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How to Build a Ceiling Dome |
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Building the Frame The first task was to build a rigid frame for the dome. The commercial domes are made from injection molded polymer that's lightweight and strong. This results in a rigid dome without a lot of weight to support. In my case I knew I was going to have to use plaster for a finish coat so I'd need a frame strong enough to support the dome as well as provide enough rigidity to prevent the dome from cracking. I finally settled on 3/4in plywood as it is plenty rigid for the size I needed and I had some scraps in the garage. I knew that weight was going to be an issue so I tried to keep the weight down from the start. As you can see below, the base of the frame is cut from a solid piece of plywood but the wagon-wheel approach helped minimize overall weight. 
The curved fingers were cut from a cardboard template which was used to determine the overall shape of the dome. Notice that the fingers stick out from the base. This helped minimize the material for the base as well as made the top of the dome smaller than the opening which would make it easier to install. The next step was to form the surface of the dome with something that I could build on. While I planned to use plaster for the exterior coat of the dome I figured it would be too heavy to make entirely from plaster. I was hoping to use cans of foam insulation to build a rigid base so that I'd only need a thin coat of plaster. This meant that I needed a base for the foam. This was easily solved using wire mesh. Since you can't easily take a flat piece of wire mesh and form it into a dome, I cut triangular sections and attached them to the fingers of the base as shown below: 
I then used smaller triangles of mesh to fill the gaps between the main pieces and 'sewed' them together using wire. This resulted in a reasonable overall dome shape. Based on the results I could see that there was quite a bit of variance between the high and low spots but I figured the foam would deal with this fairly easily without adding any significant weight. Thinking ahead a bit, I knew that to shape the foam (and later the plaster) I'd need some type of tool that I could rotate around the interior of the dome. This would have to be pretty rigid as any imperfections in the finish of the dome would be very obvious given there would be five lights haning below it. To make the tool easier to build I constructed a flat and level drywall frame around the dome which would provide a solid working surface for the construction phase: 
If you look closely, you can see that the drywall is in two sections so I can split them apart when the dome is complete. This pretty much completed the framing stage. It was now time to see if insulating foam was up to the task. NEXT > | ||||
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