A Hundred Addresses
- Shawn Ledig
- 2 days ago
- 8 min read
What to send this association about your hempcrete project, where it goes, and who sees it
By Shawn Ledig | U.S. Hemp Building Association
Afterword to the three-part history. This one is not history.
Three articles took us from a sixth-century plaster in the Ellora Caves to a small, disputed handful of American jurisdictions where Appendix BL is law. The last of them ended on an empty file drawer: five permitted American hemp-lime buildings standing, one publicly documented loan among them, and no insurer or lender in this country that has published anything at all about our material. I said the third missing piece was a record, and that it was the one item every member could act on. This is that ask, in specific terms.
I made this promise in the second part of the series, so I will quote myself and then keep it. I wrote that we would build the record of American projects "one at a time, with the full record behind each build: the jurisdiction, the permit path, the wall assembly, where the hurd came from, and, where the owner agrees to share it, the cost, appraisal, and insurance outcome." That is what follows. I have added the parts I did not know to ask for a month ago, because researching the last installment taught me where the actual holes are.
Why a File and Not a Gallery
We already have photographs. Every one of us has a phone full of beautiful walls, and they have not moved a single underwriting guideline.
Here is what a file does that a gallery cannot. When an appraiser in a county that has never seen a hemp wall opens a file and finds four comparable American sales with adjustments already documented, that appraiser can write the paragraph that supports the value. Fannie Mae's guide does not forbid our buildings. It leaves the outcome to one appraiser's judgment and one appraiser's willingness to defend it in writing, with nothing in the folder to help. We can put something in the folder.
When a code official asks who else has permitted one of these, the answer should be a list with jurisdictions, code editions and the section each plan reviewer relied on, not a story about Georgia. When ASTM subcommittee D37.07 works on the hurd grading method it opened last August, it needs field data on what builders actually received in a bag and how it behaved in a wall. That is not a laboratory question. It is our question, and only builders and members can answer it.
And when a carrier finally sits down with us, the conversation goes one of two ways. Either we arrive with an unquantified enthusiasm, or we arrive with a hundred buildings, their assemblies, their claims history and their losses. One of those is an actuarial conversation. The other is a nice meeting.
France can point to a house in Nogent-sur-Seine that a 2024 inspection by the International Hemp Building Association found sound thirty-eight years after it was built. We should be able to point to a hundred addresses in our own country. Right now I could not tell you, under oath, how many finished hempcrete buildings exist in the United States. That is not acceptable for a trade association, and it is fixable this month.
What to Send
Send what you have. An incomplete record is worth far more than a withheld one, and nobody is going to be scolded for gaps. If you can only answer three of these, answer three.
The building. Address or at least county and state, year completed, square footage, number of stories, occupancy type, and whether it is new construction or a renovation.
The wall. Assembly type, whether it was cast in place, sprayed, block or prefabricated panel, wall thickness, the frame it went around, plaster and finish systems inside and out, and your roof and floor assemblies if hemp-lime was used there too.
The material. Who supplied the hurd, what it cost delivered, what binder you used and at what ratio, and what you actually received. If a bag varied between deliveries, if the fines content was wrong, if the moisture content caused you problems, that is exactly what ASTM needs and what no laboratory can generate.
The permit. Jurisdiction, the code edition in force at the time, and the path you took. Whether you used Appendix BL, an alternate materials and methods request under Section R104.11, an engineered design, or something else. What the plan reviewer asked for, how long the review took, and what you had to produce to satisfy them. If you were required to furnish test reports, tell me which ones.
The money. Who lent, whether it was a construction loan, whether it converted to a permanent mortgage, and whether the lender required anything unusual. Who appraised it, which approach they used, what comparables they were able to find, and what the appraisal came in at against cost.
The insurance. Carrier, policy type, how the wall was described or classified on the application, whether hemp-lime was disclosed, and what the premium looked like against a comparable conventional building.
And the part nobody volunteers. What was refused, by whom, and the reason they gave. A plan reviewer who would not accept the appendix. A lender who would not write it. A carrier who declined or non-renewed. An appraiser who could not find comparables and would not extend the search.
That last item is the whole reason the drawer is empty. A private decline leaves no public trace. When I searched for a documented American case of a hempcrete building being denied insurance, failing an appraisal or being refused a mortgage, I found none, and I want to be precise about what that means. It does not mean nobody has been turned down. It means we have never collected it. If you were turned down, you are not an embarrassment to this industry. You are the missing data.
Where It Goes and Who Sees It
Send it to treasurer@ushempbuilding.org. Anything you can attach is welcome: permit documents, plan review correspondence, appraisals, policy declarations, decline letters, delivery tickets, mix records.
Now the part you are entitled to have in writing before you send me your file.
The record is for members only. It will not be published. There is no public database, no map, no press release built out of your file. If we ever want to change that, we will come and ask you first, project by project, and a no is a no with no consequence attached.
The association will use it in three ways, all of them on your behalf. We will take aggregate findings into conversations with carriers, lenders and appraisal organizations. We will use it in code hearings and rulemaking, where a list of permitted American buildings answers questions that argument does not. And we will feed the material and performance data into the ASTM work items, because those standards will be written either with our field evidence or without it.
Where a specific project would help a specific member, we will ask your permission and connect you directly rather than hand your file to anyone. Nothing identifying leaves the association without your say.
I owe you one honest caveat. A record nobody outside can inspect is a weaker instrument than a published one, and I am aware that a series arguing for verifiable numbers is closing with a confidential file. That is a deliberate trade. Members are being asked for appraisals, loan terms and refusals, and I would rather hold that material privately and actually receive it than publish it and receive nothing. If the Board and the membership later decide that aggregate figures should be public, that will be a decision taken in the open.
What Vicat Did
There is a name on the Eiffel Tower I wrote about earlier in this series. Louis Vicat worked out the chemistry of hydraulic lime in 1817, published it, and refused to patent it. He considered the discovery a gift to the public. It made him a national hero and it made him a great deal poorer than the Englishman who patented Portland cement seven years later.
Every hemp wall in this country stands on a binder that one engineer declined to own.
What I am asking for is a much smaller gift than his. Not your intellectual property, not your client list, not your margins. Your paperwork, and your honest account of what went wrong. The thing about Vicat's decision is that it only worked because he wrote it down. A method he kept in his head would have died with him in 1861, bridge and all.
We have the code text France never got and a fire dataset they do not have. What we do not have is the file. Three articles to explain how we got here. Now we write down what we know.
What Comes Next on This Blog
The history is finished. What follows is the work.
From here this blog turns to the American builders themselves, one at a time, with the full record behind each build. What we can write depends entirely on what arrives in the inbox, so if you want your building to be the one that teaches a plan reviewer in some county that has never seen a hemp wall, now is the moment to send it.
Bring Your Questions
The Board is setting the date for the next members call, and both the finance gap and this record are going on the agenda as real discussion items. Send your questions ahead of time to the association inbox: treasurer@ushempbuilding.org
Project records go to treasurer@ushempbuilding.org.
Onward,
Shawn Ledig
President, U.S. Hemp Building Association
A Note on What This Series Claimed
Across three posts this series made a number of factual claims, and a few are worth restating in one place because they are the ones members will repeat.
Hemp has been used to fortify lime and clay binders for roughly 1,500 years, and the Ellora Caves plaster is the laboratory-confirmed example. Modern hempcrete dates to 1986 and Charles Rasetti's work at Nogent-sur-Seine, not to antiquity. Appendix BL was approved in 2022 and published in the 2024 International Residential Code, and publication is not adoption. As of late August 2026 it is law in Austin, Texas and the City of Surprise, Arizona, with Maricopa County's status still being confirmed against the county's own code-adoption schedule. There is no published American grading standard for construction hurd, and the two relevant ASTM work items remain drafts.
If any of that changes, or if any of it is wrong, I would rather hear it from one of our members than from an outside critic.
Sources
Appendix BL, Hemp-Lime (Hempcrete) Construction, 2024 International Residential Code. International Code Council. https://codes.iccsafe.org/content/IRC2024P1/appendix-bl-hemp-lime-hempcrete-construction
Austin City Code § 25-12-241(A), adopting the 2024 International Residential Code and Appendix BL. Ord. No. [ordinance number pending independent confirmation], effective 10 July 2025. [P1] https://library.municode.com/TX/Austin/codes/land_development_code?nodeId=TIT25LADE_CH25-12TECO_ART11RECO_S25-12-241INRECO
City of Surprise, Arizona, local amendments adopting IRC Appendix BL in its entirety, effective 1 January 2026. https://content.civicplus.com/api/assets/az-surprise/344d569f-02e5-4c61-a40d-31dbc21580a3
Maricopa County 2024 building code implementation, 20 November 2026. https://ready.maricopa.gov/DocumentCenter/View/121890/Step-5-K-Maricopa-County-2024-Building-Code-Implementation
ASTM work item WK96216, “New Test Method for Determining Industrial Hemp Hurd Characterization using Image Analysis”, subcommittee D37.07, initiated 28 August 2025. https://www.astm.org/membership-participation/technical-committees/workitems/workitem-wk96216
ASTM work item WK97653, mineral binders for hemp construction materials, subcommittee D37.07, initiated 8 January 2026. https://www.astm.org/membership-participation/technical-committees/workitems/workitem-wk97653
Comparable sales requirements, including that comparables need not be identical and that an appraiser may expand the search and document adjustments. Fannie Mae Selling Guide B4-1.3-08. https://selling-guide.fanniemae.com/sel/b4-1.3-08/comparable-sales
Alternative materials, design and methods of construction, IRC Section R104.11, title and text as adopted verbatim in 780 CMR, the Massachusetts building code. Cited from a state adoption because the model IRC text is not freely reproducible. Cornell Legal Information Institute. https://www.law.cornell.edu/regulations/massachusetts/780-CMR-CHAPTER-51-Chapter-1-PART-2-SECTION-104-R104.11
The 72 names inscribed on the Eiffel Tower, all French scholars, Vicat among them. La tour Eiffel, official site. https://www.toureiffel.paris/en/news/130-years/whose-are-72-names-inscribed-eiffel-tower-and-why-are-they-there
Louis Vicat published his research on the hydraulic properties of lime and cement in Les Annales de Chimie in 1817, was recognized by the Royal Academy of Science in 1818, and "filed no patent," considering that he owed the discovery to the community at large. Vicat. https://www.vicat.com/about-us/vision/history-of-louis-vicat
Louis Vicat invented artificial cement in 1817 while building the Souillac bridge and "gifted his invention to the world without ever filing a patent." École Polytechnique. https://225.polytechnique.fr/en/225-stories/louis-vicat.html
Cannabis sativa identified in the sixth-century clay plaster of Cave 12, Ellora Caves. Singh and Sardesai, Current Science, Vol. 110 No. 5, 10 March 2016. https://www.currentscience.ac.in/Volumes/110/05/0884.pdf
First use of hemp hurd as timber-frame infill, Maison de la Turque, Nogent-sur-Seine, 1986, by Charles Rasetti. CAUE 77. https://www.caue77.fr/architecture-et-patrimoine/le-beton-de-chanvre
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