066 - Fire Safe Use of Wood in Buildings with Andy Buchanan

Hello, everybody. Welcome to the fire science show session 66. I'm excited today because we're gonna talk timber in fire. Let's go. I have invited professor Andy Buchanan, Andy is now with PLT structural consultants, but we all know him from. Being a professor at country Bri. In New Zealand, Christchurch. And Andy has, uh, A lifetime of experience, uh, in different aspects of structural engineering with timber. And in the last. Years he's turned into timbering fire and mass timber, brain fire and engineered timbering fire, all the topics that seem to be very important all over the world because of the trends. That we get to talk in the episode as well with Andy. Uh, the occasion is pretty good because Andy has just coauthored the book that came out with Birgit Ostman. Fire safe. Use of wood in buildings, global design guide. It's uh, A handbook on different aspects of the. Use of wood in buildings in tall buildings. And, yeah, you can bat on it. We're absolutely gonna talk to book through in this. In this podcast episode, but it's OB obviously it's not a book club podcast. We are talking about real engineering. And there is a lot of. Really useful, great information in this episode. Episodes outside of knowing what the book is about and you know what their best thing about this book. It's, it's actually free. It's it's available to download in PDF. Well, not completely free someone paid for it. That was the author's and sponsors of the book. So huge thank yous to, to all of people. Who made this book happen and who made it possible to, to have it shared as an open source research? That is absolutely amazing. And I wish more of the. Science was like this accessible and open science is. Something I live and stand for. That's why I'm doing a podcast. That's. Why I'm sharing all of this with you, because this is, this is the way. This is the way. So, uh, on the topic, in the episode, you are just gonna hear we're going. Have a really nice discussion on, on different aspects of timber bringing fire. The role of firefighting operations, how the. Timber changes that the fire environment in the building and why it matters. How we should distinguish between. Normal small. Uh, timber structures and the tallest timber buildings in the world. Why, why there are differences and how should we approach that? I, I mean, there's so many. Open topics in this talk. I, I hope you will enjoy it because it just vastly broadens. The horizons in understanding timber and fire. And that's one of the top three topics nowadays. So. Every fire engineer should be interested. Because most of us will have to deal with this in one way or another. And before we jump into the episode, I, I have to warn you. For some reason I don't understand. After one year of use, my Microsoft windows has chosen. That my default microphone is not anymore. The fancy one I have and used to record all of this, but it chosen some other random device. So. I sound like I am in a aquarium. I was not in an aquarium. I was in my studio, but. Andy is the one you want to listen today. So I, I hope my. Unfortunate technical issues do not ruin the experience for you. I'm pretty sure it's gonna be. Okay. In the little, still enjoy the whole episode, but yeah, I given the warning. And now lets spin the intro and jump into the episode. Hello everybody. Welcome to the Fire Science Show. I'm today with professor Andy Buchanan of University of Canterbury. Hello, Andy. Great to have you in the podcat

yes. Hi.

I know you a long listener of the podcast. I'm super thankful to you for your feedback. And I'm very happy that, finally, you're on the other side of the mic. I am looking forward to this discussion.

thank you. And I must say that I look forward to your show every week, because I know every week there's going to be somebody different. Some of them, some of your guests, I know. And many, I don't know, but there's always an it's a great listen. So I'm pleased to be here.

let's, let's make together a great experience for anyone listening now. And actually we have a good topic, the topic, that's probably number one topic on my, on my show. It always fires discussions. And we're going to talk about timbers and timber and fire or wood in fire. And, we have very good occasion for that because you have just, co-authored a major piece, a book on, on the fire, safe use of wood in buildings. And we're going to jump into that book just in a second, but I cannot let the opportunity pass. And I must ask you how the hell fire safety engineering on that level came to live in Canterbury. I always like in my, life of engineer, I always looked up to country re and , you guys have been such an amazing, place where real fire engineering took place. I mean, I many times I've said, Harrison Spearpoints work was, the, the one and only reason I became a scientist, even turning scientists from fire engineering consultants. I love the school of thought that has been built at. So maybe you can tell me how it began. I'm thrilled to learn that.

Let's do some history here. because the university of Canterbury is in the city of Christchurch where I was born, where I learned where I am now. And I went to the engineering school here and the structural engineering, and that was mostly earthquake engineering of concrete structures. And with that degree, I then wanted to travel and I hit it off overseas. And I went to the university of California at Berkeley to do a master's degree. I thought I would be studying earthquake engineering, but there, there were two big names there in fire engineering, Brady Williamson and PJ Pagni And by accident, I bumped into them. And they said, have you thought about doing your master's thesis in fire engineering? No. I said what's that what fire engineering. I did. project on the, the head of that. They happened to have a wall furnace there, and it was such a simple experiment now, but we were just measuring the gas flow, how much he'd went into the furnace. And it really wasn't structural engineering at all, but it introduced me to fire engineering. And from then on, I was. Back to New Zealand. I wasn't employed as a structural engineer. and I got that's when I got interested in timber buildings. And when I went overseas to do my PhD, I considered fire engineering, but I really wanted to do wood and timber engineering. So I went to the University of British Columbia, Canada, and there was no fire and that I just did it on the strength of wood and wood structures. Went back to New Zealand, had my own consultancy for a while. And then I got invited to join the university of Canterbury in 1987. And at that time I had the opportunity to start teaching a course or two on fire engineering. And the coincidence was that just about that time, the New Zealand. Code environment changed completely. And a performance-based building code was introduced. And I was approached by an old friend of mine who was in the fire service. And he said, what's the university going to do with this new performance based code? And he said, you're going to have to do something. And I said, well, I can't do it myself. We'll need some, we'd have to hire someone, but he said, how much money do you want? Hence, I ended up getting a grant from the New Zealand fire service because we're a small country and we have a national fire service organization, the fire service commissioner, my role and like. A hundred thousand dollars. It was a lot of money in those days. And then we went hunting for stuff. And the first person I contacted was Brady Williamson at Berkeley, where I had studied and he came right back and said, Hey, what about Charlie Fleischman? And that's how I met Charlie. And he came for short stay at 30 years ago and he's still here.

Yes.

And I would have to say the strength of the program at Canterbury is collaboration because the, our engagement with the New Zealand fire service has continued to this day And that one thing built on another. And so now there are five full-time staff and fire engineering. It's grind from one to five, and it's gone from strength to strength. Amazing. I love to hear people's stories and I need to start doing statistics. Like how many people purposefully went into fire science and how many by accidents. And I I'm literally, if I find anyone who just did it purposefully, actually, , how a life can, , put you on the very right track you've mentioned, Your engineering was also much related to timber. And today we're also in the, timber subjects. So, so was timber something that the combiner that you your scientific earlier around eventually you've

let me say this. First of all, I'm a structural engineer. I've always been as an engineer. And when we started teaching fire engineering at Canterbury, Charlie, and then Mike and now many others, they, we expanded that program to talk about fire safety systems and human behavior and fire all of those topics. But my area. Structural fire engineering. And if you look at the list of courses at Canterbury eng course, number 6 0 1 is structural fire engineering. And from the course notes of that course, which I taught for many years, I wrote a book on structural design for fire safety. And then the first edition was 2001, when we updated that in 2017, I invited Tony Abu to join me. He's now a co-author. And so he wrote all of the computational part of that and made the book much better. So that's structural fire engineering was for all materials And even then in 2001, we didn't see this explosion of timber buildings, but I had studied timber buildings in Canada. And then, What has happened now, of course, is that largely because of the climate crisis, there's a huge demand for timber buildings. You've had podcasts on this, that everybody is wanting to reduce their carbon footprint. They want zero carbon buildings. And the only way to make a zero carbon building with zero embodied carbon is to put lots of wood in it. And that was driving a big change. And I'm just lucky because I have a background in structural fire engineering, and structural timber. And so since I retired from the university, I've, specialized in the fire safety and timber buildings, because it's a problem. I mean, as many of your previous speakers have said in the past, The five dynamics and the structural behavior, uh, uncoupled and a steel building, you can consider them separately. We can look at the fire severe. What kind of fire do we have and what kind of structural performance do we have? And that suddenly, if you have a lot of the structure which can burn, then the, the toolbar now coupled, and it makes life a lot more difficult.

Yes, absolutely. Absolutely. I, I love how you, immediately put that perspective in front of the listeners, because if you had to, in one sentence quickly explain what's the difference between all the non-combustible structures we had in the past and why timber is different. I think that summarizes it really well, that in one case you can decouple the fire behavior from the structural behavior into some successful extensive study them separately. Um, timber it's. So it's joined on so many levels. There are so many feedback loops that, you cannot do that anymore, or you can, but the degree of success will be very, very much different because of the simplifications and the missions

right. So what we end up within, as we end up with a tension, because, from a carbon point of view, the more wood in the building, the bigger the store of carbon and the more fossil fuel emissions you can offset. But if a building owner is going to spend a lot of money on a building, a timber building the owner and the architect, they want to see the word the more, the better. And the fire engineer then is saying. We got exposed us would we should hide it all. And so if you have the building that's many people will know for while it was the tallest timber building in the world, Brock Commons building at university of British Columbia. And that was an 18 story timber building. And if you go into that building, you don't see any wood, it's all covered up with layers of gypsum plasterboard. So it's what we call an encapsulation. And so there are lots of tensions here because on the one hand, the climate people are happy because they got some wood into that building instead of steel and concrete. And the fire people are happy because. The wood has been excluded from any possible fire in the building, but what we're missing, then all the benefits of seeing the wood and feeling the wood and knowing that we're in a timber building, we can't burn them all.

Yeah. I also think a big driver. I don't know if it's a big driver, but I have this feeling that tells me it's a big driver. You know, you mentioned the tallest building in the world. I see like the tallest, the biggest timber structure in X, Y, Z region. the, the biggest, timber building in Poland, in Sweden. Everyone wants to, have a, I don't know if you can put it on your wall and diploma, I've built the biggest timber structure in, blank. I find that in the way ridiculous, because it's so egocentric to, push technology, maybe, for the sake of your own feeling of I don't know that is a factor, but it feels like a factor.

let me comment on that. I agree entirely. A lot of people will ask me how tall can we go? How can, how tall can it be? And I'm saying, well, of course, a few years ago there was, there was a kind of design competition to, to make the empire state building, do a design and timber and it can be done. Of course it can be not, but the market for, if we want to have a lot of wood and a lot of buildings to store a lot of carbon, it shouldn't be a competition for the highest. It should be the run of the mill. apartment buildings,

Hmm.

commercial office buildings, 2, 4, 6, 8 story buildings where there's a large volume. And, that's really where the, I see it in the market should be. and we can make those buildings just as safe as a steel or concrete building. But when we start getting very tall buildings, very tall timber buildings, there's a threat there, which I'm nervous about because there's still unanswered questions about what happens to the exposed wood. When at the end of a major fire, let me you, some more words you see in our, in this design guide that we've just published Fire Safe Use of Wood in Buildings with 20 authors from 12 different countries. We had a kind of. Expression. And there, we, a lot of the authors were talking about self extinguishment and we had kind of discussion. What does self extinguishment mean? Well, if you, if you're lucky you have a fire and a wooden building, the fire will go out, but only if you're lucky, only under certain circumstances. So in the end, we took the words out of the book, self extinguishment doesn't appear there anymore. We talk about burnout, but what we admit in this book is that if you have a major fire in a mass timber building, when the fire dies down and firefighters can get in there, they're going to have to go around and host the building and make sure that the chairing has stopped because it won't stop by itself. And that there presents a danger, which is not a problem for small and medium sized buildings, but it could be a problem for a very tall.

I had this conversation with the, with Mike Spearpoint and at some point when we're doing, , for experiments for all of our structural team Alliance, and these are long experiments and through the middle of it, nothing is happening. So it's filled with nice discussions. and, I guess you can imagine you can talk to Mike for quite a long period of time without being bored. So we had this one discussion, how do we define burnout? And a thing that came to my mind is. Burnout is burnout it's like quite as self-evident thing, the moment you start to define the criteria when it has been achieved and where it did not achieve you start to water it down, you know, it's do we agree on this temperature? It says burned out or not. I mean, burnout is burnout in a way someone's ridiculous that we need to, alter a definition or, or find a new definition for something self-evident it's just so, uh, another thing can, fit into the definition where it obviously can, like if you leave a timber structure with complex shapes, not extinguished, like majority of it will self extinguish or we'll stop flaming. Eventually it will stop smoldering as well. It will stop oxidizing. Yes. But wherever you have a complicated shape, you know, connection between column beam and wall and a ceiling, a concealed space, something like a box where he is trapped and rare edition cannot cure. And you know, a little more complicated shape. It's, it's quite evident. It will not go out on its own. You have to put water on it. Like eventually you have to extinguish it. And , this is a, a major difference in the, , introduction to your book, fire safe use of, of wooden buildings, global design guidance. Let's let's highlight the Birgit Ostman as the coauthor of, this fantastic book, um, in the introduction, uh, I think it was Craig Baylor who wrote that? One of the achievements of this, of this book is, is to recognition of the, that being cognizant about firefighting is a factoring in timber buildings. And I always thought that we lack the perspective of a firefighter as fire engineers. and I also feel the role of firefighting to some extent is more important in mass timber structures or large numbers structures than let's say in contemporary non-combustible buildings. Were your feelings when you introduced such a chapter in, into your book?

Well, let me thank you for that question. Before I answer the question. You're not, I'm just going to do a little plug for this book because a lot of people want to know about it, then I'll, I'll come on to that question because this book is, I didn't write the book. I'm an editor of the book. Although I wrote one chapter are 14 chapters in the book and each one has a different author and they're all over the world. And so we've got. For example, the book stops with Christian Dagon nice firm from Canada, talking about Timber Structures and wood wooden buildings. Colleen Wade talks about fire dynamics, which is a summary of all the latest research on fire behavior and buildings with exposed wood. Birgit Ostman has a chapter on fire safety requirements in different regions, and she's got maps of the world showing the different requirements for different

that was very interesting. Very, very interesting. Yeah.

the rules are very different in different countries. The fire behaves the same way, but the rules are different.

Yeah.

Um, and then Mark Jansens from. The San Antonio southwest Research institute has written a chapter on reaction to fire performance, which is all about Don calorimeter, single burning item. Test, all those desks. Norman Virta from Munich has written on fire separating assemblies and all the different ways there are to assess by test or by calculation, the performance of, of walls and floors and from Estonia has written the chapter on load-bearing timber structures, which is largely based on the new draft of Euro code five, which is won't be published for a little while yet. But if you want to get a snake brain and that's in there, and then. Uh, David Barber from Arup fire who spends his time moving between Washington, DC and Melbourne. He wrote the chapter on timber connections. And I always remind people when you compare a wooden building, a timber building was steel or concrete. Just think about the difference. Concrete is a liquid, and you can pour it into any shape steel as a wonderful material. You could weld it. You can weld the bits into any shape, but a timber building it. You cannot do either of those and many, much of the design effort and a timber building is coming up with connections way of connecting the bits together with bolts and nails and screws and brackets and the fire performance of those. There's a issue which David has covered in chapter eight and then Esko Mikkola from VTT and Finland has written the chapter on preventing fire spread within structures. Birgit Osman has talked about sprinklers and we can talk about sprinklers because they're so important. and then we've got a chapter on performance-based design and risk assessment, which is just an overview written by and Australia, and then robustness in fire, which is structural robustness. How do you avoid disproportionate collapse at one column fails? And from ETH in Zurich has written that chapter with other authors. And then the last two chapters are very important and they're a bit different from the others. So chapter 13 is written by Andrew Done in Australia. And I just give some credit to Andrew because he. He was really, it was his idea to produce this book, to write it in the first place. And he's written a chapter, which is mostly about avoiding fires during construction. And last of all, chapter 14 is firefighting considerations. And that's written by Ed Claridge from Oakland council here in New Zealand. And he's looking at what firefighters need to think about and what information the fire engineer can provide to provide some comfort to firefighters, to show that they've thought about what kind of fires would occur and identifying all of the concerns of the firefighters about, hidden spaces and voids and, Firefighter excess and it exposed timber structures , and other things. For example, the influence of wind on fire and city and most important of all is, is planning pre-incident planning and for the fire service to be involved during the design and construction of the building so that they know the building, I'm not a firefighter, but I find as I know the most important thing for them as to understand the building and how the building might work. So that was a very long answer to a short question, but I think it maybe gives you the answers that question about fire fighting in term of the buildings because of this.

Yeah. Thank you for answering that. And thank you for giving an overview of the book. It really is a, a beautiful collection of, of great mindset and a great chapters giving, uh, quite complete image on, on the, on the subject. So I would highly recommend this, uh, this read to anyone, especially that it is, widely available in open access. I wanted to just, take one more. Peek into the file firefighting. I wanted to know European. You're never out of university. You a consultant in PDL, structural consultants. And, it's this firefighting considerations, something you actually do consider in your design. You have a framework to do that, or it is just something you have in your back of your head when you are advising in the design of a structure.

No, that's the answer to that is that this is kind of very in different countries. In New Zealand. The fire engineers are not thinking about the firefighter considerations all the time, but we, have within the New Zealand fire service, they have a responsibility, but they have four major buildings. They have a kind of a power of veto where they get to look at The fire engineering brief that's normally what's done at the early stages, even before the design, before the detail design, there's a fire engineering brief, which is prepared by the fire engineer in collaboration with the building owner and the architect. And it's discussed with the fire and emergency department. And so they will, if they have concerns, they will address them. So let me just tell you something what's happened in New Zealand for this is a worldwide problem, but one of the perceived problems with timber buildings is if you have expected. Flaws and you have a poor glue line. There's the possibility of the layer falling off or having a char fall off, which exposes a new layer. And so the fire never goes out. And so fire and emergency New Zealand are aware of this. and it depends on the building, but if you have a building, we built designing a building now, which is a, a care facility for elderly people who are bedridden. And the fire service are saying, how are you going to ensure that we get burnout? And we don't have any falling off of this hot layer. And the answer is so what the fire engineers do then is that they, when they do their fire severity calculations, They're using method developed by Daniel, Brandon. Who's been on your show. Who's done lots of burnout tests on CLT compartments, and what's tends to be happening now with these buildings. Is that in a CLT building, I'm talking about a building with lots of walls and lots of floors, and they're all made of solid wood. The walls are generally covered with plaster bullet because that's what the architect wants. That there's an advantage for the acoustics between rooms. And it provides a cavity for metal surfaces, but the ceilings are exposed wood. And what the fire engineers then do they use the design method from Daniel, Brandon, which is spelled out in chapter three of this book and find out what duration of the fire is and keep it. And sometimes what happens is that if the fire duration is too long or the equivalent fire severity is too great, then the fire engineer goes to the architect and says, you've got to put more windows in this building. Why more windows, because we want more ventilation. So we have a short, sharp fire and the fire goes out. The architect says, we can't put more windows in. This is all fixed. Okay. Then we'll have to cover up. Some of the ceiling will encapsulated so that we reduce the amount of wood which can be involved in the fire. And so at the same time, the output of Daniel Brandon's calculation method is the, is the depth of charring. And we want to make sure that that depth of charring doesn't get to the first glue line. So that's a long, again, a long answer to a short question, but there's a lot of. Backwards and forwards here about the, the, the technique for doing it is, described in this new book. So I hope that will be helpful to people who are moving in this direction.

Absolutely the fact that you have provided a tool sets or a, just a tool for engineers to use through the book is of immense value. And when we were chatting before that, you've also said that there was a point to do, because you're an engineer you like tools to work with. Then you would like to give tools to people in the book. And in some places you can see, um, the importance of wind is also being broth and there in a way, it also connects to the importance of window fallout and, window damage. And then that again brings us to the complexity of compartment. And the relation between the, the fuel, the structure, the outside, the inside the window, the flow paths. I found it really interesting because it's not something we often consider that much when doing even experiments, you know, a typical way to do a fire experiment with, uh, with timber is just build a, uh, how are a lot of openings that, that represent the most critical opening factor. The worst, biggest opening factor you can have in the building, just have them open from time zero, because you don't want to build the expensive windows in a fire experiment. That is just about to be burned down. And we see where like the fires like that. Whereas if you, if you have a smaller windows, the fire costs will be completely different. If you have wind, the course of the fire may be completely different. Maybe you would like. To comment on that aspect, how it gives into the whole fire safe a use of four foods and

Absolutely. And this is a big problem for structural engineers doing fire safety of any building. but it's more difficult for the, the temper building. But I mean, if we just think about the starting point for structural fire engineering, The engineer has a steel structure or a concrete structure. The question is to the fire engineer. Well, how hot is it going to get how hard is my steel? And that's all the structural engineer wants to know. And because we can calculate a limiting temperature and as long as it doesn't reach the limiting temperature, then the structure will remain standing. Or if it's a concrete structure, what is the temperature of the reinforcing steel, which has very few centimeters inside the concrete and the traditional way of doing this is to use like what we call a parametric fire from Eurocode that's what most people use. And all we need to know is the fuel load, the ventilation and the thermal properties of the fire compartment. Of course, there are lots of uncertainties in there because we don't know what the fuel load is. We're guessing

Um,

there have been surveys of fuel load, but in New Zealand we have very low fuel loads and our building code, which we're a bit worried about because before a residential occupancy, the would just regarded as a low fire load. We use 400 mega joules per square meter. And then if we put a sprinkler system into the building, our building code says, well, to take account of the reduced probability of the fire, you can re cut the fuel load in half. So we dropped from 400 to 200 megajoules per square meter. And that is a very low. So I'm worried about that. And then you've got the thermal properties of the compartment, which are much more easily addressed. And finally, you've got this question off the windows. And in the old days, when we had single glazing of plain glass everywhere, we could assume the windows would break, but nowadays we have double glass, triple glass, and you've had a podcast on this. We have tempered glass, we have reinforced glass. And the way I look at it is that if none of the windows break let's, first of all, if we have a fire and the sprinklers don't work for some reason, that's the worst case scenario. But if none of the windows break, the fire will go. We don't need any fire resistance because we don't have a proper fire. If all the windows break, bang, bang, bang, and flashover caused by and resulting in flesh. But then we have a short, sharp fire thousand degrees for 10, 15 minutes, and the fire will die down and go out and that's, we'll have what we call burnout that by itself extinguished, but the temperatures will drop, but if only half the windows break, then we've got something in between, which is a fire that might not burn for 20 minutes, but it may burn for an hour or more. And the question then is, Do we have to consider the worst possibility of all of these variables. And if we do, we won't be able to build the building. It's like, if, if this was an airplane, it wouldn't fly. If we took all the width, the worst case of all the variables. So there's a lot of engineering judgment in here. And some of this is fire engineers will say, well, I just do what the code says that most building codes weren't written in the days of mass timber buildings. So we have still a lot of questions to answer. And this book of house doesn't give all the answers, but at least it provides the background information for people to make a considered judgment. I'm talking too long now.

that's the point of having a podcast made this, if you did not, I will not invite you here as good in your chapter, in your chapter. Uh, the, the one that, you've all thought, in the end there's like future research needs and the, this research needs. In fact, the first, the first out of them is fire severity in compartments with exposed surfaces, including traveling fires. So, you really think it's the number one unknown we, we have or number one need how. Compartment fires change. When we introduced the exposed timber. I know there has been, like, I feel we're living in, in some golden era of, fire testing, mass timber. There's a lot of large scale experiments being carried all over the planet. I would assume it is because of what you meant is mentioned in the beginning of the episode, it's a very fancy technology that fits into current, uh, politics, of reducing carbon footprint and so on. So it's, it's trendy in a way, if, uh, if a structure can be trendy, that is, and th th this brings lots of experiments. Most of them are carried in the same way, but there are.

Um,

Few really interesting ones. Like the one performed in France. Code RED. I don't you, if you've seen it where they did the CLT ceiling, over, uh, let's say traditional, a traveling fire experiments set up and it completely changed the fire dynamics. It does not answer the questions yet, but it shows the answers may be interesting. I mean, it changed the dynamic a

Yes. Yes, of course. And I mean this, the history of this over the last 10 years or so has that we used to think that all we needed was a standard fire resistance test. And that would tell us the way the material behaved in a fire. But as you know, the fire resistance test. It's not a real fire test. It's just a method of comparing one product with another. And it was really mess. Timber materials, cross laminated timber CLT was developed in Europe and upended in Europe. And it was really when north Americans wanted to start using this and the fire brigades in north America started asking questions and the manufacturer said, that's not a problem. We've got 60 minute, 90 minute fire resistance rating. And well, why don't we just do a room fire to see how it behaves? And that's when they started doing this room fires and they found that the room fire was completely different from the fire resistance test. And that's really led to a lot of changes to changes and the adhesive. Changes and understanding about how the fire behaved. more recently there've been some large fire tests and there are more coming. The Australians are planning a large 20 meter square, fire compartment with, uh, looking at the effect of ventilation on the fire. And, and that'll be very exciting if that happens. But the next question really is if we have too much wood exposed to, but then we'll have to start covering it up. And if you look at chapter seven in this guide, which is the, the Euro code requirements for structural timber, what we need to know now for our protective materials, gypsum plasterboard, we need to know the time at which the chairing will start underneath the board and the right of charring there, which will be less than the normal charity. And then the time to the falloff of the gypsum plasterboard and the chairing right after the falloff, which, which is by seeing an experiments to be about twice the standard sharing. Right? And so now there's a hot, new demand on manufacturers of protective materials, asking them to provide this information. They never got asked us before. What time does chairing start under your board? And at what time would your board fall off and have chairing a starting in under the board? Well, that's more fuel for the fire. It has to be added to the, fire load that we started with. And so this is difficult enough in a small compartment, like a, an apartment building or, a single office, but we still haven't got the answers as to how this encapsulation has gotten. So how long would I protect the wood in a larger space where we might have a traveling fire? Lots of questions.

exactly. As we speak. Now, there is an experiment happening at ITB lab where they're looking into the failure of, some protection boards on a CLT to, to investigate like what states is the seal, the, these, the protection after the fire resistance period, and to indicate what, uh, is the, failure mechanism of the encapsulation, because it's not only related to jarring, but you can reignite you can. I have witnessed myself this mythical second flashover and the third one and the fourth one in compartment. And it is, somewhat, scary. It's a behavior. Like if, if you have a steel beam protected with some boards and they fall off after 90 minutes, when the fire is in its decay phase and the temperatures are inevitably going down, it may take a long time to cool down, but they're not rising

That's fine.

it's something you can handle as a, as a structural engineer, but if your failure creates a, re-ignition another, some sort of flashover, even flaming combustion and your temperature starts to rise again, you're like experiencing a completely new set of challenges you have not, encountered before. So, so this is a major, a major thing to, to consider the fire does not stop on, on the 90th minute of when you have your furnace system off. It's not that. in your answer, you've also mentioned that like sprinklers, like when your sprinklers fail, we have a problem. Can we consider that, that if they don't fail, we, we don't have a problem. What's your opinion on, on

Yes. Yes. Look, let me just reinforce what you've just been saying. There is really some people in the timber industry. Sometimes they asked me whose side are you on? I thought you were trying to promote to the buildings. And there are lots of reasons for promoting Timberville and it's we, we have to do it, but that some of these questions are real questions. And I think that it boils down to risk. It's a risk assessment and we can handle the risk is as long as we're not building skyscrapers. If we're building modest sized buildings where people can get out and fire service have good access, then we can control these things. And we control it. for tall buildings, all the tall buildings they're going to have sprinklers. And then this raises another question because sprinklers are fantastic. Sprinklers are far and away, the best form of fire protection. There's no question about that. As a small possibility, a small probability that sprinklers one control the fire and that's been demonstrated, but why? Because the sprinklers would down for maintenance or because there was, there's an explosion somewhere or it's in a war zone or an earthquake, which takes out the water supply is a very low probability, but it's a low this event of a fire in a building where the sprinklers don't control the fire. It's a very low probability, but it's a very high consequence. And so that can only be addressed by. Some sort of quantitative risk assessment. Paul England has, and in chapter 12 of this book on performance based design has set out a framework for doing that. but it's not a, it's not the sort of tool that can be done every day in the design office. That's the sort of thing that has to be done by the code writers and the people informing the code writers. And what it means is that as the timber buildings get large and tall and complex, then they have to be larger safety factors and at a larger level of protection to mitigate the risk.

I think, you know, the low probability is, in a way subjective, because if I think it will probably be myself being mostly involved in tunnels, I would think like 10 to minus five probability. And when you talk about sprinkler reliability, I mean, 5%, 1% in the reliability, you could consider that low from one point of view, but like 5% chance to have fire that significantly damages your building and completely changes the battlefield for the firefighter. I, that that is a high probably it's not something you can go on and say, ah, it's. So probably we don't, include that in our concentrations. Uh, I like how you said that it's, it may not be necessarily the role of the building engineer to calculate this risk for their own structure, but it, it should be something that comes from a boat that, is fit within the idea of a certain country region government on what fire safety they want to provide and how they want to provide it. I, I, I like this approach a lot.

but it's very difficult let, let me just explain another kind of issue here, because if the fire regulations are very, restricted, And we do some risk assessment to relax them a little bit. Well, everybody's happy because we can make that work as long as we can demonstrate it. We have a problem in New Zealand, which is opposite because our, our fire resistance writings, which were decided by some committee 20 years ago are very low and there is no restrictions on using wood in a 20 story building. You can use as much as you like, and this, issues that we're talking about, they don't appear in the building code. And so what we're telling the authorities as well, I have to put some guidance in here or some restrictions on the use of wood. But if you, if you make the building code a little tougher than it was before, then suddenly you have a problem because all the owners of existing buildings say, what do you mean? My building's not safe anymore? And the fire engineers resist that because then it will look as if they've been designing unsafe buildings. And so, that's a.

I, I hate, I hate it when it goes through that. I absolutely hated because, you're putting people into shame, guilt, and or justify against a beneficial change, for the society. And the same goes the other way. Like we've always done like that and it hasn't been always good. You mean that does not mean you should not change the way of thinking and, and seek possibly, better solutions your

Very difficult because when we say we've always done like that, but we haven't, we have not always had mass timber buildings. These are new and the game is changing. And as long as we do it properly, we can make these buildings and safest steel or concrete buildings. But at my. Some changes to the building codes. I mean, as you know, most countries, we have two possible approaches. We have the kind of prescriptive code, the cookbook, the rules of thumb where you just tick the boxes. And the alternative approaches is a performance-based building code with a verification, a calculation method. And in both cases, we are in discussion now with the New Zealand code or authorities and saying, really, if we're going to start looking at tall timber buildings, we'll have to look at both lots of regulations just to make sure that we're consistent with the expected levels of safety and with what people are doing elsewhere in that.

But do you explicitly know them? They expect the level of safety.

No, we don't know them. We do not know them. I think structural engineers know enough about, well, let me put it this way. In structural engineering, there are not so many uncertainties as there are in fire engineering and structural engineering. Of course there are uncertainties about the strength of the material. And there are uncertainties about the modes, which might be applied from wind or snow or earthquake. And so it's not so difficult to do a risk assessment, but we're designing this building then for a fire where we, we don't know the fire load in the building. We don't know the use of the building. We don't know how it's changed. We don't know whether the windows will break and we don't know. Whether there'll be fire and more than one floor or more. I mean, that's a huge number of variables. And I guess that goes back to the discussion you had with, Mike's be a point on a previous show where, where you were talking to Mike about that consistent level of crudeness, which is an expression, which I have used a lot. I got the expression from David Elms at the university of Canterbury

mike say since he got it from you,

Yes. Rob, who got it from me, but David Elms taught me structural engineering at the University of Canterbury about 50 years ago. And he's, a neighbor of mine he's alive and well, and he's still is a great fan of this because if you're doing your CFD model of the, predicting the behavior of a fire and. You have a model for our nephew include a marble for window breakage, which you've talked about and you, have a very precise model and you can calculate an answer plus or minus 1%. But if the input to that model is completely unknown, then, then your level of crudeness is no longer consistent. And there's no point in doing a very precise calculation. And as you know, the input, and I think this is a problem that we have in the fire engineering community, because fires don't happen very often. And when they do happen, they're all. Very different from what we expected. And so we've got to be very careful about predicting behavior of something to a high degree of accuracy when we really don't know what's going to happen. And for that reason, we've got to be, we've got to have a certain level of safety and that's gotta be related to the people and property, which are exposed to the fire.

Uh, my, my mentor professor Czarnecki always said, uh, you want to be roughly correct or, wrong, but with great precision. And that's, that's also something that goes to your, consistent level of goodness. I

I agree. I like that. What did you say? The answer reside there

know, the answer is there sort of sees you roughly correct or precisely

that's right, roughly. Correct.

yeah. I really enjoyed that. Andy it's an hour has passed and it's a fantastic talk to you. And we've touched like the tip of the. Of the subjects you've covered that there are, that are covered in your, book and the subjects that would be possibly interesting to talk outside of the book. I, you know, I, I still have not talked on the podcast about the risks to, whole regions, like, are we going into the, the age of urban conflagrations? If we start building mass timber again in skies, that's something that that's interesting to me in your challenges. You've mentioned facades, that's a hell of a problem that that is a hell of a problem. How do we deal with facades in, in timber buildings and how they contribute to spread or not contribute to spread. I loved it. I you've mentioned smoldering, which is interesting problem as well, because the fact you've extinguished your fire and it looks not burning doesn't mean that the it's not disappearing. You know, you go for an hour and come back in an hour and the colony is suddenly 10 centimeters thinner than it has been. And that's our, just so processes that are occurring with your biological material, that these beings still oxidized and the composed. So, so there's so much more than covering the wealth. Maybe I should like make it there's a timber don't know it's a popular but anyway, we were, we are not able to cover it, but we are able to send people to, pick up the fire safe use of wood in buildings, poop and think into that because they will find a lot of answers. So, uh, where people

Well, just let me say that this, this book has just been published. It's a, it's a hardback book because the authors was so keen to make sure this book gets read. Does the, we did a deal with the publisher and we, the publisher was called Tyler and Francis. We did a deal with them and we paid them some money and we collected that money from different countries and we paid them some money. And so this for a change, this book is a free. Anybody can get it. And so I'll give you the address and put it on the website, but even if you Google e use of wood and you'll find the free download from Taylor and Francis, it costs you nothing. And you can download a PDF version of this book anywhere in the world. And that was really the people, the author who wrote this book said, we're not going to do this unless anyone can read it. So have a look at it, get into it. And if you've got any questions, you can ask any of the authors, for guidance, that's it?

And the, and the beautiful looking hard copies also available through CRC press, wherever you

Yes.

order scientific books,

Well from,

you showed it to me, it looks beautiful. I would like one on my

yeah, well you can get it from, from Amazon or wherever you get books from.

Fantastic. And, um, thank you so much for, uh, being a friend of the podcast. Thank you so much for taking your time to edit, such an important book. And, and your book on fire resistance, uh, is, is also important piece that should be in many. Engineers library. So that's 12, 12, 20 17 edition with Tony Abu is, absolute, great. The ends. I know a lot of engineers are using that. And thank you for your time today to talk about the important topic of safe use of wooden

Well, thank you. It was my pleasure. And, I look forward to hearing more, a few different topics next week. Thank you very much.

Thanks, man. And that's it such joy to talk to Andy? I know he's a big fan of the podcast. Andy. I'm a big fan of you <laugh> it was such a pleasure to discuss timber with you. From this talk one. Takeaway, for myself. Something that was said along the lines. Of the show. It is, it seems we have like two different. Regimes of the problem of timber in, in. Buildings. Like there's had a lot of buildings. That do not pose any. Significant threat when you introduce timber to them. Like what Andy said that the run of the mill buildings, you know, small apartment buildings, small office buildings. Ones in which you would then encapsulate walls, leave, the ceilings exposed. Once that have very good firefighter access from all directions. I mean in, in this buildings, you can really bring the, the risk to the very same level you would. Encounter in, in, let's say. Concrete or steel or Mason rebuilding. You, you really do not have a significant difference. Because you have used timber in and, and I think it it's important to highlight that there is a regime of buildings. It, we really should not have big problem with, I, I think it's possible to engineer. Them with the knowledge we have today. And with the knowledge that we'll have in like five years when all the projects are ongoing, will finish and publish. And all of the knowledge produced will be digested. I'm pretty sure we will, were gonna have a very. Safe frameworks to. Work with timber in standard buildings. And, uh, that's a future to look for because that's where the carbon sink goes. The carbon sink goes in the volume, not in the prestig. And, uh, yeah, that's a great future for the timber industry and that's a great future for fire engineering. Now, the second regime that's challenging. That's you know, the next tallest timber building, the next biggest timber building in, in wherever you are located. And these are not typical structures. These bring challenges that are truly unique to these types of structures. And I feel that discussion is somehow dominated by these types of structures. Even in my podcast, I must say I'm biased towards the, the tall buildings. I mean the cost group where we talk about tall timber buildings, we don't talk about small timber building. We talk about tall ones. So there. Definitely is a different sort of threat, a different set of issues, the different set of challenges and risks. Involved in, in tall timber buildings. Which will be much more difficult to solve than the ones that. Uh, are related to small buildings where most of them probably solve already. So here, topics of sprinkler reliability. The wind affect. The firefighters access. Self extinguishment, burnouts, smoldering fires, facades. All of these are are topics to still be. Fully understood and answered. Before we can just routinely go and build the next biggest timber building of the world. If we ever will be able to do that routinely. So, yeah, a hell of fire engineering that's required in this projects. And. I hope that. We will learn to distinguish this projects between each other. Because now I feel they're in the same bucket and they should not be. We, we, we should understand that. At some point we consider a low risk. Building. And at some point we consider a high threat building and. They should be given a completely different set of approaches, set of people, set of engineering rules. And, set of tools used to design them. So, um, that's it for the episode. That's my takeaway. Your takeaway should be the book, because as I mentioned, it's free. You can download it from the link in the episode. And I guess the authors will appreciate if you posted a hard copy and it looks beautiful on a, on, on your library. So definitely a nice, nice book to have. Thank you once again, Andy, for publishing this piece and joining me in the episode. Thank you dear listener for being here with me and. See around next Wednesday. Thank you. Bye.