Robinia a Tiny House Case Study - Tiny House Blog

Robinia a Tiny House Case Study

Sharon Bagatell and Dennis Hoffarth combine permaculture principles with passion for the planet in Robinia, a tiny house case study in pioneering an ecologically sustainable lifestyle for the future.

Permaculture is way of life that integrates all dimensions of the human condition into a collaborative whole that is greater than the sum of its parts. Practitioners weave a rich tapestry of systems for building, growing food, earning income and nurturing relationships with one another that enhance functionality and multiply our joys while meeting everyone’s needs. It is a lifestyle rooted in ethics that promote reciprocal partnerships between humankind and our environment that are based on care rather than exploitation. The endgame is an abundant world where everyone can enjoy a high quality of life, wherein our problems are solved in the garden instead of on the battlefield.

Dennis and Sharon have integrated the principles of permaculture into every aspect of Robinia’s design, from drawing board to housewarming celebration. Now they have united with Midwest Permaculture to share their expertise by using their own tiny home as an example in a comprehensive Permaculture Design Course.

Sharon is an excellent permaculture instructor, with experience in forest agriculture on her chocolate farm in Ecuador, as well as a forest garden learning center at Dancing Rabbit. She has taught many permaculture workshops throughout Georgia and Missouri, and even wrote a step-by-step manual for farmers in the small African nation of Malawi while working alongside them over several months. Check out the video below to see some of Robinia first hand and learn more about what the Permaculture Design Course includes!

I recently met with Sharon and Dennis to learn about how the guiding principles of permaculture have been featured in Robinia’s design. As I strolled up the beaten path to visit them, I paused beside their small rainwater pond to breathe in the thick, humid summer air. I identified a handful of medicinal flowers on its banks and played hide and seek with some woody brown mushrooms that peeked shyly through the foliage, before pressing on.



Their path opens onto a lush vegetable garden on the southward side of the house, where a wall of bright windows reflected swirling green and blue patterns beneath the eaves of a verdant living roof replete with fleeting butterflies and bumblebees. Chickens cheerfully chirped a greeting as I climbed onto Robinia’s front porch, which was strewn with a wide array of hand tools. I knocked on their front door, gorgeously crafted by one of our neighbors in walnut and maple – it fits snuggly into its frame without a latch, since we seldom have a use for locks in our community.

Lime Mortar with Sharon

Lime Mortar with Sharon

Sharon and Dennis shouted in unison to invite me in, and I was struck by the abrupt drop in temperature as I passed into the cool shade of their living space, (nope, no air conditioner). They had just finished eating lunch – mostly things they had grown themselves – and Dennis offered me one of the first delicious ripe tomatoes harvested this season, dressed simply with salt and olive oil. We sat at their table to talk tiny house while Sharon busied herself with organizing some of their belongings in a newly finished storage area.

Form Follows Function

Form Follows Function

Pride and passion were clear in Dennis’s smile as he expounded enthusiastically about Robinia, eagerly remarking about some aspect of the home’s design while referencing the permaculture principles that informed their choices. I learned a great deal about the realities of balancing a contemporary lifestyle with the ideals of ecological sustainability. It seems to me that the most authentic way for me to relay my experience to you is to juxtapose David Holmgren’s twelve principles of permaculture, as outlined in his book: “Permaculture: Principles and Pathways Beyond Sustainability”, (Holmgren is one of the co-founders of the Permaculture movement, along with Bill Mollison,) with some examples of the ways in which Sharon and Dennis have utilized them in their beautiful home, Robinia.

1. Observe and Interact – Form Follows Function: “By taking the time to engage with nature we can design solutions that suit our particular situation.”

In one way or another, all aspects of Robinia’s design could be used as examples of form following function. I find that the best example is the framing. The framing method, post and beam placement and even the individual timbers used were all chosen based on the planned finished form of the building.

Hand Tools

Hand Tools

The black locust timbers used to frame Robinia were harvested from nearby Sandhill Farm – an egalitarian community known for their sorghum syrup – about four miles away from Dennis and Sharon’s homestead. Specimens for framing were selected in winter, when the contours of trees are most easily visible and the saps within the trunk are withdrawn deep into the wood tissue, which facilitates easier bark removal when it comes time for timber processing. They selected timbers that were long and straight, and as close in diameter to one another as possible.

“At first, Sand Hill was reluctant to let us harvest the timbers we had carefully chosen,” Dennis told me, “because, naturally, the trees we wanted were some of the largest and oldest on their land. We were able to compromise and harvest enough for construction, but that left us with a slim margin for error – we only had one extra timber. It all turned out well in the end, but knowing we did not have many backups on hand added a level of stress to the process of framing the building.”

Dennis smiled his customary broad, toothy smile and chuckled, “I had a lot of fun during that time and I remember it fondly, though Sharon shudders a bit at the memory. I enjoyed being out in the fresh air working in construction, even in the heat of the early summer when we worked to transport all the timbers to our homestead, though I wouldn’t recommend this kind of project to someone who doesn’t like working outside!”

The framing for Robinia consists of five round-wood post and beam timber lintels – horizontal beams supported by upright posts – called bents. Sharon and Dennis decided to install a living roof on Robinia, which meant that the framing had to be especially sturdy to bear the weight of wet soil, in addition to resisting the powerful winds of northeast Missouri. “Round-wood framing has the advantage of using all of the fibers in the wood,” Dennis told me. “The fibers are not straight – they curve and move through and around each other, like the muscle fibers in your arm. Hewing or sawing timbers to square them means that fewer of these fibers are intact and able to support the structure.”

“No timber we used could be longer than the shortest timber we had available,” Dennis went on as he pointed out various aspects of the framing, “So we had to work within the limitations imposed by the timbers we were able to obtain. As a result, we had to combine two timbers to make each of the beams we needed to span the north-south dimension of the house. We did this using a bladed scarf joint for each of the beams. The joint is offset from the center in a way that allows the posts in the center of each beam to butt against solid wood rather than a joint. We used notch and peg joinery to install the 45-degree support braces. An important thing to note about the joinery is the portion of wood called the relish, which is the buffer between the 45-degree support brace and the cuts we made for each scarf joint. A strong wind could potential apply enough force to the frame to sheer that piece of wood clean off, if it was not thick enough. All of these considerations had to be accounted for, before we started cutting timbers for the framing.”



“We chose one of the post timbers intentionally because it had a wide crotch where two large branches stemmed from the trunk,” Dennis continued as he pointed out a unique joint. “The natural fibers of the timber in this place are far stronger than any sort of joinery that we could construct, so we took pains to make use of this existing element to support the beam above it. Also, two of the timbers we had were significantly curved, so we combined them in the same beam to form a sort of archway, as a decorative structural element for the road-facing end of the house. We closed the gap between the beam and the rafters with specially cut shims. The resulting post and beams viewed from floor level are clearly functional, yet add unique beauty to the house interior.”

2. Catch and Store Energy: “By developing systems that collect resources when they are abundant, we can use them in times of need.”

Robinia is rectangular in shape, oriented with its longest dimension running east west to maximize its south-facing surface area to allow solar energy to passively heat the home in winter. Myriad windows are arrayed on the south face of the building as part of this strategy, while few windows were installed in the other faces of the structure – small windows on the north side to allow for cross ventilation without compromising too much of the home’s airtightness in winter.



A custom stained-glass window, made by Dennis and Sharon’s friend Gigi, is the crown jewel of the house; it depicts a bumblebee visiting the pink blossom of the black locust, Robinia pseudoacacia, the hardest wood in North America and Robinia’s namesake. A single course of straw bales is installed above and below the row of windows. The irregular gaps between the windows are insulated with slight clay straw – a mix of chopped straw and clay slip that is packed into temporary wooden forms to fill spaces between framing elements.

The southern eave of the roof is sized and angled with the seasonal path of the sun in mind. In summer, when solar heat is unwanted in the building, direct sun is blocked by the eave while admitting ambient light. The eave is not so large that it blocks the winter sun, which is lower on the horizon. During colder seasons, sunlight can pour into the structure and conserve energy and material inputs used to heat the home.

The floor of Robinia is divided in half and finished in two ways. The southern half is made of clay, which absorbs the winter sun during the day and radiates it at night. In the summer, when the earthen floor is shaded, it acts as a heat sink, absorbing heat energy inside the house and reducing the overall temperature of the structure. “We have treated our earthen floor with several coats of linseed oil,” Dennis told me. “In the old days they used to make linoleum in this way, by painting many layers of pigmented linseed oil on the floor until it formed a water resistant barrier. We probably won’t apply than many layers, but the effect of sealing the floor is the same.”

The northern half of the floor is clad in wood planks, which overlay straw treated with borax to act as a flame retardant as well as to discourage insects from boring into the wood and living under the floor. The wooden floor will avoid moisture retention on the north side of the house, which is shaded at all times of year. Wooden and earthen floors are divided by a decorative section of six-inch thick cookies sawn from local black locust cordwood, which also serve as insulation in the transition zone of the floor.

3. Obtain a Yield – Stacking Functions: “Ensure that you are getting truly useful rewards as part of the work you are doing.”

A living roof garden is planted atop Robinia, maximizing the space available on their land for growing crops. This year, Dennis and Sharon are growing tomatoes and spuds, along with some herbs and indigenous volunteers, (weeds). In past years they have had great success with squash – in our area, squash borer insects are the bane of cucurbit crops, but the fresh micro-ecosystem of the roof garden meant that squash could grow without their impact. In addition to the massive timbers used to frame the structure, the roof is supported on 2×12 reclaimed wood rafters with blown cellulose applied in the gaps between them to provide insulation. A commercial pond liner prevents water infiltration into the home.

In winter, Sharon and Dennis heat Robinia with an airtight Harman brand steel stove, which includes a cook surface capable of accommodating three skillets simultaneously. Much of the stove’s flue is exposed on the interior of the structure, insuring that most of the heat of each fire is extracted before gases are exhausted outside. The goal is to derive as much use as possible from each measure of wood burned in the stove, both to spare Dennis and Sharon the work of chopping the wood and to avoid unnecessary carbon emissions. The brand new, high quality stove was one of the more expensive elements of the house, but it burns wood more completely than an old fashioned cast iron stove, and it will pay dividends in saved energy and labor over the years of its use.

Wexers Sawing Logs

Wexers Sawing Logs

Dennis and Sharon also stack functions in the way they manage their property. They have planted various fruit trees on the western side of their house, which shield it from icy winter winds as well as the blazing western sun in summer. They employ portable fencing to run a flock of chickens for variable periods of time in their garden, in their food forest and in the pasture adjacent to their home. This practice keeps pests under control, (like ticks, vectors of Lyme disease,) and affords their birds a healthy and humane lifestyle, which they return to Sharon and Dennis in the form of wholesome fresh eggs.

4. Apply Self-Regulation and Accept Feedback: “We need to discourage inappropriate activity to ensure that systems can continue to function well. Negative feedback is often slow to emerge.”

Pioneering an ecological lifestyle at Dancing Rabbit Eco-village involves making commitments to self-regulating consumption to promote positive ecological lifestyle changes. In the case of Robinia’s construction, Sharon and Dennis chose to limit their options in a number of ecologically savvy ways. They dug the foundation for their house by hand, rather than hiring petroleum-fueled mechanized excavation equipment. They used traditional hand-saws and chisels to cut the joinery in all the elements of their framing, both to save energy and to achieve a level of accuracy that is impossible with chainsaws. They used a drawknife and barking spud – essentially a chisel on a long handle – to remove bark from their timbers, rather than power tools like a belt sander.

No Portland cement is used anywhere in the construction of Robinia. Portland cement as a single industry accounts for roughly 5% of global CO2 emissions. Sharon and Dennis opted instead to use traditional lime mortar to bind the recycled bricks used for the hearth of their fireplace and in footings for their timber posts. “Lime mortar is plenty strong for these purposes,” Dennis explained. “It has been used for foundations long before Portland cement was invented, and you will find traditional lime mortar foundations still standing strong across this country. I use Portland cement in limited applications for its extreme strength, but it was not necessary for this project so we were able to reduce the embodied energy in the house.”



Dennis and Sharon have made many deliberate choices to regulate their own behavior in ecological ways. “We are happy with a lot less space than the average American,” Dennis told me. “I lived alone for years in Atlanta, where I had a much bigger house than I needed, with a garage full of stuff I didn’t use and no room for the car that was supposed to go in there. Here, we both have ample space in a house about a third of the size of the one I used to live in by myself.”

5. Use and Value Renewable Resources and Services: “Make the best use of nature’s abundance to reduce our consumptive behavior and dependence on non-renewable resources.”

Almost all of the materials they used are reclaimed, recycled or locally harvested. Dimensional lumber used for construction was reclaimed and upcycled from local demolition projects. Straw bales, used to insulate the north, east and west walls, were purchased from local farmers who would otherwise burn the chaff from their fields. Rather than buy petroleum-based rigid foam to insulate their floor, they packed a heavy clay straw mixture into the subfloor cavity of the home. Their foundation consists largely of waste rubble known colloquially as urbanite, mixed with crushed glass from the local bar and only as much new gravel as was necessary to meet their needs.

“Almost everything used in the construction of Robinia,” Dennis told me in a solemn tone, “can be allowed to biodegrade and return to the earth, or used by future generations in a new way. Our earthen plaster can be removed, mixed with water, and used again – the clay we used came from just a few feet away. The straw can be composted; the wood milled into something new, and so on. Current construction methods rely on extracting resources to make new materials – when the old stuff needs to be replaced it just gets thrown away into a landfill. We don’t have that problem. Buildings constructed in this manner can be made and remade here in perpetuity.”

Dennis and Sharon also do much to reduce their consumption by producing their own entertainment, in additional to participating in community functions. Dennis plays the guitar quite well, and Sharon is a frequent participant at the weekly community song circle, where members of Dancing Rabbit gather to sing folk songs. When enough Spanish-speakers are around, Sharon will often host Mesa de Español, a luncheon for people of all skill levels to practice their Spanish together. Potlucks are held at Dancing Rabbit Eco-village every other Tuesday, and Friday dinners are reserved for communitarians to bring their own meals and enjoy the company of friends and neighbors.

6. Produce No Waste: “By valuing and making use of all the resources that are available to us, nothing goes to waste.”

The north facing wall of Robinia is shielded by an earthen berm, to mitigate cold air infiltration into the building in winter. To prevent water damage to the structure of the wall, a gap was left between it and the berm. Sharon and Dennis have put this space to use by burying their cistern underneath the berm, while using the gap as an access tunnel for maintenance in addition to a storage area for items that are not sensitive to moisture exposure. An additional storage area has been set aside on the northwest corner of Robinia’s interior. In the future, this area will be walled off to avoid unnecessary heating of the space. Dennis and Sharon strive for a high level of efficiency in their storage areas, ensuring that furniture pieces of have multiple functions, and that there are no empty cavities that cannot be utilized in some way. They make use of lots of shelves to make use of vertical space, and ‘stack and pack’ is Sharon’s motto. No wasted space in Robinia!

Folks at Dancing Rabbit Eco-village compost their effluvia in order to avoid needless expenditure of drinking water while conserving the nutrients so crucial to restoring vitality to our soil, which was radically depleted in past decades when it was used as farmland. We do this using the humanure method, as described in Joe Jenkin’s ‘The Humanure Handbook’.

Straw Bale Construction

Straw Bale Construction

In summer months, Dennis and Sharon do all of their cooking outdoors. “In our modern society, people spend a lot of money and energy cooling their living space, only to heat it when they cook. In winter, they spend lots of energy cooling their food while spending more energy to heat their homes – this kind of process is very wasteful. We do our cooking outdoors on a small rocket stove when the weather is warm to avoid introducing heat into the home,” Dennis explained. “We also located our refrigerator outside, so that heat generated by the cooling unit is vented outside, instead of into the house. In the colder months, we just turn it off and let nature refrigerate our food for us.” Over the next few months they plan to finish construction on a complete outdoor kitchen.

7. Design from Patterns to Details: “By stepping back, we can observe patterns in nature and society. These can form the backbone of our designs, with the details filled in as we go.”

“Our house is a lot like a natural cave,” Dennis told me. “We designed the structure with this natural inspiration in mind, capitalizing on the properties of thermal mass. Heat energy is absorbed by our earthen floor and plaster walls on winter days and released over time at night, while our earthen floor draws heat out of the air in summer to keep the space cool. The soil covering the roof insulates the movement of heat energy in or out of the building, and during the hottest part of the year water evaporates from the soil and cools the structure. The timber framing is strong enough to support a substantial snow load as well, which acts as an extra layer of insulation in winter.”

Living Roof Garden

Living Roof Garden

8. Integrate Rather than Segregate – Versatility: “By putting the right things in the right place, relationships develop between those things and they work together to support each other.”

Robinia’s 800 square feet of floor space is an open floor plan, casually subdivided into areas for different functions by furniture placement. “We have the office area and bedroom furniture placed adjacent to one another. We can easily expand or contract one space or the other by simply moving the furniture,” Dennis told me. “This open floor plan contributes to the feeling of spaciousness in the home. Our living room is only about 10’ x 12’ – if we walled it off, it would feel a lot smaller than it is. This open floor plan is very versatile.”

Among Dennis and Sharon’s plans for the future is a unique greenhouse, where they plan to have their bathing facilities. “Humidity is unwanted in an earthen plaster house,” Dennis told me, “because it promotes mold growth. Including a shower in the plan for the house would have been difficult to accommodate. In the greenhouse, however, the extra moisture will be welcomed by out plants, and it will also be a pleasant environment for us to shower in amidst the greenery.”

9. Use Small and Slow Solutions: “Small and slow systems are easier to maintain than big ones, making better use of local resources and produce more sustainable outcomes.”

“It took a long time to build Robinia,” Dennis told me. “We didn’t even have any vertical structure to show for all our labor after the first building season, having spent the time digging the foundation trench and building the heavy-duty foundation to hold the weight of the living roof. We were disappointed, but taking our time and doing things right was much more important than getting things done quickly. This is true of the framing as well – every measurement has to be done carefully and cuts have to be made accurately by starting small and removing material a little at a time.” In the meantime, Dennis and Sharon lived in the Magic School Bus, a reclaimed school bus moved onto community property as temporary housing while Robinia was under construction.

West Interior

West Interior

Sharon beamed as she told me one of her favorite stories about the house. “We worked with the timbers across the road on the ground, before transporting them here to their final places. We wanted to have at least one of our bents installed the first year, but we didn’t, so we posed for a picture lying on the ground as though it had been. Our neighbor, Tim, stood on a ladder and took a picture while our work exchanger wrapped his arms around the beam as if he was hanging from it. We fooled lots of people in the village with that picture, for a little while!” Sharon laughed and continued, “When we finally had the first bent up, we had a party to celebrate, and sang a song about verticality based on Lloyd Price’s song, ‘Personality’.”

10. Use and Value Diversity: “Diversity reduces vulnerability to a variety of threats and takes advantage of the unique nature of the environment in which it resides.”

Robinia is wired for both AC and DC current, affording Dennis and Sharon the best of both worlds in terms of choosing their appliances. “Most appliances are wired for AC electricity usage,” Dennis explained, “but DC appliances often work more efficiently and are easier to integrate with solar and wind arrays because there is no need to convert the current. Wiring the house for both types of current was a nominal extra expense, but drastically improves the versatility of the home.”



11. Use Edges and Value the Marginal: “The interface between things is where the most interesting events take place. These are often the most valuable, diverse and productive elements in the system.”

As I sat with Dennis to hear about Robinia, I became aware of the rhyme and reason inherent to the design of their space. Their front door is right off the main road running through the village, offering easy access to vehicles for transport of materials in or out of the homestead, while their backdoor opens directly onto their garden and chicken run. Paths encircle the house to provide access to both vegetable gardens, at ground level as well as on the roof, with their food forest standing nearby. Robinia is placed at the confluence of multiple micro-ecosystems, as well as human systems; it is perched on the edge of each in a way that unifies them and facilitates ongoing oversight and maintenance by Dennis and Sharon as time goes by and new projects come online.

They extend this concept to the harvesting of marginal plants in their garden and surrounding space. As a result, they benefit from eating wild greens in the spring, like nettles, lambs quarter and dandelion long before domesticated annual greens have even been planted in their garden.

12. Creatively Use and Respond to Change: “We can have a positive impact on inevitable change by carefully observing and then intervening at the right time.”

Dennis pointed to a small round window installed between two larger windows near the dinner table, “Our work exchanger, Ashly,” (she will always be Ashly-bashly-fo-fashly to me,) “was helping us lay the bottom course of straw bales. We had room between two posts for two full bales and we were going to have to cut a third to size in order to fill an irregular gap. Ashly suddenly asked, ‘oh, are you going to put a window there?’ Sharon and I thought about it and decided to go ahead and put in an extra window – why not! We cut a slice out of a rotting log and installed a piece of glass in it to form a window. It allows a little more light into the house, and it’s a fun decorative element. It’s good to remain flexible enough to do that sort of thing in your design. Sometimes inspiration will trigger your creativity in the midst of a project and give you an opportunity to do something great with your design.”

If you want to learn more about permaculture from Dennis and Sharon first hand, take some time to review their Permaculture Design Course and decide if could be the right one for you to achieve your Permaculture certification. The course begins on August 29, 2015, and ends on September 6, 2015. The price of the course includes instruction, delicious wholesome food and a place to camp – rooms are also available in Dancing Rabbit’s very own eco bed and breakfast, the Milkweed Mercantile! In addition to seeing Robinia and learning a great deal about permaculture, you will have a chance to meet lots of folks interested in sustainability and tiny house living at Dancing Rabbit Eco-village.

Living Roof Construction

Living Roof Construction

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Erim - August 28, 2015 Reply

This is amazing, and such a comprehensive write up on the home. Love the part about coating the straw with borax. Clay slip is great too. Straw coated in clay does not burn.


Dennis Hoffarth (1948-2016) – An unsung Atlanta hero on two wheels - SaportaReport - July 31, 2016 Reply

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