Hempcrete and Building Codes: Who Certifies First, and Why It Matters

October 9, 2026

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France has been building with hempcrete for decades. Houses from that first wave are still standing outside Paris, still performing, still proof that hemp-lime wall systems aren't some speculative future material -- they're a decades-old known quantity. So it's a strange kind of milestone that the material only picked up its first entry into an American model building code in 2024. Not its first American building. Its first American code entry. People have been casting hempcrete walls in the US for over a decade, usually under one-off permits and a lot of patient negotiation with local inspectors.

That gap between "we've been building with this for years" and "it's actually in the code book" is the whole story here, and it's why the US, of all places, is suddenly the most interesting place to watch -- not because Americans use more hempcrete than the French or Belgians (they don't, not close), but because the US is where the paperwork fight is happening in real time. Sentiment was never the bottleneck. Sustainability credentials were never the bottleneck. Hempcrete has had good carbon-sequestration numbers and good vapor-permeability numbers for years. The bottleneck has always been whether a code official could point to a page in a recognized code and sign off without personally sticking their neck out.

That's what makes Austin, Texas adopting Appendix BL effective July 10, 2025, a bigger deal than any ribbon-cutting on a new hemp building. A new hemp building is a data point. A city formally adopting a code appendix is a template other cities can copy. And that distinction -- between a model code existing somewhere in a book published by the International Code Council, and a specific jurisdiction actually putting it into local law -- is really two separate races running at different speeds. One is a standards fight that happened mostly in hearing rooms in Louisville. The other is a slow, city-by-city, state-by-state crawl that could take years even after the first race is won.

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How Appendix BL Got Into the US Code Book

The mechanics of how hempcrete actually got into the International Residential Code are worth walking through, because the process itself explains why adoption is going to be slow and uneven rather than sudden. The US Hemp Building Foundation submitted hempcrete as a new appendix to the IRC on January 10, 2024. That's not a casual filing -- the ICC's code development process runs through committee hearings, public comment periods, and final action votes, and submissions routinely fail or get tabled for years if they can't survive technical scrutiny.

This one had an advantage: architect Martin Hammer co-authored the submission, and Hammer isn't a newcomer to this process. He's worked on four other IRC code appendices before this one, which matters more than it might sound like. The ICC process rewards people who understand its internal language -- how to frame a structural assembly so it survives a fire-and-life-safety subcommittee, how to answer the kind of technical objections that sink first-time submitters. Institutional memory inside a standards body is its own form of capital, and the US Hemp Building Foundation spent it well here.

Public comment closed at an ICC hearing in Louisville, and the appendix moved through the usual bureaucratic shuffle -- initially labeled Appendix BA in working drafts before being finalized as Appendix BL in the published 2024 IRC. The letter designation is trivia, but the fact that it survived committee and public comment largely intact is not.

What makes the IRC specifically significant is reach, not force. Forty-nine of the fifty US states reference the IRC as their base residential code -- Wisconsin is the long-standing holdout with its own state-specific code. That means Appendix BL isn't binding anywhere by itself. No state, county, or city is required to adopt it. What it is, is a ready-made template: a fully vetted, ICC-sanctioned set of language that any jurisdiction can bolt onto its local code with a simple adoption vote, instead of having to draft hempcrete provisions from scratch and defend them locally with no outside backing. That's the necessary-but-not-sufficient condition this whole story turns on. The book exists now. Getting any given city or state to actually open it and say yes is the second, slower fight.

Jurisdiction by Jurisdiction: Austin, Minnesota, and Washington State

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Austin, Texas has the distinction of being first, with its adoption of Appendix BL taking effect July 10, 2025 -- a little over a year after the appendix was finalized in the model code. That's a fast turnaround for a municipal code cycle, and it suggests Austin had either already been fielding hempcrete project requests informally or had a motivated advocate pushing the adoption through committee, or both.

Minnesota looks like the likely second mover, and notably the first at the state level rather than just a single city. The state's Technical Advisory Group and Construction Codes Advisory Council both approved the appendix in spring 2025, positioning it for inclusion in Minnesota's next residential code cycle. A state-level adoption carries more weight than a city-level one, because it applies the template across every municipality in the state at once rather than requiring each city to run its own separate adoption process.

Washington State is a step behind that but moving. Its Building Code Council has been processing a statewide adoption proposal filed in February 2026, which, if it clears the Council's review, would make Washington the second or third jurisdiction to formalize Appendix BL depending on how Minnesota's timeline resolves.

None of this is unusual as a pattern -- it mirrors how other IRC appendices have historically spread. A code appendix getting published is the starting gun, not the finish line. Early-adopter cities and states move within the first one to two years, usually because there's already a local advocate, a builder, or an industry group with the appendix-opening motivated enough to shepherd it through local hearings. The wider wave -- the states that adopt because the practice has simply become normalized rather than because anyone pushed for it -- tends to follow over a longer tail, sometimes five to ten years.

In the meantime, it's worth being clear about what builders in non-adopting jurisdictions can and can't do. Hempcrete construction isn't illegal where Appendix BL hasn't been adopted. It's just harder. Builders have to seek a case-by-case variance from local code officials, essentially asking permission project by project, often submitting independent engineering or test documentation to justify an exception. That path has always existed and is how most US hempcrete buildings got approved before 2024. It still works. It's just slower, more expensive, and entirely dependent on whether the specific local official is willing to sign off -- which is precisely the inconsistency Appendix BL was designed to remove.

The Fire Test That Changes the Math

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If Appendix BL's 2024 debut was about getting hempcrete recognized at all, the fire provisions slated for the 2027 IRC update are about making that recognition actually usable without extra cost. The update adds fire-rated wall assemblies directly into Appendix BL -- meaning a code official will be able to look at a hempcrete wall assembly and see it's already been tested and rated, rather than asking the builder to prove it from scratch.

The underlying test result is genuinely strong. Hemp-lime wall material scored zero on ASTM E84 surface-burning characteristics testing -- the best possible result on that scale, which measures flame spread and smoke development. Hempitecture and American Lime Technology ran these tests at Intertek, one of the major third-party testing labs US code officials actually trust, which matters for credibility as much as the number itself does. A zero score isn't a marginal pass; it's the kind of result that removes most of the fire-safety hesitation code officials have historically had about an unfamiliar wall material.

A 2025 code update wrote that compliance directly into Appendix BL's language, which is the detail that actually changes outcomes on the ground. Before that, a code official reviewing a hempcrete wall had no pre-established fire rating to point to, which meant the burden of proof sat entirely with the builder.

That burden used to be expensive in a very literal, documented way. Oregon builder Karen Rugg, of Perennial Building, paid $8,000 out of her own pocket in 2022 for ASTM E-119 fire testing just to get a single hempcrete project approved locally. That's not a hypothetical cost -- it's a real number from a real project, and it's the kind of expense that can kill a small builder's hempcrete plans before they start, regardless of how good the material's actual fire performance is.

Pre-rated assemblies baked into the code change that math entirely. Instead of every builder in every jurisdiction independently commissioning the same test to prove the same thing, the test gets run once, by an industry group, and the result gets written into the model code for everyone to reference. For small builders especially, that's arguably a more consequential shift than the appendix's original 2024 approval -- it's the difference between hempcrete being technically legal and hempcrete being affordable to build with at all.

Commercial Construction: The Unresolved Track

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Everything discussed so far applies strictly to residential construction, because Appendix BL lives inside the International Residential Code. Commercial buildings fall under a separate code document entirely, and as of now, hempcrete has no equivalent foothold there. That's not a minor gap. It means every commercial hempcrete project in the US currently operates exactly the way residential projects did before 2024: variance by variance, jurisdiction by jurisdiction, with no reusable template to point to.

The commercial code runs on its own three-year revision cycle and was open for new submissions in 2025, which means a commercial hempcrete pathway is genuinely pending rather than settled -- it's an open question right now, not a known future certainty. Nobody should describe commercial code approval as inevitable just because the residential version succeeded.

It's reasonable to sketch a plausible timeline, though, using the IRC's own history as the yardstick. The IRC path took roughly two years from the US Hemp Building Foundation's January 2024 submission to a finalized appendix in the published code. If a commercial submission follows a similar arc and clears its hearings without major setbacks, a plausible landing point would be in a future commercial code cycle some years out. That's a reasoned projection built on a documented precedent, not a prediction anyone can treat as settled. Commercial code requirements around fire and structural performance are meaningfully stricter than residential ones -- taller buildings, higher occupancy loads, different structural load paths -- and that alone could slow review well beyond the residential timeline, regardless of how clean the underlying material science is.

There's also a real counter-case worth taking seriously: this could stall out indefinitely rather than simply taking longer. The IRC's relatively fast path wasn't just a function of good test data -- it depended on Martin Hammer's standing inside the ICC process and the US Hemp Building Foundation's willingness to fund and staff a multi-year submission effort. Commercial code fights tend to be more contested, with more competing material interests at the table. If no group with comparable institutional credibility steps up to champion a commercial code submission with the same persistence brought to the IRC, there's no guarantee commercial hempcrete code language arrives on any predictable schedule at all. Submissions do die quietly in committee. That's the honest range of outcomes here -- not just slower, but potentially stalled.

Why France and Belgium Still Lead on the Ground

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It's worth stepping back from the US code fight entirely, because by raw usage, the US isn't even close to leading. France started building with hempcrete in the early 1990s and remains its largest user by built volume, decades ahead of anything happening in the US market today. That head start shows up in infrastructure, not just finished buildings -- France has an established hemp-lime processing industry, trained contractors, and a construction culture that simply treats hempcrete as a known, unremarkable building material rather than a novelty requiring special approval.

Belgium shows what industrial-scale maturity actually looks like downstream of that head start. Isohemp, a Belgian manufacturer, produces over a million hempcrete blocks a year -- evidence of manufacturing infrastructure the US market doesn't yet have at any comparable scale. That's the kind of production volume that comes from decades of steady demand, not a recent code approval.

The Netherlands, Germany, and Italy round out a genuinely mature secondary market, using hempcrete for both retrofits and new builds. That spread matters because it shows hempcrete adoption in Europe isn't dependent on one pioneer country -- it's a regional practice with multiple national markets supporting it.

The UK sits in a narrower but still real position. Local Building Standards Scotland certification exists, alongside a route to LABC certification in England, giving UK builders a defined, if more limited, regulatory path.

Canada, by contrast, is a useful cautionary case. There's no hempcrete-specific national code provision yet, though Alberta-based Just BioFiber has pursued CSA certification for specific properties like vapor permeance -- a narrower, more piecemeal approach than a full code appendix.

The real takeaway here is that code approval and market maturity are simply not the same race, and conflating them is a mistake. France won the usage race decades ago without ever needing an ICC-style appendix fight, because its regulatory and construction culture developed hempcrete acceptance organically over decades rather than through a formal standards body process. The US is currently winning a different, narrower race -- getting the material into a widely-referenced model code book -- but that's a procedural victory, not evidence of market leadership.

What Faster Certification Could Unlock

Straw-bale construction is the closest available precedent for how this plays out over time, and it's a reasonably good one because the pattern matches almost exactly. Straw-bale got picked up in regional code appendices first, then spread through slow, uneven, jurisdiction-by-jurisdiction adoption over roughly a decade before settling into its current status: a recognized, if still niche, building method that most code officials have at least heard of even where it isn't common.

If hempcrete follows that same curve -- and there's no strong reason yet to think it won't -- the realistic expectation is scattered state and city adoptions trickling in through the late 2020s, not some single national standardization moment. Austin and Minnesota first, a handful more cities and states over the next three to five years, and genuine national normalization sometime beyond that, if it happens at all in the way straw-bale eventually did.

The more concrete, near-term unlock isn't really about whether more buildings get built -- it's about insurance and lending friction. Appraisers and insurers routinely price unfamiliar materials as higher-risk when there's no code recognition to point to, because their underwriting models default to caution in the absence of a standard reference point. Each new jurisdictional adoption chips away at that premium a little, by giving lenders and insurers a recognized code citation instead of a one-off engineering report to evaluate. That's likely to happen gradually, deal by deal, rather than as a single dramatic repricing event.

There's a real risk factor that shouldn't get glossed over here: code approval doesn't fix supply chains. US hemp hurd processing infrastructure is still thin compared to France's established hemp-lime industry, and a builder in a newly-adopting state could find the code says yes while the regional supply chain says not easily, not cheaply, not fast. Certification removes a legal bottleneck; it doesn't manufacture a processing plant.

One thing that does make this corner of the blog's usual speculation more solid than most: code revision cycles are documented, scheduled, public processes, not legislative guesswork dependent on which party controls a statehouse. Predicting roughly when the next commercial code hearing window opens is a much firmer kind of forecast than predicting when Congress might act on anything cannabis-related.

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Certification was never going to be a single event, and treating it that way misses what's actually happening. It's a staggered, multi-year process by design -- an appendix gets published, then individual cities and states decide, on their own timelines and for their own local reasons, whether to adopt it. The real signal worth tracking over the next few years isn't another headline about a code appendix existing. It's the adoption list itself: which states follow Minnesota and Washington's lead by 2027 or 2028, and how long the gap stretches between the book existing and a given state actually opening it.

It's also worth sitting with an uncomfortable but useful fact: the US may well win the code-writing race while France and Belgium keep winning the usage race for years afterward. Having the most polished model code language doesn't automatically produce the most built square footage, the most trained contractors, or the most mature supply chain -- France proved decades ago that those things can develop just fine without any ICC-style fight at all. That gap between legal status and market reality is worth keeping in mind any time a code milestone gets reported as if it were a construction milestone. They're related, but they're not the same thing, and this industry has a pattern of blurring them together when the news looks encouraging.

The next genuine inflection point is commercial hempcrete, and it's worth watching for the right reason. Not another press release, not another ribbon-cutting -- the actual signal will be what happens in commercial code submission cycles over the next several years: whether a commercial pathway submission even gets filed with Hammer-level institutional backing, whether it clears committee hearings, and whether fire and structural requirements prove as tractable commercially as they did residentially. That's a slower, quieter story than Austin's adoption was, but it's the one that will determine whether hempcrete ever moves beyond single-family homes into the buildings where most construction spending actually happens.

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