What is a Geodesic Dome?
A geodesic dome is a hemispherical form in which triangular or polygonal surfaces formed by planes or frame elements are in large-scale tension and distribute the stresses on the structure. It was developed in the 20th century by American engineer and architect R. Buckminster Fuller to quickly form a sturdy and lightweight construction that can be placed directly on the ground.
Why geodesic domes?
- First of all, everyone agrees that they are eye-catching structures. Since they appeared in the 20th century and did not exist in history, they still have stylish images that are considered futuristic.
- They allow construction without foundation and can be installed quickly compared to traditional structures.
- This building architecture offers the most extensive internal volume compared to the surface area. They can cross wide spans with less material and without columns.
- They offer the most robust construction with the lightest materials. Due to the dome shape, the weight distribution on the structure is even and stable.
- They can be disassembled or transported as a whole. Considering the weight/durability ratios, it is one of the lightest architectural structures.
- Wind resistance is at the lowest level due to its aerodynamic shape.
- Since the domes are 360-degree structures, they have a high capacity of using natural light and dissipating heat. Heat control is more comfortable than other architectural structures. It requires low energy.
Some facts about geodesic domes:
- The dome of the Pantheon in Rome, with a span of 44 meters, weighs 400kg / m2.
- While a modern concrete dome is 200kg / m2 on average, the Geodesic Dome in Montreal has passed the span of 76 meters with 53kg / m2.
- With today’s technology, we can build a dome with a weight of 10kg / m2 or less.
- Honolulu Kaiser Auditorium constructed in 1957 in Hawaii. The construction of the 50-meter Geodesic Dome completed in 22 hours with 38 workers. Just 1 hour later, 2000 people gathered in the venue to listen to the Hawaiian Symphony orchestra.
- The biggest of all geodesic domes, at 216m, is in Fukuoka, Japan.
Geodesic Dome Usage Areas:
Today Geodesic domes are used for many different purposes. You can see this architecture as a climbing tower in the playground for children, or an auditorium hosting thousands of people. It is the most preferred architectural form among the ecological buildings for accommodation and frequently built as greenhouses and planetariums. Other construction purposes are to provide social spaces such as meeting tents, sports activities, shows, exhibitions, and glamping, storage, pop-up stores, aquaponic and hydroponic systems. Geodesic domes are also widely used as a shelter for pets, barns for livestock, and poultry houses.
Materials used in building Geodesic Dome Structures
The two most used material types for the frames are steel and wood.
Steel frames (Simple design)
In steel frames, steel pipes cut in various lengths according to the frame type and are bent at the angles required by the dome’s desired frequency and joined with bolts and nuts. The advantage of this frame system is that the joints do not require special connectors. It is easy to build a geodesic dome relatively lightweight. The disadvantage is that there is no other option than covering with a PVC or canvas membrane to provide a waterproof feature efficiently. PVC and canvas covers would also be flexible, less durable against all weather conditions.
Complicated steel frame systems and custom designs
Using both custom steel box profiles, flat panels, and individual metal connectors are common in geodesic dome designs, especially to cross large openings in some engineering projects. The advantage is that these dome structures are extra robust and easy to cover with various materials such as glass, metal, wood, polycarbonate panels. They require professional engineering, a costly construction process, and expertise, which is not an excellent option for relatively small geodesic domes that amateurs are looking to build.
There are two standard techniques used when working with wooden geodesic dome frames. The wooden struts are connected with metal connectors to form a dome form, or the ideal angle triangular panels made of wooden planks are combined to create a dome form without the need for an extra connector.
Wooden frames with metal connectors
The disadvantage of this technique is that it requires investment in both metal connectors and woodworking. Depending on the material of the hubs or connectors, there is also an extra weight loading. Industry standards of wood often conflict with the rigidity of metal connectors. For this reason, with an additional craft, wooden struts must be brought to a new standard.
Wooden panel frames
In this technique, while creating triangular panels at ideal angles, besides detailed calculations and quality materials, excellent craftsmanship is required, taking into account the natural stretch properties of wood. Moreover, since there are no metal hubs in the joints, weakening occurs at the connections because of the 5-6 screws used on average. The possibilities of being disassembled and reassembled are limited, and the construction also takes more time and effort.
Cover and coating materials in geodesic domes:
PVC and Canvas membranes
PVC and canvas fabrics are frequently used on domes with light steel frames and sometimes on wooden frames. As an alternative to the high cost of blackout fabrics that provide more top comfort and have less sun permeability, mostly semi-transparent and light PVC membranes are used as dome covers. Each material has different heat permeability and resistance to weather conditions, especially UV rays. In dome tent covers, some part or all of the cover can be transparent light efficiency.
Transparent polycarbonate sheets are used, especially in geodesic domes built for greenhouses and planetariums. Although it is the ideal choice for creating light, it is not easy to limit the sun’s rays when needed.
OSB and Plywood
Mostly on wooden framed domes, OSB boards and plywood are frequently used as the first cover. After the frames covered with the panels, it is also possible to cover with shingles, paint, insulation material, thin concrete plaster, and even adobe.
You can rarely see metal covered domes. They are primarily used in geodesic dome structures to be used in extreme weather conditions or built for military purposes. The most preferred metal sheets are generally lightweight aluminum panels.
Geodesic domes can be covered with a wide variety of materials, depending on their purpose of use. While it is possible to stretch flexible fabrics into the triangles of a dome that does not need waterproofing and is made for Canopy purposes only, fastening natural tree branches on the frame is also a creative solution. You can either cover some triangles pf a geodesic dome with wood panels, some with glass or polycarbonate and plaster the bottom row with concrete or strengthen the same dome covering with poultry wire and plaster with adobe. If you do a brief search on the internet, you can see that there are many different materials used.
Remember that good design and experience are paramount. The photos never reflect the experience. Many details, such as yawning materials, moisture-retaining designs, weak connectors, incorrect product choices, and poor construction, can take your experience with geodesic domes to a different point.