STEP 2: Foundation Ring

For my foundation I have chosen to work on a level spot and build the foundation up from there. Off course you can also dig into the ground and make your footer level with your ground. I opted for placing my footer on top of my leveled earth and will need to provide for some step to step into the dome later. The dimensions I worked with are as follows:

radius: 20'

radius + concrete thickness = 20' + 12" = 21'

footer ring boards are made out of 1/2" plywood boards with a 12" height

the center 19' circle is filled up with 6 yards of washed sand to create a 6" surface from the top of the footer ring boards.

Important: in order to make the boards for the footer perfectly level, you need to start with a reference stake in the center that is at exactly 12" and keep making sure that the boards are level and on 12". We actually used a laser for this and it was wonderful and fast way to work. My original idea was to use a long flat board of about 12' to lay on top of the center stake and the footer boards and use a level on top of the board to do the measurement. Luckily I never had to test that idea, but I think it should work if you can't get a hold of a laser.

Center is chosen and I have drawn a circle from the center of the dome to the outer edge of the foundation, which is 10' (radius) plus 6'' for the thickness of the concrete that I have chosen at the bottom of the dome. The dome will be sprayed later with the concrete mixture on average 4" thick, but the bottom will always be thicker than the top because it takes the most amount of weight, so I allowed in my foundation for 6" of concrete. Just outside this line is where the form boards made out of plywood will be placed, which are 1/2" thick and then the stakes are behind the boards to hold them up. The 90 degree green angle that I have drawn in the circle represents the area for the bathroom.

I bought 3 half inch plywood shop grade and had Home Depot cut them into 4 pieces of 12" by 8 ft. As it turn out you loose some of the board by cutting it so only 3 out of 4 boards where the exact measurement that I needed for the footer ring. And 8.5 of those boards was enough to make the circumference of the footer ring. In order to 'pre-bend' them - so they would not break when we were bending them into the work area of the footer ring, I placed them on my saw horses with some weights on them and watered them regularly.

saw horses, a skill saw and a screw driver are needed for this phase, as well as a hammer to hammer in the stakes. The screws needed for both attaching the boards to the stakes and the boards to each other need to be longer than just the thickness of the two materials, to give the connection extra strenght.

stakes are set at 2' distance. Nail them in deep enough so they are solid, however they need to be sticking out enough to support the boards. I worked with 18" stakes, and it was just about right, however if your soil is less hard than mine, you might need to go deeper. These stakes come in all sizes up from this, so pick the one best for you by buying one and testing it out on your surface. I was also advised to make my own stakes with 2 x 4 beams and that would have been a lot cheaper, however with my hard and rocky soil there was no way to get them in there deep enough to grab onto the boards and hold them properly.

boards are connected and then drilled into the stakes that have special holes for this purpose. Be aware while placing the stakes that the holes face forward towards the boards for easy connection ;)

the boards need to be connected with lots of screws, I think we used about 12 per connection, that are a bit longer than the 2 boards that are being connected for optimum strenght- you have to realize that a lot of pressure will be pushing against these boards once the concrete is being poured into the ring.

the ring is complete and level - we had the grace of working with a laser to make sure all was level - I am not sure of other methods - but this was awesome and fast.