^{The four subtopic chairs relayed their findings from the break-out research meetings.}

^{Click the image above or watch a video of the session here.}

The summary session featured the chairs of each of the four subtopic groups reporting on the key findings.

Architecture/Design - Andrew Waugh, Founding Director, Waugh Thistleton Architects

Chair Andrew Waugh, Founding Director, Waugh Thistleton Architects indicated that the Architecture/Design session concluded the mass timber community was in need of the equivalent of a manifesto; a set of first principles. He argued that “we need to reset our notion of success, beyond height as a measure. A better measure of success would be: How well does a building support well-being, both of individual humans and collective society, as well as that of the planet?” Waugh illustrated that hybrid timber construction is part of the evolution toward a zero-carbon construction industry, and that more research and early-stage conversations will be necessary if the movement is to be successful. He also reported that the group emphasized the conversation must not be restricted to Western nations – it must be global.

Construction Logistics - Lisa Podesto, Senior Business Development Manager, Design-Build Americas, Lendlease

Several key insights emerged from the Construction Process meeting, as described by chair Lisa Podesto, Senior Business Development Manager, Design-Build Americas, Lendlease. She broke the conversation’s key points into these categories:

1. Bidding

- Bidding needs to start at about 50% percent design development stage in order for steel-timber projects to achieve optimal cost-effectiveness.

- Early engagement from steel and timber erectors, as well as affected subcontractors, is necessary.

- Obtaining absolute clarity on the intended scope of each bidder is also necessary. One approach to assisting this would be color-coding details in bid packages.

- A “super-bidder” for subcontractors might also be advisable, one for each material (steel and timber), so that quantities can be accurately determined.

2. Schedule

- Identify crucial trades that need to be engaged at an early stage; emphasis on those that will most impact planning. (These may include façade/envelope installers).

- Engage early with AHJs (authorities having jurisdiction) and unions. Identify a preferred subcontractor to conduct conversations with the unions.

- Accounting for the role of prefabrication:

Which trades are on the critical path and for how long?

How do the assigned trades affect the approach to / timing of prefabrication?

3. Quality Assurance

- How to ensure that installers are qualified?

- Prefabricate as much off-site as possible!

4. Site Logistics

- The whole team needs to understand from an early stage how much room will be available to operate.

- Selecting standardized prefabricated parts would be helpful to this effort, as the dimensions of these products would then be well-understood.

- Shipping and staging – understand the number of pieces to be delivered, and how the availability of laydown space will affect delivery and installation schedule.

- Sequencing – a thorough understanding of the installation sequence will affect the bid – incorporate 4D (time-dimensioned) modeling.

Standardization/Guidelines

- It is key to know in advance as much as possible: what are the acceptable and differential tolerances between materials?

- Detailing

Use bolted connections with oversized holes

Project-specific tolerances need to be identified in the project documentation

Differential/elastic creep must be accounted for

The effect of moisture exposure on details must be well-understood

MEP Systems & Façades/Envelopes - Susan Jones, Principal Architect, Founder, atelierjones

The breakout research meeting on MEP Systems & Façade/Envelope had good representation in terms of both geodiversity and disciplinary diversity, reported chair Susan Jones, Principal Architect, Founder, atelierjones. Attendees included representatives from the insurance, fire engineering, architecture, development, and forestry disciplines.

Testing will be critical to the success of steel-timber project envelopes, Jones said, with particular questions developing around the difference between European and US fire-resistance testing approaches, highlighting the need to standardize the industry’s understanding of fire engineering across jurisdictions. The questions that emerged were mostly around best practices for routing services, and how and when MEP systems should be concealed.

Further points:

- How to detail acoustical mats around steel and timber connections, avoid getting water under the mats on top of the timber?

- Do the predominant European glues used in laminated timber hold up to PRG 320 18 standards? Are they as heat-resistant?

- Fire codes tend to be enormously conservative.

- Adding steel components to the connections between timber elements complicates the fire situation and warrants further testing.

Structural Engineering / LCCA - Antony Wood, President, CTBUH

As a key aspect of the research project, the structural engineering and LCCA meeting was the best-attended, and, interestingly, the most contentious. It was nearly impossible to reach a consensus, reported chair Antony Wood, President, CTBUH, but some general parameters did emerge:

- A balance should be maintained between real-word case studies and generic scenarios?

- The likely floor counts of the modeled scenarios would be 9, 18 and 60, on account of the first two being well-defined in International Building Code, and the latter being an aspirational   ultimate height for steel-timber hybrid construction.

-Instead of pitting all-timber vs all-steel structures, we should consider multiple hybrid scenarios.

- As a first step, the CTBUH research team would evaluate existing LCAs performed on steel-timber hybrid buildings to date.

- Then, the team would circulate a questionnaire to focus the study more deeply.

- Following this, CTBUH would conduct outreach to key organizational members of the Steering Committee to gather data, as well as determine the assessment platforms to be used and firms that will construct and verify the accuracy of the model scenarios.