Today, 1 in 3 humans live and work in buildings made from mud. The techniques to construct earthen buildings have been practiced across the planet for over 10,000 years.

SHIBHAM, YEMEN: “The Manhattan of the Desert”

The Mud skyscrapers within the walled city of Shibham were erected over 500 years ago. 

The mud city represents one of the earliest examples of urban planning for vertical construction.


Professor Ronal Rael is experimenting with a new combination of Mud and human ingenuity in San Luis Valley, Colorado. 

Rael 3D printed this Adobe vault without formwork or reinforcement. 

The angled slicing configuration enables the 6-axis robotic arm to build beyond the X-Y-Z axis of most gantry 3D printers.

The 3D printer by Twenty Additive Manufacturing starts at €345,000.

Rael recently printed in the heart of Denver, Colorado with the original model of his 3D printer. In the left silo of the photo above, you can see Rael’s original printer that starts at $29,500 from 3D potter.

Professor Rael, a Berkely student, and Rael’s son worked together to build the elegant towers seen above. Curious bystanders wandered up to watch with amazement as the machine deposited mud towers in front of the Denver History Museum.

A biker stopped to observe the alien machine in action. He asked Rael ‘isn’t there a guy that 3D prints mud buildings?’ Rael’s response was something along the lines of ‘yes, I am him’. Needless to say, the biker became very excited.

At some point in the 10,000 years of mud construction someone decided to add Earthen structures to the building code- just ask Rael, he lives in an inherited adobe home- and Rael’s former 3D printed Mud Silo project is permitted.

The design of the dome, or nubian vault, is in the shape of a catenary arch. 

Since a chain always hangs in complete tension, the catenary arch (the upside down chain) rests in complete compression; the arch allows materials with high compressive strength and low tensile strength, like concrete and mud, to form robust structures without reinforcement. 

The design freedom of 3D printing paired with the poor tensile strength of mud could increase the use of arches in the future of 3D printed design.

The 4th-century ruins of The Palace of Ctesiphon expresses the power of the catenary arch.

The last Persian capital in Iraq, the Palace of Ctesiphon, used mud brick to span over 25 meters (82ft.) without the use of formwork during its construction.

The Palace of Ctesiphon, aqueducts, and countless other ancient structures prove that ancient civilizations understood the omnipresent forces of compression and tension.

When these forces are understood we construct geometries that function in harmony with nature.

With that said- nature presents its challenges too.


In the photo above, the blue machine on the left is feeding dirt to the metallic 3D printer. The hole dug by the blue machine became a pond, and the dirt it moved became a 323-square-foot building; as seen completed in the photo below. 

0-kilometer supply chains are the vision of the Italian designers working at WASP; unload the printer on-site and erect your house using the dirt next to the machine. 

The rice husk, straw and mud mixture looks and feels like a coarse rope once it dries. 

The United Nations branch of Supply Chain Service recently visited the WASP headquarters to investigate this team’s disruptive potential.

From a material standpoint 3D printing mud has several challenges, but the potential upside is -to say the least- disruptive.

Typical 3D concrete printing mortar cost over $500 per ton and contain an assortment of sand, water, cement, additives, and fibers. The entire project can be ruined by an error in these sensitive mortar mixtures.

3D printable Geopolymers will cost you around $860- 2320 per ton.

According to WASP, the material cost of the building above is 900 Euro ($980)- dirt cheap. ***note from the editor, the mixing process still requires rotor stators during the print which are $1200 expendable parts good for 10-30 tons of material each***

However, to print with mud WASP had to conduct extensive material experiments on the contents of the soil on site. 

One of the hardest variables of 3D printing dirt is the components of the dirt: sand, clay, silt, etc, can drastically change from one meter to the next.

This change in components causes inconsistent material properties; and inconsistent material is the downfall of projects, literally.

Another challenge of printing with Adobe is erosion. 

To combat erosion WASP is once again looking to the past.

“Roman concrete,” CEO of WASP Massimo Moretti, explained in his deep Italian accent. 

Roman concrete is fundamentally different from the concrete that makes the bridges, buildings, and infrastructure that enables human life today. If we’re lucky, the concrete we use crumbles after 100 years; so what allows the aqueducts, the largest unreinforced concrete dome- the Pantheon- and other Roman architecture to survive 2,000 years of erosion?

First Vitruvius, and later Pliny the Elder (who died in the Pompeii volcano) recorded that the best concrete was made with ash from volcanic regions of the Gulf of Naples. 

For two millennia the recipe was lost. In 2023, the brightest and highest-funded institutions in the world teamed up to uncover the Roman secrets.

For two millennia the recipe was lost. In 2023, the brightest and highest-funded institutions in the world teamed up to uncover the Roman secrets.

The researchers discovered the Romans combined an overabundance of lime and volcanic ash to create a superheated reaction.

The ‘hot mix’ results in new reactions, faster curing rates, and self-healing concrete. 

When the concrete cures and eventually cracks, it exposes the lime to air and water; this mixture rekindles the initial reaction, bringing the lime back to life to expand and fill the crack.

In the past, the excessive amounts of lime were thought to be an accident by the Romans.

The abundance of lime in the mixture continuously causes the ancient concrete to heal itself just like a scab repairing a cut- and the volcanic ash and lime required to recreate this concrete is abundant. 

After getting into the intricacies of Roman concrete with Massimo he powerfully summed up our conversation in one word: “Alchemy!”

Massimo always speaks of his work in a philosophical light.

Just as a river melts away one layer of Earth’s sediment at a time, the building above was eroded until it had to be destroyed. There are no articles exposing the truth about this building’s unfortunate end, but I saw its gravesite first hand and according to the WASP team themselves, it lasted under a year.

The destruction of this unprecedented architectural marvel represents the bitter-sweet reality that WASP is potentially decades ahead of their time. 

“There’s a bunch of solutions for erosion, but nothing that’s natural and cheap in Africa and South America and Middle East and India or Asia areas. These are the areas to make a difference in… When I lived in Zimbabwe lots of the homes were built out of earth, structurally it can be done but erosion is still a problem.”, James Lymon, CEO of Mudbots, explained.

Shortly after James told me this I learned about the Asir Mountain Province of Saudi Arabia; a place with adobe buildings, but more importantly a natural and cheap solution to erosion. 

Slate rocks extrude from the walls and act as a watershed, preventing water from freely running down the surface and eroding it- giving the buildings an alluring facade, and expressing one of the most primitive and powerful forms of human ingenuity. 

The collaboration of ancient wisdom and sublime 21st-century technology leaves us standing at the precipice of a revolution – or as Rael calls it- The Mud Frontier.

*walk out music*

Published by Drew Walters

Drew is a student and Muay Thai Fighter for the University of Colorado, Boulder. Drew is receiving his degree in integrated design engineering with an emphasis on architectural engineering. Fueled by a fascination for innovation and architectural 3D printers Drew has embarked on journeys across continents to understand the incredible technology and people shaping our future. Drew is open to work as an architectural printing strategist and designer. drewwalters303@gmail.comLinkedIn Profile

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  1. Well written, engaging, and I learned something new. I would absolutely live in a 3D printed mud house. Awesome read!

  2. Impressive article, intresting analytics, and overall quality from Mr.Walters. I love your passion for this Drew, keep striving.

  3. Highly informative and excellent writing. I have followed Rael’s work for a few years now and I am always excited to see the progression in this tech and material. Keep experimenting!

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