DIY: Build an Outdoor Sauna + Cold Plunge

Want to build it yourself? Here’s a concise, field-tested checklist for a backyard sauna with a nearby stock-tank plunge that you can chill with ice or seasonal temps.

1) Site & Base

  • Choose well-drained ground with easy power access and short walk to the plunge.
  • Base options: compacted gravel pad, pavers, pier blocks, or slab. Extend the base past walls for drainage; keep pad slightly above grade.

2) Framing & Weather Shell

  • Typical stud walls (2×4 or 2×6), sheathed and wrapped with exterior house-wrap.
  • Roof: shed or gable with proper flashing; overhang helps protect door and vents.

3) Insulation & Vapor Seal (hot room)

  • Insulate walls/ceiling (e.g., mineral wool or batt).
  • Continuous foil vapor barrier on the sauna side, seams taped air-tight.
  • Interior cladding: tongue-and-groove softwood (cedar/hemlock) over furring to avoid contact with foil.

4) Ventilation (fresh air matters)

  • Intake low, near the heater (often ~4″ above floor) to feed the heater with fresh air.
  • Exhaust high on the opposite wall/diagonal (near ceiling) to promote cross-flow; a second low exhaust is optional.
  • A small gap under the door can serve as supplemental intake.

5) Heat Source & Power

  • Electric heater: follow manufacturer clearances; dedicated circuit, proper wire size, breaker, and licensed electrician.
  • Wood stove: observe clearances, heat shields, chimney through-roof flashing, and outside air if needed.

6) Benches, Floor & Drain

  • Two-tier benches (upper “hot”, lower “cooler”); smooth, splinter-free edges.
  • Sloped floor to a drain (if practical) or removable duckboards with an easy clean-out plan.

7) The Cold Plunge (Stock Tank / Ice-Cooled)

  • Tank: galvanized or HDPE stock tank on a level, sturdy base; add an insulated lid to slow warming and debris.
  • Cooling: ice blocks/bags in warm months; in winter, outdoor temps may suffice. Place the tank close to the sauna, but with safe walk-paths and anti-slip mats.
  • Water care (no chiller): quick pre-rinse before use, skim debris, periodic drain/refill. For multi-user setups, consider a small pump + cartridge filter and optional UV/ozone.
  • Safety: keep any outlets/pumps on GFCI, cords elevated and dry; never use improvised “live” appliances in the water.

8) Finishing & Weatherproofing

  • Exterior cladding that sheds water; seal end-grain; maintain caulks/flashing.
  • Use vent screens to keep pests out; protect intake/exhaust from wind-driven rain.

Have questions about sizing, power, or vent placement? Ask us via the form and we’ll help you dial it in.