Introduction: Building a Geodesic Dome Greenhouse - Part 5
In my latest video, I cover how the footings and drains are installed for the foundation of the dome. The good stuff is right around the corner!!!
Here's the transcript for the video:
This video is about setting up the footings for the dome. Footings and a frost wall are required here for a structure this size. Each bend along the foundation is a calculated measurement along three known points and triangulated out to each bend. The length of each board for the forms is also calculated.
Each plank for the forms is cut to a fairly accurate length so they will fit together properly. They are nailed together to temporarily hold everything in place. The stakes with the red flags are the exact corners for each bend of the finished wall. The wall will be 8 inches thick and the footings are 18 inches wide so the outer edge of the footing needs to be roughly 5 inches from each stake.
We ran into a little problem after some rain which flooded the foundation hole, so we brought back the excavator to dig a trench from the center of the dome out past the foundation so it could drain. When it was complete, we were left with a muddy mess that was nearly impossible to walk in.
Once the ground dried out a little bit I was able to install a proper drain. First all the silt had to be removed from the trench so that it wouldn’t clog the stone when it was placed in there. Three-quarter inch washed stone was placed in the base of the trench and compacted into the remaining mud so it would create a solid base. There isn’t much elevation to work with so the drain will be set nearly level and will essentially work by hydraulic pressure. 4 inch perforated pipe is then placed and leveled. The rest of the trench is then back filled with more stone. When it was complete the foundation hole was able to drain properly. It even survived the heavy rains from hurricane Irene!
Now we can get back to setting up the forms! In order to keep the footings from separating when they were filled with concrete, reinforced strapping was wrapped around each section. Each joint in the forms on any of the outside corners also had 2 pieces of strap nailed into them to prevent them from splitting apart from the force.
Using this laser level, I was able to set the forms perfectly level. Not shown, stakes were set around all the forms and they were lifted level and screwed into the stakes. Once the forms were level, any gaps under them were filled with dirt or stone so the concrete wouldn’t bleed through.
We’re finally ready for some concrete! I was able to recruit a "volunteer" to help spread and level the concrete. It took nearly 2 hours in the sweltering sun to get all the concrete poured. Once the concrete starts to set a bit, a keyway is added along the top.
That’s all for now. Up next is the foundation wall. Thanks for watching!