Building a Hobbit House

I built my first hobbit house for $500, it began as a dream and I just kept going. Although I have a beautiful 1870s log cabin close by, I moved into the hobbit house. It is not just because it is so warm and comfortable, it has a magical quality that I’d never experienced before, it’s like finding something wonderful that you didn’t know you had lost.

 I have since built a second one and that too surprised me how good it was, it also gave me a clear idea on costs and construction time. Both are built using earthbag construction techniques and have living exterior walls and roof. By happy accident I stumbled on the answer to ultra-low   cost housing and food security. Affordable housing and abundant local food are essential components to building vibrant and diverse communities. It is for that reason that I share my thoughts and experiences.

Hobbit houses work because they align perfectly with nature. The sun provides passive solar heat and solar electricity, the earth adds geothermal heat and cooling, earthbag construction insures excellent insulation and structural stability, finally, the living walls and roof become the garden. The core principles work anywhere, however the actual building materials and construction technique must be adapted to the climate and culture in which you live. My hobbit house is in central Canada. If I was building elsewhere I would blend the same mindset with the indigenous architecture of the region. The construction materials should be locally available, ideally free or at very low cost. The only caveat is that it is essential to have a practical and intuitive understanding of the core principles of construction and architecture. Ballast dreams with pragmatism.  Oh, I should mention, earthbag construction is hard work, there are about 900 bags, they weigh up to 110 lbs each and the tamper weighs 30lbs.

The four gods of architecture are: air, water, earth and sun. The ideal site is on a slope facing the sun with half the building dug into the hillside. The fill from excavation provides material for the walls. Good ventilation is essential, that means fresh air flows through the house. Cold air is heavier than warm air so site the house a third of the way up a hill, this avoids waking up to damp misty mornings. Water goes where water wants to go, read the plants and the terrain so that ground water isn’t a problem. Earth acts like a liquid not a solid, it heaves, pushes and can flow in a mudslide. The concave shape gives added strength to the building. Excavating down to bedrock or until an excavator can no longer dig prevents future subsidence. Orient the building to take full advantage of the sun. Then there is gravity, the glue of the universe, it keeps us and everything else grounded. Make gravity work for you, not against you. Earthbag buildings can be monolith structures or have a timber frame with the earth bags filling between the posts. The advantage of a timber frame is that it is uncomplicated to build and facilitates fitting door, windows and shelves. The downside for me is that I believe trees are sentient beings and killing them is a dilemma I have not resolved.

Design

The beauty of earthbag construction is that you can build in any terrain and climate, that said, choosing the optimum site saves cash and adds magic. Intuition and a feeling for a place are critical components to buildings that make people feel good. The front of the building has a rounded door and windows for that storybook look, however, the south-facing windows (northern hemisphere) are recycled quality windows that can be opened, have screens and are double glazed. The opposite wall also has a small window for cross ventilation. The airtight woodstove is also on this side with the chimney going out the wall. The interior dimensions are 20ft diameter (314 sq. ft.), the walls are 8’6” rising to 9’6” in the center (allow at least 6” for the floor). The frame is nine posts on the outside and one in the center supporting the roof. The frame design I borrowed from the traditional North American bank barn which have floors that support the weight of tractors with wagon loads of hay. The interior layout is a nod to Lao Tzu and sailboat design - it is the empty space that makes things useful. 

The bed frame is built 4ft off the floor and against the wall opposite the door so that you can wake up and watch deer grazing in the garden (no worries when the kale grows on the roof and the root veggies are safely underground). Furniture fits around the walls except for an armchair in the center facing the stove. Electricity is a 12volt DC system powered by a 100-watt solar panel. A 1.5-watt bulb is amble for lighting. Phone, tablet and power tools are recharged using a car accessory fitting wired to the battery. Convivence matters and so I built a commode by chainsawing the center out of a plastic lawn chair, zip tying a toilet seat over the hole and placing a bucket half filled with worm compost under the chair. In practice, this is more of a conversation piece, with the composting outhouse getting the daily business. Three hundred square feet living space is perfect when the blizzard howls outside, however, summers are best spent outdoors. On the south side of the hobbit house is a patio for eating and entertaining along with a woodshed, rainwater is collected off it’s roof. There was a damp spot in the floor, I busted through two feet of bed rock, filled a section of 10” water pipe. This now provides the champagne quality drinking water for half the year.   

The garden on the roof is essentially a raised bed filled with ‘black gold’ worm compost, this is worm castings made by vermicomposting organic waste with Red Wriggler worms. The exposed walls are also covered with this and climbing veggies like beans grow up the sides of the hobbit house. It takes several months to make this compost (only a few weeks in optimum conditions) and should be implemented before construction begins. The best website for info on how to do this is: wormdigest.org The 300-sq. ft. garden on the roof feeds the hobbits.

Construction

Hobbits may ramble, but their homes are solid and secure against the elements. It is essential to understand the dynamics of structural stress, water management and gravity. My dream didn’t come with a blueprint, there are times when you need to stop and think; for example, the weight of dirt bags on the window frames was a concern and so here I switched to straw bale construction. To insure a tight fit, I double bagged loose straw into used plastic wood shavings bags. The bags were sandwiched between two stands of tight twelve-gauge wire which were then cinched together. The roof has a 2ft overhang, this allows winter sun to warm the building and shades out the summer sun.

• Excavate into a hillside with a southern exposure. The excavation is thirty feet wide and the face is approximately six to eight feet high. The back half of the building is below ground and the two south facing windows are above ground. The fill should be evenly piled around the outside perimeter so that it is easier to fill and lift the bags of dirt.
• Mark out a twenty-meter circle and the nine post holes around the perimeter. Dig the post holes. The holes should be not less than four feet deep and have a firm base. The posts are locked in place from three different directions and this gives structural strength and stability – the posthole, the beam from the center post and the walls on either side of the post. There is inherent strength in a concave shape. It is critical to use massive timber that will not rot in the ground. I hit bedrock at 2ft, in this situation pound a mix of limestone screenings and dry cement around the post. This is stronger than using regular wet cement.
• Earthbag building takes tenacity. It is worth all the effort because of the advantages it has over other forms of construction. Rodents and rain aren’t an issue, insulation and structural strength far exceed building codes, the material is free, the technique is easy to grasp and you can do it on your own (my first helper lasted a day and told me I was mad).
• The trick to easy posthole digging is to use water. Dig a few inches until the ground is hard and then pour water in the hole. Do the same with the other holes, by the time you get back to the first hole the subsoil will be soft and easily broken up with a digging bar. Set the inner most poles first so that you can drop all of them in the holes with a tractor. Use a tight mason’s line and line level to mark the outer posts at 9ft and the center one at 10ft. Cut the posts to the correct length.
• The nine radial beams from the outer posts to the center post are lowered into position. Only four will fit on the center post. The first four beams form a star pattern, the remaining five then lay across the first ones.  Spike them all in place with 12” nails. It is cheaper to buy eight foot lengths of 3/8” rolled steel rod and cut it to length to make the nails. The radial logs will need to be notched so that they fit snuggly on the posts.
• It is easiest to build all the sections of wall up to four feet, except for the front section which is kept open for the door frame. The walls are built with staggered joints as in a brick wall. There are different ways to fill the bags, this worked for me: I’d fill a heavy-duty animal water bucket with soil and dump it in the bag, when the bag was half full I’d position it on the wall and fill it three-quarters full. Fold the top over and wedge it tightly against the previous one. Then pound it into a rigid rectangle with the thumper. The thumper is made by setting a pick-axe handle in a plastic tub (8” by 8”) of concrete, it weights about thirty pounds. After the bag, it is hard, solid and rectangular give the exposed end a few whacks so that it fits tightly against the previous one. Before fitting a bag against a post scoop, the soil away from the middle of the top of the bag, this enables the bag to fit with a concave shape around the post locking it into position. Occasionally the sides will need to be smacked with the sledge-hammer to maintain a vertical curved wall. The text book method of anchoring the bags in place is to lay two stands of barded wire between each layer of bags. In my hobbit house the bags were tightly wedged between the posts and I had scrap rebar. I pinned the bags together with 4ft lengths of this rod.  Stagger the bars so that the wall becomes one unit.  Earth bag construction is hard work and the integrity of the building depends upon effort and attention to detail.
•  The top two-feet of the wall is built with straw stuffed into plastic shavings bags. Wedge the bags tightly in place and then secure them between two strands of wire, one on the inside and one on the outside of the wall. Clinch the wires tightly together with baler twine in two places equidistance apart.

The roof has five layers. First, the nine radial 10” beams connecting the outer nine posts to the center post, then cedar poles form a lattice like a spider’s web over the beams. Oak planks, recycled from a paddock fence, are nailed to the poles and completely cover the roof. To prevent the roof timbers puncturing the tarp or waterproof membrane it is necessary to use at least two tarps. I used two old farm tarps, a trampoline deck an inflatable raft and old tents to soften the dips and sharp edges. These were then cover with a heavy-duty industrial tarp. The tarp is then covered with a layer of old hay to give protect from potentials pebbles in the worm compost. Finally, the roof is covered with 12” of worm compost. A rim of timber prevents the compost falling off the roof.

 The exterior wall is protected from moisture, by the roof over hang and by Tyvek or building wrap. This is then backfilled with soil or by compost on the exposed front wall. A double layer chicken wire holds the compost in place. Grading around the building directs rain water away from the house. flow.

The inside wall is parged with plaster. Chicken wire holds the plaster in place. Two thin layers prevents cracking.  Ideally, the plaster is an earth plaster made on site. I did mine when it was -20c outside and had to sacrifice clay on the altar of expediency. Instead I used a lime and mortar mix. The plastering took six weeks and added $400 to the cost, the final cost was $500. The plaster dries quickly and is then whitewashed. The floor is interlocking brick set in 3” of limestone screenings.