It is slow going, but the stack is getting taller. Because the blocks are so large, it will get more difficult soon, because it will involve going up and down ladders. A few more courses, and the hole will need to be cut into the cover.
From what I finished today, it is now just about at the level of my head. The first picture shows the first ‘tier’, which means one course of large blocks with one course of medium blocks. They will be stacked in this order to the top, a total of 10 ‘tiers’. The medium blocks leave a space on either side which needs filling with something, in this case insulating fire brick because they are far easier to cut and shape than the hard bricks.
Here is the stack 3 tiers high, and already more than 6 feet high. 10 tiers should bring the height to just under 5 meters. I use a piece of plastic strap to keep the highest large block row tensioned while I add the row on top. This keeps the blocks from shifting while I position the top row.
Anyway, it’s not the prettiest stack, but is kind of fun when you think about how all those blocks interlock. So far at least it seems very stable. As soon as the roof hole is cut, I will put on the angle iron frame, so stacking should get easier.