Sauna Foundation: What to Build Your Sauna On

A sauna is a heavy wooden box that has to stay square. When one corner sinks, the walls shift and the door stops latching. Almost Heaven calls "is my site level?" the single most important question before building a barrel. Plunge goes further: damage from an unlevel or unstable surface is not covered by its sauna warranty.

Foundations that work

What to avoid

Plunge rules out soft ground like grass or loose gravel, and loose pavers. It also warns off anywhere water pools or soil washes out. Almost Heaven's short version is "not the bare earth": erosion and soggy ground will tip a level sauna over time.

Barrel saunas: you only need to support the cradles

A barrel sits on curved cradles, so you can pour or pave just two to six strips instead of the whole footprint. Almost Heaven's numbers:

• Cradles are 53 by 6 inches on 6 foot diameter barrels and 64 by 11 inches on 7 foot barrels.
• Small barrels use two cradles; the largest use four to six.
• Set the outer cradles 4 to 5 inches from the ends of the staves and space any others evenly.
• If the site is slightly off, shims under the cradles can make up the difference.

Leave room to work while you build: Almost Heaven says you only need a few inches around a finished barrel, but enough for a person on each side during assembly. Most people bring power in at the back, behind the heater.

Common questions

Can a barrel sauna sit on gravel?

Compacted gravel, yes: Almost Heaven lists compressed gravel among its most popular bases. Loose gravel, no: Plunge lists it with grass and dirt as surfaces that shift and settle.

Can I put a sauna on pavers?

Pavers set on a prepared, level base are on Almost Heaven's list. Loose pavers are on Plunge's list of surfaces to avoid, because individual pavers can move under the weight.

How thick should a concrete pad for a sauna be?

Plunge asks for a concrete pad at least 4 inches thick under its sauna, and says the surface must support up to 1,400 lb. Check the weight for your own model; a larger sauna or one with a porch weighs more.

Do I need a base under the whole barrel sauna?

No. Almost Heaven says you can lay a base under the whole footprint or just under the cradles. Its cradles are 53 inches wide by 6 inches deep on 6 foot barrels and 64 by 11 inches on 7 foot barrels, set 4 to 5 inches in from the ends.

What floor works for an indoor sauna?

Almost Heaven's indoor saunas use your existing floor. It says solid floors from concrete to tile work, but does not recommend carpet. On bare concrete, a duckboard floor keeps your feet off the cold slab.