Back in November, we sat down with Martin Hammer to discuss his invaluable contributions to natural building and to the creation of natural building codes in the U.S. The following article is part interview, part narrative of some of Martin’s journey with building
Martin Hammer was attending a seminar at the San Francisco Institute of Architecture when his life took a major turn. A friend had asked him to sit in on a presentation by John Swearingen who was talking about a radically different way of building: straw bale construction. “To use a still relevant phrase from the ‘60s,” said Martin, “our minds were blown.”
Martin grew up in New Jersey and attended the New Jersey Institute of Technology’s School of Architecture in the 1970s. In 1980 he received a Bachelor of Architecture with a concentration in architecture and energy. He focused on passive solar design, which was revived during the ‘70s energy crisis. “I’ve always been interested in environmental issues and in sustainability, well before the term was commonly used,” said Martin.
“The seminal 1971 book The Limits to Growth was a guiding star,” he continued. “Steve Baer of Zomeworks, Ed Mazria, author of the iconic The Passive Solar Energy Book, Malcolm Wells’ underground architecture, and my professor Doug Kelbaugh who designed and constructed the first ‘Trombe wall’ in the U.S. at his Princeton home, all influenced my direction.”
After graduating, Martin explored different regions of the country on a cross-country journey, seeking architecture work along the way. He once even commuted to an office in Oregon from his itinerant home at a nearby campground. After being previously enamored with the San Francisco bay area, with its progressive values and natural beauty, he found work at a small office in Berkeley. In 1984 a friend asked Martin to design a bathroom addition. He did and ended up building it himself as well.
“Ever since architecture school, where construction experience is typically ignored or even disdained, I wanted to learn to build. In order to be a better designer and to communicate better with builders. It remains a gaping hole in most architectural education. This was a perfect project to learn construction fundamentals. I then went on to design and build a deck for a neighbor, and other design projects followed. Now, thirty-seven years later, I still have my own small, very diverse practice, with occasional small builds in my younger years, or in my international post-earthquake sustainable rebuilding work the past 15 years,” said Martin.
Martin received his architectural license in 1986, by which time he was running a small design practice in Oakland. His early projects incorporated passive solar design, salvaged materials, and rainwater collection. It was in 1994 that Martin and his friend attended John Swearingen’s talk. Martin recalled the experience:
“Trained in architecture, even with the open-minded curriculum I had, then working in conventional offices with conventional materials, you become well-versed in wood, concrete, steel and masonry. Suddenly someone says, ‘Here, you can also build with blocks of straw’…That straw bale seminar made me question the way we build and why we use the materials we do. The light bulb went on, and it forever changed the way I think of materials, design, construction, and the environmental effects of building.”
Martin’s first straw bale project, a workshop and studio / photo by Chris Poehlmann
The following year Martin and his friend Chris Poehlmann set out to design and build a 3000 square foot straw bale workshop and studio in Annapolis, California. The design used a prefabricated industrial steel frame with non-loadbearing plastered straw bale infill walls that served as shear walls. Because this was the first permitted straw bale building in Sonoma county, local building officials were conservative but reasonable. They evaluated the information Martin provided, and followed the freshly-codified California Guidelines for Straw-Bale Structures. This first-ever statewide strawbale code originated in an indirect and unusual way.
Completed straw bale workshop and studio designed and built by Martin Hammer and Chris Poehlmann
In the early 1990s, California’s Central Valley was struggling with poor air quality from the common practice of burning rice straw after the grain was harvested. The State Assembly passed legislation in 1991 to phase out air-polluting burns, so the need arose to find alternative uses for the leftover straw. The other common practice, letting the straw decompose in the field, required enormous quantities of water during the state’s driest season.
Around this time, the rebirth of straw bale construction was underway in the Southwest. Word of this eventually reached California State Assembly member Byron Sher, known for his dedication to natural preservation and landmark environmental legislation like the Clean Air Act of 1988. In 1994 Byron proposed that the California Health and Safety Code include guidelines for straw bale construction. Meanwhile, in Pima County and Tucson, Arizona, the nation’s first load-bearing straw bale code was just being finalized, thanks in large part to the testing and advocacy by strawbale pioneers David Eisenberg and Matts Myhrman. This code was used as the template for the California code that went into effect on January 1, 1996, ironically preceding Pima County and Tucson’s effective date by one day.
And so it was that Martin and Chris designed and built one of the first natural buildings in the U.S. to meet an official natural building code. That project also launched Martin’s lifelong relationship with the world of natural building codes.
Meanwhile, in the Berkeley area, a number of other folks were experimenting with straw bale and other natural building techniques, and a community began to form. This included architects Bob Theis, Dan Smith, David Arkin, Anni Tilt, and Greg Van Mechelen, structural engineer Bruce King, and natural builders Tim Owen-Kennedy and Kevin Rowell to name a few. In 1996 this community came together as the California Straw Building Association (CASBA), including straw bale design and building professionals from other parts of the state like Turko Semmes and Greg McMillan of Straw Dogs builders, and Cal Polytech professor and architect Ken Haggard. Other regional groups began popping up across the continent in New Mexico, Texas, Colorado, the Northeast, and Ontario, Canada. “All of these groups were communicating, and The Last Straw was a big part of it,” said Martin. “So much communication was done through The Last Straw, including experiences wrestling with building departments and building codes.”
Over the next few years, this growing community began forming a consensus on both minimum and best practices. Two problems surfaced again and again in permit approvals and inspections for straw bale projects. First, the building code required a water-resistive barrier behind exterior cladding in conventional construction. This barrier, frequently a plastic sheet, prevents the exceptional mechanical bond between straw and its plaster. Some water-resistive barriers also inhibit the passage of water vapor through the wall even though straw already has the capacity to manage moisture without harm in a way that wood sheathing does not. Second, “internal pinning” was required, where the bales are skewered with steel rebar from foundation to top plate to stabilize bale courses during construction. This was initially considered important for two-string bales but was later found to be unnecessary, especially for 3-string bales or when finished with reinforced plasters. Internal pinning became codified but was often unnecessary, onerous, and expensive.
In an attempt to make these important code changes, Martin contacted Byron Sher (by this time in the State Senate) to initiate a senate bill. Dan Smith, Bruce King, and Martin all testified at Senate hearings in Sacramento, and Senate Bill 332 soon passed in the Senate and Assembly. In 2001 these changes made their way to three gatekeepers of building codes in California: the Building Standards Commission, Housing and Community Development, and the Office of the State Fire Marshal. At their urging, Governor Davis planned to veto it. “They weren’t happy about the changes,” said Martin, “The problem was that the straw bale guidelines because they were approved through legislation, were placed in the Health and Safety Code, while all other building codes lived in the California Building Code and its associated codes. The Building Standards Commission, Housing and Community Development, and the State Fire Marshal didn’t have the same input and control of the Health and Safety Code.”
A meeting took place between the state agency representatives and the straw bale advocates on September 12, 2001, and they worked out a compromise. They were able to remove the two main problems the straw bale practitioners were facing: water-resistive barrier and internal pinning requirements. “It was also agreed that everyone wanted the straw bale guidelines removed from the Health and Safety Code and placed into the building code,” said Martin, “To go through the same review and adoption process, and to live with everything else in the California Building Code!”
So long as straw bale construction remained separate from all other building codes, it would never become widespread. Martin began participating in hearings and focus groups with the aim of adding straw bale construction to the California Building Code. The biggest pushback came from people with seismic concerns. “Structural and fire safety are the categories that justifiably draw the most attention in the building codes,” said Martin, “If you adequately address these subjects, folks become more comfortable and accepting of a new building system.”
For five decades three regional codes were used across the US: the Uniform Building Code in western states, the BOCA National Building Code in eastern and midwestern states, and the Standard Building Code in southeastern states. In 1994 the International Code Council was formed with the task of combining the regional building codes into a single national code. In 2000 the ICC published the first set of model codes, (frequently called I-Codes), including the widely used International Building Code (IBC) and International Residential Code (IRC). Every three years thereafter, the model codes would be updated and new editions published. Across the country states were adopting the new 2000 I-Codes, but California remained stuck on the 1997 Uniform Building Code until 2006, due to stakeholder conflict over whether to use the I-Codes or a competing code created by the National Fire Protection Association. Martin then shifted focus to the I-Codes in an attempt to include straw bale in the next edition, which could then be incorporated into building codes nationwide.
Around this time, David Eisenberg had become a member of a 50-70 person committee working on a new I-Code, the International Green Construction Code (IGCC). At a conference in Philadelphia, David showed Martin a list of potential subjects for the IGCC, and pointed to two natural building systems: straw bale construction and rammed earth. This seemed like the perfect opportunity for straw bale building to enter the I-Codes.
“I took the straw bale code draft from California and further developed it with input through many phone calls and meetings with the IGCC group,… but at the all-important Committee hearings it was not approved,” Martin remembered. Bizarre logic in the opposition testimony claimed that straw bale shouldn’t be in the IGCC, it should be in the IBC. This was said despite straw bale construction being widely seen as one of the greenest building technologies available. In one sense Martin wholeheartedly agrees. Echoing a comment David Eisenberg made to the whole committee at its first meeting, “There shouldn’t even be a separate Green Construction Code..The entire building code itself should be green!” Martin then turned his focus to the IBC.
In theory, anyone can submit a building code proposal. However, in practice, it requires significant time, energy, and funds to do testing, research, write code proposals, and testify at hearings to eventually obtain approval. Even after approval in the model codes, the all-important adoption at state and local levels often requires additional advocacy. This considerable process favors the heavily-resourced building industry.
Not surprisingly, initial pushback against straw bale construction came from the insulation industry. Even though fiberglass and foam plastic insulations completely dominated the market, manufacturers found the idea of straw as an insulating material threatening enough to oppose it. Fortunately, they did not sustain their initial resistance. Opposition also came from the American Wood Council. “Their representative argued in testimony that each straw bale is unique,” Martin laughed, “A Committee member on the dais challenged the criticism, saying ‘Isn’t it true that no two pieces of wood are alike?’” The embarrassed representative sat down in silence. Though some opposition rang hollow, the IBC strawbale proposal was disapproved, largely due to discomfort with the structural use of strawbale walls.
Martin Hammer testifying in a model code hearing
So Martin went back to work. He continued collaborating with Mark Aschheim, a professor of civil engineering at Santa Clara University , where additional structural tests on plastered straw bale walls were conducted. They also shifted focus from the IBC to the slightly lower bar of the IRC, which applies only to 1-2 family dwellings and townhouses. At the 2013 hearings in Dallas, Martin, Mark Aschheim, David Eisenberg, and long-time strawbale advocate Laura Bartels of Colorado prepared to testify on behalf of their two proposed appendices for the 2015 IRC: strawbale construction and light straw-clay construction. Light straw-clay was scheduled to be heard first. In a strategic move, the team was able to switch the two. Their hunch was that fewer people knew about light straw-clay and if it wasn’t approved, strawbale might be negatively affected. If they presented strawbale first its greater familiarity and likelihood of approval, would give straw-clay a better chance of approval.
Mark Aschheim, Martin Hammer, Laura Bartels, and David Eisenberg after the 2013 ICC hearings
“Public perception is important,” Martin says. “One needs to understand those present in the room, their relationships, and whose voices carry weight and are trusted,” said Martin. An example is a fortunate testimony in support from a senior engineer representing the National Association of Home Builders (NAHB), a highly influential stakeholder in code development for the IRC. In previous proposals for the IGCC and IBC, he testified in opposition. But over time the straw bale proposal improved, relationships and trust grew, and he became sufficiently comfortable to publicly support the proposal.
The strawbale proposal was approved 9-1, and the light straw-clay proposal was approved 6-3. Martin recalls one committee member saying, “I recommend the Committee vote to approve the proposal. This is the future.” “I was pleasantly stunned to hear this from a Committee member,” Martin said, “and I suppose you could say light straw-clay came in on strawbale’s coattails.” So in 2013, Appendix S – Straw Bale Construction and Appendix R – Light Straw-Clay Construction were approved for inclusion in the 2015 IRC.
Martin attended the ICC session where 2016 updates to those appendices were approved unanimously for the 2018 IRC, and while there he also testified in friendly opposition to an IRC proposal for ‘Small Houses’, which was then unanimously disapproved. “I saw the potential of the proposal, but wanted to help improve the code language…the subject of tiny houses was and continues to be so widespread. It’s on everyone’s radar,” said Martin. In 2016 he joined forces with tiny house (and straw bale) leader Andrew Morrison to propose IRC Appendix Q – Tiny Houses. With spirited testimony in Kansas City from the tiny house industry and advocates, as well as numerous building officials grappling with code-compliance issues for tiny houses (≤ 400 sf) for ceiling heights, lofts, and their access/egress, the proposal was narrowly approved. The remaining challenges of tiny houses on wheels and chassis standards are now being worked out by the industry with proposed changes to Appendix Q and with a new ASTM standard that is expected to be more applicable worldwide.
Next up was Appendix U – Cob Construction (Monolithic Adobe). “It was a heavy lift,” said Martin (no pun intended). “Monolithic adobe is another name for cob, a mixture of clay-subsoil and straw. We expected the Committee members and others to have positive associations with the word ‘adobe’ , especially at the hearings in Albuquerque, and to be unfamiliar with the word ‘cob’. So we included monolithic adobe in the appendix title.”
Unfortunately, the appendix was disapproved at the Committee Hearings, likely due to a proposed fire-resistance rating with insufficient testing, but was approved at the Public Comment Hearings in Las Vegas six months later with the fire rating withdrawn. “Though we claimed no fire-resistance rating, we still made our case that monolithic adobe is highly fire-resistant – used for centuries to build kilns and ovens, and classified as non-combustible in Australia. I believe the main reason for its approval is the increased frequency and intensity of wildfires in the west” said Martin. The urgent need for fire-resistant construction was dramatized when a Sonoma County official who planned to testify in support had to leave mid-hearing because his home was at that very moment threatened by raging wildfires. In 2021 an ASTM E119 test was conducted on cob walls that conservatively yielded a 2-hour fire-resistance rating. That fire rating has been proposed for Appendix AU in the 2024 IRC.
Cob Wall during ASTM E119 fire and hose stream test
In addition to updating previously approved IRC appendices, Martin is currently focused on a proposed Hemp-Lime (Hempcrete) IRC appendix, working closely with David Eisenberg and the hemp building industry. He is also working on an ASTM standard for earthen floors with David, Bruce King, and Gaya Datar, founder of the organization EarthEnable which has facilitated the installation of over 15,000 durable, hygienic and affordable earthen floors in Rwanda and Uganda.
Martin likes that all of these code proposals became appendices in the IRC. This places them in their own natural building group at the end of the code rather than being dispersed throughout the body of the code. They’re easy to access, and although they rely on many sections in the body of the code (foundations, floor, and roof systems, for example) they are coherent as stand-alone appendices. A downside is that not all states adopt all of the IRC appendices, and adoption by state or local jurisdictions is necessary for codes to become legally enforceable. “However, even if not adopted in your jurisdiction, an appendix can be proposed to the local building official on a project basis. Faced with a choice between a well-developed ICC-approved code or a vacuum, building officials often agree to use the appendix,” Martin says.
“Maybe the codes would work best as a suite or chapter of their own,” he suggests, “But what would it be called? Natural Building? Alternative Building?” Martin stresses the importance of finding the right language and takes issue with the terms currently available. If natural building practices are grouped, labeled, and “othered”, then they may never become mainstream. Perhaps the ideal term can take a cue from the title of Chris Magwood’s book, “Making Better Buildings”. Perhaps “Better Building” is the most appropriate term.
Martin and his colleagues still hope to introduce straw bale construction and other natural building systems into the IBC, so they can readily be used for non-residential occupancies. Only a flawed ‘legacy’ section on adobe exists in the IBC, saved by Martin and David Eisenberg from proposed removal in 2016, and improved in 2019 by Martin, David, and architect Ben Loescher, president of The Earth Builders Guild and another important advocate for natural building in the building codes.
The main obstacle to introducing more natural building to the IBC is how a specific computer model, developed by FEMA to simulate and evaluate a system’s lateral-force-resisting capacity, is used to judge seismic safety for new building systems. Martin is working to solve the seismic quandary with Anthony Dente, PE, and partner of Verdant Structural Engineers. Anthony is also vice president of the Cob Research Institute and was vital in developing the structural provisions for Appendix AU. In 2012 Martin, Anthony’s partner Kevin Donahue, SE, and pioneering civil engineering professor Mark Aschheim wrote two articles on the structural testing and capacities of straw bale construction in Structure Magazine, the engineering profession’s leading publication. Mark Aschheim passed away at age 56 in 2019, but Anthony and Martin’s sights remain set on the IBC, to carry Mark’s pioneering work forward.
“The presence of natural building materials and systems in the building codes gives them credibility and opens their use to design professionals, builders, and building officials. I can’t overemphasize how important it is to simply see the words straw, clay, and earth as legitimate building materials in ICC’s model building codes,” said Martin.
Natural building has also led Martin to work in global climate and housing justice. Following Pakistan’s 2005 earthquake, he worked with civil engineer Darcey Messner to help found Pakistan Straw Bale and Appropriate Building (PAKSBAB). Martin then became co-director of Builders Without Borders with natural building advocate and former Last Straw publisher Catherine Wanek. They spent 3 years working in Haiti following its devastating 2010 earthquake, and more recently in Nepal after its 2015 earthquakes.
Considering the ways that the Covid-19 pandemic has shaped attitudes around natural building, Martin said:
“The pandemic has undeniably reminded us of the interconnectedness and interdependence of all countries and societies. Global cooperation will become increasingly necessary, not only relative to global pandemics, but to the consequences of climate change. This includes associated drought, increased frequency and intensity of wildfires, disrupted access to food and water, and resulting increased pressures of migration. The global sharing of natural building solutions can help stem the tide of climate change – with low-embodied carbon materials like earth, or carbon sequestering materials like straw and hemp – and change perceptions of how to build and live in ways that promote global human and environmental health.”
As we wrapped up our interview with Martin, we sat in admiration of his energy. We thanked him for all of the work that he and his colleagues have done and continue to do to further natural building. “Well, there’s still adobe, rammed earth, earthbag, and bamboo,” said Martin with a smile.
Martin Hammer lives and works in Berkeley California. He is currently working on a Hemp-Lime (Hempcrete) IRC appendix, and an ASTM standard for earthen floors, in addition to his full time architecture practice.