Zach Horton

Author: Jessica Horton

Closure: Shotcreting the Domes

In the past three weeks our domes underwent a transformation from wire cage to metallic spaceship made of foam to one thick, continuous concrete wall. 115merge-1280x427_1 115merge-1280x427 The process was complex, the heat soared into the 100s, some work days lasted from daybreak until we stumbled back to the main house in the dark, and mistakes were made with serious consequences. Yet, for me, this was the most fun and rewarding stage of the project- especially the crazy three days when an extraordinary team taught us how to shotcrete (a special concrete blend that is shot from a giant nozzle; also a verb!).  Our last and longest visitor of the summer, Dan Steinhilber, brought the energy, hilarity, and high spirits we needed to push through the last steps of this first season of dome-building- we couldn’t have done it without him. Like all initiates, Dan cut his teeth on the neverending rebar- this time for the difficult passageway between the domes. 70 (1280x853) The next challenge was to convince rectangular sheets of foam to become dome-like. The foam creates a surface for the shotcrete, and will eventually be peeled off to leave only a concrete shell (then it will be repurposed as an insulating layer before we backfill around the entire structure with dirt). We developed techniques to measure, cut, and fit two overlapping layers of foam to every square (round?) inch of the structure.  The edges had to fit into the I-beams. It was hard to believe, at this initial stage, that our jagged cuts would ever form the slopes we desired. 60 (1280x853) The outer foam layer was covered in mylar to keep the shotcrete from sticking. This created a temporary spectacle that must have freaked out our nature-loving neighbors. Danny Pardini, our electrician who lives a mile up the road, was certain we would get a call from NAASA. We at least impressed our regular site visitors: a woodpecker, a chipmunk,  a wild turkey hen, and a sweet pair of geriatric pups. 72 (1280x853) 61edit (1280x853) 62 (1280x853) Our initial efforts at foaming left plenty of gaps. By the time we reached the second dome, these were negligible or had disappeared entirely. 76edit (1280x853) 67 (1280x853) The foam gave us a first imperfect glimpse of how our finished walls might someday look. 75edit (1280x853) 96edit After the foam panels were placed we used wood lath and wire to form the curves and tie it into the rebar grid. The hallway between the domes was especially difficult because the curves were tighter and there were many different planes meeting. IMG_0091 (1280x853) 115edit 80 (1280x853) 86edit (853x1280) We placed small squares of 1″ foam between the sheets and the rebar to create space for the shotcrete to fill. As we worked long past happy hour stabbing toothpicks to hold each one in place, we longingly nicknamed the indigestible- or more likely, toxic- chunks “cheese.” “Pass the cheese,” “its wire and cheese hour,” “you’re a cheese whiz,” and countless other stupid phrases ensued. 79edit Metal tape partially sealed the seams (but nothing wanted to stick to mylar in the hot sun and dust). My perfectionism was constantly jeopardized; I would learn in time that Dan was right to say “we are going for the gesture.” Still, at dawn on shotcrete day, the domes looked amazing. 98 (1280x853) 110edit While Dan and I were busy foaming, Zach was solving hundreds of other problems, from putting in a large portion of our electrical system, to sawing off front wall brace boards with buried screw heads, to plumbing waterlines and setting in drain pipes. While our electrician (Danny Pardini) and plumber (Tom Davis) have provided valuable advice and labor on our project, we are determined to learn and complete as much of the building process as possible- missteps included. Zach’s electrical wire sculpture: 93edit (853x1280) Still life with mistakes: still_life_with_mistakes Our tiny crew of three struggled to keep up with the flow of work especially these past weeks. We hugely appreciate that our parents have jumped in to spot ladders, wield an occasional crowbar, and generously provide delicious meals and a well-stocked tool shed- not to mention the stunning land on which we build and a share of the capital to make this project move. Here is our dad, Robert, helping out: 92edit (828x1280)   91 (1280x853) And my amazing mom, Ann: 89edit (1280x853) 97 (1280x853) 94edit (1280x853) Finally, SHOTCRETE arrived, in the expert hands of Oscar Duckworth the nozzleman. We had a very difficult time finding the right person to take on our project; the construction industry is completely saturated in California this summer and many places were only willing to take on our rural, highly unusual project for a large profit- if they could fit us into their schedule at all. (A big thanks to Phil at Delta Gunite for matching us with Oscar!) Chemist, educator, concrete sharp shooter, and blueberry farmer, Oscar is the kind of dynamic person we love to encounter on this project: someone who labors because he loves the process, wants to take on crazy challenges, and cares about the relationships he forms. He also understood our desire to be intensely involved and put us to work- hard. The finishing guys he brought on board, Dominic and Elliot Petrella with Ken Zari, were also passionate about shaping mud. This commitment to the craft especially mattered when the shit hit the fan- or more precisely, when the fan fixture crashed to the floor along with a good portion of the ceiling. We’ll get to that. 114 (1280x853) Shotcrete has to be built up slowly in layers due to the weight of the material. Our final walls are four inches thick at the top, eight at the base. 99 (1280x853) In addition to the domes, we shot three fourteen-inch thick retaining walls to be flush with the front walls, all of which will later receive a stucco finish. The retaining wall forms were built and placed by the crew at Ron’s Quality Construction, with Damien Jones at the helm. 102edit (1280x853) 124edit (1280x853) 127 (1280x853) 120edit   126 (1280x853) The force of the concrete shooting from the hose is incredible. We watched Oscar bend his whole body into the task of controlling it- and then suddenly he thrust it into my hands and shouted over the roar of machinery, “its just like frosting a cake!” Zach and Dan each took a turn, too. 130edit (1280x853) 131edit (1280x853) 133edit As the layers rose, Oscar climbed aboard the 85-foot boom we rented, with Zach driving and running an air hose to blow loose rocks from the concrete mix. Dominic followed to smooth the surface with a trowel. 134edit (1280x853) IMG_0197 (1280x853) 152 (1280x853) Things were going really well on the second and supposedly final day. Dome 2 was encased in solid concrete. Oscar prevented cracking from the 106 degree heat by ordering chemical and fiber additives to slow the curing of the mixture. The last truck of the day, filled with 8 yards, had just pulled in. Oscar and Zach were up placing a layer of shotcrete on the very last uncovered section of Dome 1, when something went terribly wrong. I happened to capture the moment on camera, though I didn’t realize it until Oscar turned toward those of us watching from the ground and made a sharp cut in the air with his hand. 137edit (1280x853) As I ran to the front of the domes, I saw our boxes of tools and hardware covered in a thick layer of shotcrete rubble. The tube of my dad’s faithful shopvac was just peeking out from the pile (this photo was taken after the cleanup began). Then I saw the gaping hole in the roof. It was actually sort of beautiful, and we each spent a second wondering if we should have put in a stained glass window (nope, it would be buried in earth). Most likely a single wire tie broke, and because we did not reinforce the area adequately, the whole section failed. 139 (1280x853) 138edit We had to turn the concrete truck back to the plant and begin reckoning. Oscar and his crew stuck by us, cancelling personal and professional plans to stay on the extra day and help us get it right. Dominic busted ragged chunks of material off the rebar grid. It took us until dark to cut, fit, and massively reinforce new foam. Somehow, Dan had the energy to grill sweet corn and brats for the concrete-covered crew when we finally limped to the main house. It was an expensive and exhausting mishap, but far less so due to the uplifting attitude and ethics of our friends. 140edit 141edit (1280x853) We were ready for the concrete truck by 6 am on Day 3. It was a beautiful morning. The crew was unfazed. The only hole remaining was Dan, who was missed by all as he caught his flight home to DC. By the time he boarded at 11 am, the domes were covered and smooth. All that remained was cleanup and regular watering down of the slow-curing concrete.  Although some steps remain before Zach and I can return to teaching on the east coast – putting in the windows, adding some weatherproofing layers, and massive site cleanup- the shotcrete gave us a sense of closure for this first season of dome-building. 144 (1280x853) 149 (1280x853) 147 (1280x853) 154edit (1280x853) 150 (1280x853)              

Raising the Bones: A Dome Building Update

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Building these domes- like building anything- involves constant coordination and creative problem solving. Every material (and human laborer) has unique properties that bend, fit, or revolt before our efforts. For example, how do we raise 18 200-lb curved steel beams that kick like stubborn mules to the 17-foot apex of the domes and bolt them in to form the basic support for our structure?  (The answer: Zach learned to drive an articulated boom, we invented a pulley system using an ancient rope from my dad’s shed, and four sets of muscles guided each into place.)  When physics,  respect, and careful oversight converge, our project slowly grows skyward. At this stage, we have built front walls out of insulated concrete forms (“ICF block”), filled them with a concrete core, created a massive rebar mesh surrounding the steel beams that has become the skeleton of our domes, and begun to lay electrical circuits.

Each friend-visitor to our site has shaped this process in distinct ways. Bryan, a traveling nurse and filmmaker, transformed ladders into stilts and danced at the top of our domes. Dan, an artist based in Washington, D.C. who is accustomed to working with diverse materials (he once made a giant Cheeto out of insulating expansion foam), is a rebar whisperer- everything he touches seems to move into place. Jenevive brought an art historian’s visualization skills to the construction site, Jeremy the sure hands of a surgeon, Alex a model of quiet persistence, etc.  The extraordinary progress you see below was not possible without the sweat and generosity of our friends and family.

Raising the beams:

R3 (1024x683)The beam team; Zach on boom

R38editLaying in the first pieces of horizontal rebar after locking in the beams

Rebar, endless rebar, every intersection tied twice:

R7 (853x1280)Zach placing the first layer of rebar

R6 (1024x683)Bryan testing the curvature

R9 (1280x853)Jenevive

R40editIMG_9778Jenevive and Jess, filthy and satisfied

R10 (1280x853)The mesh grows with the help of Jeremy and Gabe.

R39editMegan’s hat, caught in a rebar shadow web

R12 (1280x853)Zach cutting rebar

R11 (1280x853)Jeremy holding rebar for Zach to cut

R21 (1280x853)Alex tying rebar at the apex of the monkey gym

R4edit (1024x694)Job boss!

Building the front walls out of insulated concrete forms (“ICF block”):

R20edit (1280x853)Jess and Zach, pausing to admire the view through the picture window frames in Dome 1

R25 (1280x853)The wall for the bedroom and office, Dome 2

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R33edit (1280x853)Each individual ICF block has plastic webbing inside 2″ foam sides, which holds rebar and eventually, a 6″ concrete core.

R37edit (1280x853)The blocks have rows of interlocking teeth- picture a front wall made of enormous foam Legos.

R24 (1280x853) (2)The wall grows

R34 (1280x853)We inserted vent tubes into big circular holes in the wall, along with electrical penetrations.

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R32edit (1280x853)The final challenge was cutting the curves into the top of the foam to create the contour of our dome front walls. Zach did this with a reciprocating saw while I held onto his belt loops! Then tons of bracing to make sure the walls don’t shift or bulge during the concrete pour, and disgusting yellow insulating foam to fill in all the cracks.

Pouring concrete into the front wall:

R29edit (1280x853)The pump reaching over the domes and shooting concrete into the front wall:

R27edit (853x1280)Damien of Ron’s Quality Construction guiding a huge tube of concrete into the top of the front wall.

R36 (1280x853)Dan, who arrived from Vienna via D.C. the night before pour day, got up at 5:30 am to help us out. And he was EXCITED about it!

R28edit (1280x853)Dan agitating the poured concrete to prevent air pockets by pounding a 2×4 on the side of the wall

R30edit (1280x853)The now-concrete walls.

IMG_9760Evening wanderings with Jenevive and Bryan


A concrete slab, gleaming like the surface of a lake (and begging for a dance party), now permanently masks the material layers and labor that consumed our first three weeks on site. Let’s peel back the concrete for a glimpse of the ingredients:


1. A maze of metal rebar. I thought we would never find our way out!


2.  A rain of gravel.


3.  A layer of  extruded polystyrene foam plus a vapor barrier of visqueen to insulate our slab from heat loss and protect it from moisture, in preparation for the radiant floor heating system.

fitting around the plumbing


4. Radiant floor heating tubes snake across our metal rebar grid, resting on a bed of sand. They hook into a console that peeks above the finished slab, which connects to a solar water heater and allows us some measure of future control. But like every layer encased in concrete, we had to get this one absolutely right:





A snake and dragon, among other wildlife.


5. And finally, on a gorgeous misty and very early morning, the concrete trucks arrived (after a requisite hour spent lost in the mountains). Our footings were massive due to the mud churned up by several unexpected storms. It took seven trucks to completely fill the foundation for the domes.








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