I've made some excellent progress in the last month on the dome! The entire concrete block wall was built and I'm now moving on to some of the heating and plumbing that will be buried under the floor. I'm still hoping to have most of it built before the snow flies!
In this video, I will show the details about building the foundation frost wall.
There were over 500 concrete blocks, 1200 bricks, and one and a half tons of ready-mix mortar delivered. Luckily, it was brought in on a truck with a boom so they were able to place everything within the foundation hole. Watch carefully as he places this pallet of mortar. The entire back side of the truck lifts off the ground!
None of the corners in the building are 90 degrees. Most of the angles in the dome section are around 24 degrees. By dumb-luck, I found if I broke off one tab on each block, they would butt together to make a perfect angle! Roughly 1 out of 4 blocks had to be modified for these corners.
All the blocks were dry-fit into place before adding mortar. After each corner was placed, the middle blocks were added and spaced properly. If there wasn’t enough room, I would break off the tabs to shorten each block a bit.
I used 80 pound bags of ready-mixed mortar. There is enough material to set around 15 to 18 blocks. In total, there were 35 bags mixed by hand. In hind-sight, maybe investing in a mortar mixer would have been a good idea.
It didn’t take very long to realize how important it is to get the right mortar mix. If it’s too loose, it squeezes out from the blocks, and if it’s too firm, it’s hard to level them properly.
This is the first time I have ever laid concrete blocks. Once I got the first hundred blocks set, I started to get a good feel for laying them efficiently. Laying down a good line of mortar is important for setting the block properly. Each block is aligned along the row and checked to make sure it was plumb and level. On average, I was able to set 10 blocks an hour, which includes mixing mortar, cutting, and setting.
After the mortar starts to set a little, I would go back and clean up all the joints. It probably wasn’t necessary since the entire wall will be buried, but while it is still open, it sure makes it look nice!
When the wall was complete, 512 – 28 pound blocks were set. Total dry weight including the mortar was roughly 17,000 pounds, all moved by hand. It’s probably time for some new gloves.
After all the water problems in the foundation hole earlier this year, I decided it would be a good investment to install a perimeter footing drain. The 4 inch corrugated pipe worked well getting around all the angles and was connected into the existing drain that was installed before the footings were poured. For proper drainage the entire footing area was filled with three-quarter inch washed stone.
The inside floor area is going to be backfilled and used as a thermal mass to help regulate the greenhouse temperature. The entire perimeter of the foundation is covered in 2 inch R-10 Styrofoam board which will help to maintain some of the heat during the winter.
That’s all for now. Next time we will be working on the thermal mass, some plumbing, and maybe some of the frame for the dome! Thanks for watching!