Guide · contrast deck · 10 min read
A dry sauna at 90 degrees three metres from water at 4 is the most requested combination we build. It is also the one where retrofitting costs three times what planning costs, because the decisions that matter are drainage, circuits and clearances — all invisible once the boards are down.
Sauna and plunge tub are two wet zones with opposite problems. The cabin is dry inside and sheds water outside, from bodies leaving it. The tub is wet at the rim, splashes at every entry and overflows by design. Between them is a route people walk barefoot, wet, and often in poor light. Most of the engineering on a contrast deck is about that route rather than about either box.
The tub overflows, the deck sheds water, and the sauna floor drips. Trying to solve all three with one gully under the tub is the mistake we most often arrive to find. What works: a dedicated 1-inch drain valve at the lowest point of the tub for full changes, a concealed overflow under the rim piped to the same run, and a separate linear channel in the deck itself, set across the walking route between cabin and tub with a 1 per cent fall into it.
Under a timber deck the fall belongs to the slab, not the boards. We pour the pad with the fall built in and let the boards sit level on top, because a deck that visibly slopes reads as a mistake. Boards are bengkirai at 8-millimetre gaps so water passes through rather than standing, and the area under the deck must be reachable — a hatch, or removable boards over the pipe run. Anything you seal permanently under a deck is something you will one day cut out with a saw.
A 6 to 9 kW sauna heater and a 1.4 kW chiller must be on separate circuits with separate protection, and the chiller circuit must be the one with residual-current protection nearest the water. Household connections of 2,200 VA will not carry both at once; a contrast deck realistically wants 5,500 VA and upward, which for many houses in Denpasar or Mataram means a PLN upgrade before anything is built.
Two further points that cost nothing at the drawing stage. First, put the chiller's isolator where a technician can reach it without walking across a wet deck. Second, the control panel and thermometer go at chest height on a dry wall — not at ankle level beside the tub, where somebody will eventually kneel on wet boards to read it. Compressor damage from mains voltage below 180 volts without a stabiliser is excluded from our warranty, so where the evening supply sags we fit one and show you the measurement.
The chiller is the part that ruins contrast decks aesthetically and thermally. It needs free air on the intake faces, shade from direct afternoon sun, and a position where its noise does not sit against a bedroom wall — 52 to 58 dB, which is every unit we sell, falling to 45 or 48 once it stands on damping mounts behind a one-sided acoustic screen. It must not go behind the sauna cabin, which is the instinct of every builder we have ever worked with, because the cabin radiates heat into exactly the air the condenser is trying to use.
Standard insulated hose runs six metres. Beyond that every extra metre adds heat gain and we increase the diameter to compensate; past twelve metres we would rather move the unit than argue with physics. Plan the route as a straight line where possible, and leave it accessible — the hose, not the chiller, is what a gardener's spade finds.
| Build | What is in it | Installed, Java and Bali |
|---|---|---|
| Compact contrast deck | 2-person cabin, 300 L plunge, 2 HP, small deck | Rp 135-170 million |
| Standard villa deck | 4-person cabin, 400 L terrazzo, 2 HP, ozone, bengkirai deck | Rp 170-235 million |
| Large or commercial | 6-person cabin, 600 L, 4 HP, auto sanitation, covered structure | Rp 235-290 million |
Those figures include the survey, drawings, delivery within Java and Bali, installation, the cold test and two service visits in the first year. They exclude civil work — the slab, the covered roof structure and any PLN upgrade — because those are usually cheaper done by your own builder from our drawing. The combined product page is sauna and ice bath, and larger schemes fall under wellness areas.
The pattern most of our clients settle into is heat first, then cold, then rest, repeated two or three times, with the cold portion short. We are not going to prescribe durations or claim benefits — there is real research on contrast bathing and none of it is our field. What is squarely our field: the plunge must still read 4 degrees after four people have come out of a 90-degree cabin within twenty minutes, which is a chiller sizing question and is solved with headroom, not with hope. Set the target a degree below what you actually want and let the machine catch up between users.
Anyone with a heart condition, uncontrolled hypertension or a pregnancy should discuss contrast bathing with a doctor before building a deck around it, not after. That sentence appears on every page of this site for the same reason: we hold water at a temperature, and that is the entire extent of what we are qualified to promise.
They can share the run to the sewer. They should not share a single gully under the tub, because the deck and the cabin shed water over a much wider area. One channel across the walking route plus a dedicated tub drain is the layout that works.
Two and a half to four metres is comfortable — near enough that the walk is short, far enough that the cabin's radiant heat does not sit on the water surface or feed the condenser. Under two metres we start seeing measurable extra load on the chiller.
Realistically 5,500 VA or more: 6-9 kW for the heater and 1.85 kW for a 2 HP chiller, on separate circuits. On 2,200 VA you would be choosing between heat and cold, which defeats the purpose. If the supply cannot be raised, the cheaper contrast deck is no sauna at all: our panel runs to 40 degrees, so one heating and cooling chiller can warm an ofuro tub and chill the plunge on the same circuit.
Yes, if the pad, the drainage channel and a spare conduit are laid now. Retrofitting all three under an existing deck means lifting boards, cutting slab and re-laying, which typically costs three times what allowing for it would have cost at the drawing stage.
Marginally, and only if it is too close or upwind of the condenser. At three metres with the tub lidded between sessions the difference is inside the noise. The real running cost stays the chiller: Rp 214,000 a month in most coastal cities, per the pricing page.
We do, in the same workshops — timber in Tabanan, electrical assembly in Cikarang — and we install both on the same visit so there is one crew and one responsibility. Sizing for your own deck can be checked on the chiller calculator before you commit to a volume.
Langkah berikutnya
A rough plan with the doorway, the drain position and the meter rating is enough to get a layout and a price band back.
We reply with sizing, the right chiller and a full price.