The Future of Bamboo Buildings

GEORGE IMAFIDON

When I was an engineering student at uni, one of our assignments was actually to build a bicycle from scratch. It was a tough challenge, but what made it even harder was the fact that we had to build this frame out of bamboo. Surprisingly, it worked out really well. It was cheaper than carbon fibre and a great strength-to-weight ratio, so our professors were pretty impressed. Now, bamboo is probably not the first material that springs to mind for bike construction. But there are a lot of reasons to use it, not just for bicycles, but for buildings and bridges too. It's just as strong as steel in some dimensions, it's incredibly lightweight, it's flexible and it's very sustainable. In fact, bamboo is held by some people as a miracle building material for the 21st Century. So why aren't we using it more? I'm George Imafidon and you're listening to Create The Future from the Queen Elizabeth Prize for Engineering. And today we're looking at the future of building … with bamboo.

SEB KAMINSKI

If we’re trying to combat climate change now, we could plant trees now but they will take 60 years before we can use them for materials. Whereas if we plant bamboo now, it’s 3 to 5 years to start using them … so that’s a strong argument.

GEORGE IMAFIDON

My guest today is Seb Kaminski, an engineer who has been working with bamboo for over 15 years, using it to build low-cost community housing in earthquake-prone areas like El Salvador.

SEB KAMINSKI

Firstly, thank you for inviting me to this podcast. I'm really happy to be here. My name is Seb Kaminski. I'm a structural engineer. I've been working at Arup now for, I've forgotten how long, which means it's been a while, but I think it's 16, 17 years now. So Arup is an international multidisciplinary consultancy working in the built environment. We have engineers - structural, mechanical, electrical, public health. We have planners, we have architects. All different areas to do with the built environment. One project which made Arup quite famous was the Sydney Opera House. The Bird's Nest Stadium in Beijing we also did. The Millennium Bridge. Also the Gherkin in the City of London. We work a lot in sustainability and planning architecture. And within Arup, I'm a specialist in working in bamboo, and also a specialist in working in humanitarian and international development contexts.

GEORGE IMAFIDON

Would you describe yourself in any way as a humanitarian engineer? Because as I was reading some of the work that you were doing, I thought, you know, maybe … I describe myself as a humanitarian engineer. Yeah, maybe, maybe you do. Maybe you don't. I wasn't sure.

SEB KAMINSKI

I haven't used that phrase in the past, to be honest, but it's a good phrase and could apply to anyone who's trying to work towards improving humanity. And I think as engineers, we try to do that.

GEORGE IMAFIDON

Exactly. I think that is the essence of engineering that I teased out early on, but I think everyone sees it in many different ways. So with that said then, what first got you interested in working with bamboo?

SEB KAMINSKI

I was working in Latin America, in El Salvador to be specific, and I was working on some affordable housing for low-income communities. And there was an existing design that used local bamboo. And we were asked by the local NGO to review it and improve it. And we did quite a bit of research off the back of that on bamboo. We developed an improved vernacular design, which I think we'll talk about later that used local materials such as bamboo to be affordable, yet durable and seismically resistant. And after that, we started to get more phone calls internally and externally, general questions about bamboo. And so they ended up coming to me. So I just sort of grew that business.

GEORGE IMAFIDON

Everyone's heard of bamboo in some way, but maybe you can describe what the bamboo plant actually looks like and how it's structured.

SEB KAMINSKI

Bamboo itself is actually a grass. It's not a tree. It's very fast growing. So within about three to five years, a culm is typically ready for harvesting. Unlike most structural species of timber, which need probably 40, 50, 60 years at least before they're ready for harvesting. There's many different species of bamboo around 1,600, varying from very small diameter bamboo, which you'll typically find in your garden, which might be 10, 15, 20 millimetres in diameter, up to bamboo which is up to 200 millimetres diameter, so quite large. Most bamboo is hollow, but some species are solid. The large diameter tend to be hollow. And when it leaves the ground, its diameter is fixed so it doesn't change in diameter over time, like a tree. It leaves the ground, that's its diameter and it grows telescopically. As it leaves the ground, it just sort of grows vertically with cell division. And then you end up with a culm, which for a small diameter could be half a metre, a metre, two metres high … to a large diameter bamboo, which could be up to 30, even 50 metres high. And that's just one culm of bamboo.

GEORGE IMAFIDON

What is a culm, I've never heard that word before?

SEB KAMINSKI

Right, so one stalk of bamboo is called a culm. And then together, if lots of stalks of bamboo grow together, that's called a clump.

GEORGE IMAFIDON

How strong is bamboo? Maybe we can start there.

SEB KAMINSKI

Bamboo is a strong material in certain directions. In let's say, in tension, so if you try and pull it, and in compression. But in certain failure modes, it's actually not as good. It's quite weak at splitting, unfortunately, probably more so than timber, it's quite easy to basically pull it apart. And that's a problem for other failure modes and also for connections. So like any material, there's no perfect material out there. If you load it in a certain way, it's very good. If you load it in other ways, it's not so good.

GEORGE IMAFIDON

In addition to that, are there any other weaknesses that come to mind besides this splitting, and the different load cases, that it doesn't perform too well in?

SEB KAMINSKI

So also because it's hollow, it makes it quite challenging to build with, especially for connections. And it's a natural material. So it's not straight, it's wobbly. So we don't typically build out of unprocessed round timber anymore, do we? Because we want our house and our buildings to be everything flat, all our surfaces to be flat. So we build out of cut laminated timber. You can't cut bamboo because it's hollow. It's not like a solid piece of timber where you can cut a rectangle out of it. Bamboo in the round, it's a challenging material to work with. It's a very natural material. And also durability … so, because bamboo grows so fast, it doesn't have any natural toxins, which some timbers have, which protect it against beetles and termites and rot. It doesn't have that, which makes it very vulnerable to beetles and termites and rot, unfortunately. So you have to treat it and you have to keep it dry. But if you do that, bamboo can last forever in theory.

GEORGE IMAFIDON

And how good is bamboo from a carbon perspective as well? I've heard a lot from that kind of side. Maybe you can share a bit more.

SEB KAMINSKI

So, because it grows so quickly, that's a really important benefit. It does absorb a lot of carbon per unit area of terrain. I think there's still a lot of research that needs to be done there, but it's at least as good as timber in terms of the amount of carbon that it absorbs. So that's very good. But because it grows quite fast, this means it can be harvested at a higher rate. So three to five years compared with timber, where if you're harvesting every 60 years, then it takes you a lot longer to get that material. Also when you're harvesting timber you're basically clear-cutting. If you have a softwood plantation you typically clear-cut, which means you cut every single tree and you're left with an open soil surface which can then be degraded before it's replanted. With bamboo because it's a grass if you harvest one culm it doesn't kill the plant. You have actually a larger plant underground and lots of culms growing from that. So if you harvest just the ones that mature, the plant stays alive. A bit like when you're mowing your lawn. When you mow your lawn, the grass doesn't die. It's just cut. It's exactly like that. So that way you maintain that soil cover. You're not eroding it. You're not degrading it. And it also keeps a lot of animals still, it keeps their habitats. So that's another big advantage.

GEORGE IMAFIDON

That's a very, very great point. And how is building a house out of bamboo different from building a house with timber?

SEB KAMINSKI

If we're building out of round unprocessed bamboo, we're using a natural material, which … it's not vertical. It's got nodes, it tapers, changes diameter. So it's irregular to build with and that causes challenges. So if you want a very natural aesthetic and you're happy for your walls not to be vertical, then that's great. But often what they'll do, they'll plaster over the walls. So your bamboo studs might be hidden within your walls. So that's one of the challenges. And again, those connections. Bamboo in the round, it can be challenging getting strong connections and they often govern the design. So at the moment, codes typically limit bamboo construction to say two storeys. You can go higher, but we've intentionally limited the codes to low rise, say two storey buildings, because we're still very much in the infancy of developing good structural design of bamboo buildings.

GEORGE IMAFIDON

And how do we get around those challenges of the bamboo being so irregular, as you mentioned, is that standardisation pretty tricky?

SEB KAMINSKI

So this is where I think bamboo in the round is well suited for, let's say, affordable housing in low and middle income countries, and for maybe community buildings such as schools, and the odd sort of high-end building, let's say. But I can't see it breaking into the market for example in the UK in its unprocessed form. No one builds out of round timber for good reason. And again, I don't think we'll be building out of round bamboo. There's just a lot of issues with it. It's fairly tricky.

GEORGE IMAFIDON

Coming back to the humanitarian aspect - my bias there - but I've heard, you know, a lot about bamboo being resilient in earthquakes, for example, is that true? Maybe you can tell us a little bit more about that.

SEB KAMINSKI

So bamboo structures can be quite resilient in earthquakes if they're in good condition and well designed. Bamboo as a material, it's like any other material. It's not really about the material. It's about how it's used. So you can have steel structures which are very unsafe in earthquakes. You can have concrete structures which are very safe in earthquakes. So it's a bit misleading to say bamboo is good in earthquakes. There's a lot of articles out there where you read that. And personally, I don't think that's a good way of having that conversation, having that dialogue, because it means that people automatically build bamboo buildings and just claim it's earthquake resistant. Sometimes it's actually not. So what's much more important is to make sure your building is properly designed. Now, bamboo has several advantages, which makes it potentially good in earthquake zones. One of its main advantages is, like timber, it has a good strength to weight ratio. This means that bamboo buildings are typically quite light. But one has to remember to keep that bamboo structure light. You can't have a bamboo frame and then you put a heavy concrete slab on it. You've just cancelled out all those advantages. So you keep the building light, that's good. Bamboo also, like timber, is potentially, if the connections are designed properly, the connections can absorb energy, not the bamboo. Bamboo cannot really absorb energy in an earthquake, but the connections can. And the secret is steel connections. So in all earthquake resistant design, whether it’s steel, reinforced concrete, reinforced brick masonry, or timber, it's always those steel elements that are absorbing energy. So if you take a paperclip, you can bend it backwards and forwards multiple times. And that's exactly what happens in a well-designed building to resist earthquakes. Your steel connections in a bamboo frame or timber frame building are yielding, they're bending and they're absorbing that deformation and transforming it into heat in those connections. And that's what's resisting your earthquake forces. So you have to design it properly.

GEORGE IMAFIDON

Maybe we'll speak a bit more about your work as well. One of the things you've worked on is developing a system for creating walls out of bamboo that can be used to build these sustainable houses that we've spoken about in developing countries. Maybe you can tell us a little bit more about that work.

SEB KAMINSKI

Yes, definitely. So, the history of that actually goes back a long way and there's a lot of people involved with that, not just us. So the history … it’s probably worth going back a hundred years to Colombia. So within Latin America, there's a system called Bahareque, and it's similar to in the UK what we call Wattle & Daub. Wattle & Daub is basically a timber frame with timber twigs plastered in mud. Most countries around the world, nearly all countries, have a form of Wattle & Daub. It's one of the very simple, very clever, traditional vernacular systems. You're taking what's available, timber, twigs, mud, and forming basically a simple … originally it was a hut. And in Latin America, that system is called Bahareque, and that developed quite well into basically more of a formal house and actually even higher income people were living in that form of construction. And that system, if it's in good condition, can perform well. But there's a lot of data which suggests that when those buildings, typically even after 10 to 20 years, they perform worse because they've been attacked by insects and fungi. So that's really important. Now over the past 100 years that system, especially in Colombia, they started to improve the system, they started to replace the mud with a cement render. So naturally it became a slightly vernacular improved system. In the 1980s, and with the help of the UN in Costa Rica, they had a big program where they tried to formalise that system a bit better. And they built over a thousand houses of basically what we call Improved Bahareque. They took the traditional Bahareque, they replaced the mud with cement mortar, they engineered the connections, they treated the elements. And they built very successful housing projects, which you can still visit today, and the houses are still in good condition. Then in 1999 in Colombia, there was a large earthquake in the Coffee Grain region. Because of the good performance of bamboo houses, a lot of NGOs started to develop also their own form of improved vernacular Bahareque housing in Colombia, and several thousand houses of that system were also built. But also the Colombian government and many other engineering organisations decided that they should actually formalise this and they developed a code, a structural design code, for bamboo. And that became the first proper structural design code for bamboo. And since then, a lot of work around the world. And we're also contributing to that, but many other organisations are, and basically developing this improved vernacular system of bamboo housing, which we call Composite Bamboo Shear Walls. We've actually incorporated it into the latest International Standard Organisation code. And we're going to be publishing shortly a detailed guide on using bamboo and using this system, published by the Institution of Structural Engineers in the UK. So we're working on that now. We're hoping to publish it this year. That'll be open-source.

GEORGE IMAFIDON

It's amazing. And I saw, you know, kind of building on all of that. You're a bit of a YouTuber as well. I saw a video on YouTube of you testing the house that was made in this way for kind of seismic resilience. Basically, you know, recreating an earthquake in a lab, it looked like a lot of fun.

SEB KAMINSKI

I wouldn't call myself a YouTuber. That's the only video I uploaded. So that was done in Guatemala in 2015 led by the Universidad Mariano Galvez in Guatemala City. And we built a full scale one room model of the house. And we tested it on a shake table. And basically we shook it in both directions. We started with a very small shaking, replicating the 2001 El Salvador earthquake. We use that history to basically shake it in both directions. We started small and we gradually scaled it up. And we scaled it up beyond the force that we need to design for. And the building was still fine. So we were shaking it quite a lot to try and see what its behaviour would be, and it behaved well.

GEORGE IMAFIDON

Love it. Part of that work in El Salvador as well is about understanding these local perspectives when it comes to bamboo, because for many of the people, they don't necessarily see this as a luxury material. So how do you go about doing that and changing those perceptions socially when using these materials?

SEB KAMINSKI

I think that's a really good point. I think if we separate out laminated bamboo from bamboo in the round, so laminated bamboo, if you imagine you're basically cutting small rectangles from the wall and then with very thin layers of glue, gluing it back together. And that way you can build up a larger solid rectangle from lots of smaller chunks. But bamboo in the round, it's much trickier. As I mentioned, I think it'll be very hard for bamboo in the round to enter, for example, UK markets. And I don't think it's really appropriate either to try and force that because there's other materials, such as timber, which are much more appropriate. In low and middle income countries where bamboo grows, that's different. There isn't a big market at the moment for laminated timber. And indeed, some countries don't necessarily have a large market for sawn timber either. But that's where bamboo has a lot more potential. And there I think Colombia and Indonesia did a really good job of changing people's perceptions. So in Colombia, Simon Vélez and many other architects, but especially I'd say Simon Vélez, has designed a lot of large buildings out of bamboo for higher end clients. And they look very good. And he's done a great job of designing them. And that really was able to change people's perceptions to say, actually, these buildings look really good, and we can use bamboo in the round. Bamboo is no longer necessarily a poor person's material. That's the stigma that's attached. Bamboo is called a poor person's material or even a poor person's timber. So we do need more of those. And that helps to change people's perception.

GEORGE IMAFIDON

In terms of laminating the material, how does that improve the properties overall and allow everything to be a bit more durable along with the treatment?

SEB KAMINSKI

So just like timber, timber has defects. It'll have areas which are weaker. Bamboo will have the same. What laminating does … imagine you're testing one piece of timber or bamboo, in the round, then all your defects are in the same space. So you have a weaker point. What laminating does, you basically cut up your timber or bamboo and you've glued it back together, but you've glued it back together in a different way, different position. So you've offset those defects. So what it means on average, your strength has gone up. You're able to avoid having all the defects concentrated. In addition, by laminating, you can form any sort of section you want. So with bamboo in the round you're stuck with a section. Might be a hundred mil, hundred mil diameter, 20 mil wall thickness. You laminate it. In theory you can have something that's 200, 300 mil wide, 300, 400 mil deep. Same with laminated timber.

GEORGE IMAFIDON

So with everything we've spoken about in terms of bamboo and around laminated bamboo, should we be using bamboo more?

SEB KAMINSKI

Definitely. I think being realistic, I would say for countries where bamboo, large diameter bamboo, doesn't grow typically, then imported laminated bamboo could enter the market if it enters at a good price point, and at the moment it's typically more expensive. At the moment laminated timber works very well in the European space. For low and middle income countries where bamboo grows, that's where there's more potential to use bamboo in the round. And that's where I think we should be really encouraging it and we can start certainly be building social housing, affordable housing, but also community centres, schools, and other buildings. I can also see a future where in, say, Europe it potentially sits alongside laminated timber. But I would say only the laminated bamboo species which are stronger, such as Guadua, where it'll be seen as a material that's superior to laminated timber, probably more expensive. And so only used for certain elements where you need a stronger material. I don't think we're far away from it, but that's the future that I can see.

GEORGE IMAFIDON

Next question in terms of barriers, what are the barriers and how do we overcome those?

SEB KAMINSKI

I think codes is one big barrier. And unfortunately, many codes are written without funding. So for example, a few of us developed the international standard organisation code without funding. People say, I want to build out of bamboo, but there's no codes. There's no guides. One of the first barriers is that, but if there's no funding available and if people are doing it in their own time, then how are we going to advance it? So that's one way, one way of speeding things up would be to fund those properly.

GEORGE IMAFIDON

Well, hopefully our listeners can change that. That's why I asked the question because you know, if they get involved, then we have more people, more firepower to actually solve these problems. There's nothing that we can't accelerate. So thank you so much for your time today, for sharing your vision of the future as it pertains to bamboo.

SEB KAMINSKI

Thank you for inviting me. Been a pleasure.

GEORGE IMAFIDON

You've been listening to Create The Future, a podcast from the Queen Elizabeth Prize for Engineering and Peanut & Crumb. This episode was presented by me George Imafidon, and was produced by Anand Jagatia. To find out more about the podcast and the work of the Queen Elizabeth Prize for Engineering follow QEPrize on Twitter, Instagram and Facebook.