The flatwork guy (Gough Concrete) poured the lower-level slab on Thursday and saw-cut the control joints on Friday. I stopped by on Saturday to take a look. We used a 2% mix of Solomon liquid color, which they call “smoke.” It’s just right. The tint is significantly darker than natural concrete, but still comes across as gray, not black. This color in this concentration costs $39 per cubic yard of concrete. Given that the mud itself only costs $110 per yard, that’s pretty significant. However, given that for this I get a finished floor, I consider the tinted concrete a bargain. This floor cost $5.40 per square foot for everything (#4 rebar, pump truck, concrete, tinting, placing the concrete, finishing the concrete, coating with an acrylic sealer, and saw cuts). This did not include the 15 mil vapor barrier and the under-slab insulation, which my plumbing and heating guy did.
The slab ended up being 6 inches thick instead of 5 inches (meaning the gravel was a bit low), which cost an extra $270 for another 2.5 yards of concrete. The control joints are basically on the same grid as the rooms, stairwell, and passageways, although I split the larger rooms in half so that the joints are not more than about 10 feet apart. (Control joints are created by sawing a 3/4 inch deep groove in the concrete. This gives some visual definition to the space and encourages the concrete to crack on the lines instead of diagonally across the room. (That sort of works…but avoiding cracks altogether is a fool’s errand.)
There’s a fair bit of dirt and footprints on the slab in the photo, as there had been some rain overnight and the dust from the sawing made a bit of a mess. The framers rolled out floor protection before beginning a couple of days later, and I’ll tidy that up next week when the lower level is framed.
The protrusions in the photo are (a) the hydronic heating tubes, which were embedded in the floor, (b) a couple of in-floor electrical outlets, and (c) the waste lines for for the bathrooms and bar sink.