Fortress Update

Davy (the mason) and his son Alfredo arrived early this morning, and immediately plowed into the work of laying more block. It is a pleasure to watch this quiet, competent man work – there are no theatrics, no drama; just a wall that slowly and steadily appears. As the wall gets higher and higher, the amount of work to lay each block gets larger and larger. When I took the photo at right (early this morning), Davy's head is about 12 feet off the ground. Each block must be lifted up to him (that's what Alfredo does), and buckets full of mortar must be raised the same way. Also, Davy's motions are now constrained to the size of the scaffold – which is just a couple 2 x 12s supported on steel ends.

But other than taking more effort (per block), the work is the same as it has been the past few days. The only thing that I spotted that was different today is visible in the photo at right, where it appears that the distant wall has a block missing. That's where one of the building's two vents will be located; there will be another one directly opposite it. If you look carefully, you can see that Davy – a bit of a perfectionist – used two half-blocks in order to locate the vent in the exact center of the wall. I wouldn't have cared if he was five feet off in either direction!

By the time they'd finished for the day, as they did shortly after I took the photo above, one entire wall was at full 10' height, along with one other corner (the one that Davy is working on). Tomorrow, Davy believes, they will finish all the block work. After that, the form for the roof goes up – and after that, the two layers of rebar for the reinforced concrete roof.

The form should be interesting to watch; I've never seen anything even remotely like this constructed. As best I understand it, the form inside the building will consist of a large number of 4 x 4 posts, on approximately 18" centers, supporting sheets of 3/4" plywood that will comprise the form for the bottom of the interior. The roof will project 8" outside the walls, forming short eaves. The form will be made from 2 x 8s for the bottom and 2 x 12s for the sides, with this assembly held up by more 4 x 4 posts. I haven't yet deciphered how they're planning to keep the pressure of the concrete from forcing the form away from the walls.

The plans call for two layers of rebar inside the roof. Both layers are constructed from #5 (5/8" diameter) rebar – that's big, heavy, “industrial strength” rebar! The top layer will be made of rebar on 16" centers (forming 16" squares); the bottom layer on 8" centers. That's a lot of rebar – about 1,600 feet if I did the math right.

I did learn something new today, talking with Davy: once we pour the roof, the form must stay in place for 15 to 22 days. This is much longer than the three days we waited after pouring the slab before starting to lay the block. Apparently it is critical for the concrete in the roof to completely cure before it first takes the loads and stresses of holding up the roof by itself. I'm not too surprised at this: reinforced concrete weighs roughly 160 pounds per cubic feet, and this roof will be 290 cubic feet – that works out to just over 23 tons of concrete! I want that to be well-cured before we remove those forms – and I don't want to be underneath it when we do!