We’re living in a thrilling era for natural building! Although constructing with earth has been a worldwide practice for centuries, its resurgence in the Western Hemisphere is relatively recent, spanning just the past 30 to 40 years. During this period, development was often hindered by building codes and regulations that weren’t designed with natural or sustainable construction in mind.
However, this field is now expanding rapidly. People are increasingly drawn to homes and communities that offer a deeper sense of connection, seeking sustainable building methods and a more genuine way of life. This surge in interest is fueling a wave of innovation and creativity among natural builders, who are constantly finding new ways to create beautiful, long-lasting structures. One such innovative approach is Balecob.
What is balecob?
Balecob is an innovative construction method combining straw bales and cob to quickly build highly insulative, roof-supporting, and load-bearing walls without relying on wood framing. Cob is a mixture of clay, sand, and straw blended with water.
In balecob construction, straw bales are stacked like bricks, with cob packed into the seams to stabilize them. This hybrid technique harnesses the strengths of both cob and straw bale construction, resulting in buildings that are not only functional and natural but also aesthetically pleasing.
Pioneered by Ianto Evans and the Cob Cottage Company in Oregon, balecob has gained traction as a practical and beautiful building method. I learned about this technique from a close friend who uses a slightly different approach. My hope is that, as more people discover balecob, they’ll see its practicality and choose to incorporate it into their own building projects.
Beyond traditional wall systems
We often define a house by its wall system: timber frame, stick frame, concrete block, and so on. The same concept applies to natural building with materials like straw bale, cob, and earthbag. However, choosing a single wall system can be restrictive. I believe the best homes are hybrids, utilizing different materials in optimal locations.
Got lots of windows and doors on the south side? Consider using cob or wood framing. For a long, cold north wall, balecob or straw bale could be ideal. If you’re planning to stick-frame your interior walls, filling them with light straw clay is a great option. By embracing flexibility in our building methods, we can create homes that better suit our needs and desires. Additionally, using natural materials and intelligent design helps us minimize our ecological footprint.
Cob and Straw Bales – A strong pair
Since balecob combines both cob and straw bales, it’s essential to understand what each material brings to the table.
Cob is known for its strength and durability, and it can be shaped easily to fit the builder’s vision. It offers significant thermal mass, although it isn’t very insulative on its own. Due to its flexibility, cob is excellent for leveling stem walls and other uneven areas, making it a perfect complement to earthbag, recycled concrete (“urbanite”), or other unconventional foundation techniques. Cob is typically sourced locally—sometimes from the soil excavated for the building’s foundation trenches—making it accessible to nearly any builder.
Straw bales, on the other hand, aren’t as durable as cob but offer much better insulation. Their uniform size and shape make it easy to construct rectilinear walls. Some of the labor in straw bale construction is handled during bale production, which can be a pro or con depending on your perspective. However, straw bales require a lot of space, as their insulation largely comes from the wall thickness they provide.
In summary, cob excels in strength, mass, and creating curves, while straw bales are ideal for volume and insulation. Both materials are cost-effective, fire-resistant, and require minimal tools and skills, promoting community building projects. By combining the strengths of both materials, balecob offers a faster construction method that is both insulative and strong, suitable for both curved and rectilinear walls.
A strong foundation for Balecob walls
A balecob wall is built from the ground up with the following components:
- Rubble Trench: This foundation consists of loose stone, gravel, or rubble placed in a trench beneath the walls, providing essential support and drainage.
- Stem Wall: A short wall made from stone, earthbags, concrete, or other rigid, impermeable materials. It bridges the rubble trench and the vertical walls, offering protection from water.
- Base Cob Layer: An 8- to 10-inch thick layer of cob placed on top of the stem wall. This layer smooths out any irregularities and creates an even base for the straw bales.
- Bales and Cob Pillars: Straw bales form the bulk of the wall, with cob “pillars” at the corners and intermittently along long walls to ensure structural integrity. Cob is packed between the bales to hold the wall together and compress the bales.
- Top Cob Layer: The final cob layer, typically at least 1 foot thick, further compresses the bales and provides a solid connection to the roof.
- Roof: Rafters are secured into the top cob layer, enhancing the overall stability of the structure.
When constructing a balecob wall, don’t skimp on the depth or tamping of the rubble trench, as it needs to be stable to prevent settling and cracking later. The stem wall should also be carefully built, a few inches wider than the bales to accommodate plaster layers that ensure the wall is plumb from the stem wall up to the roof.
Once the stem wall is up and relatively level, start with an 8- to 10-inch-thick layer of cob. Fill any gaps in the stem wall as you go to create a more even base for the straw bales. This layer should cover the full width of the stem wall to connect all its components effectively.
Stacking straw bales
When building with straw bales, you can stack them on either their narrow or broad sides.
Narrow Side Stacking:
- Builds taller structures more quickly.
- Requires fewer bales and a narrower stem wall, resulting in a smaller overall footprint.
- Increases wall insulation as the straw fibers don’t span the entire width of the wall.
- Makes plastering more challenging due to the orientation of the straw strands.
Broad Side Stacking:
- Requires more bales but results in thicker walls.
- Allows for gently curved walls by bending the bales during construction.
- Slightly lower insulation factor compared to narrow stacking but still higher than conventional walls.
- Easier to plaster due to the orientation of the straw strands.
Whichever method you choose, always use strong, clean, and intact straw bales. Center the bales on the base cob layer for stability.
To enhance the connection between bales and facilitate plastering, apply a clay slip (a milk-consistency clay slurry) to all sides of each bale before placing them on the cob layer. This slip serves two purposes:
- Provides friction between layers, keeping the bales better connected as you build.
- Acts as a primer for easier application of a base coat of earthen plaster.
Stack the bales in a staggered pattern, similar to bricklaying, to maximize strength. Cut and re-tie bales as needed to fill shorter spaces.
Cob Pillars and Cob Jamming
As you stack straw bales, construct cob pillars to provide lateral compressive support, hold the bales firmly together, and structurally support the roof. Place a cob pillar at each corner of the structure. For spans longer than 10 feet, add additional pillars along the wall. For instance, in a house we built in South Dakota with 30-foot-long walls, we constructed 2-foot-square pillars at each corner and another pillar of the same size in the middle. For our smaller balecob pig hut, the corner pillars were only 1 foot square.
As you build, thoroughly fill all gaps and seams between the bales with cob, a process we call “cob jamming.” This cob acts like numerous wedges, further compressing the bales and minimizing or eliminating bale settling. Settling is a common issue with straw bale homes, leading to significant plaster cracking, decreased wall strength, and reduced insulation due to the air gaps created as the wall settles. Balecob effectively addresses these problems.
Top Cob Layer
Once the final row of bales is in place, you can proceed to lay the upper layer of cob. This layer serves three essential purposes: it further compresses the bales, levels the walls while allowing for any final shaping, and attaches the roof anchors to the walls. For larger structures, make this layer at least 1 foot thick, although it can be as thick as 20 inches. For smaller structures, such as my pig hut, a 4-inch layer may suffice. Use the cob to even out any high or low spots in the bale wall so that the top plate and roof beams sit level.
It’s crucial to securely connect your roof to the wall’s mass to ensure a strong and stable building. We achieve this using “deadmen” and metal strapping. A deadman is a piece of wood, usually dimensional lumber, embedded in and surrounded by cob. It serves as an anchor for various supports like shelves, stairs, benches, and roofs.
In traditional cob construction, we’d set metal strapping with deadmen into the cob walls at least 1 foot from the top, spaced about every 2 feet. This creates numerous well-anchored points for attaching the roof along the wall. The top plate or rafters are then secured to the wall using the metal strapping.
We use similar methods in balecob construction: placing deadmen and metal strapping in all cob pillars and at intervals along the wall beneath the top cob layer. Lay the deadmen on the last course of bales, ensuring enough metal strapping extends beyond the top cob layer to connect with the roof.
Applying the base coat of earthen plaster
Once the walls are up, the cob has dried, and any settling has occurred, it’s time to apply a base coat of earthen plaster. This step isn’t just about aesthetics; balecob walls gain strength from the interlaced cob and plaster that surrounds and fills the spaces between the bales, as well as from the cob pillars and layers that compress them.
Begin by covering the sides of the bales, which should already have a layer of clay slip, with a 1- to 2-inch layer of earthen plaster. You can finish a balecob wall with several layers of earthen plaster, similar to finishing a straw bale wall. We recommend starting with a straw-rich plaster, which sticks easily and goes on smoothly. After applying the base coat, you can add layers of finer earthen plaster to complete the finish.
Moving forward
Windows, doors, electrical systems, and plumbing can all be integrated into a balecob structure, but detailing these specifics would take more space than available here.
There are many books and online resources on natural building techniques, although information on balecob specifically is still somewhat limited. Consider taking a workshop or experimenting with the building materials yourself. Natural building encourages experimentation and is perfect for projects smaller than a whole house or cabin.
Why not start with a smaller project, like a root cellar, cold room, sauna, animal housing, or a seasonal workshop? We began by building a garden shed, so the key is to just get started with something manageable.
Suggested resources for survivalists:
25 projects for your quarantined homestead
Here in Florida, a house that way is called, “Lunch for Termites”.
Second, here in Florida we have some of the strictest building codes. After Hurricane Andrew turned stick-built house into broken toothpicks, most house are now CBS Block. Someone trying to built a house with straw would get laughed right out of the Code Enforcement Office.
Maybe somewhere, where a really strong wind is 35 mph and only happens once in 10 years, a straw house is fine. (As along as no wolves come by to Huff & Puff).