Create Sacred Space
A 9 day Straw Bale Roundhouse Natural Building Workshop
August 21-30, 2026
Nevada City, CA
Taught by Rob Pollacek
Founder of California Cob
$1100
Space Limited to 12 Students
About the Workshop
In this comprehensive 9 day workshop, you will learn the basics of building a small Straw Bale cottage.
We’ll be building a 20’ diameter Straw Bale round-house with a cob and earth plaster finish coat, under a new conical metal roof.
Small natural buildings, such as a cob sauna or a small Straw Bale cabin, are a fantastic workshop teaching project. They are big enough to learn and practice your building skills over many days, but also small enough to see the project through to a good level of completion during the workshop and to explore some of the other crucial aspects of the building process that often get overlooked on larger workshop projects.
This includes door and window framing and installation, box beam headers, wood trim and window sills, electrical and plumbing, exterior and interior plaster finishes, roof construction, stud wall carpentry, insulation concepts, flooring options and gutter systems.
We will take you on a journey of discovery as we install the Straw Bales for this roundhouse cabin, using the vertical Straw Bale technique knows as B.O.E.B.S., which stands for Bales On End Between Studs. This is a fantastic, cutting edge technique, where the Straw Bales are oriented vertically within a light stud-wall frame, with the 15” narrow dimension of the bale as the wall thickness, as opposed to the standard thicker 23” wall thickness. The use of the narrower orientation of the bales allows for a quicker installation process, significantly less bales used in the walls, and an overall lower cost per square foot for the building. This is due to the fact that the narrower wall system allows for a smaller building footprint. This means a smaller foundation, a smaller floor, less bales and plaster, and a smaller roof, while keeping the same interior square footage. All of this adds up to significant cost savings.
Using the Straw Bales in this way has a natural positive design aspect, as the gaps on the exterior wall created by the curving Straw Bales, are naturally filled with each stud. In addition , the standard 24” stud spacing, which is the common spacing used in most construction designs, is the perfect spacing to fit a Straw Bale between.
We’ll cover the Straw Bales in a site made, clay-straw leveling coat earth plaster and finish it off with a local earthen plaster finish coat, made from scratch. We’ll also be learning how to make Cob and will be building a sculpted Cob window seat inside the building. We’ll learn how these two sister techniques work together, to create a building that has both high insulation and thermal mass. Along the way, we’ll explore clay sculpting by using a special Bas-relief mix, to create altars and niches with stone sills, and sculpted curved wall shapes.
This Straw Bale roundhouse will be capped with a metal conical roof. This is the perfect roof for a round building. We’ll go through all the important details on how to build a conical roof.
This workshop is an amazing opportunity to get to see first hand the creation of a new kind of Straw Bale roundhouse building, and partake in the magical experience of turning it into a sculpted earthen sanctuary.
All Inclusive
Location Near the Beautiful Yuba River
- 3 fresh made meals a day
- Natural Building Tour
- Private location Yuba river swimming trip
- Camping
- Hot Showers
Here's What You Will Learn:
GROUNDWORK
Choosing a great building site
What are the most important things to look for when choosing a great building site? And what are things to avoid? Learn how to lay out a comprehensive building site that can handle large piles of clay, sand, gravel, rocks, a Straw Bale or Cob building under construction, and most importantly, people, in a safe and efficient way.
Site Development
Learn to use a builders level on a tripod , to understand slope, drainage and how to modify the site, so that water easily flows away from your building.
Foundation
Learn the important factors to building a great foundation for a Straw Bale or Cob building. Every great building starts with a solid foundation, using rocks, gravel and concrete, to give your Natural walls a solid and beautiful base.
Anatomy of a great Natural building
Learn the basics of Straw Bale and Cob building design, working with small spaces and Passive Solar design, how to draw “to scale” and how to create building plans that your building department will be able to understand. Learn the latest in how to permit a Cob building.
DESIGN
straw bale wall building
We’ll use freshly screened local clay, chopped straw and sand to make a clay-straw leveling coat, which will transform the rough Straw Bales into beautiful sculpted earthen walls. Learn how to make and apply this leveling coat in the most efficient way possible, and how to make this recipe using your own clay from your home. We’ll top it off by making and applying a smooth clay finish plaster, applied with a hawk and a trowel, and then sponged and hard troweled.
We’ll also explore white Kaolin clay plasters, clay Alis paints, and pigmented washes and faux finishes.
All three of these earthen plaster recipes will become staples on your natural building journey, whether you use them over Straw Bale, Cob or sheetrock.
Earthen Plaster
Cob
We’ll learn to make Cob, a mixture of clay, sand and straw, used for centuries to build earthen walls.
We’ll be using it in this workshop as a sculptural medium over the Straw Bales and to sculpt a Cob window seat bench inside the roundhouse. We’ll learn how to test and modify the 3 ingredients, to understand the relationship between these simple materials, and learn how to make the best Cob for Cob wall building and to put over our Straw Bales. You’ll learn how to use these two sister techniques in the best way possible.
We’ll also dive deep into the history of Cob construction through the ages, where it stands today and how to permit a Cob building in these modern times. We’ll also be visiting a number of Cob buildings on our natural building tour.
Learn the basics of how to frame an opening for a door or window in a Straw Bale or Cob building, using Box Beam Headers and rough framed openings. Learn how to properly waterproof these openings, using sticky flashing.
You’ll also learn how to make and install wooden sloping window sills and wood trim from scratch, using a table saw and planer.
We’ll be fully installing at least one window during this workshop.
We’ll also be installing a double pane glass block as a sculpted window altar with an interior and exterior stone sill.
Doors and windows
Conical Roof Design
We’ll study the important principles of building a conical roof, from the radial rafters, wooden compression ring and dome lid, to the curved top plates, tension cable, and metal roof. You’ll leave feeling confident in the principles of building a conical roof, and will have a first hand look at all of the important building details.
We’ll study this conical roof carefully, as we install the Straw Bale walls and Cob plaster beneath it.
Photo – Living Intent Yurt Co.
We’ll explore the other roof designs that you can put on top of a Straw Bale or Cob building, including an earthen roof, a reciprocal roof, a turtle shell roof, and a square metal roof. You’ll learn all the important structural components of roof design, including rafters, beams, blocking, fascia, soffits, headers, sheathing, border edges and gutters, and how they all come together for a comprehensive roof design.
Other Roof Designs
Hearth, floors and stoves
Learn all about the radial wood framing design for a Straw Bale roundhouse wood floor. We’ll go through the entire design process, from curved concrete stemwall, curved mud- sill, radial floor joists , posts and beams, blocking, venting, sheathing and finish floor material, right into curved bottom plates and studs.
Learn how to set a flagstone hearth for a wood stove or propane heater, and how to install a chimney.
We’ll also be making a special Bas-relief clay sculpting mix, and will be exploring sculpting shapes, designs and curves on the Straw Bale earthen walls, including some built in altar niches.
You’ll also learn how to use a diamond blade on an angle grinder to cut stone sills out of flagstone and quartzite, and Install them into the Cob as a stone sill for an altar.
Sculpture, Bas-relief, Niches, altars and stone cutting
Carpentry AND utilities
Learn the different ways that carpentry adds structure to our natural buildings, whether through different wall systems used in Straw Bale construction or through different roof systems for Cob buildings. We’ll go into detail about the necessary framing designs for B.O.E.B.S. stud framing and roundhouse carpentry systems.
We’ll also explore how utilities, such as power, water and gas, get into and out of our buildings.
Our Time Together
Other Workshop Events
Yuba River Swimming trip
Join us as we explore a remote swimming hole on the famous South Yuba River. A bagged picnic lunch will be provided.
Natural Building Tour
Join us as we travel around Nevada County and visit some epic natural buildings. We’ll visit a 35’ B.O.E.B.S. Straw Bale roundhouse temple with conical roof, a 42’ Hemp Crete roundhouse with conical roof, a 3000 sf cob and Straw Bale home, as well as other Cob and Straw Bale buildings , such as a Cob sauna, Straw Bale bath house, Cob roundhouse cabin and a Cob and Straw Bale retreat house. This is a private tour for workshop participants and their immediate family only. A bagged picnic lunch will be provided for a picnic at one of the tour spots
3 organic, gourmet meals a day
Let go of the need to cook, and let us take care of you. Dietary restrictions are available upon request.
The site
Enjoy this beautiful and remote site in Nevada County, tucked into a shady pine forest, with gentle camping meadow, on private Yuba River access property. There is a full kitchen house, for our chefs to feed you, and a bathroom with a hot shower for your pleasure.
Basic Workshop Schedule
- 8:00 - Breakfast
- 9:00 - On site - building
- 1:00 - Lunch
- 2:00 - Class
- 3:00 - On site - building
- 6:00 - Dinner
- Evenings free for showers and rest
Your Teacher
Rob Pollacek is a master Cob and Straw Bale builder, having been a professional Natural Builder since 1999. He trained and apprenticed with the Cob Cottage Co. in 2000 and 2001, with founders Ianto Evans, Linda Smiley and Michael Smith.
He specializes in tractor cob, moveable form systems, temple and sauna spaces, timber framed earthen roofs, conical roofs, poured adobe floors, earthen plasters, garden courtyard walls, and teaching comprehensive workshops where the students build a miniature cob house, in the form of a cob sauna, straw bale roundhouse, or cob cabin, learning all the elements of a how to build a natural cottage.
He is well known for his “California Cob” website, which highlights many of his past projects, including his 3000 square foot permitted Cob and Straw Bale house, built between 2004 and 2007.
This house will be on our natural building tour.
He continues to focus on building small sacred spaces and larger Cob and Straw Bale buildings.
After 27 years, He still loves building with mud and straw, and hopes to share his passion for natural building with you.
About the Project
The Project
We’ll be building the Straw Bale and Cob plastered walls for a 20’ diameter roundhouse, used for guest accommodations at the Yuba Retreat. We’ll be using the vertically oriented B.O.E.B.S. system of Straw Bale installation on this project. This cutting edge system allows for quick Straw Bale installation within an easily permittable stick frame, using the 15” narrow dimension of the Straw Bale as the wall thickness. This creates a more cost effective building design with a lower cost per square foot.
The conical roof kit for this project is supplied by Living Intent Yurt Co, our local solid walled yurt company.
We are thrilled to work with Living Intent to merge their conical roof kit with our Straw Bale building design, to create a cost effective roof system for a Straw Bale roundhouse. We hope that it is the first of many such collaborative projects with Living Intent.
Who should come?
- Brand new builders who want to explore Straw Bale for the first time.
- Experienced Straw Bale builders who want to explore a different way of using the bales in the vertical B.O.E.B.S. orientation.
- Experienced Cob builders who want to learn how to incorporate Straw Bales into their Cob buildings.
- Curious natural building enthusiasts who want to explore Cob and Straw Bale and see how they fit together.
- Roundhouse enthusiasts who are intrigued with a new take on this ancient circular craft.
- Temple builders who want to use straw and clay to create sacred space with sculpted niches and altars.
- Clay artists who want to explore large scale clay sculpting.
- Carpenters who want to incorporate Straw Bales into their carpentry craft.
- All ages welcome.
- Families with children welcome.
The Books
We will be referencing the book “Straw Bale building details” by CASBA.
Please arrive with your own copy.
We may also be referencing the book “Hand Sculpted House “ by Evan’s, Smiley and Smith, and the book , “ Essential Cob Construction” by Dente, Smith and Burke. I’ve worked closely with these teachers and highly recommend these books.