Everything you need to know about Mass Timber Building


Nick Hewson, chartered structural engineer and Head of Design at XLam discussed the benefits of building with mass timber on the PROTECT Podcast. I’ve provided a transcript of notes below for your reference.

Attributes of Timber

What engineered timber does is it takes the tree and breaks it down into smaller parts so whether thats a 2×4 or whether thats peeling the log and turning it into veneers, we then glue those back together in various shapes and sizes depending on the product and what that does is it gives us the ability to make much larger sections, bigger beams, bigger columns, bigger panel than we ever could of made with stick frame timber and it helps us to utilise the lower grade timber because when we design a piece of timber we have to make assumptions around the strength in that because it may have a knot in it or a defect. It’s a natural material so we kind of designed quite a low strength but the rest of that piece of timber may be quite a high strength but we need to work on it as a probability basis where we take that engineered timber and take all those pieces and glue them back together. They call them potential weak spots and we spread them out throughout the whole beam or column. We end up with something thats much greater than the sum of its parts so it enables us to capture the best of the material to utilise lower grade material that otherwise might have gone to be chipped or pulled but we can upgrade it into very strong, very capable materials.

Benefits of Timber

It is the only construction material we have that is effectively grown from thin air. We need a seed and a lot of air and water so it’s the only kind of truly sustainable material we have and as we continue growing in our built environment we can’t continue extracting iron ore and cement out of the ground as it’s contributing far too much to global greenhouse emissions. So one of the key advantages of timber is that timber takes in carbon dioxide as it grows so we’re actually taking the carbon dioxide out of the atmosphere and we lock it into the structure for its lifetime and that could be 60 to 100 years. There’s plenty of buildings that have been around for that long. We can offset carbon emissions with running costs of the building and offset other materials.

Strength of Timber

Certain engineered timber can be up to the strength of concrete. It’s incredibly lightweight. The average density of a piece of timber might be a quarter or 20% of the weight of meter of concrete and many times less the density of steel. It has a very high strength to weight ratio which is critical to building design. Concrete is very heavy so when we’re building concrete buildings it spends a lot of time holding up whereas when we’re building timber because its that much lighter we have less load on the structure so we can use the timber to its maximum effect. We’re actually utilising the material more effectively in a timber building.

Timber Sourcing/Deforestation Concerns

The timber that goes into our products is all from sustainably sourced plantations. They’re all either PEFC and FSC certified.They’re too large forestry schemes that basically say that for every tree that we harvest we have to plant at least one tree – we tend to plant at least two back in their place. We’re actually kind of growing the amount of timber on the planet. What a lot of people don’t understand and don’t realise is that the trees as they grow take in carbon dioxide as they grow as part of their process of converting sunlight into energy but when they get to a mature height the amount of carbon dioxide they take in reduces to a point where they stop taking income on a net basis. Once they get to 40/50 years they really don’t offer a lot of net benefit so by harvesting them and putting new trees in their place were actually taking more carbon dioxide out than if we left those trees to grow slowly so its the most effective use of the material to take the carbon dioxide out of the atmosphere. 

Where can build with Timber

Timber can be viable in almost any application. We don’t need to be timber purists, The building doesn’t have to be 100% timber for us to be interested in it. We see that it can be part of a suite of products that can be used in your building where’s its appropriate to use timber, where it’s cost effective, where it makes sense environmentally you can use it but there are other materials out there that have benefits as well and what we’re seeing more of is more hybrid construction. We sort of see that a more pure mass timber building is probably going to struggle to go above 15 stories – maybe – just in terms of its strength characteristics and the amount of fixings, steel brackets and screws it needs to hold it all together but as we get taller than that we can start to use hybrid structures that may have some steel in it and may have some concrete so we can really start to maximise the benefits of every material through that process.

But in terms of our cities we see a lot of opportunity at the moment. We’ve had most of our enquiries around commercial offices. There’s a big push in Australia to build commercial offices out of timber. We’re seeing a lot of projects, some in every state at the moment and i think one of the reasons for that is the internal environment. Humans have evolved to be surrounded by natural materials. We’ve grown living in caves, woodlands things like that, so when we’re surrounded by natural materials, we’re calmer, we’re happier. Great studies out there showing the wellness benefits from being in a timber building are significant. We’re definitely seeing more and more clients now that are looking to tap into that. Certainly seeing more sustainable awareness in our buildings. Twelve months ago when a client came to us we asked why do you want to build out of mass timber? Sustainability was only one of their prerequisites but it was down the bottom and it was only a priority if it was cheaper.

In the last 12 months, we’ve seen a big shift. More clients coming saying they want a timber building because they want to be sustainable. They want to do the right thing by the planet. They want to be seen to be doing the right thing by the staff and they’re prepared to pay a premium for that. Because they see the wellness benefits they see the higher rental returns and in some cases other offices in timber because people want that environment. I think that any building we see there is a potential for timber.

We see a lot of cases in cities, with a fairly limited amount of land available to build on. We see a lot of enquiries for people who are looking at vertical extensions. They have  a building and maximise the building of that asset so one to do that is to to build floors on top so in a lot of cases the buildings in most  of our CBDS were designed and built a few years ago when building design was less sophisticated, when building codes were more conservative, A lot of buildings have the ability to have additional floors on top so going back to timber being lightweight and its the best materials for these projects for those extensions, because you can build more levels without having to strengthen your existing building because its pretty fabricated and easy to lift on site. It’s not easy to add onto an existing building. Melbourne has the example of the tallest mass timber extension in the world project – 55 Southbank Boulevard where they put an additional ten stories of hotel on top of an existing office building. Just to put that into perspective, the design, until they came into mass timber was to put another six stories on so they’ve increased the variability of their building. They’ve disrupted the people in the office less because they’re building with a quieter form of construction and they’ve offset the carbon emissions from the building by building with timber so it really has a lot of buildings when you start to find those right projects that capture those differentiators for mass timber.

Fire Concerns/Safety 

It’s a hot  topic if you’ll excuse the pun. You spend a lot of time trying to help people understand how it works at a basic level. When timber burns it creates a char layer so that’s charcoal on a piece of timber but because we’re building with such large pieces – for a start they’re very difficult to set on fire. If you’re ever tried to start a camp fire you start with the small little pieces of kindling you don’t start with the big logs. But then if a fire does take hold, the char as it forms as the timber starts to burn does take hold and protects the timber below. So it’s got its own inherent fire rating in it and because we’re using such big sections – you know some of the columns on these buildings could be half a metre square or bigger. Over the course of a fire, percentage wise, you don’t actually lose very much of the section of the column. You lose very little strength over that period so it’s got a lot of inherent capability the way things work. So if you had your campfire and you put the big logs on it when you come back to it the next morning they’re still there. They’ve got some char on the outside but the timber in the middle is being insulated and it’s still just as capable as it was before so what we’re doing is a lot of fire testing at the moment to demonstrate that. To give more information to designers to make sure that we’re complaint with the building code. It’s a never-ending journey.

There’s always more testing that we could be doing there’s more details and situations that we find ourselves on in every project so we’re very aware that this is a perception of timber and it is something that we really need to work hard to counter but there is a lot of information, a lot of data out there for designers and for the general public on how these buildings performs and they do perform exceptionally well and fine.

Current Projects

We’ve probably got something like 300 active projects that we’re tracking across various areas of design. I think some of the more exciting work, some of the larger projects – we’ve just finished the Adelaide Oval Hotel that wraps around our side of the oval so that was built around XLam’ss CLT. So we designed that in collaboration with the builder because it was so fast to build, because it was lightweight – we were building over an existing basement which had some weight restrictions on it and you’re building in a very live environment with the whole site so it had to be shut down if there was an event or a footy game so being able to build in this big panelised form is was much easier for them to be able to program and build the building quickly between those events so that’s been a really great example. We’ve got some really good ones coming up. We’re working on the Bendigo GovHub which is a new government building office building in Bendigo. So that’s going to be about 12,000 metres of CLT floor panel in that and that will be the first completely Australian supplied commercial office that’s been built in Australia so where the company in Gippsland will supply the beams and columns and XLam will supply the floors so that’s been a really good journey and it’s going to be a good example of project out there.

Australia’s Timber Industry

I think Australia is punching above its weight for the size of the country. We’ve got a number of landmark buildings that have been built in Australia that have been kind of world’s tallest or largest. Lend Lease built the first modern mass timber apartment in Melbourne five or six years ago and since then they’ve gone on to build office buildings, student accommodation, those buildings are very large. They’re held up on a global level as being great examples of mass timber construction. There are hundreds more examples around the place. So it’s really starting to take on here so I think the local supply capabilities is really starting to catch up so a lot of that had been employed from Europe and Italy so XLam has been operating for about two to three years now but more and more factories are coming, and coming online as people start to get comfortable with the market. 

Community Conversations

What I’d like to see from Australia is I’d like to see them demand better buildings. I’m from the UK, and I was kind of shocked when I first came over. I thought Australia was just all sunshine and warm all the time. I’ve never been cold indoors until I moved here. I think there’s an acceptance that Melbourne buildings are cold and damp and you just put another sweatshirt on and turn the heating up but the reality is that it doesn’t take a lot of effort to make our buildings better to use more sustainable materials to better seal our buildings. One advantage to mass timber is because it’s this big solid monolithic construction you naturally end up with a building that’s kind of air tight and doesn’t leak all the heat out, so it’s one of the nicest things you hear from clients is that they building a CLT house and they cant believe the environment in there. It’s a lovely constant temperature all year round, its quiet, has a feeling of quality and they’ve hardly turned the heating on for a whole year so if I can say one thing, Australia you need to be asking for better buildings.

You need to look beyond the simple star ratings. Six star homes are marketed as being great but they’re kind of not, if you look at global standards of building and energy use, Australia is real lagged in that respect. I think mass timber construction can be a vehicle for that conversation for that quality building. The other thing I can say is making sure when you specify if you’re looking for the responsibility sourced timber, looking for those FSC logos, PEFC buying from reputable suppliers, Australian suppliers if you can. There’s a lot of timber industry in Australia and a lot was impacted by the bushfires last summer and we want to support those communities and we want to promote buying local material to support those businesses and help those communities get back on their feet. 

Leave a Comment

Your email address will not be published. Required fields are marked *

Pin It on Pinterest