Renovation is typically understood as the repair or improvement of existing buildings. But what if we extended this idea to the act of building itself? Questioning how we build challenges us to examine the material and technological frameworks that shape the built environment. Navigating between a labor-intensive, ecologically- and locally-attuned low-tech past and the high-tech present—marked by globalization, extractive practices, environmental degradation, and overconsumption—we at kuidas.works situate ourselves between extremes, developing what we call a local-tech approach: a practice that integrates historical and contemporary building techniques while grounding them in local material and cultural contexts.1
Before the twentieth century, ecological building traditions evolved in relation to place, climate, resources, and geology. These practices were displaced by industrial systems that prioritize standardization, speed, and global supply chains—often at the cost of environmental and cultural loss. According to the UN Environment Programme, nearly 39 percent of global CO2 emissions are linked to buildings, with embodied carbon in construction materials alone accounting for 11 percent. To meaningfully reduce that footprint, we must first renovate the building process itself: shifting from extractive, industrial modes toward relational, regenerative ones. This means working with existing structures, local raw materials, and construction waste—even if at first it can be slow, inconvenient, and labor-intensive.
Local Resources as Building Materials
Our 2023 exhibition “From Excavation to Elevation” examined the potential of construction waste—specifically clay-rich earth and crushed concrete—as a resource rather than debris.2 Foundation pits are excavated daily across the globe, and while the composition of earth varies, much of it contains the vital binder: clay. This soil, typically trucked to landfills, can instead be utilized as a construction material with minimal processing. The advantages of this are tangible: reduced emissions from transport and manufacturing, hyper-local reuse of site-specific waste, and improved indoor environments due to clay’s hygroscopic and thermal-regulating properties. With these potentials in mind, we set out to work through the entire process—from sourcing to applying, from excavation to construction—to develop various material types: rammed earth, compressed earth block (CEB), plaster formulations ranging from rough base coats to fine stucco and marmorino finishes, clay paint, and mortar to bind bricks.
Clay is an astonishingly versatile and seemingly simple raw material. Clay can serve as a load-bearing material, as in rammed earth; it can be shaped into raw or stabilized compressed blocks; and it can form the basis of mortars, plasters, and paints. When mixed with bio-based aggregates like straw, woodchips, reed, or hemp, it becomes a flexible binder for light-earth mixtures with potentially good insulating and acoustic properties. These versatile construction materials are compatible and can be combined into high-performing wall systems made from simple, local ingredients—materials that are not only low-impact but also recyclable and reusable.
Clay’s high thermal mass allows it to absorb, store, and gradually release heat, helping to regulate indoor temperatures by retaining warmth during cold weather and providing cooling effects in the heat—contributing to a more energy-efficient indoor climate. Its hygroscopic nature allows it to regulate humidity by absorbing excess moisture when humidity rises above 60 percent, and releasing it when levels drop below 40 percent; keeping the indoor environment within the ideal range for human comfort. Clay’s porous structure also contributes to odor neutralization—absorbing smells from cooking or smoking—and includes naturally antibacterial minerals such as illite and smectite. Acoustically, clay’s coarse texture reduces sound reflection and echo, enhancing indoor sound quality. And clay’s ability to be infinitely recycled—so long as it remains unfired and free of chemical stabilizers like cement or lime—means it can be repeatedly repurposed without loss of quality. This makes it not only a versatile building material but a regenerative one, aligned with circular building practices.
In Tallinn, the use of earth in construction dates back to the nineteenth century countryside, but this knowledge died out with the emergence of new global construction materials and models of fabrication. Clay is still used today on surfaces in plasters and paints in bohemian neighborhoods, but its potential as a volume, as a construction material, remains largely untapped in contemporary practice. With no local precedents to follow, we prototyped the entire process ourselves: from identifying and sourcing excavation material to processing and constructing it into a finished architectural wall section. Lacking formal approval or developer buy-in, we used a typology we’ve employed before for such speculative work—a white cube gallery space—to house and present the resulting construction materials. Framed in this way, the research is simultaneously material development, spatial installation, and architectural proposition.
Excavation on the construction site.
The first step was to locate a suitable excavation site. We mapped active construction sites, photographed exposed soil profiles, and noted potential partners. Our criteria included the visibility of clay in the soil, the site’s proximity to our studio, and the likelihood of encountering an open-minded construction site manager. After identifying a promising site, we made a phone call to the construction manager with an unusual request: to save a truckload of excavation waste for us instead of sending it to the landfill. They agreed, and so arrived five tons of heavy, wet, unprocessed clay at our doorstep—a dense, muddy mass that bore little resemblance to anything easily handled or shaped.
The next phase was to pre-process the raw earth. This began with drying and breaking it into manageable chunks. Fortunately, the warm, dry spring air and exposure to sunlight made the process manageable. We were completely dependent on the weather, as we did not have an indoor space to work with such a large quantity of material. We used a large patch of asphalt in front of our garage-studio as a drying surface, which helped evaporate moisture while protecting the clay from soil humidity. Each afternoon, someone from our team would gather the dried chunks, crush and bag them, then lay out fresh shovelfuls to dry. This simple, repetitive task became a shared ritual—refreshing and tactile, a welcomed break from screen-based work. Sometimes we would all participate after work hours, shoveling, crushing, and discussing while working with the earth.
In parallel, we sourced crushed concrete—construction rubble—to test its compatibility as an additive in rammed earth and compressed earth block (CEB) mixes. We manually sieved the rubble, using a repurposed wire bed frame as a makeshift screen to remove large particles, metal fragments, ceramics, and wire. Once both materials were cleaned, sieved, and bagged, we transported them to the Earth Building Competence Center in Mooste, where we had access to specialized tools and machinery for earth-based material development. To better understand the properties of the excavated earth, we also sent samples to the Geology Department at the University of Tartu for mineralogical analysis. Understanding the soil’s composition—its clay content, grain size, and mineral profile—is key to determining the proportions of other ingredients in each material recipe. While empirical tests like shrinkage trials are useful, laboratory results provide faster and more precise guidance for recipe development.
Material testing and production took place during an intensive residency at the Competence Center. Our entire team participated hands-on, operating machines, preparing mixtures, and producing test samples.3 This full immersion was essential for understanding not only the properties of the materials but also the labor, process, and scalability of working with earth. We began by interpreting the lab results and conducting shrinkage tests to see how the earth held together as it dried. While one part of the team finely crushed the dried clay, others began mixing it with sand, crushed concrete (instead of gravel), and water. Because all clay-based materials are applied in a wet state and gain strength through drying, determining the correct water content is critical. A mix that is too wet will not be sufficiently moldable, will shrink excessively, and crack; too dry, and it will not bind properly. For this specific clay, it took a full day of iterative testing through dozens of small samples to arrive at stable, workable recipes.
Unlike bricks or rammed earth, plasters dry quicker and can be evaluated sooner. For plaster, key concerns are shrinkage and abrasion resistance. Because pure clay always shrinks upon drying, it must be tempered with aggregates such as sand, dust, fine gravel, or natural fibers to reduce cracking and improve workability.
Rammed earth and compressed earth block tests carried out under the guidance of Mikk Luht and Marko Kikas. Photo: Tõnu Tunnel.
The CEBs and rammed earth samples, however, required longer curing times. Typically, CEBs must dry for at least three weeks, while rammed earth walls cure for one to three weeks, depending on thickness and ambient humidity. Although we didn’t have time to wait for full curing, we assessed the early-phase quality by checking for micro-cracks after pressing, observing how blocks broke when dropped from shoulder height (larger, fewer pieces indicate strength), and comparing shrinkage rates. While the material composition of CEBs and rammed earth is similar, their scale and behavior differ: rammed earth, larger in volume, must accommodate more shrinkage, so it requires larger aggregate fractions, whereas CEBs, being smaller in volume, rely on finer aggregates to ensure internal cohesion.
Once production was complete, we allowed the blocks to cure for a month. The dry components of plasters and paints were packaged for later rehydration and application. The rammed earth mixture, however, must be mixed fresh just before use, as its performance depends on precise moisture content. After curing and before installation, we conducted both strength and moisture tests on the blocks and rammed earth samples to determine whether they met the required compressive strength for earth-based load-bearing materials, which ranges from 2–10 MPa. We tested both unstabilized and lime-stabilized (under 6 percent of lime) versions of the blocks to assess the impact of stabilization. Lime stabilization typically improves moisture resistance and compressive strength, but in this case, the results were nuanced.
In terms of moisture resistance, the lime-stabilized block performed exceptionally well: after spending a full month submerged in a bucket of water, it emerged virtually unchanged. However, when tested for compressive strength, both the stabilized and unstabilized blocks—as well as the rammed earth mix—showed similar results, averaging around 5 MPa. While stabilization significantly enhances water resistance, it reduces the recyclability of the mixture and would therefore only be recommended for use in parts of a structure exposed to direct moisture, such as the base of a wall.
The construction of the wall section. Photo: Maria Helena Luiga.
The resulting collection of materials—named Mustamäe Grey, after the neighborhood of excavation—included rammed earth, CEBs, clay plasters, mortar, and clay-based paint. All of the developed materials were brought together into a single wall section, demonstrating the diverse possibilities of clay as a construction material. With each of our projects, we aim to push at least one conventional boundary. This time, the question was: How thin can an earthen wall be? Typically, such walls measure between 400 and 600 mm in thickness. But here, the base of the wall consists of a thin rammed earth section, just 200 mm thick and 1200 mm high.
The second layer of the wall was built from CEBs. The mortar binding the bricks was made using the same recipe as the blocks themselves, simply mixed into a wetter, more pliable paste. On one side of the wall, clay plaster was applied; on the other, compressed earth tiles—a thinner alternative to blocks—were fixed to the block surface using the same clay-based mortar. An opening in the wall and a smaller transverse wall suggests the beginning of an interior space, a room to be inhabited, signaling that this is not mere material speculation but a proposition for construction.
The installation’s composition was intentionally minimal, bare, and technical—freeing earthen construction from naturalistic or rustic connotations. Technical details and traces of production were left visible, allowing the method of construction to speak. From these ethical constraints emerged an aesthetic—not one based on surface, but on substance.
After a month of display, the final chapter began: dismantling. This last phase is as critical as any other in a circular construction process. The key question is, what can be directly reused, and what should be recycled? The blocks were disassembled whole, as clay mortar is soft enough to allow for gentle removal. They were restacked on pallets and delivered to a renovation site of a timber frame building, where they could provide thermal mass. The rammed earth and mortar were crushed and bagged, ready to be rehydrated and reused. The plaster was stripped from the wall and reincorporated into the dry plaster mix. Any broken bricks or tiles were collected in bulk bags for future reuse. In their dry state, these materials can be stored indefinitely—awaiting their next cycle of application.
Material Processes and Production Possibilities
Using earth and crushed concrete is just one example of how local resources and waste from construction or agriculture can be harnessed to develop building materials. More broadly, this process models an inversion of the typical construction sequence, with the development process starting from the material and raw resource. And it is only the beginning. With enough precedents, shared knowledge, and continued experimentation, these types of processes will become more efficient, less resource-intensive, and increasingly integrated into the norms of construction practice.
“From Excavation to Elevation” explored how discarded excavation materials can be transformed into contemporary construction materials using low-tech, low-emission processes. Materials like clay soil and crushed concrete can be processed onsite or nearby, requiring fairly simple processes such as sieving, drying, mixing, and pressing. With a mobile production setup, the material can even be processed on-site. Both the source and production can remain locally anchored.
There are limits, of course. Seasonal climate plays a critical role. In Estonia, for instance, earth is workable primarily in summer months. But this temporal limitation offers a different kind of logic: one that aligns construction with seasonal rhythms. Raw, bioregional materials can also be stockpiled for year-round use. Such planning transforms seasonality from a barrier into a design principle. The potential for mobile or regional production centers makes these processes scalable. This is particularly relevant for the Baltic states, three small countries that share the same climate and a similar bioregion, and could have a shared competence center, and a static production plant with mobile production units to be transported to the site on demand.
Mustamäe Grey was both a prototype and a proof-of-concept: a material narrative that traced the full arc from geology and lab analysis to tactile load-bearing wall. Insisting on location, specificity, and mineral history as part of architectural identity is not a call for a return to vernacular or a romanticization of pre-industrial methods. Rather, it is a re-synchronization; a way of re-aligning architecture with the ecological, cultural, and temporal contours of a place.
Global supply chains will probably not be going anywhere anytime soon. But they could be supplemented by context-specific material strategies. The current system prioritizes uniformity, speed, and low-cost scalability, but hides the real costs: extraction, emissions, and the erasure of material and cultural specificity. The origin and production of materials have become immaterial to the end user. That must change and become tangible and conscious again.
Designers, architects, and engineers today are tasked with more than simply creating beautiful buildings or astonishing structures. Renovating the construction process itself means preserving what already exists, researching and promoting local resources, developing ecological materials, planning around seasonality and availability, and cultivating a contemporary architectural language grounded in context. A local-tech approach is neither nostalgic nor utopian. It is a recalibration: an effort to embed sustainability through locality at the core of architectural practice—not as an optional add-on, but as an embodied imperative.
Kuidas.works is a research-led design and architecture studio based in Tallinn, Estonia, founded in 2021. Specializing in site-specific, earth-based building solutions, the studio explores how excavated, left-over earth can be transformed into sustainable materials—from rammed earth and compressed earth blocks to plasters and paints.
“From Excavation to Elevation” was made by Andrea Tamm, Henri Papson, Hannes Praks, and Maria Helena Luiga.
We were guided by the head of the Earth Building Competence Center, Mikk Luht, and the founder of UKU Pure Earth, Marko Kikas. UKU Pure Earth is an Estonian company that produces lime- and clay-based plasters and paints, and operates the only CEB production facility in the Baltics and Scandinavia.