When it comes to building your Trillium Dome or Zome, one of the most crucial decisions you'll face is choosing the right foundation. What foundation does a dome or a zome need? The size, purpose, and location of your dome will determine what kind of foundation will give you the best results. Whether you’re setting up a dome or zome greenhouse, living space, or something in between, this guide will walk you through everything you need to know about foundation options, so you can make the best choice for your project.
A gravel pad is generally sufficient for smaller a dome or zome greenhouse 400 sq ft or less - From our 23' / 7m Dome Plans - Built by Trillium Domes in Washington
In this guide, we’ll cover the different types of foundations, their benefits, and how to choose the best one for your dome. With years of experience in geodesic dome construction, I’ve seen what works in various climates and conditions. This guide is packed with practical advice to help you avoid costly mistakes and get your build off on the right foot.
Let’s dive in!
Why Is Choosing the Right Foundation So Important?
The foundation is literally what your dome or zome is built on, so it’s essential to get it right. A strong, stable foundation ensures your dome will stand the test of time, regardless of weather conditions or structural stresses. The type of foundation you choose also impacts how well your dome can handle insulation, moisture, and heating, especially for domes used as living spaces.
For example, a poorly chosen foundation can lead to long-term structural issues, drainage problems, or even difficulty securing the dome to the ground. Different climates and purposes require different foundation approaches, so this is an important early decision in your dome-building process.
In general your foundation does two things - It keeps your structure from sinking and it keeps your structure from floating away. With that in mind, let’s explore the most common foundation options and what makes them suitable for different dome applications.
What are the Best Foundation Types for Your Dome or Zome Build?
1. Gravel Foundation: Simple and Effective for Greenhouses
This Zome greenhouse sits on a gravel pad with a flagstone patio on top. It is anchored down with earth anchors made for sheds. From our 16' / 5m Zome Plans - Built by Trillium Domes in Washington
For greenhouse domes, a gravel foundation is an affordable, straightforward option. It's ideal for smaller, lightweight structures that don’t need heavy-duty foundations. A packed gravel foundation is great for drainage, and when combined with earth anchors, it keeps your dome stable even in inclement weather.
Price Range: Gravel foundations are budget-friendly, typically ranging from $0.25 to $1 per square foot, depending on the size, type of gravel used, and depth.
Best for: Greenhouses or smaller domes used for gardening and light structures.
How to Build:
Dig a 1-foot-wide, 4–6-inch-deep trench around the circumference of your dome.
Fill the trench with gravel and tamp it down.
Place a pressure-treated dome base on top for solid support and drainage.
For a more robust option, consider a full gravel pad. This expands the gravel beyond the perimeter, creating a stone patio or base for a wood deck inside the dome. This allows for insulation or even radiant heat underneath—a perfect setup if you're planning a more comfortable, usable space year-round. You can even use the measurements in our build plans to create a wood form and fill that with packed gravel!
Our Trillium Dome and Zome Build Plans include detailed instructions on how to create these types of foundations, ensuring a smooth build from the ground up.
2. Wood-Framed Deck: Versatile and Ideal for Insulated Domes
From our Deck Plans - Every Dome and Zome plan comes with one!
A wood-framed deck is an excellent choice for insulated domes, such as those used as cabins, saunas, or Airbnbs. Wood decks can be easily built on concrete piers, foundation blocks, or helical piles, giving your dome a stable platform that's well insulated and suitable for people-centric spaces.
Price Range: Expect to pay around $10 to $20 per square foot for a wood-framed deck, including piers and insulation.
Best for: Insulated living spaces, saunas, and multi-use domes that need a stable, insulated foundation.
How to Build:
Set concrete piers or foundation blocks, then frame out your deck on top with the cut list provided in the plans
Insulate beneath the deck to keep your dome cozy.
Our build plans include the specs for creating a wood deck that can integrate utilities, making it easy to run plumbing or electrical wiring.
Wood decks also give you the flexibility to add additional features, like a surrounding deck for outdoor seating, or integrating utilities like heating and water systems.
3. Concrete Pad or Stem Wall: Strong and Permanent
A pony wall sitting on a concrete pad with radiant heat installed - in general it's better for the pad to be formed exactly to the dimensions of your structure. This is easily done with our plans. 20' / 6m dome at SeaTsu Sauna in Washington.
A concrete pad or stem wall is a more permanent solution, ideal for larger domes or zomes that will serve as workshops, living spaces, or workspaces. Concrete provides a strong base that can distribute the structure’s weight evenly, making it an excellent choice for heavier or larger domes. However, it can be intimidating for a DIYer and isn’t as easy to modify once poured.
Price Range: Concrete foundations can range from $8 to $15 per square foot, depending on thickness and whether you include insulation or radiant heat.
Best for: Long-term structures like workshops, studios, or homes that need a permanent foundation.
How to Build: Use the measurements in the plans to form a flat concrete pad, or use forms to create a stem wall around the base. You can embed plumbing for radiant heat or add insulation to improve energy efficiency.
Concrete can be tricky for DIY builders, but the payoff is a solid, weather-resistant foundation that can be used for living spaces or high-traffic areas. Our Trillium Dome and Zome Build Plans offer guidance for working with concrete, including how to incorporate utilities and insulation. You can always hire a concrete company to pour your foundation from our plans as well.
4. Insulated Concrete Foundation (ICF): Energy-Efficient and Durable
For those looking for a high-performance, energy-efficient foundation, an Insulated Concrete Foundation (ICF) system may be the way to go. ICF blocks provide excellent insulation while maintaining the strength and durability of concrete. These blocks are stacked and filled with concrete, creating a strong foundation with superior insulation.
Best for: Living spaces where thermal insulation and energy efficiency are priorities.
How to Build: Install ICF blocks to the plan specifications, then fill them with concrete to create a well-insulated, strong foundation.
While more expensive and complex to install than other options, ICF foundations provide long-term energy savings, especially in colder climates. They are perfect for homes or insulated domes that will be heated regularly.
The Next Steps Toward Starting Your Dome or Zome Foundation!
Choosing the right foundation for your Trillium Dome or Zome can seem overwhelming, but with the right information, it's easier to make an informed decision that fits your budget, climate, and project needs. Whether you’re building a simple greenhouse with a gravel foundation or a full-time living space with a concrete pad, there’s a foundation that’s perfect for your dome.
Now that you know the key differences between gravel, wood-framed, and concrete foundations, you can confidently start your build. Be sure to check out our Trillium Dome and Zome Build Plans for more detailed instructions and specs, as well as pricing and availability for materials.
And remember, if you need any help along the way or have additional questions, leave a comment below or reach out to us for more personalized guidance!