Substrate Roofing Solutions: Balancing Cost and Quality

Shane Clarke: Kia ora, tēnā tātou katoa. My name's Shane Clark. I'm the general manager here at Nuralite , New Zealand's waterproofing leader. Welcome to webinar 39; today's particular topic, time is money, is a continuation of our cost-conscious theme that we've been running for the past six months. Our previous webinars can be seen on our education page, and each half-hour section is accredited for five NZIA CPD points. So at the completion of this webinar, there will automatically be a survey that pops out to all the participants. More specifically, today, we take a deep dive into substrate selections, specifically around traditional plywood structures that would be found in a typical NZ 3604 timber structure, in comparison to an alternative profile metal tray substrate for your flat roof. So if there's one key message I'd like you to take away today would be that we believe true value engineering occurs at the design stage. What I can also tell you today is that you are surrounded by some like-minded designers, architects, and specifiers. how do we know this? it's our database. So we know who's here. So, as a group of designers, specifiers, and architects, you have the ability to design some very clever value engineering systems. At the concept or early design stage, so we are challenging the traditional method of going through consented drawings and making changes where potential cost savings could actually be offset by the cost of a redesign. So today's webinar is set for around 30 minutes. Towards the end we'll have time for a Q& A section. During this webinar, please feel free to pop your questions into the Q& A section below. Luckily for you, I'm not the only one on the panel today. I'm joined by Dr. Benedict Pacorel, Nuralite Technical Advisor, who has been involved in the construction sector both here and overseas for many years. Also joined by licensed builder and Nuralite-approved applicator Micah Hoskins from Complete Waterproofing Limited, who, with his vast experience, is going to help us illustrate What it's like at the coalface and what's required to actually build these types of substrates. So although this is a webinar platform, we do try and make this as interactive as possible. Along with the Q& A function, we're also going to run a few polls. this actually, helps us establish who's in the audience and how best to fix our message. So for the first poll, we're just going to wonder and ask the question, is Anybody specified a roof substrate other than a timber lightweight roof? So feel free, to take a moment, pop your answers in there, Cool, so we'll be able to pop those results up. There we go, 50 50. More or less, this wasn't my strong point, but, yep, there we go. Excellent. All right, so first off, welcome, Bene. Thank you again for your time. Now, on your first slide here, you've got a couple of examples here just to give us a bit of an overview. Benedicte Pacorel: Yes, Shane. Kia Ora, everyone. So you can see on this slide, if you look at the top left, we start with a plywood substrate. it's usually the preferred choice for domestic construction and it requires a lot of, rafters and nocks to, build a substrate on top. You then have in the top middle, the concrete substrate. Concrete substrate is mostly used for commercial, construction, and it's also the preferred choice for green roof built up. You then have on the top right, the concrete substrate and it has no fall in it. So, in some of your projects, you'd have a flat substrate, which is absolutely fine because we supply some tapered PIR where you can easily build the fall. It comes as a one degree fall. It's then, going back to the bottom left, the metal tray substrate. So we'll expand on this, but, it's very quick and easy to install. and it's often used for, let's say, warehouses or school buildings. And then, in the middle, you have here some CLT, so cross-laminated timber. It is a mass timber slab. it's heavy-duty, and it could also, for example, welcome a green roof on it. We know when the heavy structure is possible. and the last one is one of our preferred choices at Nuralite . We like to rejuvenate your existing roof. So if you have, let's say an We can easily build on top of this. Shane Clarke: So that's a good overview. So it shows that we've got a vast offering when it comes to substrate types. A particular favourite of mine is that unique substrate around the CLT. We are seeing more and more of that. And, in my opinion, it is quite a clever way to create the full because, obviously, the underneath of your CLT panel is your finished ceiling. Benedicte Pacorel: So that's right. We do have a current project with CLT at the moment. Shane Clarke: Today, we're diving deeper into a particular substrate, which may not be the most sexiest of subjects, but it's quite real. yeah, so we're diving into the metal trace substrate today. So I just want to run through our system, Bene. Like we've got here. Benedicte Pacorel: So the metal tray substrate, so the big advantage with this is that you can quickly install the metal tray on top of a few purlins and, while your roof is being built up on top of the metal tray, the construction can carry on underneath the metal tray. So it's very effective to save time and then you can see in this image on top of the metal tray, you've got the vapour barrier. Then here, the PIR insulation, and on top of this here, you have the, 3PM bitumen membrane, which is a two layers. So you could instead have a TPO membrane or a green roof membrane, if you wish. Shane Clarke: Nice, nice. so this is an interesting slide. What are you, what are you telling us here, Bene? Benedicte Pacorel: So you can see the dollar sign. So, on the left inside, you have a typical cold roof built up with lofted insulation, then plywood on top and a membrane. You do need cavity and to ventilate the cavity to avoid institute connation. On the left, you can actually see some lofted installation. So over time you are likely to get some institute connation and as the lofted installation flatten the installation becomes less effective. we believe it's more of more extensive build up compared to a warmer roof build up on the right-hand side where there would be no in situ condensation, and, it's very time efficient, you save a lot of time by having a metal tray and then build a roof on top of this. Shane Clarke: Yeah, no, I have to agree with you there. Now there's a bit of an overview there of a comparison between the two. And so, just before we go to our next panellist, Micah, I'm going to get some help solving a little internal battle we have here. It's around square meter rates, and some people ask for square meter rates, some people don't, some people find them helpful, some people find them conflicting because they don't include everything, or they may not include, or they may include too much. So just want to ask the panel today. Do you personally find square meter rates helpful? If you want to run that poll, it would be interesting to see. Excellent, so let's see the results there. They're quite, ah, OK, so quite a strong favour of square meter rates. This is interesting. We're going to try to stay away from square meter rates in this particular, comparison, we can give you some indicative rates if it's specific to a project, but it's just there's just so many variables and we're happy to do it on a project-specific basis, but for a broad 30-minute webinar like this, we're going to stay away from it. But what we will focus in on is time and everyone knows time is money. Micah will be able to give us a rundown on that. I'm lucky enough to have known Micah over the last eight years; many of you may not know him, but he's got a bit of a background in building and just want to introduce yourself, Micah, and tell us a bit about your background and where you come from. Micah Hoskins: Thanks Shane. Thanks for having me. yeah, I've been in the building industry for about 18 years, and my background was mainly residential buildings. Also, some commercial, and I've been the owner and managing director of Complete Waterproofing for eight years now. And we specialize obviously in membrane roofing, but particularly, renewal type projects, so refurbishing existing membrane roofs and the associated works that come with it. So yeah, we have a pretty good idea of what's involved from both the building side of the membrane roof and then, obviously, the application of the membrane. Shane Clarke: That's really good. I think it's really good to get some info from the coalface. So this first slide here, we're just showing, on the left hand side a lot of timber. See the finished product on the right-hand side. Do you want to point to what we're looking at here? Micah Hoskins: Although that slide shows a truss roof build-up, it does illustrate what we're explaining, which is the amount of timber and time that goes into constructing a plywood substrate or a cold roof. As a bare minimum, you have to have your, rafters or millicentres, and then nog lines as well at 600 centres to form basically a grid. So a lot of timber goes into forming a roof like that, not to mention the hardware fixings required as well. Shane Clarke: And just in your experience, Micah, what's happened to the price of timber over the last few years? Micah Hoskins: Oh, yes, it's extraordinarily increased. Yeah. And fixings as well. Yeah, not just timber. In this slide, you can see a pretty straightforward plywood roof. And although it is just a big square, there's still a lot of time that we go into constructing that. you can see the amount of ply sheets there, though, usually a 2 by 2.4 they all have to be staggered in that brickbond layout. and then you've got to install screws at centres around the perimeter. And then 200 mils down the nock, so it ends up being around about 80 screws per sheet you have to put in, and that's 50 mils stainless steel screws, and then obviously the glue you have to put onto the timber frame as well. So yeah, a lot of time and effort goes into that. as well as, the margin for error, and then some remedial work to, sand apply or not before you can lay any membranes on top. the one other issue we really, struggle with as membrane roofing applicators is, moisture in ply. On a roof like this, where we don't have a temporary roof over the top, all it takes is one heavy shower and the ply is soaked, and it can take days for it to get to the point of less than 20 per cent that we can lay membrane on. And particularly so in all of the plywood joins, they love to soak in the moisture and in those areas in particular, it is really hard to get dry. So that's a downside to ply. For sure. Shane Clarke: Excellent. What we are proposing today is an alternative to traditional plywood substrates, and many have touched on our system on the metal tray. But just from the installation of the metal tray perspective. I know that you also installed this particular substrate, so there are some pointed differences from plywood. Micah Hoskins: Yeah, absolutely. We're starting to lay more and more of these types of roofs and on residential buildings as well, which is great to see because it's so much faster. You can see in that picture there, the timber frame, the amount of timber in that just in that small section of 600 mil spacings, and then you can see in this slide below, with the metal tray. So significantly less reframing is required, but we can still achieve a very strong structure. And obviously the metal tray comes in, you can cut to length, so pretty well any length that a man can handle. And then you drop that onto your purlins and screw that in with a metal tray screw. So much faster to lay a metal tray substrate. We've laid this basic roof about 300 square meters with just three guys and a day. So there's no way you're getting close to that with a plywood roof. Shane Clarke: How long would that 300 square meters you think, take you with a traditional timber and plywood structure? Micah Hoskins: If you were doing the framing as well, sometimes, if not more, longer. Yes. Frame that. So yeah, when you're just putting in straight rafters or purlins for the metal tray, it's simple, easy work. So by the time we come along, we're laying the metal tray in one day and then we're straight into the membrane the next, So it's, yeah, it's a lot cheaper, a lot easier. The other upside to the metal tray is that it doesn't absorb moisture. So if it rains that night you simply just dry it off, blow it off, and then you can get straight into it. Shane Clarke: I know, that's fantastic. So good comparison there, Micah. Nice and fast, nice and light. I've got a bit of a case study here, that we were involved with. It's a commercial project out at the Auckland airport, and we were asked to come in and see if we could offer some value engineering for a better term at this. At that point, the roof had already been designed. They had designed in a com floor system, so this is a heavy steel structure with a heavy metal tray with about 120 millimeter thick concrete slab on top, and this had been poured in was in situ. Thank you. Now, the reason they designed and called up the com floor concrete roof system was they needed a very strong roof structure to hold up a cementitious screed to fall for the membrane. It was pretty much the only reason. They were using this com floor system to hold up a relatively heavy cementitious screed to the fault and then lay a membrane roof. We were, in this instance, able to offer some cost savings using the tapered PIR board that Bene mentioned earlier at one degree fall. So we're able to offer cost savings by the way of time. So the cementitious screeds take time to cure, etc., As Micah mentioned with the plywood, they're affected by moisture, whereas the PIR board is an inert product, doesn't absorb water, and can be laid upon straight away. But, I think the key point here with this particular case study is, had we been involved earlier in the design process, We would have been able to put forward a lightweight metal tray substrate, as Micah pointed to earlier, we would have probably put that, structure to four, and then install the warm roof on top of that. Which would have forgone the need and the cost and the time to install a very heavy duty comfloor system to hold screed to hold the membrane then. So yeah, I guess, like I say, the key takeaway there is if we can get involved early enough, we think we can help you cleverly design some real cost-saving or value engineering systems and things like that. So looks like we've got a bit of time for our Q& A. We've got one here, for you probably, Bene. What compliance pathway do you have for your membrane roof when using metal tray as a substrate? Benedicte Pacorel: So when you use the metal tray as a substrate, the roof buildup that you have, drawn, as you have specified, is part of our Codemark Certificates. So this is your, the buildup is Codemark Certified, which is your compliance pathway. And it's also brand appraised. Shane Clarke: There's a similar question, Bene, on that topic. Someone has asked here why is the tapered PIR board one degree when the code states two degrees, the building code? Benedicte Pacorel: That's a good question. So the building code says two degrees. That would be for a TPO membrane. However, Nuralite has a code mark certification for a Nuraply 3PM bituminous membrane for one degree fall. So therefore supply our PIR tapered at a one degree fall. But you can easily build it to degrees, if you wish, from the one degree. Shane Clarke: Yeah, so a one-degree fall is within the scope and limitations of the Codemark Certificate. So a good way to get compliance there. Excuse me, run through these. Micah, I think this one's for you, mate. What type of screws do you use for the plywood roof, and do they differ for a metal roof? is there a comparison there between the screws, i. e. cost savings? Micah Hoskins: yep. So for timber, for plywood roof into timber frame, you use a 50 mil, 10 gauge stainless screw. And then for metal tray, so metal tray you can either install into a timber purlin or a metal purlin. So obviously, you'd use a roofing screw a tech screw for both of those. There's obviously a timber version and a metal version. and depending on the timber, I think it's 40 mil, 40 gauge. And then the steel purlin is 25 mil screw. and if you're using a timber purlin, we do have to put a separation layer between the timber and the metal. Just so we don't get the transfer of treatment to the metal tray. So you either use DPC or building paper for that. Shane Clarke: Cool, thanks for that answer. It also answers one of the other questions is, do you have to use a metal purlin or can you use timber? Like you've just said, you can use either. This one here, Bene, I think for you again, can you confirm that it is possible to overlay an existing metal roof? Benedicte Pacorel: So you can overlay an existing metal roof by ensuring that your existing metallic structure is structurally sound, and then you would wash it, and then from there, you can build the roof build-up of your choice. Shane Clarke: So you'd overlap with the warmers, is that what you're saying? Benedicte Pacorel: Yes, you could use PIR insulation. So you'd use a vapor barrier on top of your metallic substrates, then PIR insulation, and then the waterproof membrane of your choice, being TPO, 3PM, or 3PG for a green roof. Shane Clarke: Nice. There's a question here about the roof spans. I guess we can all have a crack at this. So the, the span that we used in the presentation at 3.6 meters is an internal span for a restricted access roof. so there's a question here around, what span could you use for a deck situation? there is a span table that we use, from Diamond. I can't remember exactly what it is, but what we will do is we'll include that table in the transcript of the Q&A. So it depends whether it's a restricted roof access or a full access roof or a non-access roof. We'll put that one in the, in the Q&A. that's the question here. You guys can rock paper scissors for this one. Doesn't a roof membrane substrate in timber have to be supported at 400 centres each way? Benedicte Pacorel: Outside the Nuralite code mark, it has to be 400 mil centred; however, Nuralite has a code mark certificate for 600 mil centred. So by using the Nuralite systems, you can actually have further out nocks and rafters. Shane Clarke: So at 600 centres, Micah, would that instantly make your job easier if you had to build that? Micah Hoskins: Over 400 sensors. Shane Clarke: Yeah, as opposed to 400. Micah Hoskins: Yeah, of course, it's yeah, 1.5 times less. Yeah, so definitely a lot less time. Benedicte Pacorel: And less screws, and less timber. Shane Clarke: Ah, there's a favorite question of mine. Is there still, is there a dew point, or is there condensation on the underside of the metal tray in the warm roof system? The answer is no, because the underside of the metal tray is the same temperature as the inside of the building. So therefore, there's no condensation on that buildup. What we do here at Nuralite in-house is run an interstitial condensation risk analysis on our software for every warm roof we do. Combined with our experience guarantees that there's no accumulation of moisture. It's a good question here for either of you. What could you do with an old butanol roof? Could you insulate that as well? Benedicte Pacorel: So for an existing roof with a waterproof membrane, you could then keep the waterproof membrane, and this becomes the vapour barrier. From this existing membrane, you can build up your roof. So you would then install the PIR installation on top and then, the membrane of your choice. Micah Hoskins: And we've done many roofs like that, reusing the existing membrane. Obviously, some invasive, minimally invasive, but some investigation work has to be done to ensure the substrate is okay, it's not rotten, but if it's all okay, then that method works really well. Benedicte Pacorel: And it saves you landfills as well. Shane Clarke: Yeah. Yeah. Nice. Nice. Lots of questions are coming in as they come fast. We probably won't get a chance to go through all of them, but like I say, the transcript will come out with them all in there. So there's a question here, Bene, around the R-value of the PIR board. Again, we can put a full table in the chat. Benedicte Pacorel: so, a PIR R-value, the insulation at the PIR insulation is twice more efficient than lofted insulation. So the R value of 100 mil thickness of PIR is 4.5, 4.55 R value. Shane Clarke: Yes. Yeah. That's the one. All right, there's lots and lots of questions there. I'm not going to take up too much of your time, but like I say, this Q&A will be given to everybody as a transcript. So I just got a final poll here. Look, if you're working on something currently and you feel like a follow-up from the team, all means feel free to drop your vote in here, and we can be in contact with you. Thank you very much to all our panellists today and our audience for attending. the topic was a rather, detailed deep dive into a specific flat roof substrate and how this can reflect in cost savings for your project. And, just to reiterate we firmly believe that true value engineering occurs at the design stage. And we'll see you at the next webinar. Thanks very much. Thanks, folks. Benedicte Pacorel: Thank you. Shane Clarke: See ya.