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Observatory build Reference

Pour day checklist

Printable checklist for the one irreversible day.

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This is one person’s build, not engineering guidance. Local codes, soils and loads vary.

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Before you mix

The form

  • Rim at the correct height — re-check off a level line from the joist tops
  • Rim cut square all around (measure at 4 points)
  • Plumb in two directions 90° apart
  • Braced so it cannot move — push hard on it
  • Centered in the deck opening, gap measured at 4 points
  • Bottom sealed to the ground so paste cannot escape

The cage

  • 3″ clear off the hole bottom
  • Roughly centered, ~1½″ of soil clearance all around (13″ hole, bars on a 9.6″ circle)
  • Hanger stick across the rim, 3–4 doubled wires
  • Every tie twisted tight, tails bent inward
  • Nothing touching the form or the soil

The conduit

  • Both capped or taped
  • Pull string in both, tied off at each end
  • Braced so they cannot float
  • Confirmed clear end to end

North

  • Two stakes on the north line, 15–20 ft apart, clear of steel
  • Verified on the bench which way the index rod points with the mount fitted

The adapter

  • Assembled, torqued, re-measured
  • Buried nut + fender washer on each rod, dry — no anti-seize
  • Projecting threads taped against splash
  • Depth mark taped on a rod
  • Bottom rotor face clean, degreased, unpainted
  • Within arm's reach of the pier, not in the garage

Tools staged

  • Mixing tub, hoe, buckets, water
  • Rod for consolidating each lift
  • Trowel, float, torpedo level, tape
  • Wire snips · spare steadying stick
  • Plastic sheeting · gloves · eye protection

Pouring

  • Mix on the stiff side of soupy
  • Place in ~12″ lifts, rod each one, tap the form
  • Watch the cage — if it shifts, stop and reset
  • Stop ½″ below the rim
  • Screed flat, snip hanger wires, lift the stick off

Setting the adapter — the 30 minutes that count

  • Lower straight down, no rocking
  • Press until paste squeezes out all around
  • Level on the rotor, at 0° / 45° / 90° / 135°
  • Index rod sighted to the north stakes
  • Rods plumb
  • Re-check all three every 10 minutes for half an hour
  • Slope the surface slightly away from the rotor

After

  • Cover with plastic, keep damp 3 days
  • Do not touch for 24 hours
  • 24–48 hrs: back out tube screws, slide the crossbar out
  • Leave the form on through day 7 — it is a curing jacket
  • 7 days minimum before any load

Weather

Do not pour below ~40°F or with a freeze in the next 48 hours. Above ~85°F it sets fast and you lose the adjustment window. Shade the pier if it is sunny.