Mass timber has moved from architectural statement to mainstream structural option, and the building code has moved with it. The 2021 International Building Code introduced three new construction types — IV-A, IV-B, and IV-C under Section 602.4 — that allow tall wood buildings up to 18 stories and 270 feet, limits carried forward in the 2024 IBC. One industry projection puts the global mass timber market at $4.9 billion by 2030, up from $1.6 billion in 2022. For the architects and engineers now asked to take this work on, the design opportunity is real. So is the professional liability question underneath it: when the standard of care is measured against what a reasonably prudent peer would do, what happens when the body of peers is still thin?
The code is settled. The precedent is not. The tall wood provisions were not improvised — the ICC’s Ad Hoc Committee on Tall Wood Buildings, established in December 2015, worked through 82 identified issues and relied on five full-scale fire tests at the ATF Research Laboratory before the 2021 IBC language was adopted. The framework is mature; the built record behind it is not. By one count, Europe holds 60 of the world’s 84 mass timber buildings at least eight stories tall, concentrating the detailing and fire-engineering experience there rather than here. A standard of care is a comparative judgment, and a firm taking on its first tall mass timber project is operating where that comparison is genuinely unsettled.
The fire question is the better-understood half. The IBC approach is prescriptive and testable: for an 18-story building the primary structural frame carries a 3-hour fire-resistance rating, with roughly one-third from the timber’s own charring mass and two-thirds from noncombustible protection, typically layered Type X gypsum. Exposed timber is permitted but bounded — Type IV-C allows fully exposed mass timber up to 85 feet, while Type IV-B limits exposed surfaces to a defined share of ceiling and wall area. This is engineering a structural practice can document and defend. It is also the discipline underwriters flag hardest: in the Ames & Gough 2026 survey of 15 leading insurers, 80% ranked structural engineering as their highest-severity exposure.
Moisture, not fire, is where the claims tend to surface. AXA XL, which underwrites this risk, states plainly that water can do as much or more damage than fire when timber is exposed during construction or enclosure is delayed. Here the standard-of-care problem sharpens, because no prescribed industry standard governs moisture management during mass timber construction. The ANSI/APA PRG 320 product standard specifies that CLT be used in dry service conditions — average equilibrium moisture content below 16% — but does not mandate how to achieve that in the field. Guidance such as AIA Seattle’s recommendation to include a moisture protection plan in the project manual is exactly that. As one 2025 construction-claims analysis noted, that recommendation “implicates the standard of care for design professionals” precisely because it is suggestive rather than mandatory, leaving room for plaintiffs and their experts to argue after the fact about what was standard.
That gap is the hidden exposure. CLT and glulam check and crack as they equilibrate; panels wetted and dried unevenly show surface damage; mass timber built without weather protection can grow mold. When any of that drives rework and schedule loss, the dispute rarely stays with the contractor — it reaches for the design professional’s specifications, the detailing, and the question of who owned the protection plan. A firm that has documented its moisture strategy, drawn the boundary between design responsibility and means-and-methods, and said so in writing holds a defensible position. A firm that left it to be inferred does not.
Underwriters read this through two policies at once. On the project side, builders’ risk carriers have often grouped mass timber with light-frame wood despite its different performance, driving premiums up and placement toward harder terms. On the practice side, the A&E professional liability market entered 2026 tightening: Ames & Gough found 73% of insurers planning rate increases, 60% reporting higher claim severity in 2025, and 93% citing rising defense costs, while WTW’s 2026 outlook projects professional liability rates of roughly 5% to 15% for more challenging risks. Limited loss data on a new method does not make underwriters comfortable — it makes them cautious, and cautious underwriters price and scrutinize accordingly.
None of this argues against the work. It argues for taking it on with intention — scoping services deliberately, qualifying any delegated design for connections or panel engineering, resisting the pull to over-promise fully exposed timber where the code or the moisture reality argues otherwise, and bringing the insurer into the conversation early rather than at binding. The submission that illuminates how a firm manages mass timber risk, rather than obscuring its novelty, is the one that earns better terms.
This discipline is the center of how we work with design firms. Our 4-Step Strategic Process begins with Strategic Discovery to surface where mass timber actually sits in your practice, moves to Risk Assessment of the standard-of-care and coverage exposures it creates, into Solution Design that aligns your professional liability program and contract language with the work, and continues through Ongoing Optimization as both the code and the claims record mature. Mass timber is not a risk to avoid. It is a risk to carry with ownership — and the firms that hold that torch deliberately keep control of it.
— Ryan Mefford, President & Risk Advisor