Gear

Sauna Stones: Which Types to Use and How Many Pounds Your Heater Needs

Use stones sold specifically for sauna heaters, such as olivine diabase, in the size your heater’s manual names, and load the weight the manual gives for your exact model. That weight varies a lot: Harvia lists 44 lb (20 kg) for its 6 kW KIP wall heater and 90.72 kg (about 200 lb) for its 6 kW Cilindro, a floor-standing heater. Decorative stones are where the makers differ: HUUM’s DROP manual says not to use them at all, because they “do not accumulate enough heat and break easily,” and that defects from unsuitable stones aren’t covered by its warranty, while Harvia sells decorative stones for the top layer only, one box per heater.

Which stones to use in a sauna heater

HUUM’s manual names “natural stones (e.g. olivine diabase, olivine), which are sold specifically for use in sauna heaters.” Harvia calls olivine diabase “the most common and used sauna stone for all heater types,” a rock “mined in Western Finland” that “stores and releases heat well.” Size follows the heater type. Harvia says smaller 5–10 cm (2–4 in) stones “are usually used in electric heaters as they fit well between heating elements,” and larger 10–15 cm (4–6 in) stones go in wood-burning heaters and in some Harvia electric heaters with larger stone capacity.

How many stones your heater needs

The heater’s manual or spec sheet is the only reliable number. Here is what the makers list for common models:

Heater	Type	Stone amount (maker’s listing)	Stone size
Harvia KIP60B, 6 kW, 240 V	Electric, wall	44 lb (20 kg)	2–4 in (5–10 cm)
Harvia Spirit SP60E, 6 kW, 240 V	Electric, wall	49.9 kg (about 110 lb)	5–10 cm
Harvia Virta HL60E, 6 kW, 240 V	Electric, floor	49.9 kg (about 110 lb)	5–10 cm
HUUM DROP (EU manual)	Electric, wall	“approximately 55kg” (about 121 lb)	5–10 cm
Harvia Cilindro PC60, 6 kW, 240 V	Electric, floor	90.72 kg (about 200 lb)	5–10 cm
Harvia Pro 20	Wood-burning	40 kg (about 88 lb)	10–15 cm
Harvia Legend 150	Wood-burning	120 kg (about 265 lb)	10–15 cm

Pound conversions are ours; Harvia lists the Virta among its floor heaters. Sellers don’t always match the maker: Redwood Outdoors lists 99 lbs of “Rock Capacity” for the Harvia Spirit (6 and 8 kW), while Harvia lists 49.9 kg (about 110 lb) for the 6 kW Spirit. When two numbers disagree, use the manual that came in your heater’s box. Some outdoor sauna kits ship with stones (Almost Heaven lists “Sauna stones included,” Redwood Outdoors “Heater Stones”), so check before you order more; what’s included in an outdoor sauna kit has the full list.

Stone types compared

Type (Harvia’s names)	What Harvia says it’s for
Olivine diabase	“most common” stone, for all heater types
Elite Pro Heavy Duty	Olivine diabase heat-treated at about 1,000 °C; “optimal for public saunas with intensive use”
Black Vulcanite	“Hard and durable”; shines black when wet, “with selected Harvia heaters”
Rounded olivine diabase	Top layer, for “soft steam”; Harvia recommends angular stones in the bottom layers
Decorative white or red granite	“Top layer stone only,” and “at a maximum of one box per heater”

Loading stones correctly

Paper-cut cutaway of an electric sauna heater with stones of mixed sizes stacked loosely around the heating elements — Stones go in loosely so air can move between them; which sizes go where depends on your heater's manual.

Load stones only with the heater switched off; HUUM’s manual says “Make sure the heater is turned off.” Each maker writes for its own heaters, but most of these steps appear in more than one guide:

Rinse the dust off the stones first (Harvia, HUUM, and Almost Heaven for its Harvia wall heater).
Place them one by one. HUUM: “don’t pour or throw them into the heater”; Harvia: “do not drop stones into the heater.”
Keep the heating elements straight and supported. Almost Heaven, for its Harvia wall heater: “The stones should touch the elements, but not bend them.”
For Harvia heaters: don’t build a high pile on top or set stones on the heater frame, and place elongated stones vertically.

They differ on the order of stones. HUUM, for the DROP, says to “start with bigger stones, placing them to the bottom and to the sides”; Almost Heaven’s guide for its Harvia wall heater puts the smaller stones “in between and around the three heating elements” and reserves “the larger stones for placement on top.”

They also differ on how tight to pack. HUUM says to “lay the stones tightly, but leave some room for air to circulate in the heater,” and to make sure the elements aren’t visible through the stones, warning in capitals that a “too sparsely filled stone container causes fire hazard.” For its heaters, Harvia says to “arrange the stones evenly and sparsely to make sure air can flow between the stones,” and Almost Heaven’s guide for its Harvia wall heater says “packing stones in too tightly will restrict airflow.” That’s why the instruction for your own heater wins. Almost Heaven adds: “It is common to have 5-10 stones left over.” HUUM’s manual says the heater “may be used only when it has been correctly filled with stones.”

Water on the stones also follows the heater’s manual. For Harvia heaters, Harvia recommends heating the sauna after loading and throwing enough water to douse all the stones, so the new-stone scent goes away. For its DROP heater, HUUM’s manual recommends “about 80 ml of water on the stones at a time,” only once the stones are fully heated. Follow your own heater’s manual. Infrared saunas have no heater stones. More on the two systems in infrared vs traditional and wood-burning vs electric.

When to replace sauna stones

Stones crack and crumble from repeated heating. Two schedules from the makers:

Maker	What it recommends
Harvia	Rearrange “at least once a year or even more often if the sauna is in frequent use”; knock stones together, and “if stones crack and sound shallow it is time to change” them; clear debris from the bottom of the heater. Harvia’s stone page, which sells the stones, also says “Annual replacement of sauna stones extends the lifetime of the sauna heater”
HUUM (DROP)	Visual check after 100 hours of use or at least once a year; after 200 hours rearrange and replace cracked stones; after 400 hours “replace all stones”

Stone pieces on the sauna floor are a sign they’re breaking down, Harvia notes.

Where to buy sauna stones

Heater makers and sauna sellers sell stones in boxes by weight. Harvia’s standard olivine diabase comes in 20 kg boxes (its smaller rounded stones in 15 kg boxes, decorative stones in 10 kg). Two U.S. listings checked November 1, 2026: Almost Heaven’s Standard Sauna Stones 40lbs (olivine diabase) at $135, and Redwood Outdoors’ Harvia Black Vulcanite, 2–4”, 44 lb, at $79, shown as out of stock. Prices change. Divide your heater’s stone weight by the box weight to get the count (our arithmetic): a KIP 6 kW takes one 44 lb box, and a single 40 lb box falls a little short of its 44 lb; a HUUM DROP’s roughly 55 kg is about three 20 kg boxes.

Sizing a heater or pricing a setup? Run the Sauna Planner — volume, kW, breaker and cost in one place.

Illustrations on this page are AI-generated to help you picture the situation. They are not photos of real homes, jobs or people.

Sources

Updated 2026-11-02

Safety and permits

A sauna heater needs its own circuit sized to the maker's manual — have a licensed electrician wire it and pull the permit. Wood-burning stoves need the clearances and chimney in the stove's manual and local code approval. Before digging for a foundation, call 811. This site doesn't give medical advice: if you're pregnant or have a health condition, ask your doctor before using a sauna.