Foundational Fundamentals: (Part 3) The Pour and Flatwork Finish

We poured and finished the concrete floor.

This phase of the project, more than others leading up to it, make the house seem all the more real to me. There is no turning back now.

For the concrete slab floor, which will be my interior floor, I had insisted upon a glassy finish. The tradesmen did a solid and fine job at pouring and smoothing the concrete. However, the great Cherry Tree in my backyard, for which I dedicated an earlier post, had other ideas about my glassy finish, mocking me yet again. More on that momentarily...

This five minute video is a series of nine shorter videos that capture the stages of the concrete slab pour and finish.



The concrete slab pour and the delicate steel-troweled flat finish all happen in one quick day. The concrete team doesn't work on rainy days because the concrete won't cure properly. If it's not raining, they work.

And if it's windy, they work. As it so happened, this day was a windy day. On windy days, trees in full bloom, tend to lose grip upon their flowers.  And "The Cherry tree" as I wrote in my post, "is in full bloom".

During the final sweeps and steel troweled finish of the concrete, it was snowing cherry flowers all over the wet concrete slab. The concrete guys would diligently sweep and pick the flowers off the wet concrete floor, but the flowers kept falling.

Eventually, in the arced sweep of their steel trowels, they pressed the remaining flowers under a thin layer of concrete. And, when the wind died down, and the concrete finish was done, it appeared as though the cherry leaves had been forever buried by concrete, forgotten to all but those who had seen the leaves swept under the final finish. That night, as the concrete set, the flatwork finish looked picture perfect.

24 hours later, the concrete has dried and the smooth finish has revealed its disposition. Scattered Cherry leaves have emerged through the top layer of concrete, leaving cherry tree flower fossils densely speckled throughout the glassy smooth finish. My best guess is that the concrete dried and shrank downward just enough to allow the thin veneer of Cherry flower leaves to emerge through the drying concrete.

Instead of a steel troweled smooth finish, this laughing tree has left a permanent etching of its character. Despite our crafty effort, the natural world has left another unforeseeable biotic stamp in its wake.

My eyes and feet will be left with an unforgettable memory of this day in the foundation.

The fossilized imprints of Cherry flowers in otherwise perfect concrete flatwork

Foundational Fundamentals (Part 2): Rigid Foam, Spray Foam and Pex Tubing

The foundation work that we did today was about preventing heat loss through the floor, and providing a secure structural foundation for the ADU framing, which will begin next week.

We finished filling in the structure with gravel, and tamped it down. The gravel was leveled with a laser level. Then, the concrete was covered with a vapor barrier, which will serve to prevent moisture from rising and wicking through the concrete slab. Concrete wicks moisture upwards through a process called capillary action.

Next, the 3" of XPS rigid foam was cut out and laid evenly on top of the gravel. 1" of foam was adhered along the top of the foundation walls. This foam will help prevent heat loss from the heated slab to the uninsulated foundation walls. Any significant gaps in between the pieces of rigid foam were filled in with spray foam.

Rebar was laid out in a criss-cross fashion on top of the rigid foam to provide structural support for the concrete slab. Then, cross-linked polyethylene tubing, aka, PEX tubing was laid out and tied to the rebar with tie fasteners. The PEX tubing was laid out in two circuits that originate where the water heater will be installed.

The front porch was filled in with gravel, except around the edges. This will not be a heated portion of the concrete slab. Rebar was laid on top of the gravel for structural support. The edges of that concrete slab will be filled in with concrete, which will be more than a foot thick. This thickness will ensure that the slab is structurally supported and will help prevent settling and cracking

Lastly, the sewer line and water main from the main house were connected together and covered with soil. A sewer clean out was also installed near the foundation wall.

This video is six minutes long and covers these construction elements. Next, we're pouring the concrete slab!

Foundational Fundamentals: Gravel, Rigid Foam, the Water Main, and the Sewer Line

Today, we started to build up the foundation floor. Now that the foundation walls are complete, we've poured gravel, and tamped it down. We've also added rigid foam insulation along the inside of the foundation walls and will add more on top of the gravel to prevent 'thermal bridging'. Basically, this means that we're trying to prevent heat loss through the walls and floors. We're also connecting the sewer line and the water main.

This early building stage is fascinating because, moving forward, these elements will all be invisible. These infrastructural elements exist in most homes, but if you're like me, you're totally unaware of them. And, if you're aware that they're there, you probably have no idea where they are and how they connect together.

Here's a video of the gravel and the rigid foam installation.



Connecting the Sewer line to the ADU



Installing the water main