testing” is vague. There are international guidelines on how to conduct it properly, but no real specific regulations in New Zealand. Someone could put a hose on a roof and call it a flood test. Auckland Council does have a definition of a flood test, so do all membrane suppliers… why aren’t they following it?

The official method involves flooding a whole roof or a roof section with water and monitoring the level against water filled isolated buckets to see if there is a difference in water levels over a long period of time (48 hours). But most people just flood test the outlets. It’s not accurate, and even when done properly, if you find a leak, you still don’t know where it’s coming from. With Green or Warm roofs, you have to dig up areas hoping to find the exact point of water ingress, quite an effort.

On a high-rise buildings, you’ve got to get water up to the roof level, then dispose of it through the stormwater system. Not to mention the weight of the water on top of a roof structure that may require sign off from an engineer prior to the flood test. Done properly, flood testing will always cost more than EFVM testing, and for a lesser result.

EFVM is far superior and accurate. The membrane is tested, and any areas of concern are tested with a comprehensive report. If they find mechanical damage or a breach, you can fix it on the spot with before and after photos. The client can see that issues were found and fixed immediately.

The risk of not doing proper QA/EFVM testing is that when something fails, you have no evidence to support your possible innocence. By providing an evidential report at the end of the job showing the roof was waterproof when you left it, you have protection, not just for yourself but also for other parties such as consultants and main contractors. It is also an helpful tool for ongoing maintenance, if there’s an issue later, you can re-test again, find the problem straight away, and solve it. It’s beneficial for all parties involved especially for the building owners.

Sansom will not do any roofs without EFVM testing, with the exception of a few membranes where it’s not feasible. In those cases, we look at other options such as conductive primers, though these are still in the early days. We always include EFVM testing costs it in our proposals. Not QA testing our completed membranes is not an option because it’s such a good safeguard for the client, the main contractor, and us.

For warm roofs specifically, EFVM testing becomes critical. It’s impractical to flood test, given the size of these roofs and the amount of water needed and the weight build up. Water can enter a warm roof and remain undiscovered for a long time, staying undetected due to the vapour barrier and potentially destructive. Annual maintenance EFVM testing should be standard practice for these systems.

If you cover a membrane properly and it’s well maintained, it can last way beyond the 20-year specification. A well-maintained roof can perform for 30 years or more, maximising the benefit of the client’s investment when quality assurance is prioritised.

Quality assurance protects the applicator, the main contractor, the designer, the architect, consultants, and suppliers & manufacturers. It seems like a no-brainer, yet it’s still not standard practice across the industry.

How can we be better at what we know? How can we make clients and consultants more aware and engaged?

Perhaps the answer lies in education around waterproofing as a certified trade. As an industry, we have a long way to go. As applicators, we need to be better at what we do and more unified. Mistakes made under pressure can potentially bankrupt a company in this industry.

Nationwide certification for waterproofing is critical for the next phase of this industry’s development. At Sansom, we believe we have a part to play in it.

Instead of punishing people at the end through court cases, we should focus as an industry on prevention: building quality from the start and finding the right balance between cost and quality.

We tend to build in New Zealand to minimum requirements instead of maximum requirements. If we could shift that mindset, buildings would be significantly better and provide longer lifespans and may actually reach the 50 year or more durability timeframe in a good condition.

Making Quality Non-Negotiable

Over 50 years of troubleshooting and fixing roofing problems, we’ve learned what happens when QA isn’t prioritised. We’ve identified the patterns and developed systems to address them.

We register our Quality Assurance daily in CONQA, document everything, and take a critical look at substrates before installation. We adopt a belt and braces approach and demand the same standards from everyone involved in our projects where we have the influence to do so.

The industry needs to move beyond just avoiding liability and start focusing on delivering genuine, long-term performance. That requires better education, proper certification, and a collective commitment to building to higher standards rather than minimum requirements.

Quality assurance isn’t just a process. It’s a responsibility to everyone involved in the building, from the applicators to the clients who will depend on these roofs for decades to come.

Get in touch to discuss your next roofing project: sansom.co.nz/contact-us/