“It’s a new engineering product and we’re always interested to see how these things pan out.”
IT ALL started with Shaun Thodey because without him it’s unlikely Andrew Hastie would be in the picture. It shouldn’t be surprising because innovative people know other innovative people and Shaun knew Andrew.
“We’ve done a fair bit of work with Shaun Thodey Design,” said Andrew, a structural engineer with ACOR Consultants.
“Shaun proposed using this new product with Chris Swadling and that’s how we were brought into the deal.
“We had done a lot of work with Shaun and he recommended us as an engineering company.”
Mr Hastie was probably the one with the most experience with CLT and even that was fairly minimal.
“I’d done a concept using CLT but it only went as far as the concept it never went any further than that so I had heard of CLT and it was certainly something that’s interesting, one to put on the CV,” said Mr Hastie.
“It’s a new engineering product and we’re always interested to see how these things pan out.
“Because I’d done some prelim work with it on a previous project I had an understanding of CLT.
“What was different on this one was we were using a combination of CLT and timber sandwich panels for the flooring. “
As with Shaun Thodey, Andrew Hastie also consulted Xlam in New Zealand about the general design process, what to look for, what to do and for general guidance.
Since Mr Hastie is a structural engineer he had a different perspective on the job at hand than Mr Thodey, he was fixing his sights on the nuts and bolts of the problem – in more ways that one.
“It was a really mixed design in terms of materials,” he said.
“Downstairs is a combination of full brick, brick veneer, timber and then trying to tie that into the timber framing upstairs, where you’re not using conventional timber framing upstairs that was challenging.
“We had to try to use as much timber as possible and minimise the steel work because we were trying to showcase the product. “That was a fair bit of challenge for us. “Then once we moved on from that we were looking at the connections, trying to simplify the connections as much as possible.
“And that all came as a last minute rush during construction when the panels were delivered and we had to organise screws and everything like that.”
Mr Hastie is sure that should more CLT come into use in Australia some of the issues he faced would disappear. There would be a much better understanding not only of the product but also of the connectors and there would probably even be guidance in terms of connector designs.
“A lot of the connection design was coming out of Europe and we also looked at a Canadian guide,” said Mr Hastie. “There’s no real guide based on our standards.” Not only was guidance lacking in terms of how to meet Australian standards but there was little in the way of stock in Australia of suitable connectors particularly brackets such as those that connected the floor to the walls, ones with the correct capacity. Connectors were harder than the actual use and designing with CLT.
“Designing it was quite simple because you only have to look a few different options you’re not going to change your floor plate thickness throughout so we just had to look at a couple of spans,” said Mr Hastie.
“The roof came together quite easily because it was a nominal thickness that we used for insulation purposes and we had advice from Xlam. That was really easy.
“All the walls were simple residential construction. The panel design was quite easy.
“It was probably the connections and the intricate parts of making sure the CLT was completely supported, that was where the project had more thought and was more complex.”
In fact Mr Hastie, like Mr Thodey, was more than happy with the material finding it easy to use.
“I thought CLT was really easy to use, things went together really easily onsite once we got over a few design hurdles,” he said. “I guess if we ever did a similar project again we would have a bit of forethought - ideas to avoid or better design ideas - everything came out fairly well; there were no real major design issues that we couldn’t deal with.”
In the future simplifying the process would come down constructing a whole house or project with CLT as it would go together very quickly and from an engineering standpoint the ideal would be a concrete slab as a solid base. It was definitely a more difficult project because it was a mixed construction.
Engineering the project took longer than a normal project as everyone was using CLT as new material; if the job had been a standard two-storey residential build it is quite likely that Mr Hastie would not have even been called in.
According to Mr Hastie there is a future for the product in Australia but not in small-scale residential construction such as this project but rather in low to medium rise residential buildings where you have common floor areas.
“Xlam gave us a presentation where you can see the benefits of CLT are in construction, there can be quite good time saving,” he said.
“For general residential I don’t think it will ever be competitive with your standard residential framing.
“It would work really well but it would come down to the cost. I have no reason to believe that it can’t be used in residential but it’s such a tight market.
“I would certainly be interested in doing more CLT design, I’ve done it once and I don’t want to waste my experience.
“It’s a product we’ve been looking into and we’ve had meetings with Xlam and other builders who are looking at the option of CLT.
“Builders are starting to catch on but it’s finding the right market.”