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Wood-Fired Hot TubConcept — sign-off required

The Ogua

The catalog's first pure pleasure build — everything before it sold on utility or independence. Cedar and copper, heated by an external firebox through a pump-free thermosiphon loop, filled off the same cascade and draining to the same food forest as everything else.

Why the name

Named for the Ogua, a Cherokee water-monster legend tied to the French Broad River in the southern Appalachians. The one build on the catalog that exists purely for pleasure gets a name with some genuine menace behind it, on purpose.

An external wood firebox heats water through a copper coil by thermosiphon — the same passive, no-pump principle as the Great Hearth's water coil, at every tier. Fill water can come straight off the Uktena cascade; drain water routes to food forest irrigation, the same as the Flatwoods washer's greywater. Salt water sanitization (salt cell electrolysis) is standard at every tier instead of chemical treatment.

Tier Ladder

  • Settler — Simple Soak: 1–2 person, external firebox, no insulation jacket.
  • Homesteader — Cedar & Copper: 2–3 person, side-mount firebox, basic insulation wrap.
  • Foreman — Full Soak: 3–4 person, full insulation jacket, built-in bench seating, ~2–3 hr heat-up from cold fill.
  • Monticello — Whole-Property Soak: 5–6 person, dual-zone firebox, gabion stone plinth, standing seam cover structure.
  • Mythic — The Ogua: 6–8 person, cast bronze fittings, integrated cattle-panel hop trellis for living shade.

Technical Specifications (Foreman tier baseline)

  • Tub: cedar staves, insulation jacket, built-in bench seating
  • Heater: external wood firebox, copper heat exchanger coil, thermosiphon circulation (no pump)
  • Water system: salt water sanitization (salt cell electrolysis), standard at every tier
  • Heat-up time: ~2–3 hrs from cold fill to soak temperature

Construction Variant: Geopolymer Monolithic

An alternate build casts the tub basin as poured monolithic geopolymer (same recipe as Ogopogo's caps) instead of cedar staves, with cedar dropped to an accent role — cap rail, bench slats, cover structure. Heavier and permanent, but likely better heat retention and a tighter match to the whole-property poured-material language; best fit for Monticello and Mythic tiers already pouring a gabion plinth.

Construction Variant: IBC Tote (Budget Settler Build)

A cheaper Settler-tier path to the same Simple Soak: a 275/330-gallon IBC tote, framed and insulated (3.5" fiberglass batt cavity), clad in cedar, instead of a raw cedar-stave tub — solves the watertightness problem a thin wood-only tub is genuinely prone to, while keeping the cedar look and feel. A real, buildable budget technique (~$600–1,000 all-in), but it must still meet the Ogua standard at every tier, not the version it's sourced from: wood-fired external firebox and copper thermosiphon circulation (not the propane tankless heater and electric pump loop the source build used), plus the salt cell sanitization already locked in above — a filtration-only loop with no active sanitizer is a real Legionella/Pseudomonas risk in water held at soak temperature for days between fills.

  • Vessel/frame/insulation/cedar-cladding method: take as-is, genuinely solid technique.
  • Heat source and circulation: correct to wood-fired firebox + copper thermosiphon — do not build the propane/pumped version.
  • Sanitization: add the salt cell, standard at every Ogua tier — do not rely on filtration alone.
  • Foundation: a filled 330-gal tote is ~2,750 lbs of water alone, roughly 3,000+ lbs concentrated on a 4x4 ft footprint — needs a real gravel or poured pad, not bare ground.
  • Verify tote provenance before use — avoid any tote that held waste oil, corrosives, or unknown chemical cargo.

Specialist Sign-Offs Required Before Construction

  • Structural engineer — a filled tub at this size is several thousand pounds of water alone; deck, pad, or plinth needs load verification
  • Fire safety clearance — firebox clearance-to-combustibles, especially near the cedar tub body
  • Water quality/sanitation — salt water and bare copper don't always mix well long-term; sizing the salt cell and confirming compatibility needs a real check

Open Items

  • Salt water compatibility with the copper coil not yet confirmed — may need a sacrificial anode or coil coating
  • Hop trellis structural tie-in (Mythic tier) needs a pass to confirm it doesn't shade the firebox's air intake
  • Geopolymer variant's actual heat retention vs. an insulation-jacketed cedar stave tub not yet tested — the "may not need a jacket" claim needs real data before it's a spec, not a guess
  • IBC tote variant: foundation/pad spec not yet finalized — see kb-build/drafts/mm-pin-vetting-kb.json (pin_016_cedar_hot_tub_ibc_tote)