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Picture a downtown site at dawn, where contractors gently swing a 50-foot-long, 2 feet wide and feet deep timber bream into place. Not for building, but a parking structure.
That’s the reality of what's happening in the world of mass timber right now. And to unpack it, we spoke with the Systems Wizard himself, Corey Hokanson, the Design Manager at SmartLam North America.
An Industry Scales Up: From Mass to Mega Timber
Columns and beams once considered “big” are now growing so large that onlookers knock on them to check if they’re hollow. That’s exactly what happened when SmartLam North America showcased its new 24-inch by 42-inch glulam at a recent conference. They drew immediate curiosity about how glulam could possibly reach such dimensions - and be produced economically. Until recently, achieving a beam two feet wide by up to four feet deep often meant a time-consuming, custom hand-layup process. Now, SmartLam presses in Dothan can turn out these jumbo glulam members seamlessly.
Driving this transformation is a practical desire to manage higher loads and longer spans with fewer pieces, all while addressing fire and sustainability requirements. In Hokanson’s view, “There’s a lot of things that change when you start getting into pieces that big and that heavy.”
One direct technical gain is the potential to reduce overall piece counts—doing away with multiple smaller beams in favor of a single member. Fewer members means fewer connections and labor hours, but it also demands bigger handling equipment and more careful planning. Because single pieces can top 12,000 pounds, oversights in design, sequencing or installation can erode those hoped-for benefits. The industrial leap from “mass” to “mega” marks a moment where “everything has changed in the last couple years,” adding fresh options that simply did not exist at this scale before.
3-Hour Fire Rating: A Bold New Frontier
Not long ago, few imagined that exposed timber could endure three hours of direct fire exposure. Yet Hokanson describes new furnace tests showing mass timber assemblies charring for three hours with “no coatings, no intumescent paint, no drywall wrapping.” During these tests, the timber effectively formed a thick char layer on the surface, protecting an undamaged structural core. He notes, “They put it in a furnace and basically blast it with a blowtorch for three hours… it’s like you threw it in a bonfire.”
From a design perspective, this changes the conversation around heavy timber in spaces that demand ultra-safe, code-driven solutions. It also means teams have a legitimate alternative to expensive encapsulation or the steel and/or concrete typical for high fire-rating assemblies. In tangible terms, using these 3-hour rated timber assemblies frees projects from adding extensive gypsum board or intumescent coatings. The cause-and-effect is straightforward: by allowing enough mass for extended charring, the material retains a stable core, preserves structural performance, and satisfies the code. Hokanson points out the real advantage of timber’s char characteristic: “You figure three hours… that’s a long time… you can get a lot of people, everybody out of a building in three hours.” It’s an endorsement that large wood members are stepping decisively into applications once reserved for concrete or steel.
Podiums and Parking Decks: Challenging Concrete’s Turf
Now, timber can claim spaces long dominated by concrete—like podium levels and parking decks. SmartLam is already fielding designs that swap out concrete beams, slabs, and rebar with 7+ layer CLT and heavy glulam. Hokanson captures the schedule benefit in practical terms:
“I can come drop in these four pieces of timber off the semi-truck in two hours. Or we can sit there and form this all up for the concrete and then put all the rebar in… then we can pour the concrete. Then we can sit around and wait for it to cure….”
That contrast grapples with weeks of site labor, specialized forming and bracing, and the wait time that inevitably follows a wet pour.
Replacing a conventional podium system (concrete beams plus a concrete deck) with large glulam beams spanned by nine-ply CLT does come with its own unique set of consideration, though. Hokanson describes a project employing 12.5-inch-thick CLT panels: “That piece weighs 12,000 lbs.… we better make sure it’s in the right order on the truck,” emphasizing the need for careful sequencing and onsite logistics.
Mastering the Logistics Puzzle
Enormous structural members offer clear benefits, but only if carefully choreographed from manufacturing to final install. It starts the moment a 12,000-pound panel is pressed and ends with that panel being correctly sequenced on-site. Hokanson warns, “If you get partway through putting it together and you’re like, ‘Oh, I should have put that one in first,’ now I got to go pull three pieces out… you’re losing all that time schedule savings.”
A concrete deck might allow continuous pour after pour without worrying about piece-by-piece staging. Timber, however, arrives “basically a puzzle piece,” so just-in-time sequencing is crucial.
The upside? Mastering that puzzle yields an impressively streamlined crew—“on a mass timber install, you might have five or six people,” Hokanson notes. With fewer trades on-site, the risk of coordination clashes drops. But to keep that advantage, each piece must arrive when needed and in the exact orientation for rigging and lifting into position. For those tackling a podium job or large commercial floorplate, the short yet precise staging can be a major edge—provided the entire supply chain works in lockstep, from the press operator in Dothan to the crane operator on the job site.
The Four-Foot Screw: New Realities for Field Install
Hardly anyone expects to drive a four-foot screw into solid wood, but the new wave of massive beams demands equally massive fasteners. “You’re not going to find a lot of 16-inch screws at your local hardware store,” Hokanson observes. That leads to specialized torque drivers, batteries that can handle heavy loads, and yes, an awareness that if the tool overheats or the screw seizes, installation will be disrupted. “You have to drive it in one go all the way in,” he explains, because if mid-thread cooling occurs, the screw can bind and snap.
The consequences of using the wrong method can be devastating. “Worst case scenario, you’re taking all those screws back out and replacing them all because you voided the warranty… or you broke the screws off,” Hokanson says. In the absolute worst case, snapping a critical fastener inside a beam can require full beam replacement—a cost nobody wants. This scenario flips a standard wood framing approach (laborers with practice at sinking three- or four-inch screws) into a new territory where site managers must plan for specialty equipment, factor in slow-driving drivers, and equip extra drills to cycle in when batteries begin overheating. In short, ignoring the fastener hardware dimension might jeopardize the very speed advantage that large mass timber promises.
Automated Presses Meet Sky-High Loads
No one doubted that big glulam members could be made by hand. But producing them at scale—“a press load of beams every fifteen minutes,” as Hokanson puts it? Utilizing a uniform, factory-tight layup with presses sized for these larger members makes it possible. And more reliable.
Fasteners and connections can fail if there are gaps in the lamellas, something mitigated with a consistently dense beam. Hokanson explains, “Simpson Strong Tie has an actual study and a formula for how much you have to reduce the capacity if there’s gaps between boards,” referencing the risk with hand layup members of this size. The new automated llines mitigate that capacity drop. The result is more reliable performance, higher design loads, and a confidence that timber can compete head-to-head with steel or concrete in major structural roles. As Hokanson says of the new system, “We can make anything in between this and this,” meaning wide, deep, or a combination of both, all without the manual constraints of older methods.
Pushing Off-Site Construction Principles Further
Massive beams magnify a core principle of mass timber: “You really don’t want to have to do that” on site, Hokanson quips when describing the labor of drilling a hole through 42 inches of solid wood. A routine task might become an hour-long ordeal, requiring two people, multiple drill bits, and a shop vacuum to clear sawdust along the way.
The obvious takeaway: incorporate all cuts, holes, and service runs into the CNC stage. “If that shows up in the wrong order and you have to move that somewhere… how do you move that?” quickly transforms from a rhetorical question to a budget-busting predicament.
In a world where beams can approach 4 feet in depth, that coordination starts early and runs deep. Whether it’s a parking deck or an office building with hidden conduit, everything from the largest structural connection to the smallest wire chase needs to be pinned down before the press and the CNC do their work.
Future of Mega Mass Timber
“Don’t assume that we can’t do something,” Hokanson says, stressing that many long-discussed but previously unfeasible mass timber ideas deserve revisiting.
The giant beams are here—and they are more than a novelty. “Everything has changed in the last couple years… we’ve got bigger screws, bigger fasteners, bigger brackets… let’s just do more of it.” Then, with that, he closes the door on doubt and opens it to a new scale of timber.
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Latest episodes
An Actual Solution to the Housing Crisis w/ OD Krieg of Intelligent City.
We have a housing problem.
It's not because of zoning, not interest rates, not labor shortages — those are real, but they’re downstream. The upstream problem is that we still build buildings essentially the same way we did sixty years ago. Custom, on-site, one at a time. Every project is a snowflake.
If that’s the problem, then any real solution has to look fundamentally different from how the industry currently operates. It has to be industrialized. It has to be productized. And it has to scale across cities, not just succeed once.
Oliver David Krieg (OD) has been working on what that actually looks like for the better part of a decade. Now president of Intelligent City, he has a PhD in robotics in timber construction from Germany, and used to be the CTO at the company since 2018. Intelligent City is a Vancouver-based company that designs and manufactures flat-pack envelope and floor systems for multifamily buildings. Their project pipeline includes a 420-unit project in Ottawa and a 1,000-unit project in Barrie, Ontario — which, when it breaks ground, will be the largest prefabricated AND mass timber residential project in North America.
But here’s what’s interesting for us timber nerds.
Intelligent City didn’t pick mass timber because they love wood. They picked it because it was the right product decision for an industrialized building system. And that distinction matters more than it sounds.
What “industrialized” actually means
The first thing to clear up is what we’re not talking about. Industrialization isn’t standardization. It doesn’t mean every building needs to look the same.
“It just means the process that is underlying needs to be repeatable, not the result,” OD told me.
The clothing industry is industrialized. So is the car industry. Both produce enormous variability for the customer while running highly repeatable manufacturing processes.
But multifamily construction has neither. It produces moderate variability (most apartment buildings look pretty similar) through a process that’s almost entirely custom every time. That’s the worst of both worlds.
Single-family housing is closer to being solved. Several European companies offer catalogs of 12 or so house designs with online configurators; you press a button and the building is engineered, cut and shipped. But single-family tends to sit on cookie-cutter lots with minimal constraints.
Multifamily is harder because every building is a stack of unique combinations. Different sites, unit mixes, setbacks, parking requirements, etc. You can’t productize the whole building, or you’d lose all the design flexibility that makes each project work for its site.
What you CAN productize is components. Intelligent City’s bet is on the envelope panels and floor cassettes. Get those right, and you can erect and enclose a building dramatically faster than conventional methods, while preserving architectural flexibility on everything else.
Why mass timber
This is where the material decision gets interesting.
Intelligent City didn’t start out to be a “mass timber company”. They were founded to solve a manufacturing and logistics problem. How do you build a flat-pack panelized system for mid and high-rise multifamily? That question dictated the material requirements.
The system needed something easily machinable, since no two projects require identical systems. It needed to be lightweight enough to flat-pack, ship cross-country, and install with reasonably-sized cranes. And it needed to be cost-efficient enough to move panels from a factory to a job site.
CLT was the only material that hit all three. Concrete was too heavy. Steel didn’t offer the same machinability for the panel format they needed. CLT was the consequence of the requirements, not the goal. The sustainability aspect of mass timber just happened to be the cherry on top of the product-fit sundae.
This reframes a conversation the industry has been having backwards. Most mass timber pitches lead with carbon, biophilia, or aesthetics. The arguments aimed at people who already want wood. But the stronger case for mass timber as a growth material might not be those values at all. Instead, it might be that it’s the right product decision for industrialized construction. If that’s true, the addressable market for CLT isn’t just clients who love timber or focused on carbon goals.
It’s anyone trying to build housing at scale.
Projects and Lessons
The proof point so far is 230 Royal York Rd in Toronto. Nine stories, 60 units, developed by Windmill Developments and Leader Lane under their Hauser brand. Manufactured by Intelligent City last year, now nearly complete.
It used 103 envelope panels in the building, and a floor goes up in a day. In theory, you could erect and enclose a 9–10 story building in about 30 days, cutting roughly three months off total construction time. That leads to real savings on general conditions, on financing, on time to lease-up.
That’s the theory. Royal York didn’t fully realize it. Not because of the system, but the scale of operations.
Intelligent City’s Vancouver factory couldn’t feed the Toronto site fast enough. Shipping itself wasn’t the bottleneck — once panels were on a truck, two hours or forty hours didn’t really matter. The bottleneck was factory output. The demonstration plant they’d built to prove the system to developers was too small to deliver a building in Toronto at the speed the system was designed for.
That’s a setback worth being clear-eyed about. It’s also, OD argues, exactly the lesson he needed to learn before scaling.
The next step
The demonstration plant in Vancouver is 15,000 square feet and produces 100–150 units a year. It was never intended to be the final version, only the start. It exists because no developer was going to sign with a prefab company that didn’t have a working factory, so they built the smallest one that could prove the system, and used Royal York to validate it.
The next factory — 100,000 square feet, targeting 1,000–1,200 units annually — is the commercial unit. Intelligent City’s goal is to greenlight the new factory this year and start deliveries in 2027.
That’s where the 420-unit Ottawa project and the 1,000-unit Barrie project sit in the timeline. They’re not built yet. They’re the projects the new factory is being built to deliver.
What it would take
None of this is a silver bullet to housing… yet. This is one company doing amazing things. But the lessons here are something that can be applied industry-wide.
The features that make Intelligent City credible as a model — productized components instead of fully productized buildings, in-house manufacturing, mass timber chosen on functional fit (not just feel-good points), and a demonstration plant before a full commercial factory are features any real solution to the housing problem will probably share.
OD’s long-term vision is a factory like the one he’s about to build in every major city in North America. A thousand homes a year is nothing against the total demand. The model has to be replicable, not a one-off.
CLT Home Construction w/ Kyle Hanson of Timber Age Systems
Most homes built today are the largest investment a family will ever make. A lot of them will fall apart within a lifetime. Construction productivity has gone backwards since 1965 while every other major industry has gotten more efficient, and the building science behind the average stick-framed house too often creates the exact conditions that cause it to rot from the inside out.
Kyle Hanson , Founder and CEO of Timber Age Systems, set out to build a company that solves that problem. Based in southwestern Colorado, with an office in Durango and manufacturing in Mancos, Timber Age is a vertically integrated CLT building system manufacturer that designs, mills, fabricates, and delivers high-performance single-family homes meant to last hundreds of years. The pricing is competitive with a standard code-built house. The system gets built while the foundation is still being poured, and a crew of four can dry in a house in days, not months.
This article walks through why so many modern homes are designed to fall apart, how Kyle's CLT-based system fixes those problems, what the build process looks like on site, and what design and build teams need to know to make the whole thing work.
Why Our Houses Are Designed to Fall Apart
Somewhere between the 1970s and 1990s, the residential industry started tightening up envelopes and adding more insulation without really understanding how air and moisture moved through a wall. Put a condensation layer in the wrong place, add a family that cooks, showers, and breathes inside, and moisture finds somewhere to collect. It settles, drains, and rots the sill plate thirty or forty years later.
"We built a lot of houses that really have been designed to fall apart without meaning to. No one intended for a house to do that."
That's the building science problem. The second problem is productivity. There's a long-running graph that tracks the output you get for $100 spent in a given industry, indexed to 1965. Construction is one of the only major worldwide industries whose productivity has gone backwards since then. Manufacturing improved. Agriculture improved. Construction got worse, and the industry keeps defending the way it has always done things.
The third problem is how the industry competes. Builders who compete primarily on cost grab market share for a while, then get squeezed out because they have no real differentiator. The race to the bottom pushes everyone toward the cheapest materials, the thinnest drawing sets, and the tightest schedules. Nothing in that model rewards longevity, better building science, or worker safety.
Stack the three together and you get a housing stock that wasn't designed to last, built by an industry that can't afford to change, in a market that doesn't reward getting it right.
If the problem starts in the wall, the fix has to start there too.
The Case for a Monolithic Wall
A standard stick-framed wall is a collection of parts. Studs every 16 inches. Sheathing. House wrap. Cavity insulation. Maybe exterior insulation if the builder is paying attention. Drywall on the inside. Each layer does a different job, and each one gets installed by a different trade at a different point in the schedule.
Kyle's argument is simple: the part count is the problem. The more variability inside a wall, the harder it is to predict how that wall will behave over time. Every connection is a potential failure point. If 1% of your connections fail and you have 5,000 of them, that's 500 places you have to go fix later. Cut the part count way down and you might be looking at five.
A three-inch-thick CLT panel replaces most of that with one continuous surface. It handles compression. It handles shear. It stores and releases humidity, acting as a hygrothermal buffer for the indoor environment. It's a fastening surface anywhere you want to drive a screw. And because the molecules in wood are tightly packed, it creates a thermal mass effect that delays how fast temperature changes move across the wall. Where Kyle lives in Colorado, nights drop to 40 degrees and days can hit 95. The mass of the panel smooths out the swing.
Wood also shows up differently in the material itself. CLT is typically 1% or less glue by weight. OSB and plywood can run 10 to 15%. Getting closer to whole wood means fewer chemicals inside the home and a surface that's naturally antimicrobial. Kyle pointed to research in Oregon around the use of wood in hospitals, where stainless steel is hard to keep clean enough to actually stay antimicrobial. Wood does it on its own.
The panel is the backbone. But a Timber Age wall is more than the panel.
Inside the Timber Age Panel
The CLT itself starts with 11-foot logs, many of them sourced from overcrowded federal and state forests in Colorado. The 11-foot length is deliberate; it lets Timber Age use more of each tree than a traditional saw log operation would. The logs get milled into boards, sorted, kiln-dried to 12% moisture plus or minus three, and planed into precisely dimensioned rectangles. Three layers of those boards get stacked at 90-degree rotations with adhesive between them, pressed, and cut to panel size.
The result is a three-inch-thick panel that stays within plus or minus one millimeter of its specified dimensions over time, because the defects and movement tendencies of individual boards cancel each other out across the three layers.
But the CLT alone only gives about R4. It's the backbone, not the finished assembly. From there, Timber Age layers the rest of the wall:
- An air control membrane on the outside of the CLT. The CLT already controls air movement, but the membrane lets them guarantee how much air moves through.
- Wood I-joists on outside, running perpendicular to the panel, which tie the 5-foot by 10-foot CLT panels together into larger 10-foot by 20-foot assemblies and create a 12-inch cavity on the outside.
- Dense pack cellulose blown into the cavity behind the WRB. Recycled content, class A fire resistant, and enough depth to bring the assembly up to R48.
- A weather-resistant barrier on the outside of the cellulose.
- A rain screen batten ready for whatever siding the project calls for.
- Pre-installed windows, taped and sealed in the factory.
The R48 matters because of dew point. In a standard R19 stick-framed wall, warm, moist indoor air can move through the cavity and hit the sheathing or house wrap before all that moisture has a chance to spread out. When it does, it condenses into liquid water and runs down into places none of the building materials were designed to get wet. With R48 across the assembly, the temperature gradient is gentle enough that nothing inside the wall ever reaches dew point.
The panel is one thing. Watching it land on a foundation is another.
One Trip Around the Building
Kyle designed the system around a specific goal: one trip around the building.
Think about how many times a square foot of wall gets addressed in a standard build. Framers put up the studs. Someone sheaths it. Someone else wraps it. Insulators come for the cavity. Electricians run wire. Drywallers hang the inside. Each trip involves a different crew, a different schedule, and different exposure to weather, heights, and sequencing mistakes. Most of the work happens above the waist or below the knees, meaning workers spend a lot of their day on ladders and scaffolding, addressing the same wall over and over from opposite sides.
A Timber Age build compresses that into something very different. A crew of four to five, plus a crane operator, shows up with a trailer. Because every Timber Age building has a digital twin, the crew walks in with an animation of the full sequence and a scripted role for each person. One person lays out screws. One preps the caulk and air barrier. One rigs. One does quality checks.
By mid-morning on the first day, a crew is typically setting one 10-foot by 20-foot assembly every 20 minutes. That works out to roughly 800 to 1,200 square feet of enclosure per day. A typical house is stood up and weather-tight in two to three days from the time the trailer shows up. After that, the crew makes its one trip around the outside, stitching panel joints, filling the 12-inch cavity, pulling the WRB across, and installing rain screen and siding.
"We’re trying to make the cruddy or the hard jobs better so that the people that are the trades folks that are coming into that area have a better place to be able to work in."
The safety piece matters to Kyle. He points out that construction is one of the only industries that still treats ladders and working on roofs as normal, and that the people most exposed to it are framers, who leave the trade at a rate of four or five for every one who joins.
A Timber Age build is built around taking that exposure out of the equation. Panels lie flat while the crew preps them, keeping most of the work between waist and shoulders instead of forcing people up on scaffolding. Scaffolding that does go up - goes up once. The roof panel arrives as a walking surface the crew can tie off to. The framing crew that would normally be tipping rafters in place isn't on the job at all.
The trades that follow get something even better. They're working inside a closed, super-insulated shell that can be warmed with a hair dryer, doing finish carpentry, plumbing, and electrical in a space that's already weather-tight.
Put it all together and the total schedule for a 1,200 to 1,400 square foot two-story home drops from the industry-standard six to eight months down to roughly two to three months, assuming the trades stay engaged. That last assumption is where a lot of projects stumble.
Getting the schedule compression the system promises depends on something most residential projects never do.
The Big Room: Coordination Before the First Shovel
The construction industry has known for a long time that integrated project delivery works. The Lean Construction Institute has been publishing on it. AIA has an integrated project delivery outline. The problem is that most of those tools only show up on very large commercial jobs. The residential world keeps doing business the way it always has: the GC starts construction, and the electrician has never talked to the framer or the plumber before they show up on site.
A Timber Age build exposes that gap fast. When panels go up in three days instead of three weeks, every downstream trade is suddenly the critical path. If the electrician has other jobs booked in the five-week window they usually get between the framer leaving and the drywaller arriving, the job comes to a halt even though the envelope is done.
The fix is what manufacturing calls Obeya: the big room. Get everyone in the same space before the job starts. Watch the sequencing animation together. Talk about who goes first, second, and third. Sign up for arrival dates. Agree on what the handoffs look like.
Kyle's advice on this is direct. Pay the trades to be there. If an electrician or a plumber needs to be compensated for the hours they spend in the room, budget for it. A thousand or two thousand dollars per subcontractor for a planning session is a rounding error on a project where the envelope just got cut from eight months to three. What comes back is a job site where nobody shows up confused, frustrated, or blocked by the crew that came before them.
The material is what makes the speed possible. The coordination is what makes the speed real.
The Bigger Idea
Kyle keeps coming back to the same frame. The investment in a house is the largest one most people will ever make. Sustainability, in his words, means that person and five more generations get the chance to use it. That takes a house that can last hundreds of years, built with materials that don't introduce new problems, assembled by people whose jobs are safer and more dignified than the industry has historically offered them.
The Timber Age system is one expression of that idea. Smarter, healthier assemblies. A factory process that uses production intelligence the industry has been stripping out. A build process that protects workers and compresses schedules. A coordination model borrowed from manufacturing because manufacturing has already solved problems residential construction is still arguing about.
"We’re doing something, and trying to preserve something, that really needs to go away."
The Envelope: What Every Mass Timber Designer Needs to Know
Most mass timber conversations focus on the middle of the building. Things like spans and grid layouts. Chris O’Hara says that’s the easy part. And most engineers need to give the edges more attention. He’s a structural engineer and a founding principal at Studio NYL, now a Lerch Bates company. He’s worked on 25+ mass timber structural projects and another dozen on the facade side. On many of them, he’s done both.
That combination is rare. And it’s why Chris sees things most structural engineers miss. Getting the wood to perform in the middle of a building is straightforward. It’s what happens at the edges that determines whether a building lasts 20 years or 200: where the timber meets the facade, where the floor meets the wall, where the warm inside meets the cold outside.
This piece covers what Chris thinks about on every project: thermal performance and condensation, construction phase moisture risk, the transitions that become failure points, and the fabrication capabilities that are expanding what’s possible now.
Fast Envelope Systems & Moisture Mitigation
Every mass timber building faces its highest moisture exposure during construction, not over decades of use. Wood retains the capacity it had as a living tree to absorb and move water. Once moisture reaches the end grain of a cut timber element, it spreads. And unlike a living tree, a mass timber floor or wall can’t manage it out.
Temporary membranes, protective coatings, and onsite SOPs are important, but Chris says the more durable answer is getting the enclosure on fast.
That’s one reason panelized and unitized curtain wall systems fit naturally with mass timber. Both are prefabricated off-site. Both install quickly. Marry the speed of mass timber erection with the speed of a panelized facade system and the building gets weathered in before a bad rainstorm can do lasting damage.
Speed also has an economic dimension. Faster enclosure means fewer general conditions days on the contract. It gets the building to sale or occupancy sooner. When mass timber is being weighed against alternative structural systems, speed is often what tips the balance.
Panelized systems help the construction moisture problem. But they introduce a new one. Their aluminum-heavy assemblies can create condensation risk long after the building is occupied.
The Cookware Problem: Thermal Performance and Condensation
That’s why the facade details matter so much. Aluminum is everywhere in building facades. It’s also what we make cookware out of. The problem is, it transfers thermal energy extremely well. Chris uses that comparison on purpose. When you wrap a mass timber building in aluminum facade systems, those elements sweat. And if you let that condensation reach the timber, you have a problem.
The fix is getting the insulation to the outside. Putting insulation inside the stud cavity draws the dew point into the wall assembly. The dew point is where water vapor turns to liquid water. Put insulation on the exterior and that dew point stays outside the weather barrier. Condensation doesn’t reach the timber.
As Chris puts it: "When you get cold, you put the sweater on the outside. You don't swallow it."
At transitions where aluminum has to be used, thermally broken systems (where a low-conductivity material interrupts the aluminum from going continuously inside to outside) reduce the rate of heat transfer. It’s not a true break in the thermal line, but it meaningfully reduces the conductivity compared to unbroken aluminum. For attachment points, Chris favors low-conductivity materials like fiber-reinforced polymers wherever the geometry allows.
The opaque wall is the easier problem. The harder one is what happens when glazing and structure meet, and that’s where the most consequential details live.
Critical Transitions: The Details That Decide Durability
The floor-to-wall interface is the condition Chris is most focused on. It’s where the end grain of the mass timber floor system sits right against the facade. It’s where the window frame, surrounded by aluminum, comes closest to the most moisture-sensitive part of the timber. And it’s where most of the energy loss in a curtain wall system happens.
Panelized and unitized curtain wall systems tend to carry more aluminum, which increases condensation risk at the stack joints, where one panel meets the panel above. Chris lifts the glazing up 18 inches from the mass timber floor deck wherever possible. If condensation does form at that joint, it has room to dry before it reaches the wood.
The glazing interface is one version of this problem. It's relatively manageable because you can see it coming. The harder version is when the structural system creates geometry that the envelope has to wrap around, and nobody has thought through what that actually looks like in the field.
The US Forest Service Museum in Missoula is a good example of all three systems colliding at once. The project used mass timber shear walls, which is the right call structurally, but the hold-down hardware tying those shear walls to the foundation created a plate on the side of the timber that Chris describes as looking like a cheese grater: angled screws at a batter, all kinds of different planes and jogs. That geometry doesn't come from a bad structural decision. It comes from doing the structural job correctly and then having to figure out how the envelope survives it.
Running a waterproofing membrane over that kind of surface without tearing it is nearly impossible. Chris worked through how to protect those membranes while also getting enough insulation over the steel plates. The steel is far more conductive than the timber, so insulation placement at those connections mattered as much as anywhere else on the building. It doesn't show up clearly in a 3D model, he notes, unless you've worked through it a few times. Getting it boxed out on paper before construction started was what kept it from becoming a problem in the field.
Fasteners and the Waterproofing Membrane
One of the things Chris watches closely on CLT wall projects is fastener penetrations. A CLT wall is all structure, so crews tend to fire fasteners wherever they need them. Each one perforates the waterproofing membrane. Some membranes are marketed as self-sealing, but Chris notes those are typically designed for nails, not screws. His approach: put a small amount of silicone on the wall and fasten through it, so the threads draw the silicone into the hole, then seal over the top of the fastener. A small step. Easy to do during construction. Harder to fix after the fact.
The Pen Test
The pen test, sometimes called the pencil test, is a standard quality control check used in building enclosure consulting and commissioning. The concept is simple: take a wall section or building detail and trace each control layer continuously from one end to the other without lifting your pen. There are four layers to check: thermal, air, water, and vapor. Any point where you have to lift the pen is a discontinuity, and discontinuities are where buildings leak, lose energy, and accumulate moisture.
Chris applies this check on every project. In his version, you trace the thermal line and the air and water line around the full building perimeter. If you ever have to pick up your pen because something got in the way, that's where it's going to leak or let thermal energy through and create a condensation problem. The goal is a continuous, unbroken line from grade to roof. Every detail in this article is a place where the pen comes up: the stack joint at the floor line, the cheese grater shear wall plate, the fastener through the membrane. The pen test is how you find them before the building does.
Every one of these details has to be solved before anyone picks up a tool on site. The fabrication capabilities now available are changing how much of that problem can be designed out entirely.
Advanced Fabrication: Designing the Thermal Problem Out at the Source
The details covered so far, the stack joints, the shear wall connections, the fastener penetrations, all have one thing in common: steel and aluminum creating thermal bridges where the envelope is most vulnerable. One of the ways Chris addresses that problem at its source is through the connections themselves.
Ten years ago, he was careful with cuts. Complex geometry meant complex steel connections, which meant more metal at the perimeter, more thermal bridging, and more coordination risk. The rule was to simplify.
That has changed. The milling and cutting equipment at today's mass timber fabricators can produce bearing cuts at a level of complexity that wasn't practical before. Connections that once required significant steel hardware can now be handled by the timber itself. The wood carries the load. Fewer pins, less steel, and better fire performance because there's less exposed metal. And fewer metal connections at the perimeter means fewer places where the thermal line gets interrupted.
The same logic extends to the facade structure itself. Rather than accepting aluminum extrusion as the default spanning element in a curtain wall, Chris uses glue-laminated timber instead. He calls it a timber curtain wall: the glass capture and thermal break hardware come from a conventional glazing veneer, but the structural element spanning floor to floor is glulam instead of aluminum. Aluminum curtain wall systems are optimized for spans of 10 to 15 feet. A glulam can go 30 to 40 feet. The geometry can be anything. And the material conducting heat from outside to inside is wood, not metal. His team recently completed a version of this in Boston, a curtain wall with a 25-foot glulam spanning a historic library, alongside an original glulam facade from decades earlier.
What's now possible with complex CLT geometry tells the same story. A demonstration project at Post Office Square in Boston, currently in permit, has around 1,400 square feet, roughly 20 different roof slopes, all CLT, three-ply and five-ply mixed depending on structural need, and naturally ventilated. Chris calls it thermally one of the best buildings his team has designed. He couldn't have built it 10 years ago. When he brought the geometry to fabricators now, the response was: no problem.
Getting the Wood to Last
Chris has spent 20 years watching mass timber projects succeed and fail at the same place: not in the structure, but in the decisions made at the perimeter. Whether it's a construction phase moisture event, an aluminum stack joint sitting against a floor deck, a cheese grater shear wall plate that nobody detailed around, or a fastener through an unsealed membrane, the problems are almost never structural. They're envelope failures that compound until someone has a reason to say timber doesn't work.
That's the argument Chris is making with every project. The material is right. The fabrication capabilities are there. The industry is getting better at designing thermal bridges out at the source, replacing aluminum spans with glulam, cutting connections so wood carries the load instead of steel. What's still catching teams is the assumption that if the structure is good, the building is good.
That’s not enough. Getting the wood to work in the middle is the easy part. It's everything that happens at the edges that determines whether a building lasts 20 years or 200.
Chris O'Hara is a senior design principal at Lerch Bates. You can find him on LinkedIn or at studionyl.com.
Pick Mass Timber in SD to Avoid These Problems
Most mass timber projects don’t fail on the jobsite. They fail in a conference room somewhere around DD, when the estimate lands and the number is twice what anyone expected. At that point the conversation shifts from how do we build this to can we still build this. And a lot of the time, the answer is no.
Mason Brandt, P.E. has been in that room. He’s the president of WoodCore Engineering , a structural engineering firm out of Lancaster, Pennsylvania focused on wood and timber. He’s worked on north of 25 mass timber projects, and on more than one of them he’s been the person who kept timber on the table when the budget said otherwise.
In this piece he breaks down the decisions that determine whether or not a mass timber project makes it to construction, starting with the one most teams make too late.
Timber or Not: The Make-or-Break Decision in SD
The structural grid for timber is different from steel. It’s different from concrete. Beam spacing, column layouts, span directions. These aren’t interchangeable. Which means if a team gets to 50% or 90% DD with a steel grid and decides to explore timber, they’re not making a design decision. They’re starting over.
Mason has seen this play out more than once. A project comes in with a steel layout, someone raises the idea of timber late in the process, and suddenly the team is trying to make timber perform like steel. That’s where cost becomes a problem. Not because timber is inherently expensive, but because inefficiency is expensive. Every span, every beam that’s not optimized, every column that doesn’t fit the grid - it all adds fiber volume, and fiber volume drives cost.
The fix isn’t complicated. Decide in SD.
If timber is on the table, flesh it out before the grid gets locked down. It doesn’t have to be all or nothing either. Hybrid structures work. Timber plays well with steel and concrete. But the time to make that call is schematic design, not halfway through DD.
But even when the timber decision happens at the right time, the first estimate doesn’t always land where you need it. Here’s what you can actually do about it.
The Cost Problem and How to Pull It Back
Even when timber is decided early, the estimate can still come in high. On one project Mason's team joined mid-stream, the number came back 40% over the owner's budget. The straightforward response would have been to switch to steel. Instead they went back through the structure.
They rotated CLT panels to span the shorter direction, eliminating entire rows of girders. They cut beams and downsized columns from 12x12 to 10x10 across the building. It added up to significant fiber savings. Fewer pieces also meant faster erection.
Each change was small on its own. Together they brought the project back to a full timber building at a number the owner could live with.
The Cost Lever: What Moves the Needle
The lever here is fiber volume. With timber, material cost is driven by how much wood you're using. Reducing piece count, column sizes, optimizing spans - these are budget decisions. The first number you get back isn't always the final number. Having someone on the team who knows how to pull it back down makes the difference between a timber building and a steel one.
One of the biggest variables in that fiber volume equation, and one most teams don't think about early enough, is species selection.
Species Selection: A Hidden Deal-Breaker
Specifying a structural steel beam is straightforward. You pick a grade, put it on a drawing, and multiple fabricators can source it. Bidding is competitive. With timber it doesn’t work that way.
Not every species or grade has multiple manufacturers who can competitively bid it. The NDS supplement lists glulam grades and layups with different material properties, but not everything in that document is commercially available.
In some cases there’s one manufacturer who makes a given product. That’s not a bidding situation. That’s a take-it-or-leave-it situation.
Species choice also affects structural capacity. A 20F glulam and a 24F glulam have different strength values. The lower grade might cost less per cubic foot, but if you need more volume to achieve the same structural performance, the savings disappear. If beam depth or column size is constrained by the architecture, you might not have a real choice at all.
Bonus Tip: Funding Sources & Species Decisions
Your funding source might decide your species for you. Buy America requirements, for example, eliminate Canadian and European products entirely. If that question isn't addressed early, you could be deep into design with a species not available in the United States before finding out you have to switch to another. Then you’re forced to revalidate the structure, resize members, and explain to the owner why the building looks different than expected.
Regional Sourcing and the Doug Fir Default
Most mass timber case studies in the US come from the Pacific Northwest, where Doug Fir is the local species and the supply chain is well established. As a result, a lot of architects, especially on their second or third timber project, default to Doug Fir because it’s what they know.
On an East Coast project, that default comes with a shipping cost. Shipping finished elements from the West Coast may offset any material savings. Southern Pine and European Spruce are both structurally viable alternatives that can be easier and cheaper to source depending on where the project is. The right answer depends on the project. But the team needs to have the conversation early enough for it to matter.
The question is who’s the right person to navigate all of this, and when do you bring them in.
Design Assist vs. Delegated Design: Getting the Right People in the Room
There are two primary ways a specialty timber engineer like Mason engages on a project. Understanding the difference matters because each one covers different ground and carries different responsibilities.
Design Assist
In a design assist engagement, the specialty engineer comes in alongside the design team and provides real-time feedback as decisions are being made. Member sizing, species selection, grid layout, connection approach -- all of these have cost implications, and design assist is the opportunity to get that feedback before the bid requests go out.
The design assist engineer doesn’t stamp the drawings. That responsibility stays with the engineer of record. But having a timber specialist in the room early means fewer surprises when the estimate comes in, and fewer situations where the team is trying to reverse-engineer a cost reduction under pressure.
Delegated Design
Delegated design typically comes later in the process. The engineer of record specifies performance criteria and loads for connections, and the specialty engineer designs to those criteria and stamps those calculations.
This approach makes sense because different timber manufacturers have different connection preferences. Some lean toward steel hardware. Others prefer wood-to-wood connections. Delegating the connection design gives the fabricator flexibility to work within their own system while still meeting the structural requirements set by the EOR.
One thing that comes up in delegated design, and in timber construction generally, is field welding. Mason’s position is straightforward: avoid it. The difference between 300 field-welded connections and 300 bolted connections is significant in time, labor, and complexity. Bolted connections are an assembly task. Welded connections are a skilled trade task that introduces variables you don’t want to manage on a timber job.
The connection decisions made on paper are the same ones the crew has to live with on site. Which is why what happens in the field deserves as much attention as what happens in the model.
Solving Field Problems Before They Hit the Site
Mass timber is a finished product. Elements come off the truck ready to install which means there’s very little room for field modification. If something doesn’t fit, the options are limited and expensive.
Mason’s approach is to pull field problems back into the office as early as possible. Tolerances, install sequencing, connection geometry. If a bolt can’t physically fit given the geometry of three beams meeting at a single point, that’s something to solve on paper, not with a piece swinging 20 feet in the air and a crane on standby.
A Real Example
Mason worked through exactly this on a train station project in Maine. The assembly sequence on that job wasn't flexible. Each piece supported the next. A glulam beam bears on a CLT wall panel, which supports a floor panel, which carries a wall above. They also had to work around existing steel and coordinate with railroad schedules for limited installation windows. Every one of those constraints got worked through before anyone picked up a tool. This avoided idle crane time, or the crew standing around while someone figures out what should have been solved at a desk.
Clarity Is Kindness
Clarity in the documents is one of the most valuable things a design team can provide. What’s a minimum performance requirement? What’s flexible? What species is mandatory and what’s open to alternates? When those questions are answered clearly and early, every team bidding the job is working from the same information, and the owner isn’t absorbing the cost of ambiguity through change orders.
The flip side is also true. When a project goes sideways, people rarely say the design was bad. They say timber is expensive, timber is complicated, timber isn’t worth the hassle. Most of the time that’s not a timber problem. It’s a process problem. A decision that came too late, a species specified without checking availability, a fabricator who wasn’t in the room early enough.
The projects that work are the ones where the right people are involved early, the documents are clear, and the team is asking questions before the answers get expensive. That’s not specific to timber. But in timber, the margin for error is smaller and the cost of getting it wrong is higher.
As Mason puts it: clarity is kindness.