System 11 · Timber · private homes
A heated timber tub for the garden: white liner, no hoops, 38 °C by evening
The warm twin of our timber cold tub: the same ash staves and smooth white liner, an electric heater and a filter instead of a chiller, an insulated cover that works every night, and water at 37–39 °C for two to six people under a pergola.
The timber cold tub on this site has a warm twin. Same vertical staves of thermally modified ash, same smooth white fibreglass liner rising above the waterline, no metal hoops, proportions built for an adult rather than a brochure. The difference is the plant: an electric heater and a filter instead of a chiller, an insulated cover that earns its keep every night, and water at 37–39 °C for two to six people in a private garden.
The same shell as the cold tub, heated instead of chilled
- Liner. The white fibreglass shell holds the water and takes the heat; the ash staves are cladding, which is why there are no hoops to heat up in the sun or stain a limestone terrace.
- Heater. Electric, 3–9 kW by volume, with its own flow switch and thermostat, in a shaded cabinet beside the tub with the pump and a cartridge filter.
- Sanitiser. Dosed to a schedule; warm water needs it more than cold water does.
- Cover. Insulated and timber-faced, in two hinged halves: the single most important part of a hot tub in a Gulf garden.
Timber hot tub or acrylic spa shell: an honest comparison
| Timber hot tub | Drop-in acrylic spa shell | |
|---|---|---|
| Look | warm timber on the terrace, white inside | a moulded shell in a deck with a cabinet skirt |
| Seats | a bench around the inside, shoulder-deep | moulded loungers and seats |
| Jets | none by default; a few on request | many, on one or two jet pumps |
| Heat-up and running | slower, a lower load, a cover and a thermostat | faster on a bigger heater; a higher load with jets and lights |
| Suits | a private garden, a courtyard, a shaded roof | a deck or terrace that wants jets |
| Range | $4.8–13k (SAR 18–49k) | the lower half of the built-in hot tub range |
Heating 1,400 litres in a Gulf garden: the arithmetic
Water takes about 1.16 kWh to raise 1,000 litres by one degree. In summer the mains in Riyadh or Doha arrive warm and the tub needs only a few degrees: 1,400 L from 32 to 38 °C is six degrees, about 9.7 kWh, which a 6 kW heater delivers in a little over an hour and a half; the summer problem is keeping the water below 39 °C in the afternoon, which is shade and the cover. In January the sums change: Riyadh's nights average 6.9 °C and its days 20.1 °C (National Center for Meteorology normals for 1982-2011, via the WMO World Weather Information Service), an uncovered tub falls towards the night air, and heating from 18 to 38 °C is twenty degrees, about 32 kWh, or five and a half hours on the same heater. That is why the tub is kept warm under its cover and topped up by the thermostat rather than heated from cold for each evening, and why the cover, a screen against the wind and the shade are drawn before the heater is chosen.
Electric heater, and why we do not quote a wood-fired stove here
In colder countries a timber tub is often heated by a wood-fired stove hanging on its side. In a Gulf garden we specify an electric heater: a stove beside a villa is a smoke and fire-separation question for civil defence and for the building, and a thermostat under a cover keeps the water ready at a running cost a stove cannot plan for. If a brief insists on a stove for a mountain lodge in Oman or a desert retreat, ask us; it is a different drawing.
Water, drainage and the cover
A 1,400 L tub is 1.4 tonnes of water. On a terrace or a roof the slab is checked first; on a garden platform the base is a level slab with a fall to a gully. The tub is filled from a hose, topped up by a float valve, and emptied through a low drain valve to a gully the municipality accepts, which the plumber confirms. Warm water held for weeks needs the sanitiser dosed to its schedule and the cartridge rinsed weekly; the care sheet in the layout sets it out, and the first year's assisted service visits teach it. With the cover on, evaporation and heat loss are a fraction of an open tub's, and sand and leaves stay out.
Where it goes in a villa, and why not in a hotel
- Under a pergola or a courtyard wall. Shade in the afternoon, a wall against the wind, privacy from the next roof.
- Beside the terrace sauna. The classic pair for a private garden: a cabin ready in 40 minutes and a tub already at 38. See terrace saunas.
- Not on a hotel deck. Timber wants oiling and moves with the season, and a tub that fills and empties for guests needs a filtration plant it was not drawn for; hotels and clubs get the built-in hot tub instead.
What a heated timber tub costs
The indicative range is $4.8–13k (SAR 18–49k): a 1,000 L tub for two with a 3 kW heater, filter and cover at the bottom; a 1,800 L six-person tub with a 9 kW heater, a step, a bench and lighting at the top. It covers the tub, liner, heater, pump, filter, cover and commissioning; the base, the power feed, the drain and freight handling are quoted in the layout, as the price guide explains. The cold version is on the wooden cold tubs page; the suite builder prices cold tubs only.
Can the same timber tub be hot in winter and cold in summer?
It can be plumbed for both, with a heater and a chiller on one circuit and a valve between them, which means a larger plant cabinet and a larger figure. Most families prefer two tubs: a cold one that runs all year and a hot one for the cooler months.
Will the timber survive the sun?
Thermally modified ash moves little with heat and takes outdoor oil well; under a pergola it stays handsome for years with an oiling on the care sheet's schedule. In full sun with no shade, no timber does.
Which heater size do I need?
3 kW for 1,000 L, 6 kW for 1,400 L, 9 kW for 1,800 L; single-phase up to 6 kW and three-phase above. In Saudi Arabia the pump and the controls are 60 Hz builds; see heaters and chillers on Saudi 60 Hz.
Other systems
The tub's usual neighbours
Wooden cold tubs
Timber outside, smooth white liner inside, no metal hoops, built for adults. For private gardens and terraces only.
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Terrace and rooftop saunas
Free-standing cabins with one or two glass faces, flat roof, screens and shade. Made for 45 °C summers and cool winter evenings.
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Hydromassage hot tubs
Tiled or mosaic, cast into the floor at 36–38 °C with jets and a seat ledge; or an acrylic spa shell dropped into a deck. Plant on another floor.
Open the pageTwo, four or six?
Tell us how many people and where the shade is: we size the heater and draw the cabinet
A photo of the corner in the afternoon tells us more than a plan: it shows the sun.
One message starts the layout
Send a plan or three photographs of the space and say who will use it. The project desk answers with questions first, then a 3D layout and an indicative range.
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