Sunday, February 20, 2011


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So I got to thinking. In the turnaround part of our driveway, a nice circular slab would be a great place to set up the telescope. And what better time than while I'm pouring concrete for the retainer wall? So Gun Girl and I staked out the center and I played with the diameter dimensions. The inside white line seemed too small, so I used the outer white line, which made a 24' diameter slab. The orange outer line was the excavation line. I dug down enough so that the slab ended up level with the ground. And the orange lines coming from the center were for the conduit trench. Gotta have power for the scope.

After the dig, I ripped up some plywood into 4"-wide strips, calculated the length needed for a 24'-diameter circle (75'-4 3/4"), and connected them together into one long piece. When I was bending it into shape, it broke a couple of times, so I soaked the plywood with water and came back to it next day. Notice in this pic the hole in the middle. Where the power will come up in the center I'll make a concrete table. The hole is for a little thicker concrete where the table will be.

Next step is to get a center nail where I can hook my tape measure to make the circle spot-on curve-a-licious.

Staked! I just walked around the circle pulling a tape from the center and driving in stakes. Nice and round.

The rebar in the middle is for the concrete table. I poured it in with mud leftover from one of the footing pours. That way I had no rebar template in the way of the slab pour. The conduit is inside the column. The 110v outlet will be nicely flush after the column is poured. Notice the white paint marks on the dirt. That's layout for the rebar.

Time to cut some rebar. This is a rebar shear. I had some #5 bars (5/8") leftover from building the house, so I'll use those for this slab.

Rebar is in, dobied-up, ready to pour.

Kenny is finishing the slab. The center of the slab is about 1/2" higher than the edges so that water will run off. Kenny put a nice radial broom finish on the slab just before the concrete set up.

The next day I layed out control joints and then made the saw cuts with a Skilsaw and a diamond blade. Turned out nice!

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  1. My nautical brain read "astrolabe" on the title, ha ha! Man you've been busy! More power to ya, I hate concrete work. My wavy footer on the shop I built shows that concrete work hates me too : )

  2. Hi Mayberry,

    Even though I love formwork and I'm damn good at setting up a pour, I despise the actual pouring of concrete. I'm a lousy finisher and utterly clueless when it comes to making a flat pour. Fortunately, I have a talent for surrounding myself with people who do well what I can't.



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