For a low-profile dome spanning 60 ft., you will need really good reinforcement at the base/foundation to prevent the walls from splaying. You should get an engineer to review and approve your design before construction. I'll try to upload a jpg depicting a low-profile dome based on geodesic geometry that allows the ratio of dome height to base diameter to be used as a design variable. I've had trouble in the past uploading images to this site, so cross your fingers.
- Gerry in Quebec, Canada
Sorry, but the website will not let me upload the jpg image. Contact me at icosacloud AT sympatico DOT ca" if you wish.
You may wish to consider stringing a wire rope properly fastened with wire clamps and turnbuckles for adjustment, around the base of the perimeter to keep the dome from spreading. It is likely the most in-expensive and require the least material as a solution to the problem. That said you may not have any breaks in the rope as it has to be continuous all the way round. So you won't be able to have a door going through it. If you have vertical walls and the dome only comprises the roof, then you could run the rope above the door. You will likely need an engineer's plans to ensure that you have the needed tensile strength in the wire rope. The rope will have to fasten at all points in a circle, again requiring an engineer's consideration. In Quebec, my home province, snow load will be a very serious consideration.
- Pieter (P.Eng. ON)