Prep for pouring slab

We (or rather they) got the steel reinforcing grid laid out, wired together, and up on ‘chairs’ in preparation for pouring concrete. The inspector came and passed the rough plumbing. We got all the air ducts covered. You can see these in the photos as the wood (strandboard) strips down the middle and along the sides, with concrete blocks in between. The blocks look dark because it rained last night.The floor register cans were built too long, so are back in the shop to be cut down, but we got the return air ducts installed and all the holes are cut for the floor registers.

We also found a source for the siliconate concrete hardener to use on the garage floor. It combines with the residual lime in the cement to seal and harden the surface, and is applied after the concrete is set but before it has completely hydrated (typically 28 days).

The shower pan is recessed below the main floor slab, so rests on 10” (rather than 12”) concrete blocks. We also need to form a curb around the shower, so the wall sills cannot get wet and rot. The photo shows this, plus the holes cut into the foundation forms to join the shower pan with the foundation. The left air duct is covered, but the right duct was not covered so the plumbing could be inspected. And we had not installed the reinforcing steel. I spent most of the day on my knees. First I was cutting out the holes for the sheet-metal-bound floor registers into the ducts.

Second, I was installing thermometers that will be cast into the slab. These thermometers are DS18B20 tiny computers that are strung onto a ‘1-wire’ bus. Each has a distinct address and computes the temperature on command. I will record the temperature every hour at (at least) ten places around the house, including under the insulation, outside in the garden dirt, five places in the floor slab, and probably in the air ducts and under the roof.

The thermometers themselves are embedded in stainless steel, but the wires might be damaged while pouring concrete, so I carefully taped each wire to the underside of the reinforcing steel. I also labeled each wire with its computer address and location plus recording the location and address on paper. A 8Gb SD memory card will hold 99 years worth of temperature recordings taken every hour!

We spent the entire Thursday finishing little details before the slab and foundation is poured tomorrow at 7am. Here are some of the things we did:

• Fastened treated lumber to the forms that will be used to fasten the exterior door sills.
• Fill a few not-so-little gaps between the blocks where concrete could enter the air ducts.

• Install 14 floor register cans (white boxes in photo to right - click on the photo to open it larger and turn it right side up - Google can't do this). Turns out they are just a bit bigger than the holes I cut yesterday, so the holes had to be enlarged.Cut and insert styrofoam blocks into the floor register cans so they won’t collapse under the pressure of wet concrete or allow concrete to enter the air ducts. The tops are right at the finished slab height, so we can screed (scrape) the concrete over the top of them.
• Add rebar to connect the foundations to the (future) garage entry apron and north patio floors.

What nerds won’t do in their old age.

>>> Next <<<