Mass Timber As Lego: Flyvbjerg’s Modularity Meets Low-Carbon Construction

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Mass timber is being promoted as a way to cut carbon in construction, speed up schedules, and reduce costs. But there is another lens through which to view it that comes from project management research. Professor Bent Flyvbjerg has spent decades studying why large projects fail and what can be done to make them succeed. He is known for showing how often big projects run late and go over budget, and for offering solutions rooted in data and modularity. He came to greater prominence in 2023 with his multiple-chart topping non-fiction book, How Big Things Get Done, co-authored with Dan Gardner.

One of his most compelling ideas is that successful projects behave like Lego. They use repeatable, scalable modules rather than bespoke parts, making them easier to design, easier to build, and less prone to risk. Thinking about mass timber as Lego is a useful way to frame its role in the future of construction.

This is one of the last articles in my series examining the role of mass timber in Canada’s housing and climate future, and by extension the rest of the world. The first piece laid out Canada’s timber moment, framing cross-laminated timber (CLT) and modular construction as the fastest lever for addressing housing shortages, jobs, and embodied carbon. The second explored how Mark Carney’s housing initiative could industrialize the sector through pre-approved designs, offtake contracts, and regional factories. The third explored the requirement for vertical integration within the industry to maximize efficiencies. The fourth showed how CLT displacement could bend the demand curves for cement and steel, making their decarbonization pathways more realistic. The fifth demonstrated that from harvest to housing, CLT already locks away more carbon than it emits, strengthening its climate case.

The sixth turned to the forestry supply chain, arguing that electrification of harvesting, transport, and processing is essential to maintaining CLT’s carbon advantage. The seventh piece addressed systemic barriers, focusing on high insurance costs and bespoke code approvals, and argued that normalizing mass timber in regulatory and financial frameworks is the key to scaling. The eighth piece, arguably one that should have been much earlier in the series, explored the various technologies in mass timber and its currently dominant form, CLT. The ninth piece assessed the global leaders, opportunities and competition for Canada’s mass timber industry and considers lessons to learn. The tenth piece deals with input regarding labor and financing I received over the course of the series from professionals engaged in the space. The eleventh piece focused more on a speed and labor opportunities that mass timber construction has demonstrated. The twelfth turned to carbon accounting and international standards. The 13th article turned to the subject of end-of-life final resting places for mass timber, something introduced in the previous piece. The thirteenth piece turned to a question that was raised at various times in comments, the question of fire safety. The fourteenth piece turned to interesting examples of mass timber construction from around the world. Finally, I think, I turn to a key set of intellectual concepts for derisking and speeding projects from How Big Things Get Done author, Professor Bent Flyvbjerg.

CLT panels and glulam beams are already factory made to high tolerances. They are transported to site as standardized blocks and assembled quickly with cranes and bolts. This repeatable, kit-of-parts quality is exactly what Flyvbjerg recommends. He has pointed out that the most successful megaprojects are those built from modules that have been tried before and scaled up, not those designed as one-offs. In that sense mass timber is not just a lower carbon alternative to concrete and steel, but a pathway to modularity in construction. Each panel is like a Lego brick, predictable in its performance and easy to assemble in many configurations. The more the industry embraces that mindset, the closer it gets to Flyvbjerg’s recipe for reliable project delivery.

A second lesson from Flyvbjerg’s work is the importance of reference class forecasting (RCF). Builders and planners routinely fall into optimism bias, assuming schedules will be faster and costs lower than experience shows. Flyvbjerg advocates creating a reference class of similar projects and forecasting based on their real outcomes.

For mass timber this would mean, cautiously, comparing new projects to the growing database of completed timber buildings, not to traditional concrete baselines. If the data shows that a five-story office in timber takes six months rather than twelve, or that a mid-rise residential tower can be built with a smaller crew, those results should be baked into forecasts. That way developers, lenders, and insurers are working with evidence rather than assumptions. Timber can help close the gap between planned and actual outcomes, but only if planners measure it against the right reference class.

Note that mass timber provably accelerates the construction of the structural elements of the building, but doesn’t accelerate finishing. Much of the press regarding mass timber focuses on the major speed advantages of putting up the beams and walls, but excludes the time spent on wiring, plumbing, building control systems, cladding, painting, doors and windows. Make sure that the reference set schedule is from shovel in the ground to the final inspection to avoid optimism bias due to mass timber. Use the average as the anchor and adjust upward and downward for clear variances in your project. Then think slow about how to accelerate and derisk each aspect of the process so that buildings go up fast once construction starts.

Modularity also opens up opportunities in adaptive reuse and extensions. One of the most compelling applications of mass timber so far has been vertical additions on top of existing buildings. Lightweight CLT floors and glulam frames make it possible to add new stories to old concrete shells without overloading foundations. Projects in Melbourne and Rotterdam have already proven the concept. This is a clear expression of the Lego principle. Instead of demolishing and starting from scratch, add new blocks on top. Flyvbjerg’s point about modularity is that it allows for repurposing and scaling without redesigning everything each time. Timber fits that bill perfectly, giving cities a way to expand their building stock while keeping the carbon and cost impacts in check.

Scaling capacity is another area where the Lego lens helps. Flyvbjerg stresses that scaling up successfully requires industrialized production of modules, not artisanal one-offs. Mass timber is still young, but heading in that direction. New CLT plants in Australia, Canada, and the US are being built with automation and standardization in mind. Panels roll off production lines, CNC cut to specifications, much like car parts. That is the kind of modular production Flyvbjerg argues is necessary for large scale success. If the industry can standardize connections, floor systems, and wall assemblies, then designers will be able to draw from a catalog of proven parts rather than reinventing the wheel. That will reduce risk, reduce cost, and make timber construction more like stacking Legos than crafting custom furniture.

Policy and procurement need to support this shift. Flyvbjerg’s research shows that cost overruns and failures often come from misaligned incentives. If public procurement rewards unique designs rather than modular repeatability, projects will tend to become more complex and less predictable. If instead, governments specify that projects should use standardized timber systems where possible, they will reinforce the Lego principle. Incentives for embodied carbon reduction already tilt the field toward timber, but embedding modularity in codes and procurement rules will strengthen the effect. Lenders and insurers can play a role too by recognizing the lower risk of modular systems and pricing premiums accordingly.

Carney’s Canadian housing initiative could be a proving ground for this approach. The country faces a pressing need for affordable units delivered at scale, and mass timber’s modularity offers a way to meet that demand quickly without repeating the mistakes of mid-century public housing blocks that were efficient on paper but socially barren in practice. Featureless, identical towers eroded community rather than building it. To succeed, Canada should pair standardized timber systems with architectural variety and integration of public amenities, green spaces, and local design input. That would preserve the cost and schedule advantages of Lego-like repeatability while ensuring the neighborhoods built are livable, diverse, and reflective of community character. Remember that Lego builds anything a child imagines, not featureless, identical cubes.

Mass timber is already gaining traction for its carbon profile, its speed, and its aesthetic appeal. But its real power may lie in its alignment with Flyvbjerg’s modularity insights. Treating CLT panels and glulam beams as Lego bricks rather than bespoke parts reframes the entire value proposition. It makes projects easier to plan, easier to build, and easier to scale. It reduces the chronic problem of optimism bias by anchoring forecasts in data from similar projects. It enables adaptive reuse and vertical extensions that extend the life of existing assets. It supports factory production that brings construction closer to industrial efficiency.

As a strong recommendation, if you are engaged in policy, development or manufacturing in any way related to mass timber, get How Big Things Get Done, read it carefully and apply its lessons. Take the Coda, Eleven Heuristics for Better Project Leadership, and paste it on your wall. Discuss it with your teams.

The metaphor of Lego is not just playful. It is a serious way to think about how construction can change from a sector plagued by delays and overruns to one that delivers on time and on budget. Flyvbjerg has argued that modularity is the single most important factor in project success. Mass timber is one of the first structural materials in decades that makes true modularity feasible across a wide range of building types. If governments, industry, and financiers embrace that potential, timber could become the Lego of construction. And if it does, the sector could finally begin to match the reliability of the industries it so often lags behind.