Introduction: Geodesic Dome Greenhouse - Part 7 - Filling the Foundation Hole
This extra-length segment shows all the various layers that are buried in the foundation hole. There is tubing for the thermal mass and draining piping going into the sump tank. The next video will show the dome structure going up!
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I had too much video to cram into 5 or 6 minutes so you get a double-feature today!
We’ll start with the sump tank that’s located in the center of the dome area. Plastic tanks can’t be buried directly in dirt since they expand and contract with temperature change and the weight of the dirt will eventually crush them. I surrounded the entire tank with scrap 2 by 4’s and built a brick wall around it. When the well was completed, the goal was to simply lift the tank out, remove the boards and set the tank back in the well, resulting in a space between the tank and the well wall.
I didn’t realize that the tank was slightly tapered so the bottom was larger than the top - the tank was trapped inside the well! If you watch carefully, you can see the entire well lift slightly with the tank. Some extra pondering was required…
I decided to slide each board out one at a time until enough were removed to loosen the tank. I drilled part-way through the board, inserted a bolt, wrapped a strap around it, and lifted the board until it hit against the rim of the tank. Then cut the section of board off and repeated the process until the board came out. This was a few hours wasted, but it worked!
There is a larger sump tank that is located in the shed area that also needed a well built around it. This is a cone bottom tank so I tightly strapped some 2 by 4’s as legs to it to keep it level, then set the rest of the spacer boards around it. After leveling out the area, I set some cement blocks on the ground to act as a footing for the brick work. When it was complete, a perfectly round well was surrounding the tank and we were able to pull the tank out with the excavator.
This is the baby brother excavator compared to the one that dug the foundation hole. With a slightly smaller bucket, it was able to place the dirt back into the bottom half of the hole. Bruce, the operator, was very careful and didn’t hit a single block off the wall! When the area was roughly level, he tamped the dirt into place to help prevent future settling.
While Bruce graded around the exterior of the foundation, I set the tubing for the thermal mass. There are 5 equal length perforated pipes that connect to a central manifold which will eventually be connected to a heating system. The tubing zigzags around the floor to help spread the heat evenly throughout the dome. The exhaust for each tube then vents to a different area in the dome.
Six inches of stone was placed around the tubing. This is partly to protect the tubing from larger rocks, and partly to allow some more air flow for heat distribution into the thermal mass floor.
Earlier in the project, I didn’t have time to set the anchor bolts in the foundation wall. To make sure they were placed in the correct locations, I first cut all the treated lumber sill plates to their correct lengths and labeled them. I then drilled a hole for the anchor bolt into each plate, roughly in the center of a one of the block cavities.
The entire cavity didn’t need to be filled with concrete so I filled them half way with stone first. It was a nice day so I got a helper. Her job was to vibrate the air pockets out of the concrete as I shoveled it into the cavity. I then leveled off the area and set the j-bolt into the concrete, and then set the sill plate over the area to make sure the bolt was in the correct location.
This is what happens when you don’t wear boots in a construction area!
There will be an outer ring of grow beds around the perimeter of the dome, and also a central ring. This 2 inch drain pipe will allow the beds to drain into the central sump tank. The piping is temporarily set on bricks to make sure they are sloped in the right direction.
More dirt is filled between the pipe areas and sand is filled around the pipes. This helps to protect them from stone and allows them to be fine-tuned for the proper slope.
Now that all the drain pipes are installed, the sump tank can be dropped into the well. Holes are cut through the side of the tank and the pipes are pushed through the holes. I plan on installing an elbow at the end of each drain to try and swirl the water a bit.
The large sump tank is a bit trickier to install since the cone shape needs to be properly supported. I made a quick template that was equal to the angle of the cone. Sand was then added to the bottom of the well and I used the template as a guide to shape the sand into the same angle as the cone. The tank dropped into place perfectly!
The dome will sit on a 16 inch knee wall. Although each section should match perfectly with the dome, they will be left loose until the dome is assembled so they can be adjusted. Each section is placed on a strip of foam to help prevent air from leaking between the concrete wall and the boards. They are then loosely bolted into place.
That’s it for now. Thanks for watching and don’t forget to join our Facebook page at the link below.
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