The dome combines the advantage of a circle and a octagon. The dome/octagon hybrid has a 185 sq. ft of living area. It measures 15'4" from one end to the other and 9'8" tall with a 2' knee wall on the sides. It is constructed out of 2" or 4" thick rigid Styrofoam and parged (covered in thin layer) with either an acrylic modified surface bonding cement or grancrete with fibers added. Creating a very strong, well insulated and very affordable shelter.

Goals of my design:


Extremely Affordable


Extremely Strong


Very Efficient


Built with minimal tools and power


Built with minimal experience


Built very quickly


Built using commerically avaible materials


Hackable and Adaptive


Unique and fun

The basic shape of a sphere is known to be the strongest shape . It deflects environmental pressures evenly throughout the shape. It's a self supporting shape which makes it easy to assemble. A minimal variety of materials can be used to build from.

The octagon part of the hybrid of it was adapted to conform to the preference of square items that people have and to allow the use of standard dimension sheet goods to be used. The windows, the tables, the couches, the Styrofoam. If we used a perfect sphere non of these items would fit with out being made custom which takes additional time and money.

By using the octagon dome hybrid vs. a geodesic dome you gain predictability and symmetry ( also maybe a bit less wasted materials). Each of the 8 sides is exactly the same you know that a door section can fit on any surface. The windows will fit facing any direction. I would also wager a guess that on a small structure like this giving the compromises a geodesic dome would have to make to phsyicate a door and windows that it should be stronger. The 2' knee wall extends the amount of useable "standing" interior space. Leaving the outer edges of the interior for shelfs, futons, or other things that want to be out of the way.

Erecting the open dome:

Building the dome would be very easy and could be done with minimal tools,supplies and skill. A standard saw or common drywall saw that can puncture the foam easily would be required to cut the sheet goods into the usable dimensions. The design has been optimized for standard 4x8 or 2x8 sheets to keep cost down and it's easy to find. After cutting all 56 Styrofoam pieces a good quality water resistant or waterproof tape would be used to adhere the edges together creating a seamless dome. I'm speculating b/c I have not built it yet that starting from the bottom the 8 2' knee wall pieces would be taped together. After this each section going up horizontal would be added until the dome is completely assembled.

At this stage the dome could be stayed in for a bit if nessicery however covering with a tarp or parging before the sun degrades the Styrofoam. The door frame made out of Styrofoam would be traced onto dome face and the outline cut into dome. The frame then installed. Windows then would be cut out where needed.

Window options:

1. Car windows with a length or width less the 2' would be prefered however i bet you could be creative

2. Single glass panes windows , used both inside and out to create a double paned window

3. Wine glass could be used to bring interesting light patterns into the living area

4. Glass bowls like punch bowls could be especially useful as the main skylight

Trace and cut out the windows (make sure to give yourself a good inch to the inside of hole) or make the puncture holes for the wine bottles. If you want strong mount points such as a hanging bed or plant hangers now would also be a good time to run bolts through shell. Ways to adhere the glass to the shell would variety as shapes would dictate. Using tape should meet most shapes and sizes. A fast acting construction adhesive might also do the trick.

Covering the insulated shell

We now have our dome basically how we want it to look. It's time to use either surface bonding cement with an acrylic modifier (the modifier will resist cracking and damaged caused by the sun) or grancrete which is a fairly new magnesium based cement like material which doesn't have the same UV problems as Portland cement but as of now harder to find locally.

Tools required:

1. a trowel ( using rubber gloves, would be possible in order to save or give different texture)

2. a mixing container

3. a hoe of sorts (could be mixed other ways )

Working your way from the bottom to the top making sure to coat the corners good as this is where the stress load ends up. I believe an 1/4" thickness would be possible however most likely a bit thicker would be better. If you only had money enough for an 1/8th this step could be done in stages. Now you can either leave it grey or stain it.

Platform for dome:

The dome could be erected on a multitude of foundations or platforms.

1. A simple rubble trench below the foam that would be below frost line . A plastic 6 mil vapor barrier would go on the floor of the ground and covered by a rug. This would prove the most affordable and would give you a very nice floor. This method was used in Mike Olehers $500 dollar underground house and is the most easy and cost effective of the options.

2. A wooden deck upon concrete piers. This would be the best in environments where flat or easy level able ground would be an issue but would cost more.

3. A poured concrete slab that could be coupled with a simple radiant floor heat to provide a very nice floor. This would not have to very thick as the weight of the dome is not very much.

4. A rammed earth or poured earth floor. This would be better in dryer conditions

5. Any other creative floor that a person could come up with. Be creative...try shit out!

Making the door:

The best way to install a door will come when I build the dome. The door could be made either using the same materials as the dome or could be fashioned out of salvaged or purchased wood.

Finishing the inside: The inside could simply be painted after filling in the gaps with caulk to provide a pleasant immediate interior wall or could be parged with surface bonding cement or grancrete to make a stronger interior coating. There is also paints that have a very hard shell that would easier to apply esp on the inside where you have a ceiling above .Before finishing with concrete or grancrete, use scraps from the Styrofoam panels to create some shelf using the same techniques of taping or Lacquer thinner ( which bonds Styrofoam together ) then finish with concrete/grancrete.

Thoughts

I hope that someone might find this very useful and impowering. The plan has been to building a working protype. Until that is built I have posted the model renderings. I am saving up the money to build and will have enough shortly. However being that my time is devided between fatherhood,steady playing drums in band, preping to build a passive solar earth bermed home this spring (2008).
At least I know have the money :) After building the prototype alot of details will fall into place. If there is anyone intrested in the open octa-dome ( I should give it a shorter name ) I love to hear from you. I believe I have come up with with something pretty cool and hope others find it so also.

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