Saturday, August 15, 2009

Slab floor Phase Two






Prepping the third slab went even more quickly than the first two, because we had learned a few tricks: electrical conduit is more easily run in the footings than under the floor; keeping the insulated copper water pipes deeper makes leveling the sand easier; and the 4" form board around the perimeter was installed with tap cons and "L" blocks. All of the work of floor prep: gravel bed, vapor barrier, insulation, sand, steel, and radiant tubing took Khyber, Danny, and Terra one day.
For the floor mix we tried a different system than on the first two slabs. This time we used Bob Noble's volumetric mixer, set up with 3/4" rock in one bin and a blend of 90% sand and 10% screened Calaveras red clay in the other bin. Volumetric mixers are different from transit mixers in that the gravel, sand, and cement are proportioned and blended with water in an auger on the back of the truck. This type of equipment allows for a wider variation in the formulation. In this case, it allowed us to add our dry red clay into the formula without going through the slurry step that we used for the first floors. We also increased the percentage of clay in the mix to add more color to the floor. The extra clay may have the disadvantage of increasing shrinkage cracking. To control the shrinkage, Khyber used a diamond saw and cut score lines in the finished slab. We've covered it with black plastic to slow the cure, and will leave the plastic in place until after the walls are built.
The photos in this post show the steel, radiant tubing, and perimeter form board in place; pouring and screeding; floating; finishing; and cutting the score lines.
With the master bedroom footings and floor complete, we're now returning to the kitchen. We've organized a larger workforce for the kitchen walls than we used in the baby's room, so that, barring equipment breakdowns we'll be able to install all of the rammed earth in one day.

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