ARBV Webinar - Waterproofing in Design
00:00:08 Giorgio Marfella
Okay, so I think we are ready. Good afternoon, everybody. Welcome back to another ARBV webinar. My name is Giorgio Marfella and I'm the chairperson of the Architects Registration Board of Victoria.
00:00:20 Giorgio Marfella
So as always, I'd like to start by acknowledging the traditional owners of the land in which we are meeting today, in the land of the Wurundjeri people of the Kulin Nation and I pay my respects to the elders past and present.
00:00:34 Giorgio Marfella
So today, as you would have seen from the title, we have another presentation that is technically focused and we've had a few in the past and where we spoke about the importance of dealing with water in buildings. And I'm sure you all agree, it's an important aspect of the architect's jobs that we all have at heart, and we understand the implications of that, of course. So to that end, we have a guest here today who is going to help us to understand design principles in waterproofing specifically.
00:01:05 Giorgio Marfella
So, we have Sophie Favilla. Sophie is an environmental engineer and a consultant with Australian Waterproofing Consultants. And she's also a member of the Victorian Chapter of the Australian Institute of Waterproofing. Now, before I hand over to Sophie, who will help us to understand what kind of toolkit and solutions we can keep in mind for the design of waterproofing, fust a few housekeeping things.
00:01:33 Giorgio Marfella
As always, this is an opportunity to use this presentation for formal CPD. So it's valid for one point. In order to prove your attendance, you can scan this QR code that will take you to a questionnaire, and you'll have another bit of time after this to do to complete the questionnaire in the next 24 hours.
00:01:57 Giorgio Marfella
And also, as always, if you do have questions, please put them in the Q&A and we'll moderate questions that are pertinent for Sophie and we'll come back towards the end to moderate and have a discussion. So I really look forward for that part of today's webinar. So with this, Sophie, I can just hand over to you. And so I'll be back in about 45 minutes or so. Over to you.
00:02:23 Sophie Favilla
Okay. All right. Thank you very much for that, Giorgio. Yes, so I will be talking about waterproofing design principles and what is in the architect's toolkit to implement those designs.
00:02:39 Sophie Favilla
So just to introduce, today's presentation comes to you from the Australian Institute of Waterproofing, or the AIW, who I'll be representing today. The AIW is an industry association that represents and supports the waterproofing sector across Australia. So we bring together waterproofing consultants, contractors, manufacturers, suppliers and other industry professionals.
00:03:03 Sophie Favilla
I like to think of us as kind of a waterproofing club. We're a neutral party with the goal of lifting the whole industry without any stake in any particular product or company.
We promote education, technical knowledge, industry best practice, and improved waterproofing outcomes across the construction industry, and ultimately the end user, which is just regular people in their homes.
00:03:27 Sophie Favilla
Even if waterproofing isn't your core area of practice, I really encourage architects to keep AIW on your radar, because not only does it give you access to a concentrated pool of people who spend their working lives dealing with waterproofing, but also the AIW engages with regulators and industry bodies that are represented here on screen.
This is how we bring the waterproofing industry's practical experience from the ground into discussions about codes, building practice and professional clients.
To talk a little bit about myself and my experience with waterproofing, I've been working as a waterproofing consultant for AWC since 2020. AWC is a waterproofing consultancy headed by Karl Wootton, who is the chairman of the Australian Standards Committee for Internal and External Waterproofing. You can look forward to the latest version of the external waterproofing standard AS4654, which he's been working on with the committee for some time. It's actually expected to be released later this year and it's currently out for public comment. So if you're so inclined, it's a great opportunity to take a look at it before it's finalised and let your feelings be known.
00:04:37 Sophie Favilla
So, my journey with waterproofing started off with mostly investigation work, learning about water leaks and their main causes by attending site and literally digging around in the moss and the dirt on the hunt for waterproofing failures. I've worked in a lot of residential settings, so mostly for owners corporations or individual owners, essentially taking those findings that I make on site, bring them back to the office and repair a report that explains what went wrong and what to do about it.
00:05:07 Sophie Favilla
Over time, though, I have become more involved with commercial work. So that can involve like working for builders to carry out condition assessments and inspections of their completed waterproofing. And especially, the new design space has really begun to grow recently. And now I have more and more projects working within a design team rather than just on our own, and this is to either provide waterproofing peer review or produce waterproofing designs that other architects can review. So a lot of what I want to talk about today has to do with this experience of reviewing waterproofing designs produced by others and the challenges that come along with it.
00:05:45 Sophie Favilla
And just to emphasise before jumping in is that my role with waterproofing is pretty niche, and I'm lucky to be in a position where I can put all of my intentional focus into just waterproofing. I can't imagine what it's like to be an architect across all aspects of a structure. It's actually quite overwhelming to imagine that for everything I know about waterproofing, there is just as much to know about literally every other part of a building.
00:06:09 Sophie Favilla
So with that in mind, I hope that what we cover today can be a useful insight from someone who spends all their time with one subject and has a great respect for what architects have to do.
To step through today's presentation format, I'm just first going to discuss a little bit about the impact of waterproofing and water leaks in Australian buildings, and then how we can use design to combat this. I'll then go over some key waterproofing design principles, so that regardless of what it is that we're detailing, the basic tenants are understood.
00:06:42 Sophie Favilla
And then I want to talk, like take those design principles and talk about how to actually implement them, what is at your disposal or what is in the toolkit, so to speak.
Okay, so why does this matter? What is the significance of waterproofing? Well, I think most people would agree that they are beginning to hear more and more about perhaps not necessarily waterproofing, but water damage, both in the media and among projects. We're in the midst of a real growing interest in this area.
That's for good reason. The figures on the slide give us some context for the scale of the waterproofing problem in Australia.
00:07:22 Sophie Favilla
The Building and Plumbing Commission, called BPC, says that water ingress and moisture damage routinely tops the list of issues in complaints, insurance claims and domestic building disputes. Engineers Australia has estimated that resulting cost to owners and insurers may be as high as $3 billion each year.
Research undertaken by the Victorian Government tells a similar story. We have about 47% of recently completed strata buildings surveyed had water leaking associated with balconies and 19% had waterproofing related defects generally. The Cladding Safety Victoria annual report of 2023 found one in three buildings had inadequate waterproofing.
00:08:03 Sophie Favilla
So, waterproofing defects are not unusual and they're not isolated failures. They are unfortunately a recurring industry-wide problem, and that makes waterproofing a really important consideration during design.
00:08:17 Sophie Favilla
Just to dive a little deeper, I have some more data from the Cladding Safety Victoria study, which talks about defects associated with Class 2 building balconies. As you can see, the overwhelming majority of issues are associated with water ingress. Interestingly, only 2% has to do with pipe leakage. So we're talking about water ingress from the environment only, not plumbing.
00:08:42 Sophie Favilla
So there are also other aspects of waterproofing. We have internal waterproofing for bathrooms, below ground waterproofing for basements, and these definitely factor into the equation as well for waterproofing defects, but today I'll just focus on external waterproofing, otherwise we'd be here all day.
00:08:59 Sophie Favilla
So, where do things go wrong? Well, the success of a waterproofing project is ultimately reliant on the installation. Waterproofing is always going to have a workmanship component, and I appreciate that designers can't control the person on the other end of the brush, so to speak. A very well-designed system can and does
fail if poorly installed. So this is not about saying designers need to be responsible for what happens after the drawing set is handed over, but design has a significant role to play in controlling that installation once it starts. It's up to the design to create the conditions in which good installation can occur. We need to think about
design, giving installation the best possible chance of succeeding, rather than expecting workmanship to compensate for unresolved design. But this can't happen when there are gaps in the design. I really want to stress that these are gaps because it's not that I come across waterproofing shown incorrectly or see requirements for waterproofing being misinterpreted.
00:10:03 Sophie Favilla
It's more of whether it actually gets shown at all. It's a bit of a less is less situation. So what are the examples of gaps in design? To cover this broadly, I will discuss interfaces, ambiguity, and delaying decisions.
00:10:21 Sophie Favilla
To talk to the first gap in design, we have interfaces. Waterproofing rarely fails in the middle. The challenge is at the edges, junctions, and transitions, such as these photos up on the right here, where we've got a weatherboard fa ade, meets a tile roof terrace, which becomes tile floor, meeting yet another weatherboard facade, and there's a glass balustrade running through it as well.
00:10:21 Sophie Favilla
I can certainly say from experience that majority of leaks cause found on site have to do with interfaces. It's not often at all that you inspect a waterproofing membrane and find, oh look, there's a great big tear in the surface, problem solved. It's all the things you can't see, like in this photo here. If the sliding door has been installed onto the tiles, with no hob or set down, how is the waterproofing supposed to be terminated? How is it meant to prevent lateral movement of water under the door? Well, short answer, it can't be. The waterproofing membrane didn't fail, but the interface did. And why is it with interfaces? Well, they can be challenging due to a number of reasons.
00:11:24 Sophie Favilla
We often have competing requirements at junctions where interfaces may need to accommodate the waterproofing, drainage, movement, structure, and finishes all simultaneously. And notably, this is not just an interface of the materials, but one of expertise and responsibility. Different membranes, substrates, facade systems,
and drainage strategies need a deliberate means of connection. And this is very important when dealing with building movement or differential movement between those materials. Individual details may be technically sound, but become problematic when they meet another building element.
00:12:03 Sophie Favilla
So we almost always have three-dimensional conditions represented in 2D. Now, personally, I would love to have every waterproofing detail in pristine, isometric form, but in reality, there isn't going to always be time or budget for this. So I'm not saying that the solution is to crack open Revit for every waterproofing detail, but it's more about keeping in mind that things that often look simple in cross section can conceal a hidden threat. For example, an expansion joint detail is rather straightforward from one view as a cross section, but that joint continues through the structure and eventually meets other building elements to become a T-junction. Or, such as the example on screen, the waterproofing upturn fit appears fairly neat and simple against one side of the column. But the joint detailing, which includes a rigid metal angle, actually has to wrap around all four sides of the column and intersect with yet another joint in the substrate as well.
00:13:06 Sophie Favilla
Moving on to the next gap, we have ambiguity. What does ambiguity look like? Often it's having waterproofing represented as a single line. Waterproofing systems really are that - systems. They comprise the membranes, primers, reinforcement, sealants and accessories, but drawings may only communicate waterproofing. This kind of design only tells you that it should be waterproof, but not how to actually install it or what is required at each area. In some of these examples on the screen, you can see how the waterproofing is just sort of vaguely indicated across a whole junction without any information of how the junction or interface will be managed.
00:13:50 Sophie Favilla
We can also get notation on drawings that looks like this, this, or equivalent, where there are multiple nominated products all in one drawing, which these would all have very different substrate requirements, detailing requirements, final thicknesses, and installation methods that just cannot be accounted for in one single representation.
Often we get generic specifications, which often include really broad clauses that attempt to cover every situation, but don't clearly identify what applies to this particular project. For example, basic stuff to the effect of waterproofing shall be installed in accordance to the standard, or service preparation shall be carried out in accordance with the manufacturer s requirements.
00:14:36 Sophie Favilla
This also comes along with generic details. So these can be a great start. And we'll talk to these a bit later. But often generic details are used without resolving the actual geometry, interfaces, levels, and materials at a project-specific junction. Essentially, if the design can be interpreted in multiple ways, the final outcome might not be the one intended.
00:15:03 Sophie Favilla
Then we have delaying or deferring decisions. What do we mean by this? Well, what I'm referring to is essentially when the design, sorry, when the decision is taken out of the design phase or rather is planned to be made during construction. Like I alluded to at the beginning of this presentation, the worst design decisions I see are actually just decisions that were never made. So this can look like waterproofing to specialist detail without identifying who the specialist is or when the detail will be developed.
00:15:36 Sophie Favilla
Contractor designed waterproofing where specifications and drawing sets I have reviewed like frequently include statements like contractor to provide . But if we're relying on the contractor to provide shop drawings, this misses the opportunity to actually finalise them during design before a contractor is nominated.
And if any shop drawings end up being provided at all by the contractor, and they often aren't, they're extremely likely to be highly generic from the material manufacturer and not developed with any consideration for the project.
00:16:10 Sophie Favilla
We also have waiting for construction to finalise waterproofing system selection. And this goes a little bit back to that ambiguity I mentioned before where drawings will mention multiple systems. If a nominated and finalised system is not included in the design, then the design shows a highly generic detail that technically represents
any waterproofing and therefore in a way doesn't represent anything for practical guidance.
Many, many times I've been asked to review the suitability of a waterproofing system against the project's requirements, and I'm told it needs to be done immediately because it's starting the waterproofing on Monday. So what's the point of this? What if the product wasn't suitable? Well, if the answer is yes, in theory, but there are a number of risks to consider with this particular product. What if the answer is yes, but here are all the steps you need to do before you install that? Essentially, the response to any advice that I give that isn't just, yeah, proceed with waterproofing is going to be quietly ignored because it's too late to do anything. And then of course, there's responsibility gaps, where interfaces and other aspects of waterproofing fall between the scopes of different designers, suppliers, and trades, and thus fall through the proverbial cracks in the membrane.
00:17:26 Sophie Favilla
So importantly, decisions don't disappear when they're deferred. They actually just move downstream where there's less time and less flexibility to do anything about it.
So just to talk broadly about what is at the heart of waterproofing design and how we can fill these gaps, we should be aiming to minimise unnecessary complexity, resolve interfaces before construction, avoid details that rely on perfect workmanship, clearly communicate what needs to happen at unusual junctions, and perhaps most importantly, reduce the number of decisions that need to be made on site. Good design doesn't eliminate the risk of installation error, but it does reduce the opportunities for it.
00:18:17 Sophie Favilla
Okay, so now that we have established these common design gaps, I'd like to talk a little bit about basic waterproofing design principles, which we can break down into a neat little system known as The 5Ds of Waterproofing , or what James Cameron might refer to as the way of water . So all of these principles, they work together and they're highly interrelated, so we need to consider them collectively. These are deflection, so how we can direct water away from vulnerable areas. Drainage, how we get water off a building. Drying, how that retained moisture can vent. Durability, which is how through the management of deflective deflection, drainage, and drying, this enables protection of the building, and of course, details, which is how we tie these concepts together and represent them.
00:19:08 Sophie Favilla
So, in the past, a lot of these concepts came built in when we were designing buildings, as there was no alternative. Think of like pitched roofs or ancient churches, which didn't have a single flat surface on them. These structures naturally dealt with water as a part of their geometry, and water shedding design was the default before the time of membranes. But over time, building design and of course building materials are getting more creative. So we have to think a little bit more consciously and deliberately about these principles.
00:19:44 Sophie Favilla
First principle is deflection, which is essentially how we implement the barrier against water. So it's how we can control where water goes before we have to actually rely on the waterproofing to resist it. We know that roofs and balconies are going to get wet, but good design should involve, oh sorry, rather, should avoid unnecessarily directing or holding that water against vulnerable building elements.
The most obvious example is falls in the floor, which is going to be towards drainage points, but we should also think about what the water is falling away from. Wherever possible, water should be directed away from falls, door thresholds, penetrations, and other interfaces. This same principle applies vertically.
Upstands, overflashings, drip edges, subseals, these all help to interrupt or redirect the path that water might otherwise take into our building.
00:20:41 Sophie Favilla
I'll talk about drainage and drying simultaneously, just as they go together quite well. Drying is, of course, a natural consequence of good drainage. We drain water from surfaces generally through falls and clear paths to drainage points. It's important not to obstruct these paths, such as the corridor formed between the plant points
in the photo on the top right.
We also want to promote rapid drying, as effective drainage limits residual moisture, debris, and contamination buildup. The soft format that I'm pulling back in the photo in the bottom left, this was preventing the drainage of water from the surface, which caused the underlying cement modified membrane to blister. These materials in particular hate being in constant contact with water and the membrane will take in moisture through osmosis if water cannot be removed from the surface.
00:21:32 Sophie Favilla
Similarly, the photos on the bottom right I took on a roof where the stone ballast was retaining a huge amount of moisture and the drainage cell below the ballast that is supposed to actually provide the drainage was choked by dirt and debris that likely came into the roof on that very ballast.
The roof parapet had a very small retaining section to prevent the ballast from going through the roof overflow, but the tiny gap that was meant to allow water to actually discharge through the overflow and drain from the roof was so small that a little moss accumulation was all it needed to become blocked. So we have in that design like a competing interest between how do we hold back this ballast? How do we provide for drainage?
00:22:17 Sophie Favilla
So of course, like obviously there's falls is a really big aspect of drainage and drying. We need to design positive falls to all outlets to ensure efficient evacuation of surface water. But we should also be thinking beyond falls when it comes to drainage. Drainage needs to be considered in any space that water can become trapped, which includes inside the building envelope, and we need to prepare for this and give the water a way out. The photo here on the bottom left shows a very typical site observation of mine, which includes lightweight cladding that has been sealed to the floor of the balcony. So this completely takes away the ability of the wall cavity to drain.
00:22:59 Sophie Favilla
We cannot rely on keeping water out only or trying to completely seal up a building. We have to assume that water will one day get in there, either through a crack in the render of the cladding or through a roof leak, and then we need to prepare a path for it to exit. The detail on the right shows an example of how a lightweight cladding wall can successfully vent the water outside of the waterproof layer.
00:23:24 Sophie Favilla
By ensuring adequate falls and that good drainage paths are provided without obstruction, we will ensure that the surface water removed will only leave behind water held by surface tension. This in turn will dry relatively quickly, preventing the buildup of moisture, mould and debris.
Durability. So durability is about thinking beyond whether a waterproofing material is capable of keeping out water on the day that it's installed. We need to consider whether it can continue performing for an appropriate period within the environment that we've put it in. That starts with material selection.
00:24:03 Sophie Favilla
We want systems that are supported by appropriate testing, certification, and technical evidence. Then we need to think about the real surface environment. Is the membrane permanently concealed and protected? Or will it experience UV, temperature, cycling, pedestrian traffic, debris, chemicals, or regular wetting?
Something like a membrane beneath a pavers and pedestals floor system is a good example. We might instinctively think of it as a protected finish because there are pavers over it, but it will still be exposed to rainwater and debris. There's definitely going to be some UV exposure through the gaps in the pavers, and the membrane remains part of an accessible external environment.
00:24:47 Sophie Favilla
That photo in the sort of middle bottom row is an example of how waterproofing membranes typically look once you lift the paver and pedestal up from it. The wrinkled eldritch horror in the top right is when a butanol rubber sheet membrane is introduced to boiling hot water from the plant roof.
To talk to detailing, detailing is how we communicate our design, obviously, and it's a solution to things being done on the fly during construction. Not every possible case has to be perfectly resolved during design, but we really do want to limit the amount of items that are left up to the construction phase.
In the photos on screen, here is an example of the design overriding an on-site decision that's very common. Conduit penetration details are so often a yucky mass of sealant or just waterproofing membrane applied around bendy ripped surface of half a dozen tubes and it just crumbles apart over time.
00:25:50 Sophie Favilla
But if we document from the start how these tricky penetrations should be dealt with, like with a deliberate fitting, something that can be installed, waterproofed, and maintained, then that's one less, she'll be right, sort of installation moment happening on our build site.
And also, this makes it easier to enforce corrective actions when something is spotted on site. Ultimately, it's a lot more straightforward and direct when someone like me comes along to inspect something, and I can say that it's not in accordance with the design and therefore the contract. That's easier to say than not to best practice or not my preferred method . Because of course, even the Australian standard provisions, these are minimum requirements only. So a compliant method is not necessarily going to achieve the performance you require, especially in a non-typical configuration.
00:26:47 Sophie Favilla
So, time to get drawing. Having talked about the principles behind good waterproofing design, I want to shift now into our practical toolkit and how we can actually translate these principles into design documentation. How are we going to communicate the principles of deflection, drainage, durability and drying.
Good waterproofing design doesn't require you to become an expert in every membrane chemistry or installation technique. It's more about knowing where to find reliable information, how to apply it to your project, and when you're going to need additional expertise.
00:27:30 Sophie Favilla
The first tool is codes, standards and practice guides. The NCC and Australian Standards give us the regulatory framework and minimum requirements. AS 4654 parts one and two talks to external above ground waterproofing and AS 3740 is for internal wet areas and they both form part of the deemed to satisfy solutions for the respective areas within the NCC.
We also have documents like the Design Documentation Practice Guide for Class 2 residential buildings. This provides practical documentation inclusions for all parts of the building, including waterproofing.
00:28:11 Sophie Favilla
And of course, we have technical data and manufacturer literature, which explains how a particular product is to be installed.
The second tool is precedence, so we don't need to reinvent every waterproofing detail for every project. If a detail has worked successfully before, we can understand why it worked and use that knowledge again.
The third tool is coordination. Waterproofing doesn't sit neatly within one discipline. It interacts with structure, facades, hydraulics, landscape, doors, windows, and finishes.
00:28:45 Sophie Favilla
So finally, we have review. Architects have to understand and coordinate an enormous amount of building systems. So there is value in having someone who spends all day thinking about one particular subject look at your waterproofing.
So, jumping into our first tool, which is standards. The primary standards at our disposal for waterproofing are, as I mentioned, AS 4654 for external waterproofing. So this includes things like balconies, roofs, landscaped areas and podiums. And AS3740 for internal wet areas such as bathrooms or back of house service rooms.
00:29:28 Sophie Favilla
We don't unfortunately have in Australia a current standard for below ground waterproofing. A lot of people piggyback off the British standard for below ground waterproofing, but just insider info, this is being worked on within the standard committee, so hopefully we will get something of our own coming soon.
I will just focus on AS 465 though for today. So this standard is an incredibly useful starting point for architects because it gives us the basic rules that should inform the waterproofing design before we even start thinking about anything else. It gives us requirements for things like falls, drainage, termination heights, movement joints, and overflows. Now, these aren't necessarily decisions that we want to discover late in documentation, because many of them actually have knock-on effects to fundamental architectural dimensions and levels within your project.
00:30:24 Sophie Favilla
So it's important to remember that standards are at the starting point, but they are also not finished design. They provide a common language and a minimum level of detail from which the project-specific solutions can then be developed. For example, if we know that a particular waterproofing termination is required at a door threshold, that requirement then needs to be reconciled with accessibility, internal and external finished floor levels, drainage, and of course, the door system itself. The standard gives us the requirement, but it's not going to coordinate all those things for us.
00:31:04 Sophie Favilla
So to reiterate, the AS 4654 for external waterproofing, it sort of represents the waterproofing commandments, if you will. It's the thou shalt always install a fillet, those sort of things. So here's some screen grabs up on the screen. It's standard details from AS465, which thankfully, in the latest version of the standard coming to you later this year, we'll actually be in glorious technique colour, so they're going to look a lot nicer. But yeah, so with these drawings, I will note that they are typical. So when a drawing in a standard says typical, obviously it is not required to be copied exactly.
00:31:46 Sophie Favilla
So it's just demonstrating one way that you can achieve compliance. Similarly, I just highlight the distinction between where something says shall , and this obviously describes a requirement or something mandatory to achieve compliance, and when we have should , which describes a recommendation. So I'd encourage architects to use AS 4654 almost as like your first design checklist. If I'm drawing a drain, what does it say the waterproofing must do? For example, clause 2.10 for a drain, the membrane has to connect to and turn down the inlet. Once we've established those fundamentals, we can then bring in the manufacturer's requirements, coordination with other disciplines, and specialist advice to actually develop project-specific solutions.
00:32:37 Sophie Favilla
So, the design documentation practice guide, I think, is also particularly useful for architects, and it brings together quite a lot of the ideas that we're discussing today. So, the practice guide was actually developed here in Victoria with input from a broad range of industry stakeholders, which actually includes the ARBV, Australian Institute of Architects, Engineers, Building Surveyors, and the Australian Institute of Waterproofing. Now, what's useful about it is that it goes beyond simply telling us what the technical waterproofing requirements are. Instead, the practice guide asks what information should actually appear in the design documentation.
And waterproofing is specifically addressed within that framework in section 1.2.3. So this guide is quite a helpful companion to the standards. So AS 4654 helps tell us what our waterproofing needs to achieve. And then the practice guide comes in to help us think about what we need to document so that somebody can actually build it that way.
00:33:43 Sophie Favilla
There is also manufacturers literature, which becomes a really another useful part of the toolkit. If you have a waterproofing system nominated, the technical data sheet that comes along with it isn't just there to tell you the product name and how many coats the contractor needs to apply. You can actually tell us quite a lot about what conditions we need to design around when we're thinking about our waterproofing.
00:34:05 Sophie Favilla
So what substrates can it go over and to what moisture content can that substrate be? Does it require a primer and what primers for which surfaces? How thick is the overall system going to be? Does it need protection? Can it tolerate immersion? What are its limitations? And what does the manufacturer require with other products to carry out our joint penetration and termination details? So this is another reason why leaving your system selection sort of late in the project and close to construction can become problematic. If we don't know what the proposed system requires, we may inadvertently designed a substrate, interface buildup or sequence that isn't actually compatible with.
00:34:54 Sophie Favilla
Good technical data will walk through the steps of how this system is to be detailed at particular features such as joints, upstands and drains, which helps to bridge that gap between the general requirements of the standards and the specific requirements of the waterproofing system that we're actually fitting in the building.
How do we know which manufacturers have good technical data? Well, we'll get to that in a few slides.
Right, moving on to our next tool, we have precedence. So waterproofing details do not need to be created from scratch, and I certainly don't start from nothing when I'm preparing my own drawings.
Using a precedent gives you a starting base, and we can find these in, of course, the standards, as we just mentioned, successful details from other projects, manufacturer details, technical guides, and by asking waterproofing consultants.
00:35:47 Sophie Favilla
Just to highlight though, while we don't need to reinvent the wheel, we do need to understand why it rolls. It's important to distinguish between reusing a proven principle and simply copying a standard detail without considering whether the conditions are actually the same. So precedent is not a detail to copy blindly.
We need to adapt for our climate, exposure, membrane system, finish buildup, maintenance requirements, and accessibility requirements.
00:36:16 Sophie Favilla
Just as an example, certain manufacturers will have a really comprehensive standard detail for their system, but because it originates from another country, they might not show something that is required by Australian standards, such as a fillet at a change in direction. So it's important to review the waterproofing requirements in a hierarchy where NCC and Australian Standards comes first, and then we can start sort of making our way down to the manufacturer's requirements.
Here on the screen, I've just got some examples of how I've used standard details from AS 4654 to develop my own project specific details, such as this planner box where I started with the standard detail and then incorporated what the actual wall and floor substrates that the project had, as well as like the sort of boundary junction between an adjoining courtyard and the terrace planter.
00:37:15 Sophie Favilla
So once I know that the standard requirements are covered and in the drawing, that's when I can start to get creative and add more detail, such as the layers within the waterproofing system from primer, base coat, top coat, and start thinking about the life of this planter box. Once I knew that one wall of the planter was going to adjoin the apartment wall, I really wanted to be sure that the system I was using was robust and less prone to installation error. I also added a waterproof acrylic paint to the block work wall on the left of the planter, which wasn't originally in the design, because as it was exposed, I didn't want those blocks sucking up water and acting like a sponge to the environment, bringing moisture to the rear side of the waterproofing membrane.
00:38:03 Sophie Favilla
Then our next tool is coordination. So waterproofing is inherently a coordination exercise. Very rarely are we concerned about what happens in the middle of a large, uninterrupted area of membrane. The difficult parts are where that membrane needs something else. That's where we can end up with a gap. The structural engineer has designed their element, hydraulics has designed theirs, the facade consultant has designed theirs, and the waterproofing itself may be perfectly reasonable, but has anyone actually designed the connection between them? So ask yourself, who is responsible for this interface? It doesn't necessarily mean that the architect personally has to design every component, but someone needs to identify the interface, bring relevant information together, and make sure there is a solution.
00:38:53 Sophie Favilla
Coordination means designing the connection, not just each system, either side of it. And this may take the form of design workshops and collaborative work that is shared between design team members. I'm thinking this, what do you think? Or, hey, Mrs. Structural Engineer, I need integral hubs of this height and a greater structural slab of this fall, and having those conversations in really early days of a design.
00:39:17 Sophie Favilla
For me personally, being involved in a design from about concept design onwards is fantastic, and a completely different experience to being brought in at the end. All the questioning and nitpicking actually serves a purpose, and it allows the waterproofing to develop naturally alongside all the other elements, not just tacking it on once the building surveyor asks for it.
00:39:41 Sophie Favilla
Just got some examples of failed coordination here, which I know they're not drones, but I thought it might be a bit more interesting to see some real life things from the field. So we've got some very difficult pipe penetrations to the floor that are hard to waterproof. I know this is technically a retrofit job, but and didn't come with the original drawings of this building, but it was still someone's decision at one point. We have a sliding door buried below the tile bed, so all the water that falls on that door and is meant to drain out of the frame subsill is actually just directed below the waterproofing membrane. Shockingly common detail on site, unfortunately. Of course, we have our lightweight cladding sealed to the floor, which is a site observation so common for me, I don't think I've ever actually seen it done the other way correctly in person. We've also got a corroding balustrade that was below, buried below the tiles when that type of the metal powder coating that was used is not suitable for being buried. It looked very neat and tidy until orange water starts to leak up out of the grout.
00:40:50 Sophie Favilla
We have a storm water pipe penetration through the substrate and tile in a manner that is just, there is very little the waterproofing applicator can do in this scenario to form an adequate detail. And then of course, we have some delaminating waterproofing due to adhesion failure, which is a bit of a sequencing issue and a lack of documentation to keep everyone informed of what can actually happen if the top coat is not applied in time.
00:41:20 Sophie Favilla
So just to emphasise coordination, waterproofing infamously makes up only about 2% of the value of a building project, but the costs of ignoring it are astronomical. So invest early, resolve early. A little more time spent integrating waterproofing into the design can avoid significantly greater cost, disruption and compromise later. Ideally, coordination happens while questions are still cheap and easy to answer. Finding an unresolved threshold in a drawing is very different from finding it after the door has been installed and the balcony levels have been poured.
So be sure to get your coordination in early and your peer review, which we'll talk about next.
00:42:06 Sophie Favilla
So peer review. Architects are responsible for integrating the whole building, but no individual can maintain specialist expertise across every discipline. This is where consultants and manufacturers can step in and assist you with material selection, details, confirmation of assumptions, identification of risks, lessons learned from previous failures that they might have investigated, and just generally a fresh set of eyes.
One of the benefits of independent consultant peer review in particular is that we don't have a product to sell or a construction methodology to defend. Our interest is in whether the waterproofing design works, not just at completion, but for the building and its occupants over the long term.
So we are product agnostic and performance focused. Independent review asks what is best for the building, not what is easiest for any one party.
00:42:59 Sophie Favilla
So here on the screen, I just have some examples of peer review findings we've got such as sort of explaining that why you should not waterproof above and below your screed. You don't really see this happening anymore due to NCC 2025 changes the use of screed to create floor, but it was very frequent and something we did have to talk to a lot and explain that double the waterproofing layer is not double the protection. It's kind of like a, I hate to use this metaphor, but it's sort of like thinking 2 condoms is better when actually it's worse.
00:43:34 Sophie Favilla
So just for some other things we have. You know, just pointing out with a planter box that the acrylic-based render that was going to go on the side is not going to achieve long-term adhesion to the polyurethane-based membrane that was specified inside the planter. We've got questioning, flashing and fixing arrangements that both hinder movement and prevent drainage out of the parapet.
00:43:59 Sophie Favilla
And yeah, just in general, like recommendations for materials that have the right characteristics to address tricky geometry. Especially with product selection in particular, there are so many types of waterproofing out there. And especially from the big name suppliers, they're all going to have, you know, they will come along with their certifications, compliance requirements are met, fancy scientific backing, and they all work on paper. But in my opinion, some things just shouldn't be used because they're too hard to install correctly, or too many parts can go wrong. And that's what we're not afraid to say up front. Or rather, that's the freedom we have when we're not producing any waterproofing materials.
00:44:43 Sophie Favilla
Another example here is just translating the sort of wordy and branching NCC requirements for internal waterproofing and representing that in a visual diagram so that one can easily understand where waterproofing and water stops are required depending on the space. So peer review brings the benefit of specialist expertise.
It's about taking what I see every day in design reviews, investigations, and on-site, combining it with an understanding of current waterproofing requirements, and turning that knowledge into practical advice that can be applied to your project before issues become problems. We can also have really unique experience with failure mechanisms, since a lot of my work is investigation, I see unusual scenarios pretty frequently, such as condensation suddenly developing in the roof cavity of a decades old building, because a new waterproofing membrane with a different color was applied over the roof as part of maintenance. This new membrane, a white liquid applied coating, had a completely different solar reflectivity value to the original bitumen sheet membrane, which changed the dew point of the roof entirely.
00:45:55 Sophie Favilla
So just to sort of close, key takeaways, we can put, you know, all these concepts back into our toolkit, standards, precedents, coordination and review. The aim isn't for every architect to become a waterproofing specialist overnight. It's to have practical processes for recognising risks, a sking the right questions, using available resources, and getting the right people involved before those gaps reach construction.
That's basically it. Thank you all for listening. There's some information about the Australian Institute of Waterproofing on the screen and some contact details if anyone was interested. But otherwise, Giorgio can step in.
00:46:40 Giorgio Marfella
Thank you very much, Sophie. That was brilliant. Now, there's quite a few questions. I'll try to cover them all. We've got a bit of time. And those who might head right now, perhaps I'll miss as we have this discussion, but we might endeavour to come back generally through our newsletter. So please, if you do have further questions, put them in whilst we talk, okay? So I think there's about four themes that came up. One is about regulations and the standards. So you mentioned about AS 4654, right? So which is about to be amended, is that correct?
00:47:14 Sophie Favilla
Yes, so the...I'm not sure if it'll be called AS 4654. I think it'll be called AS 4654 2026, but that is currently out for current review and is set to be released later in the year.
00:47:29 Giorgio Marfella
That's right, and apparently there was a comment that followed up saying that it's out for public comments, I believe, right? And so I was...
00:47:36 Sophie Favilla
Yes, please tear it to shreds.
00:47:39 Giorgio Marfella
And is that the full suit because there's two of them, there's 0.1 and 0.2 or?
00:47:42 Sophie Favilla
No, so at the moment it's just AS 4654. I think AS 3740 will be coming a bit later, so next year. Yep.
00:47:49 Giorgio Marfella
Okay. Okay. And then there's another question talks about the NCC 2025 and minimum falls of 1 to 80 for open concrete deck roofs. And further, the question goes, this requirements for the membrane to be bonded to the substrate concrete and not to a screed. Um, is that is that does can you say something about this? Is that your understanding?
00:48:15 Sophie Favilla
Yeah, it's been a really, really interesting change that has had a lot of impact, not just in new design, but in particularly remedial spaces, because of course, there are so many structures that exist with a screed on them, but now any works to change that become quite challenging. So the decision happened in the 2025 NCC. They've basically said, you know, no more screeds have issues, so we're not going to use them anymore, which is, I don't know, it's kind of crazy because, you know, waterproofing has issues, but you don't just ban waterproofing. So now, yeah, the fall has to be in the structural substrate and the waterproofing has to be over that.
00:48:56 Sophie Favilla
So it does, and they've also made it one on 80, which is quite interesting, I think, from a concrete forming perspective. Yeah, it's posed a lot of challenges and certainly a lot of performance solution work is propping up for me all over the shop.
00:49:10 Giorgio Marfella
Yeah. So, so the directions is showing, I mean, myself, practicing in the past, I remember, you know, concrete flat provider, you have a screed on top of was often commercial buildings was not unusual to put a liquid membrane on top of the screed, right? And, as you just pointed out, this is pointless to have two, but you say the direction might be two actually, which is the other school of thought that I'm aware has been around for a while to actually fold the structure. And so this is the direction instead in which we are going to, right?
00:49:41 Sophie Favilla
Yeah, exactly. So they've basically just taken out that extra layer. And I mean, it even has implications to other sort of roof buildups. We've, you know, we used to get kind of excited about flat slabs with tapered insulation on top, but now that's not acceptable in 2025 either. So it's really caused a shift.
00:50:06 Giorgio Marfella
Now, there was another question. I'm going to come back on that about basements, but there was another critical thing to discuss, I suppose, with the role of the waterproofing consultant, I suppose, like yourself. And so at what stage would you recommend the waterproofing consultants come in? Are they necessary? And also suppose which kind of scales and scope of projects they become affordable, who pays them? So would you like to say a bit more? This is obviously an area of growth, I imagine, waterproofing consultant.
00:50:44 Sophie Favilla
Yeah, yeah, I think obviously the earlier is better because then, as I said, you can actually work together for things to develop naturally rather than having to fit, you know, if the design is mostly complete for all other aspects of the building, then you're just sort of trying to retrofit your waterproofing to that rather than sort of coming up with something that works along the way.
I will actually say I am seeing a positive trend in us getting involved earlier and earlier with new designs, which is actually quite nice to see. So I think if we can get in the, and this is the thing, it's not saying that like at the very start of your project, you're going to have a waterproofing specification. It's more like what might happen in just the concept design as we give like, you know, a more high level design report that includes, you know, okay, we've had a look at your concept design. We have a feel for the performance requirements you need. Here are some things to consider and here are some possible systems to consider. So you're not necessarily saying, oh, you know, let's get this design package rocking and rolling immediately, but you're just giving, you know, the time to, like you would with any other part of the building, step through multiple sort of iterations, get more and more detailed over time.
00:51:52 Giorgio Marfella
And who pays for that? I mean, suppose that's the, obviously, if it's in the retro, you know, in the front-end side of the consultancy, not the inspection works when you're solving the troubles for that change. So who's normally the client in your case?
00:52:09 Sophie Favilla
I think it's generally like the head contract that the architect has with the developer or asset owner. Like we'll generally have a back-to-back agreement as their sub-consultant. Sometimes we're sort of involved independently or we're organised through the project manager who's acting on behalf of the developer or asset owner.
00:52:29 Giorgio Marfella
Okay.
00:52:30 Sophie Favilla
Yeah.
00:52:31 Giorgio Marfella
Okay, and then there's the role of the peer review you mentioned. So there's also some scope of, is that something you see happening more? Would you recommend that?
00:52:42 Sophie Favilla
Yeah, yeah, peer review is really growing, which is great. We have a lot of projects on the go where, you know, people are preparing their designs and then at key stages, we're sort of stepping in to take a look and say, you know, give feedback and opinions and just help guide that process, which I think is good. So often we kind of offer to people that you know, we can either produce the bulk of the work and then you review it, or we can do it the other way around where you have a go at the waterproofing design, then we review it. And it kind of just depends often that, you know, for us to review is cheaper than for us to produce the waterproofing design. So sometimes it's a financial decision which option to go with.
00:53:22 Giorgio Marfella
OK, another topic that always comes up, the architects love that were procurement and DNC contracts, so I suppose that the comments that I'm reading, the more comments the question perhaps, and then they sort of very usual perception. And of course, in some procurement systems, there might be a lack of scrutiny or say, for example, classic scenario, the architects may specify a particular solution, then it gets changed further down the track and so forth. So in your experience, do you think that is the critical issue we're dealing with? What would you recommend architects? What would you recommend to architects in order to mitigate the risks?
00:54:06 Sophie Favilla
Yeah, it's a really good point because it does happen a lot where we come up with something or the designer comes up saying it, then as soon as a contractor is appointed, everything changes. And I've even had a job where the proposal that we sent even included, we'll do the initial round of review and then when the contractor inevitably submits what he wants to do and said, we'll review that too. That was like the structure because we all knew it was going to happen. It was requested that way. So honestly, I'm not too sure what the solution is because I think it's a bit of, it's an Australian cultural thing, things are quite contractor driven, whereas perhaps in other areas of the world, it's a bit more design driven. So hopefully over time, less and less of that is going to happen. But I guess it requires pushing back a little bit on the contractors, yeah.
00:54:58 Giorgio Marfella
Pushing back, and perhaps what you've mentioned in your interfaces, ambiguity, or what's the other decision? So, so it seems to me that perhaps you know the importance of documentation, not withstanding the procurement, right? So, and obviously well done documentation that is meaningful, with that is clear, could be an antidote to prevent things to go down the track.
00:55:21 Sophie Favilla
Yeah, yeah, definitely. Because a lot of the times, like, we'll be involved in a project where they say, like, oh, well, the contractor is providing the design, so could you please review it? What the design is, is the contractor sending you a bunch of data sheets. That's not a design. That's saying, I'm picking these products and I'm going to install them. So it's quite a...you know, by leaving that up to the contractor, unfortunately, you get basically nothing, essentially, so it's very, and maybe people aren't super aware of what they actually end up giving over in a project, but yeah, I would say, you know, take control when you can early on, don't leave it for them to do it, because they won't do it, unfortunately. Apologies to any contractors in the room.
00:56:07 Giorgio Marfella
Okay, and the next topic, the more specific, I suppose, the first one talks about basements. I know you mentioned that we have British standards we rely on, for example, but I'll go forward with the question and it asks you, can you talk about some of your strategy for effective basement waterproofing? And a follow-up with that was also, could you share criteria for deciding if the basement is a dry or a wet basement?
00:56:38 Sophie Favilla
You've touched a very interesting, very passionate subject of mine, which is wet basements. To cover that wet basement, the way, unfortunately, there is no definition of the wet basement, which is provided by a standard or code that we could use. The way that me and my company interpret it is that you are, if it's a wet basement, then you are deliberately relieving hydrostatic pressure from the wall internally. So when you have those drainage against the soil side of the wall, you then intentionally bring that water into the basement to drain it in stormwater connection. And that might be because you have restricted access, like maybe you're building against a neck.
a neighbouring existing basement where you don't have the space to put the stormwater system behind the wall, so you bring it inside. That does not mean your basement can leak, which unfortunately is a defence that we see over and over and over, which is, and even in litigation or VCAT,
00:57:34 Sophie Favilla
so the basement leaks, people say oh, but it's a wet basement. And I'm like, no, no, no, no. Wet basement doesn't mean it just leaks willy-nilly through every crack and junction and all of that. So it's very misunderstood.
What I would say for the principles of basement waterproofing is multiple stages of protection.
00:57:51 Sophie Favilla
So we have, and the British standard covers this quite well, but we have type A, B, and C levels of waterproofing protection and ideally, all of those should work together. So type A is the barrier membrane, so the actual waterproofing membrane to the soil side. We have B, which is structurally integral waterproofing, so things like using concrete admixtures and water stops that are inside the concrete structure. And then type C is your drained cavity.
00:58:17 Sophie Favilla
So if any should anything get through that first layer and then second layer and enters the basement, that there is like a specific method to direct that water take to the stormwater system. So unfortunately, that sounds like a lot and it can be difficult to get all those items over the line from a budgetary perspective,
00:58:41 Sophie Favilla
like we've had clients where they said, you know, I do not want this to leak and so we say, well, you need to do this and they go, no. So it can be tricky, but yeah, it's multiple lines of defence. You need to have those fail safes because unlike other areas, there is nothing you can do to the rear of the waterproofing once the basement's finished. So, have your backups, you know, going in.
00:59:04 Giorgio Marfella
Yeah, I mean, ultimately, waterproofing is part of the issue, sometimes water management, I suppose, as well, you know, in the sense that the fact that water seeps through buildings doesn't, that has to be thought, like the example you've shown for a rain screen where
00:59:22 Giorgio Marfella
you can allow some water through the building fabric, but then you have to think where it's going to go after that, right? So, yeah.
00:59:28 Sophie Favilla
Yeah, it just, it needs to be deliberate and not just, oh, it can, you know, that defect is because it's a wet basement. Well, it's not, it doesn't cover defects. It's, yeah, it's very interesting. But it comes up a lot in disputes, unfortunately.
00:59:44 Giorgio Marfella
Fortunately, there is a British standard here that can help, so, so we can recommend architects to be familiar with that, perhaps.
00:59:52 Sophie Favilla
Yeah, and there is talk amongst the committees, like just a bit insider knowledge. I think they are in the process of adopting it for Australian standards. So we can look forward to that.
01:00:03 Giorgio Marfella
Yeah, excellent. Okay, so it could be embedded in the NCC as a, as a, is that what we're talking about? Yeah, good.
01:00:07 Sophie Favilla
Yeah, yeah, they're starting to really notice that there's a gap there.
01:00:12 Giorgio Marfella
Yeah. Another question, again, on the specifics, balconies, of course, you mentioned one of the areas that, of course, creates some of the most vulnerable points of water entry.
01:00:23 Giorgio Marfella
And there's a comment to your question actually says, do you know why the porous port and paver system, I think I'm assuming this is the balcony on polypads or something like that for balconies. It's now attracting a performance solution approach, it seems, whereas in the past it wasn't. Are you aware of this or do you have any specific?
01:00:48 Sophie Favilla
No, I haven't. I haven't come across that. I'm not sure if that's perhaps a wind uplift thing or...
01:00:55 Giorgio Marfella
Oh, I see. OK, yeah, I see.
01:00:57 Sophie Favilla
Possibly, depending on where you put them, it might trigger that sort of thing. But I haven't actually encountered a performance solution for pavers and pedestals.
01:01:07 Giorgio Marfella
Yeah, and so, so we clarify for the answer. I interpret this question to be the balconies that have pavers on pedestals or polypads as they called for the commercial product, but then the understanding that the assumption is that the gaps are open water.
01:01:26 Sophie Favilla
Yeah, yeah, exactly. Yeah, there's generally like a 10 mill gap, yeah, yeah.
01:01:28 Giorgio Marfella
It percolates through, and then it, but then it was, yeah, it's 10 million gap, but you're saying that this could be actually driven by uplift for wind, because in essence the pavers are simply relying on their weight to stay in place.
01:01:38 Sophie Favilla
Yeah, it depends like if it's going to be on the top of a roof and there's not a lot of shelter, but generally they've always been fine on the projects I've seen and like they just get putting because the pavers are obviously quite heavy.
01:01:50 Giorgio Marfella
Yeah. Good. And so this was the questions I collected through the, but I can see there's a few others that have popped up, but we always like to wrap up at one and we would like to be at lunch time. So, Sophie, thank you very much. I'm sure this was great value for our audience. And as I said, you know, we'll collect these questions and go back and feed them to Sophie and then, you know, share a general response if possible. So thank you again, everybody, and we really look forward to see you again at the next webinar. So have a good afternoon, everyone.
01:02:26 Sophie Favilla
Brilliant. Thank you so much. See you then.
01:02:27 Giorgio Marfella
Bye, bye-bye.
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