Swapping a calculator for a screwdriver
At Arboralis we like to practice what we preach, so we were delighted to spend a day on site with the team at Standstruct on a small school project in Melbourne to get some hands on experience of the A part of DFMA. It was a great experience and gave us a lot of valuable insight into a typical mass timber build, much of which will help inform our own designs moving forwards. We think this should be an essential part of engineering education for mass timber!
What did we learn?
Coordination with other materials sets things back. Timber can be fast to install but often it's far simpler when it's connected to another timber element. Where things get challenging is where there is an interaction with another structural material. It's a common refrain I hear from mass timber installers...
"We gave the contractor a program telling them when we would have things installed, but we have to wait for other parts of the structure to catch up because they didn't believe we would be that fast!"
It's very difficult to install columns when you've already had to install the beams they're supporting above! 😂 All the major time delays we saw on site were due to coordination issues with other materials and these details have to be a huge focus to increase speed of install.
Single source of truth. One thing which makes things unnecessarily complex is the amount of different documents that needed to be referenced on site. We had structural drawings, GLT shop drawings, CLT shop drawings and temporary works drawings and they all needed to be referred to at some point to find connection information. Then you find out there's a secret 5th document somewhere that requires a sealant in the CLT lap joint! It's a lot to try and review simultaneously and the opportunity for error or contradiction is high. Other structure which interacts also needs to be accurately modelled too - the CLT had to be expertly cut with a chainsaw after a cut out for a column was missed. I would be advocating for a single source of truth set of documents which includes all necessary information in a single place and avoids the potential for errors. Arboralis can offer this service through our partners and this can massively reduce the risk of errors and rework.
Tolerance. We've all heard that you can cut timber to millimetre tolerance and to an extent that is true. However, timber can change dimensions due to changes in moisture and tolerances with other materials or between different suppliers can be challenging to manage. There's always a balance to be had with and it was really interesting to see how certain areas needed more than others. What was awesome to see was the pride in which the installers take in getting things as close to the millimetre as they can - no "she'll be right" attitude on display here!
Safety is of paramount importance and the use of pre-installed balustrades, lifting devices and safety harnesses etc was a big part of the work we ended up doing and it was a clear focus of the installers. I'm sure the temptation to move a bit faster and save on these measures can be high, but it's so important to make sure everyone goes home at the end of the day
The weather ended up playing a big part in the day's labour with some heavy rain at times and the odd gust of wind making things difficult to programme and causing some delays. The building is small and the unfortunate stage meant that it was difficult to programme any works under cover this particular day, but larger sites might be able to consider leaving more detailed fixing works (full bracket screwing etc) later in the programme when undercover to allow the effective utilisation of labour.
Lap joints are a drag! There's a significant difference between installing 10mm screws at 150cts and 8mm screws at 300cts, both in cost and effort screwing them all in! We would love to see some more rationalisation in these to reduce the work on site, whether than is through more detailed engineering or testing to support performance. It was great to get a physical feel for the effort involved in these and will be a renewed focus for our designs moving forwards.
Waste. It's long been a bugbear of ours, but is there a sustainable way of packaging up mass timber for delivery? The mass timber is wonderful to see, but the large amount of plastic wrapping and straps that is getting tossed in the skip is very sad. Is there a recycling opportunity for these elements, and can the timber industry take responsibility for these? At least some of the timber dunnage and packing seemed like it was getting moved on to another home after the project
