Can You Put an Outdoor Sauna on a Deck? Weight, Cradles, Rain

Not legal or electrical advice. This guide summarizes published manuals, codes and agency pages as of the date above. Rules change and vary by jurisdiction. Confirm your plans with a licensed electrician or contractor and your local building department before you buy or install.

Key facts

Redwood Outdoors 6 Person barrel: 900 lb, 2 cradles, 6 ft 0.75 in W x 5 ft 11 in L outside. 8 Person barrel: 1,150 lb, 3 cradles, 6 ft 0.75 in W x 7 ft 8.5 in L.
Redwood Outdoors: "The foundation must support the full weight of the sauna and all occupants." Its listed options include a "solid deck or reinforced platform."
Almost Heaven lists a wooden platform among popular barrel bases. Its cradles are 53 in W x 6 in D for 6 ft diameter barrels and 64 in W x 11 in D for 7 ft barrels, placed 4 to 5 in from the ends of the staves.
IRC decks are designed for a uniform 40 psf live load. The American Wood Council's DCA 6 guide sizes framing for 40 psf live plus 10 psf dead load and says concentrated loads such as hot tubs are beyond its scope.

The weight, worked out

Saunas weigh less than a filled cold plunge for their size, which is why people assume a deck is fine. The difference is that a sauna fills up with people. A full six-seat barrel carries more in occupants than the sauna itself weighs.

Sauna (maker figures)	Dry weight	Outside footprint	Dry load	Full, at 200 lb per seat (assumption)
Redwood Outdoors 6 Person barrel	900 lb	72.75 x 71 in, about 35.9 sq ft	about 25 psf	2,100 lb, about 59 psf
Redwood Outdoors 8 Person barrel	1,150 lb	72.75 x 92.5 in, about 46.7 sq ft	about 25 psf	2,750 lb, about 59 psf
Typical IRC deck design load	Spread evenly over the whole deck		40 psf live + 10 psf dead

Our arithmetic from Redwood Outdoors' published weights and dimensions, converted to inches. Heater stones are extra: Redwood lists rock capacities from 44 lb for its wall-mounted heaters up to 264 lb for its 9 kW floor-standing heater. Seating capacity is the maker's; the 200 lb per person is our planning assumption. Almost Heaven does not list weights on the product pages we checked, so ask for them before planning a deck install.

Why the average understates it: cradles

A footprint average assumes the weight is spread across the whole rectangle. A barrel sauna rests on cradles instead. Using Almost Heaven's published cradle size for 6 ft barrels as an illustration, two 53 by 6 inch cradles touch about 4.4 sq ft of deck. Put a full 2,100 lb six-seat barrel on that and the boards right under the cradles carry roughly 475 psf, several times a deck's design load, along two narrow lines. Redwood does not publish its cradle dimensions, so treat this as an illustration of the effect, not a figure for any one sauna.

What an engineer will look at:

Which joists each cradle lands on, and whether the cradles can run across the joists so each one bears on several of them.
Whether the cradles can sit over a beam or close to posts instead of mid-span.
Post and footing size under the sauna area, and the ledger connection if the deck is attached to the house.
Snow. The AWC FAQ says its 40 psf criteria assume snow loads where snow is not prone to sliding or drifting. A curved barrel roof sheds snow onto the deck around it.

Common fixes are added joists or blocking under the cradles, a new beam with posts and footings under the sauna, or a separate framed platform on its own footings. Most of that is permit work.

Wood-burning heaters on a wood deck

IRC M1410.2 calls for a noncombustible floor extending 18 inches beyond a solid-fuel heater on all sides, unless the listed heater's instructions specify different floor protection. The sauna floor is between the stove and the deck, but the stove's manual still governs what goes under it, and a deck is a combustible surface right below a firebox. Washington and Oregon also restrict when wood sauna stoves may burn. See our guide to wood-burning sauna stoves in Washington and Oregon.

Pacific Northwest decks: keep the boards under it dry

This part is our editorial advice from how decks fail in wet climates, not a maker requirement. A barrel sauna sheds rain off a curved roof onto the deck along both sides, and the deck boards under it never see sun. On a Seattle or Portland deck that stays damp from fall to spring, that combination keeps boards and joist tops wet for months.

Keep the cradles on the boards and leave air space under the barrel so the deck can dry. Do not lay a solid mat or membrane under it.
Add a roof cover or rain jacket so water runs off the ends rather than pooling at the cradles. See barrel sauna roofing.
Plan for the heater circuit: the wiring has to reach the sauna without running loose across a walking surface, and it needs an electrical permit in Seattle and Portland.
Check the deck every spring for soft boards and loose fasteners under and around the cradles.

Permits for the deck itself

Portland's Brochure 3 requires a building permit for any deck whose walking surface is more than 30 inches above grade, and Portland's hot tub page says a tub on such a deck brings structural requirements. We found no sauna-specific deck rule in either city, so expect the same structural questions for a full sauna. Reinforcing or rebuilding a deck generally needs a permit. The sauna itself has its own size and setback rules: see Washington and Oregon and Portland sauna permits.

The simpler answer: a pad next to the deck

Both makers accept concrete, pavers or compacted gravel, and Redwood also lists concrete footings under each cradle. Almost Heaven says you can keep the base to the footprint of the cradles. Two footings or paver strips under the cradles beside a ground-level deck are usually cheaper than reinforcing framing and drain better. Our barrel sauna foundation guide gives pad sizes and depths, and the rainy-climate guide covers wood and roofs.

Before you buy

Get the dry weight, cradle count and cradle dimensions from the maker.
Add stones and a full house of occupants, then do the psf math above.
If it is over 40 psf, and a full barrel usually is, plan a pad or have an engineer design the support.
Check your panel for the heater circuit. See can one panel run a sauna and a cold plunge.

Sources

This guide explains the math from published figures. It is not a structural approval for your deck.

Related guides

Frequently asked questions

Can you put a barrel sauna on a deck?

Makers allow it, but the deck has to be built for it. Redwood Outdoors lists a solid deck or reinforced platform among its foundation options and says the foundation must support the full weight of the sauna and all occupants. Almost Heaven lists a wooden platform as a common base. A standard deck is designed for 40 psf spread evenly, and a full barrel sauna can average close to 60 psf by our arithmetic, with the weight landing on two or three narrow cradles.

How much does an outdoor barrel sauna weigh?

Redwood Outdoors lists its 6 person barrel at 900 lb on 2 cradles and its 8 person barrel at 1,150 lb on 3 cradles. Heater stones add more: Redwood lists rock capacities from 44 lb for its wall-mounted heaters to 264 lb for a 9 kW floor-standing model. Then add the people. Six adults at 200 lb each (our assumption) is another 1,200 lb.

How many pounds per square foot is a sauna on a deck?

Divide the total weight by the footprint. For the Redwood 6 person barrel, 900 lb plus six 200 lb adults is 2,100 lb on about 35.9 sq ft of outside footprint, or about 59 psf. The 8 person barrel with eight adults comes to about 59 psf too. Both are above the 40 psf a typical IRC deck is designed for, before counting stones or snow.

Why do sauna cradles matter on a deck?

A barrel does not sit flat. It rests on cradles, so the load lands on narrow strips. Almost Heaven lists its cradles as 53 by 6 inches for 6 ft diameter barrels. Two of those cover only about 4.4 sq ft. An engineer will want to know where each cradle lands relative to joists, beams and posts.

Can a wood-burning sauna stove sit on a wooden deck?

Only with the floor protection its listing and manual call for. IRC M1410.2 calls for a noncombustible floor extending 18 inches beyond a solid-fuel heater on all sides, unless the listed heater specifies different floor protection. Inside a barrel the stove sits on the sauna floor, so the deck below still needs protecting from heat and embers per the manual. Check your local burn rules too.

Do I need a permit to put a sauna on a deck in Seattle or Portland?

The sauna and the deck are separate questions. The heater circuit needs an electrical permit in both cities. Portland requires a building permit for any deck whose walking surface is more than 30 inches above grade, and says a hot tub on such a deck brings structural requirements; expect the same scrutiny for a sauna. Reinforcing an existing deck is usually permit work. Ask your building department first.

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