Spherical Structures
Do it Yourself - Dome kit website
Cut and build the dome kits yourself and save
or Spherical Building Services will build you a turnkey custom geodesic dome home.
Heading 1This is the website for the do it yourself. All the information you need to cut and build wood or light gauge steel geodesic dome home building kits. Fast, strong and distinctively innovative construction methods with extraordinary engineering and unlimited design options. It's easy to recognize a leader, but hard to copy. Spherical Structures shares over fifty years of dome building and construction history with the tradition of excellence that has built it's reputation on unsurpassed quality and exceptional hand craftsmanship.
Dome Kits owner builder option is intended for those people who want to cut their own Dome Kits and save from purchasing over priced kits from the dome manufactures. All the information is in this website to cut and fabricate the components to build a 3 or 4 frequency geodesic dome structure from wood or light gauge steel.
This information is designed to share some simple and inexpensive dome building methods that we have been using for over thirty-five years. All components are patented, licensed and certified by the Underwriters Laboratories and can be purchased from your local hardware store and construction supply house. You can act as your own general contractor, project manager and design consultant in every phase of construction and build sweat equity in the process.
Dome Kits main goal and inspiration is to build a better way of life with the use of modern materials and innovative designs. Dome Kits continues to design affordable housing for as many people as possible and believes each family deserves the opportunity to participate in home ownership.
Dome Kits specialty is spherical structures for any use, with the ability of being independent, self-sustaining habitats. Dome Kits is a diversified full-service building contractor. Offering the most affordable dome kits for the do-it-yourselfer or for turnkey custom homes . From consultation to design and engineering of your dome kit plans to the manufacturing and prefabrication of your dome kits.
It is our goal to accurately match the needs and design criteria of each individual customer with the dome kits best suited for their project. Dome Kits bases building design details on the needs of the client, rather than molding the needs of the client to fit an available dome kits. Clients are free to choose from a number of spherically designed roof truss profiles. Dome Kits manufacturers single-family homes, condominium units, multi-family homes and commercial structures.
Dome Kits status as an original manufacturer also allows customers to make informed decisions on the best engineered design for their project. Our dome kits are a combination of the highest quality UL certified components available regardless of the application or site loads.
Contact our experts to initiate a detailed discussion about the needs and budget allocated to your project, and learn how Dome Kits corporate strength can be placed solidly behind your project requirements.
Dome Kits advantages
Dome Kits continues to provide the most user friendly dome kits. Creating energy efficient, low cost dome homes has been the driving force to designing and engineering structurally sound dome kits with a novice owner build construction method. One of the unique advantages to geodesic dome truss is the structure is free standing and needs no interior load bearing walls to support the dome roof system. This gives you the option to complete the dome structure to a lockable and water tight stage and finish the interior at your leisure.
There are very few dome home manufactures offering pre-fabricated dome kits . In the last 30 plus years most all dome home companies have changed owners but not their products. There are only 3 or 4 different dome home construction methods. After building all other dome kits 3 or 4 times it was important to Dome Kits to design and engineer a better construction method to lower the cost of not only the dome kits but the cost and safety of the dome home construction method.
The triangulated sphere is superior in design to the box shape structure. This should lead you to believe it would be less expensive to build. Most companies are only interested in selling their dome kits and not the finished building. Dome Kits believes it has designed the construction methods and materials choices to build the superior dome home for LESS than box structures. We hope to share some of the unique advantages and differences Dome Kits has over the rest of the dome homes in the world.
- Lighter and smaller components.
- More accurate connection systems creating identical triangles.
- All dome kits available in wood or light gauge steel.
- Wood dome kits with the compound angles cut
- 10 sided truncated geometry on the ground level
- Pre-framed door and window openings
- Designed for one person to complete all phases.
- Components are light enough to be held in one hand.
- No need for mechanical lifts during construction.
- Architectural options not available from other dome companies.
- Any exterior finishes are possible and available in your dome kit.
- Any insulation can be used and any R-value can be achieved.
- A ventilated exterior panel of plywood and rigid foam is available.
- Any interior finish is possible and available in your building kit.
- The pre-finished T-beam frame creates a finished interior.
- Pre-finished interior drop-in panels, (any color, any material).
- Any roofing and side wall finishes are possible and available.
- Many pre-cut and pre-fabricated building components.
- Pre-cut foundation and floor systems in wood or light gauge steel.
- Pre-fabricated interior wall panels in wood or light gauge steel.
- Pre-manufactured decks, stairs, cupolas and dormers.
Engineering
The two greatest problems facing any structural design engineer is weight and compression from gravitational pull and shear quality against wind loads and earth quacks. The spherical structures and dome shapes will always have the advantage over the square or box shaped structures.
As the spherical dome structures become lighter and stronger with height the rectangular shape becomes weaker. The triangle is the strongest geometric shape and the triangulated sphere the strongest structure. The weakest area on any rectangular or spherical structure is closest to the ground or foundation. With this thought in mind the worst structural engineering idea is to put a rectangular wall at the base of a geodesic structure.
The 3 frequency icosahedrons geodesic structures struts (made of wood) and connections become to weak to safely support the dome larger than 35 feet in diameter. For larger buildings Dome kits recommends using 4 frequency and higher geometric designs. The 4V(frequency) icosahedrons is flat at the hemisphere. With almost twice the amount of triangles and the struts almost half the length the 4V building can safely be built twice the diameter as a 3V building.
The construction industry continues to change as every other technology. New materials and technologies are being used to built the latest projects usually by the lowest bidder. In the big cities inspections are pretty strict and usually have competent inspectors. Out in the more rural areas you may never see an inspector. Especially if your building a geodesic dome structure.
All spherical and box shaped roof trusses are required to have an engineering stamp of approval. You can find engineers to stamp anything and risk losing their license if the structure falls down. It is sad to see that we will never see the end of poorly engineered products in the hands of unknowing consumers for the sake of a fast buck.
Every dome kit manufacture has a web site nowadays. Look at the pictures of their dome kits and see how big their components are and how many people it takes to build it. Not even the experienced construction person wants to handle a 300 pound plywood hexagon 20 feet in the air. How many days can you afford 600$ for the crane and operator.
Putting the dome kits frame up is not the only phase of construction to be concerned about. Fifteen and twenty sided foundations are always fun for even experienced form carpenters. Exterior sheathing and roofing can be a challenge if your triangles are out of alignment which is very common on the bolt together steel hub designed dome kits. Even a quarter or half inch can cause real headaches and a rise in construction cost.
On the 3V geodesic structures the triangles are 7 to 10 feet tall. On a 4V geodesic structure the triangles are 4 to 6 feet tall. The smaller triangles are much easier to handle when doing the out side plywood sheathing or inside drywall.
I don't believe there is any structures prettier and more spectacular inside than the spherical geodesic structure. After 40 years I find building boxes to be very boring. They do have their advantages. They tow down the highway pretty well and you can stack them very close together.
4 V Steel T Bar - geodesic frame
Dome Kits answer to low cost housing. The introduction to geodesic dome building. Light gauge steel T-bar (drywall) ceiling grid geodesic frame. Rigid foam insulation, waterproof stucco exterior and your choice of finished interiors. Ideal for a garage, barn, storage shed or small home. The material cost starts at under $1200. These are the smallest do-it-yourself geodesic structures that Dome Kits offers. These geodesic structures were designed to range under 30' in diameter or 900 square feet of floor space.
The Drywall T-bar ceiling grid can be purchased at the local drywall and light gauge steel stud contractors supply house. It comes in boxes of 4' cross T's and 12' main T's. This is also your source for 1-1/2" x 1-1/2" wall angle for the bottom foundation D struts, rigid foam insulation, exterior synthetic stucco, screws and tools. Once you know the diameter of the geodesic structure you wish to building and have calculated your strut lengths you can optimize the materials that will work best for your dome structure. These geodesic structures were designed by Dome Kits to range under 30' in diameter or 900 square feet using these products. There are 250 struts in the 4 frequency geodesic structure which 20 of these will be 1-1/2" angle for the foundation row.
An extra pair of hands is always nice to have. Drywall carpenters work with light gauge steel studs all the time and will always have adjustable C-clamps. When using your self drilling screws you must have the steel clamped tightly together. These C-clamps come in 4" and 6" sizes and with and without feet. Any locking pliers will work. A pair of tin snips (metal cutting scissors) is needed to cut the light gauge T-bar steel. A cordless drill with a magnetic Philips head screw tip works well for this project, but any drill motor with a screw tip will work.
These are #10 X 5/8" Pancake head self-drilling screws. The self-Tapping (drilling ) screws are needed to screw threw the connector washer and t-bar steel strut. Other self-tapping screws can be used and this structure can be built without these connectors . The reducer washers are not something you find in the average hardware store. You will need to find a contractors Electrical Supply house during week days.
In the Dome Kits connection system the T-bar struts will come together in the center of the 3" to 1/2" reducer washer. Center your reducer washer at the apex of the strut points. The sides will need to over lap each other so you can connect the two T-bar struts and the connector together with a screw. You will have to cut the corner off at lest one side of the T-bar strut to get the ends to meet in the center.
All your T-bar struts will be cut square or flat on the ends to proper length. During the construction you will cut the 30 degree angle off one side of the corner to create a tight fit and meet in the center of your connection. You will find one screw in the center of your strut will hold securely since all the struts are holding each other in alignment. This is your completed connection on the inside of the geodesic structure.
For the outside connection you can use a larger reducer washer than you used on the inside. A 4" to 3" works well to center itself over the 18 degree angle that peaks in the center. The screws must penetrate the center of your T-bar and it can be difficult to clamp this connection for this process. Let the self tapping screw do the work and don't apply a lot of pressure. You will find that spinning the self-tapping screws at high speeds may burn up the cutting tip.
Dome Kits prefers using the 4V (frequency) Icosahedrons geometry to create geodesic structures. Unlike the 3V used by most dome manufactures the 4V has a horizontal flat line (great circle) at the hemisphere. This makes your foundation connection easier using the geodesic triangles. Once your structure is complete you can remove the area you have decided for your doors and windows.
The 4 frequency (V) uses smaller triangles than the 3V dome structures. This makes a stronger geodesic structure and also makes the components smaller, easier and safer to handle by one person during construction. Looking up at the center of the hemisphere you see the pentagon point of the five sided Icosahedrons pyramid.
We need some way of checking our 18 degree connections and strut angle during construction. My method for this is to use one of the 4' T's and cut the back side 2' from the ends so it will bend to a total of 18 degrees. Take one of the inside reducer washers and screw it in place over the cut out area on your T to hold it from moving. Once you have screwed your washer in place double check your new template to see if it is holding at 18 degrees.
Now during construction, once you have screwed the inside strut and connector in place you can clamp your new 18 degree jig to the inside of your struts face to face to hold it in place while you screw your outside reducer washer in place. Once your outside reducer washer is connected your strut should hold itself at your 18 degree angle. It never hurts to have another pair of eye's double checking the construction diagram. This is the fun part of the puzzle. This connection system is very forgiving and the light weight materials make this spherical geodesic structure a great project to start your geodesic dome building adventures.
You will be starting from the bottom on your frame work with the D lettered struts. These bottom 20 struts will be of different material than the rest of the frame. 1 1/2" X 1 1/2" framing angle. Locate the center of your circle and place a stack or nail to hold your tape to measure the radius and location of the D struts. These structures do not require to be built on a level surface and can be built on any surface. As you complete each row of triangles you will notice that the structure will begin to level itself and take shape. The bottom D struts will become flat and straight.
In Dome Kits framing diagram you will notice all the A struts make up the Pentagons. The Icosahedrons geodesic structure uses the same major triangle to create the total geodesic frame. Start from the center of the pentagon where all five A struts meet and follow it down from the A-B-B-A struts to the next corner and pentagon of the major triangle. Now if you travel horizontal across the A-B-B-A struts you will meet the third corner of the major triangle. Bellow this major triangle you have the same triangle turned upside down. You have five major triangles at the top of your Icosahedrons geodesic frame (the icosa cap). Around the middle of your spherical structure you have ten major triangles facing each other. And to complete the Spherical ball shaped structure you would have five major triangles (the Icosa cap) at the bottom facing down. In the major triangles there is what is called the Frequency ( the total number of struts from the pentagon center to pentagon center). Dome Kits uses the 4V (frequency) Icosahedrons A-B-B-A.
This diagram is to represent a 4' x 8' piece of foam or any other sheet material you wish to use. There are five triangles in the Dome Kits 4V geometry. In Dome Kits T-bar geodesic frame we have optimized the 4' T-bar strut to build the 24' geodesic structure.
The diagram is showing one of the ways to optimize your sheet goods. You have five triangle combinations; A-A-C, C-C-C, B-C-D, D-D-E, E-E-E. You can save some time and materials by cutting the triangles to align the equilateral sides. The B-C-D triangle can be turned over (reversed) to optimize fabrication. You can glue the two end pieces together to create another triangle.
The cord lengths are calculated by multiplying the formula X the diameter you wish to build.
Example for the 24' diameter Dome Kits 4V dome.
A - 1.52 (30 struts) _____1.52 X 24' = 36.48 -- 36"-1/2"
B - 1.79 (30 struts) _____1.79 X 24' = 42.96 -- 43"
C - 1.76 (90 struts) _____1.76 X 24' = 42.24 -- 42"-1/4"
D - 1.88 (70 struts) _____1.88 X 24' = 45.12 -- 45"
E - 1.94 (30 struts) _____1.94 X 24' = 46.56 -- 46"-1/2"
Your measurements are calculated in decimals. If you round them off to the nearest 1/4" you should be fine. The 24' diameter was chosen because the longest strut is the E strut with a final length of 46-1/2". Using cross T's with a length of 47-1/4" we could not go much longer. The 30' diameter is ideally optimizes 10' strut material and 4' sheet materials. The 39' diameter optimizes 12' long strut materials. Light gauge steel has always been the superior building material over wood. The Spherical Designs Organization offers many prefabricated light gauge steel spherical structures designed to work with rigid foam insulation for the owner-builder and general building contractor.
3 V wood - geodesic frame
Dome Kits no connector connection. I don't believe there is anything prettier made of wood than the spherical geodesic structure connected with the compound angles cut on the ends. This connection method shows all the geometric angles and done correctly is truly a piece of art. The steel hub connects sold by other dome kit manufactures cost over $50 each. The same time is taken to cut the proper compound angles as to cut and drill bolt holes for steel hub connectors at a savings of $5000.
All the wood geodesic dome kits manufactured by Dome Kits are cut with a radial arm saw. All the different angles are cut within one-tenth of one degree. You can not be this accurate with a 60 degree skill saw or modified miter saw. A bolt together steel hub system may move in and out fifteen degrees or more. If your geodesic structure gets to far out of round at the lower levels it can become difficult and even impossible to complete.
This web page is created to share some generic connection systems for a 2"x 2" wood 3 Frequency geodesic Green house or Gazebo under 16' in diameter. One of the advantages of using the 2"x 2" lumber is the ability to cut the 54 and 60 degree angles with any type saw. All these compound angles were cut with a circular saw. If your connections are not as perfect as the pre-cut kits from Dome Kits your exterior plywood may not fit as accurately.
The pentagon connection angle cut is 54 degrees and 12 degrees. The hexagon angle cut is 60 degrees and 12 degrees. You will be cutting these angles off each side of the strut and both ends. REMEMBER! The A lettered strut is one directional. The one end is the pentagon and the other is a hexagon. Dome Kits will mark the A struts with an arrow (A>) so we know what end is the 54 degree pentagon and which end will be a 60 degree hexagon cut.
If you don't like the way your connection looks or fits together this connector can be a nice compliment to the rigidity of your connection and structure. This is the Simpson Stronge-tie Gazebo connector #GT6Z. Listed under Home Project connectors in the SIMPSON catalog. This are designed for 6-sided (hexagon) roof trusses. A case of 8 connectors cost under $50. These can be used on any size dome kit made of wood or light gauge steel.
This is possible Dome Kits easiest wood connection system. You will cut 12 degrees on the ends of all your wood struts which can be done with a hand saw. Your cord lengths (struts) will be measured on the same side and longest side. When all six 1" 1/2" struts come together corner to corner you will have a 3" hole in the center of your node point.
The lower levels of your geodesic dome structure carry all the weight of the structure. This adds a great deal of pressure pushing downward and outward on your connections. One off the best ways to enhance the structural integrity of your connection and geodesic structure is to add a piece of 3" plastic pipe or coupling for the ends to rest on. This also helps you during construction to keep your strut ends the same distance from the center
The simplest and least expensive connector for this geodesic structure comes from the Electrical Contractors supply house . These are called Reducer Washers. For the inside connection Dome Kits prefers the 3" outside diameter 1/2" inside diameter center hole. The self-Tapping (drilling ) screws are needed to screw threw the heavy steel connector. Also the self-drilling screws keep from splitting the small lumber.
For the outside connector Domekits uses a larger Reducer Washer, 4" outside dia. with a 3" center hole. The larger reducer washer is needed on the outside connection of the structure to allow for the 24 degree angles at the ends of the struts. The 3" center hole allows the reducer washer to lie flatter on the outside surface. One of the added advantages is the extra strength but they are also flexible enough to be adjusted with a hammer or pliers so they don't interfere with your exterior sheeting.
These reducer washers can be used in many combinations on the inside or out. You may feel you need the structural strength or in the case of the connection in the picture you may want to hide the poor workmanship you did trying to cut the compound angles. During construction Dome Kits has found that they are a real benefit keeping your struts in alignment. All hardware stores offer Simpson Strong -Tie galvanized engineered connectors, hangers, strapping and smaller electrical reducer washers.
Your outside sheathing is the most important structural part to any structure not just geodesic structures. If you don't plan on gluing, screwing or nailing any plastic or other rigid material please use some type of steel strapping or connector on the lower connections. Once you have your spherical geodesic structure completed you can create the openings for your doors and windows. The reducer washer work very well for these connections.
In Dome Kits framing diagram you will notice all the A struts make up the Pentagons. The Icosahedrons geodesic structure uses the same major triangle to create the total geodesic frame. Starting from the top of the sphere where all five A struts meet and follow it down from the A-B-A struts to the next pentagon corner of the major triangle. Now if you travel horizontal across the A-B-A struts you will meet the third pentagon corner of the major triangle. Bellow this major triangle you have the same triangle turned upside down. You have five major triangles at the top of your Icosahedrons geodesic frame (the icosa cap). Around the middle of your spherical structure you have ten major triangles facing each other. And to complete the spherical ball shaped structure you would have five major triangles (the Icosa cap) at the bottom facing up. In the major triangles there is what is called the Frequency ( the total number of struts from the pentagon center to pentagon center). This is Dome kits 3V (frequency) Icosahedrons A-B-A.
In Dome Kits 3V geodesic structure there will be 6 pentagon connections and all the others will be hexagon connections. There will be 2 different triangles in the Domekits 3V geodesic frame.
This diagram is to represent a 36"x 72" piece of plastic (Lexan) storm window or any other sheet material you wish to use. In our 3V geodesic frame we have optimized the strut length to create 36" tall triangles to build the 16' geodesic structure.
This diagram is to represent a 36"x 72" piece of plastic (Lexan) storm window or any other sheet material you wish to use. In our 3V geodesic frame we have optimized the strut length to create 36" tall triangles to build the 16' geodesic structure.
The diagram is showing one of the ways to optimize your sheet goods. You have two triangle combinations; A-A-B, B-C-C. You can save some time and materials by cutting the triangles to align the equilateral sides.
The cord lengths are calculated by multiplying the formula X the diameter you wish to build.
Example for Dome Kits 16' diameter 3V geodesic structure.
3/8 5/8
A - .17425 (30 struts) (30 struts) _____.17425 X 16' = 2.788 -- 33"-1/2"
B - .20175 (45 struts) (55 struts) _____.20175 X 16' = 3.228 -- 38"-3/4"
C - .20625 (50 struts) (80 struts) _____.20625 X 16' = 3.299 -- 39"-1/2"
Your measurements are calculated in decimals. Using our A-strut length of 2.788 the 2 stands for 2' and if we multiply the numbers after the decimal point .788 by 12" we will get 9.456. The 9 is 9" and to create our final fraction of an inch we can multiply .456 x 8 (8th of an inch) = 3.648. I would round this off to 4/8 or 1/2". If you round them off to the nearest 1/4" you should be fine. The 16' diameter was chosen because the longest strut is the C strut with a final length of 39"-1/2". Using precut treated handrail balusters with a length of 42" we could not go much longer. This also created our largest triangle with the total height under 36".
Dome Kits has been building spherical light gauge steel structures for over 30 years and changed the design and engineering of geodesic dome kits to more user friendly construction methods. Light gauge steel has always been the superior building product over wood. With the continual rise in wood prices and poorer quality the use of light gauge steel has become feasible for use in the residential housing market. Dome kits are designed and engineered using light gauge steel and rigid foam insulation. Superior products and design this is the Dome Kits standard.
Cold formed steel members are used for studs, joists, rafters and headers. It is zinc coated (galvanized) to prevent corrosion. Steel framing provides excellent design flexibility due to the inherent strength of steel. Light gauge steel has been used for many years in commercial structures and recently has become more common in residential construction. Many shapes are available, but the primary shapes are the C-shape stud and the U-shaped track. Framing members are generally produced in thickness of 12 to 25 gauges with 3-1/2" to 12" widths
Cold formed steel members are used for studs, joists, rafters and headers. It is zinc coated (galvanized) to prevent corrosion. Steel framing provides excellent design flexibility due to the inherent strength of steel. Light gauge steel has been used for many years in commercial structures and recently has become more common in residential construction. Many shapes are available, but the primary shapes are the C-shape stud and the U-shaped track. Framing members are generally produced in thickness of 12 to 25 gauges with 3-1/2" to 12" widths
# GT6Z is the ID number for the Gazebo Connectors. Listed under Home Project connectors in the SIMPSON catalog. These are designed for 6-sided (hexagon) roof trusses. A case of 8 connectors cost under $50. Simpson makes many different straps. # MSTA24Z is what is used here. The number 24 stands for the length in inches and for dome building 18" to 24" works well.
All Dome Kits spherical geodesic structures are designed to be built by one person. To screw two pieces of steel together they need to be clamped together. Locking adjustable C-clamps are a must when building with steel. They come in two sizes 6" and 4" with or without round feet on the ends. These are your extra hands and for safety you need them. Cordless drills work well for steel framing because they spin slow and don't burn up the screw tip.
The 6" stud gives you the minimum insulation space for the nation building code standard of R-19 using fiberglass bat materials. Most commercial structures built in steel studs use 3 1/2" rigid foam on the exterior to achieve R-19 or better, so the use of 3 5/8" steel stud walls are acceptable. You have cut all your struts to length with something close to 9 degrees on the ends and measuring from the long sides to get your proper cord length (strut length).
Screw your steel strapping to your Simpson Gazebo connector. 2 screws in each strap in the center of your connector. I suggest you put the screws in from the outside of your connector so the tips don't get in the way of your plywood later. You can bend your 9 degree angle on all six ends of the connector and strap. The steel stud slides in between the connector and the strap.
The stud will stop at the recess in the connector and also this is were your screws connected the connector and strap. All your struts should stop close to the same place all around the connector for each strut. The strap will be on the inside of the steel stud and the connector on the outside of the stud. No straps are needed on the connectors for the inside of the hub
There are 6 pentagons you need connectors for and more than 75 hexagons. With the use of your clamps and a hammer you can make adjustments to your gazebo connector and use them for your pentagon connector. All the weight of the dome structure is pushing out on the bottom levels. This is the importance of the strapping. If you wish to not use the straps on the 3rd, 4th and 5th rows that is fine. There is less outward force on the connectors the higher you go up the structure.
Diagonal bracing is required on all structures. On box shaped structures you must have a diagonal brace every 12 feet of wall and from every corner. This is the national building code. This is why we see plywood used a great deal on the outside of wood structures and especially two-story structures. Were the building codes are enforced with inspections, the nailing is inspected on the plywood shear panels and roof sheathing. Spherical geodesic structures are all diagonals so they don't need the shear panels or diagonal braces. The plywood is most important to the structural integrity of the geodesic structure.
The connection from one triangle to the next relies on end nailing or screwing. OSB or particle board should NEVER be used for exterior sheathing on a geodesic structure. The edges have no structural strength and it is very susceptible to moisture damage. Multi-ply wood sheathing is the only acceptable standard for geodesic structures. The bottom two rows should be sheathed first. This is the weakest area on the geodesic structure and any other shaped structure. The lower two rows are usually easy to reach and from there sheathing from the top down is easiest on dome structures. Nails are required every 6" on the outside edges of your plywood. Screws are required every 8". Screws have more holding power than nails and screws are coated and do not rust.
Dome Kits no connector connection. We don't believe there is anything prettier made of wood than the spherical geodesic structure connected with the compound angles cut on the ends. This connection method shows all the geometric angles and done correctly is truly a piece of art.
There are different types of geodesic geometry and different frequencies. They all have the basic concept to finding the angles at the node points (connection of the struts). From the center of the sphere (ball) a line is projected through the outside surface. This gives you the radial and axial angles. Where these intersections take place depends on the geodesic geometry and the frequency of the intersections.
This is definitely the most labor intensive and difficult connection system to cut with all the proper angles. Most all geodesic dome kit manufactures will not attempt this connection method and instead try to sell you a $5000 steel connectors. Dome Kits uses the 4 frequency Icosahedrons geodesic geometry. This only adds to the complexity of the manufacturing process but simplifies the construction method.
The geodesic geometry Dome Kits uses has been changed from the original 4 frequency Icosahedrons geometry and any other geodesic dome manufactures use. The changes were made to simplify the manufacturing and construction methods. There are 5 different cord lengths and different angles on each end of the 5 struts.
There are a few inherent advantages to this connection system over the steel bolt together hub connectors. You are not drilling big holes down the center of your wood strut. With the compound angles cut to properly fit under compression, as the wood swells and contracts it does not move or change the connection angle as the steel bolted hubs. 3" wood screws have great holding power without undermining the integrity of your wood strut.
This web page is created to share a generic connection for an all wood connection system. There are three saws I have used over the past 30 years that can cut a 60 degree angle and a 9 degree angle at the same time. The radial arm saw, a modified miter saw with the stops removed and drilled out and Sears sells a 60 degree worm drive skill saw. This is a special order item and cost near $300. This is a must if your a dome building contractor.
All the wood geodesic dome kits manufactured by Dome Kits are cut with a radial arm saw. All the different angles are cut within one-tenth of one degree. You can not be this accurate with a skill saw. A bolt together steel hub system may move in and out fifteen degrees or more. If your geodesic structure gets to far out of round at the lower levels it can become difficult and even impossible to complete.
All these compound angles were cut with my 60 degree Sears worm-drive circular hand saw. You don't need a tape measure or level to put together your geodesic frame together. If your connections are not as perfect as the pre-cut kits from Dome Kits your exterior plywood may not fit as accurately. This also holds true with the drywall on the inside of your geodesic structure.
In the hemisphere of the 4V geodesic structure there will be 6 pentagon connections and all the others will be hexagon connections. There will be 5 deferent triangles if you use the construction method that Dome Kits uses. If your connections come together accurately you can cut 4 to 5 pieces of plywood at a time. This is one of the advantages of using the 4V Icosahedrons. Your plywood and drywall can be mass produced and easier to handle by one person
The pentagon connection angles are 72 degrees and 9 degrees. The hexagon angles are 60 degrees and 9 degrees. You will be cutting 54 degrees off each side of the pentagon strut. REMEMBER! The A lettered strut is one directional. The one end is the pentagon and the other is a hexagon. I mark my A struts with an arrow (A>) so I know what end is the 54 degree pentagon and the other will be a 60 degree hexagon cut.
The pentagon connection angles are 72 degrees and 9 degrees. The hexagon angles are 60 degrees and 9 degrees. You will be cutting 54 degrees off each side of the pentagon strut. REMEMBER! The A lettered strut is one directional. The one end is the pentagon and the other is a hexagon. I mark my A struts with an arrow (A>) so I know what end is the 54 degree pentagon and the other will be a 60 degree hexagon cut.
The pentagon connection angles are 72 degrees and 9 degrees. The hexagon angles are 60 degrees and 9 degrees. You will be cutting 54 degrees off each side of the pentagon strut. REMEMBER! The A lettered strut is one directional. The one end is the pentagon and the other is a hexagon. I mark my A struts with an arrow (A>) so I know what end is the 54 degree pentagon and the other will be a 60 degree hexagon cut.
On the geodesic structures you are relying on end nailing or perimeter nailing. OSB and particleboard have poor shear quality and should NEVER be used on geodesic dome structures. Multi layer plywood is your best choice for a lasting structurally strong geodesic wood structure. If you are building a structure to live in you will want to use 2X6 material. This will give you the minimum insulation R-value of R-19 using fiberglass bat material. The roof area of geodesic structures are not vented. Dome Kits recommends you use spray on foam or rigid foam insulation. This gives you a moisture barrier and triple the R-value.
With a close look you will see that Dome Kits uses a different geodesic geometry to simplify the manufacturing and construction methods. The original 4V history uses 6 cord factors with the letters B and C very close to the same. On spherical geodesic structures over 50 feet in diameter this difference can begin to be a concern in more accurate connection systems. To make construction of 4V geodesic dome kits more user friendly. Dome Kits has combined the B and C cords and lettered them C's. We have renamed the F cords as B's.
Looking at the top down on the 4V hemisphere we can see the five major triangles that make the Icosahydron cap. The A struts connecting at the centers of the pentagons. Following the A-B-B-A struts you can find the corners and (pentagon centers) of the major triangles.
There are four struts that run from corner to corner of the major triangle. This is why it is called a 4 frequency geodesic structure. There are twenty major triangles to create the complete 4V icosahedrons sphere. Five on each of the ends and ten facing each other around the middle or center.
The side view showing the great circles are represented by the letters D. One of the construction advantages of the 4 frequency icosahedrons is the horizontal great circle at the hemisphere which greatly simplifies the connection to the foundation and eliminates the need for rectangular riser walls. This diagram shows one row under the hemisphere that may be used for extra interior height in smaller spherical geodesic structures.
The cord lengths are calculated by multiplying the formula X the diameter you wish to build.
Example for 24' diameter dome
A - 1.52 (30 struts) _____1.52 X 24' = 36.48 -- 36"-1/2"
B - 1.79 (30 struts) _____1.79 X 24' = 42.96 -- 43"
C - 1.76 (90 struts) _____1.76 X 24' = 42.24 -- 42"-1/4"
D - 1.88 (70 struts) _____1.88 X 24' = 45.12 -- 45"
E - 1.95 (30 struts) _____1.95 X 24' = 46.8 -- 46"-3/4"
Your measurements are calculated in decimals. If you round them off to the nearest 1/4" you should be fine. The 24' diameter was chosen because the longest strut is the E strut with a final length of 46-3/4". Using cross Tee's with a length of 47-1/4" we could not go much longer. The 30' diameter is ideal for 10' strut material and 4' sheet materials. The 39' diameter optimizes 12' long strut materials. Lumber prices have caught up with the light gauge steel prices. Light gauge steel offers many ecological and structural advantages over wood structures. Dome Kits may be the only dome kit manufacture to offer this advanced building material in a spherical geodesic structure
On spherical geodesic structures under 35' in diameter the use of a riser wall can be used to gain extra interior ceiling hight for the second floor. As shown in this diagram there are five E-E-E triangles and five C-C-C triangles around the lower level that are horizontal and lend themselves for simple framing of vertical wall sections 4' to 6' wide for conventional windows and doors. This shows another of the advantages the 4V Icosahedrons has over the 3V. You may not desire to use all 10 locations for windows or doors but at least you have the option. In using the TRIANGULATED riser wall you will be keeping the shear quality and structural integrity of the spherical geodesic structure. You may remove some of your C and D struts in your window and door areas. These can be used at higher levels if you don't complete the frame before adding your openings. Try to keep your D struts at the hemisphere horizontally flat and level to ensure you have no problems finishing your geodesic structure. All geodesic structures are sensitive to being out of round and this can cause difficulty during construction. This geodesic geometry is not the same as others but has been built over one hundred times successfully by owner builders.