Saturday, September 12, 2009

Third and final ramming

The master bedroom was the final piece of the wall tryptic that anchors the house. The walls for this building were sixteen inches taller than the first two modules, plus the room was eighteen inches longer to accommodate the big closets and the fireplace, both built within the walls. (We''ll discuss the whole process of niches and spaces "carved" out of walls in an upcoming post.)
We allowed three days for the ramming and bond beam and used a crew of seven: Edward on the mix machine, Khyber on the delivery conveyor with Terra helping to check lift depth, and Taj, Gabe, Abe, and Rigo on rammers. It took roughly 120 man-hours for the placement of sixty yards of rammed earth plus six yards of bond beam.
One of the time consuming elements in constructing a system like this is prepping for the changes in wall top elevations and the locators for roof framing. Terra and I calculated that we spent twenty man-hours installing shut-offs, top of wall ledgers, and block-outs for beam pockets. This all took place the morning of the third day, after most of the rammed earth had been installed but before the bond beam was poured.
The living room side of the wall also has the Rumford fireplace plus the pizza oven/wood-fired water heating system for the floor slab. Basically, everything that gets embedded in a rammed earth wall, whether it's an electrical box, closet, beam pocket, or fireplace, takes extra time and extra care to make sure it is square, plumb, and precise.
It was a great three days and we celebrated with a chocolate cake at lunch. All of the equipment, including the rotating delivery conveyor, worked flawlessly. We designed and built a new chute for the outfall end that gave Khyber more accurate control over placement. Edward added 2% more water to the mix which combined with slightly smaller lift depths (seven to eight inches rather than eight to ten) gave us tighter compaction. Smaller lifts did decrease production rates, but not significantly. We'll see whether the decreased lift depth translated to improved quality when we strip the forms on Monday.
The photos in this post illustrate the formwork, delivery, ramming, plus one special shot of the homeowners, looking like they built the walls single handedly.