Sauna stones: types, sizes and prices

Sauna stones are the rock a sauna heater is filled with: they store its heat, and water ladled onto them makes the steam. They’re sold by weight, most often in 20 kg boxes and in two main sizes, and the makers say to replace them as they crumble. We recorded 26 listings for sauna stones at five UK retailers, from £24.99 to £130, and worked out the price per kilogram for the 25 that state one weight. Below the table: which stones the heater makers specify, how many you need, how to stack them and when to replace them. Prices were checked on 3 October 2026.

Sauna stones compared

Sort by “Price per kg” to compare boxes of different weights.

Prices and specifications as shown on each retailer's own website on 3 October 2026; the retailer's checkout price is what counts. Aqualine Saunas and Leisurequip do not say whether their prices include VAT; for the other retailers we recorded the displayed price and didn't check for a VAT statement. “From” marks a starting price where the retailer sells several sizes or options: the shop's own “from” price, or the cheapest size we noted for the item named. The listings for 9 of these items didn't show whether they were in stock. “Not recorded” means we don't hold the figure, usually because the listing didn't state it. We haven't tested these products. We may earn a commission if you buy through some of these links.

Where a retailer sells two stone sizes at one price, the row covers both. Finnmark’s olivine diabase is the exception: the price shown is for the 10 to 15 cm size, and the 5 to 10 cm size is £40. One row has no price per kilogram, because Leisurequip’s rounded pebbles are sold at one price in two box weights. These are not the shops’ whole ranges, and Aqualine Saunas and Leisurequip don’t say whether their prices include VAT, so allow for that when you compare.

Which stones can you use in a sauna heater?

Use the stone type your heater’s manual names. What the makers we’ve read say:

• Olivine diabase and similar dark, dense rock. Harvia says suitable stone materials include peridotite, olivine and olivine diabase, and that heater stones should be as heavy as possible, dark and large, so they store as much heat as possible. HUUM’s DROP manual names olivine diabase or olivine sold for sauna heaters. Narvi specifies split olivine diabase for its Velvet electric heater, and Tylö’s US guide for its Sense Sport heater says always to use dolerite. HUUM’s manual for its HIVE Wood stove is broader: it says any natural granite stones, or sauna stove stones sold at hardware stores, are suitable.
• Not rocks picked up outdoors, Harvia says. Harvia says surface rocks collected in nature are not suitable for heaters.
• Not ceramic or soapstone, for these heaters. Harvia says ceramic stones and soft soapstones must not be used. Narvi says soapstone and ceramic stones are not suitable for its Velvet, Tylö’s US guide says ceramic stones can damage the heater, and HUUM says ceramic stones may shorten the life of its HIVE Wood stove.
• Rounded or split? It depends on the heater. HUUM recommends round stones for its heaters, and Harvia sells rounded stones in a 15 kg box. Narvi’s manual for its NC wood-burning heaters forbids stones with a regular shape, giving rectangular ones as its example, because they risk being stacked too tightly.

In our table, 12 listings are olivine diabase or dolerite, 6 of them rounded, and 8 are vulcanite. The other six are decorative stones or don’t name the rock in the listing we read. Vulcanite is sold under the Tylö, Harvia, Helo and Narvi names, but the manuals we’ve read don’t mention it, so check yours before you buy it.

Sources: Harvia support: Can any stones be used as heater stones?; HUUM: DROP electric heater user manual (EU, 2025), p. 8; Narvi: Velvet Electric (Flow) heater manual, English section, p. 76; Tylö (US edition): Sense Sport heater installation and user guide (SSU 5, 7, 8), p. 5; HUUM: HIVE Wood stove user manual (EU, v1), p. 8; HUUM: Sauna stones product page; Harvia: product page R-991, Sauna heater stones Harvia rounded 5-10 cm 15 kg; Narvi: NC 16 / 20 / 20 VS / 24 wood-burning heater manual, English section, p. 24. Checked 3 October 2026.

What size sauna stones?

Sauna stones come in two main sizes, and the heater decides which.

• 5 to 10 cm for most electric heaters. Harvia says the smaller 5 to 10 cm stones are usually used in electric heaters, HUUM’s DROP manual gives 5 to 10 cm, and so does Narvi for its Velvet.
• 10 to 15 cm for wood-burning stoves and some larger electric heaters. Harvia says the larger stones are used in wood-burning heaters and in selected Harvia electric heaters.
• 3 to 5 cm for some HUUM heaters. HUUM sells round stones in a 5 to 10 cm size, and Finnmark lists a 3 to 5 cm box of HUUM stones for HUUM’s CLIFF and STEEL electric heaters. HUUM also suggests stacking a denser top layer with slightly smaller stones.

Sources: Harvia: Sauna heater stones; HUUM: DROP electric heater user manual (EU, 2025), p. 8; Narvi: Velvet Electric (Flow) heater manual, English section, p. 76; HUUM: Sauna stones product page. Checked 3 October 2026.

How many sauna stones do you need?

It depends on the heater. The Finnish Sauna Society says the amount depends on the heater’s output and model, from a few dozen kilograms to several hundred. HUUM says its DROP electric heater needs about 55 kg, for example, and Tylö’s US guide gives about 44 lb (20 kg) for the Sense Sport. These are the capacities stated in the heater listings we track:

From the 48 heater listings in our data that state a stone capacity, as each retailer gives it. The last column is that weight divided by 20 and rounded up. Some heaters are sold with stones included: check the listing.

Compare heaters, with the stone capacity where it’s stated, on sauna heaters, Harvia heaters and HUUM heaters. For log-fired models, see wood-burning sauna stoves.

Sources: Finnish Sauna Society: Sauna heater; HUUM: DROP electric heater user manual (EU, 2025), p. 8; Tylö (US edition): Sense Sport heater installation and user guide (SSU 5, 7, 8), p. 5. Checked between 30 September and 3 October 2026.

Sauna stone prices per kilogram

16 of the 26 listings are 20 kg boxes, but 10 kg and 15 kg boxes and a 40 kg bag are sold too, so the price per kilogram is the fair comparison. Across the 25 listings with one stated weight, it runs from £1.40 to £6.50 a kilogram, with a median of £3.00. For olivine diabase and dolerite, the range is £1.40 to £5.00.

The five lowest per kilogram:

Leisurequip does not say whether its prices include VAT; for the other retailers we recorded the displayed price and didn't check for a VAT statement. “From” marks a starting price where the retailer sells several sizes or options: the shop's own “from” price, or the cheapest size we noted for the item named.

Stones are heavy, so check the delivery charge. Leisurequip says sauna stones are excluded from its free delivery and shipped separately.

How to stack sauna stones

Each manual describes its own heater, and they differ on how tightly to pack, so follow yours. The instructions we’ve read:

1. Wash them first. Harvia’s stone guide and HUUM’s DROP manual both say to wash the dust off the stones before they go in the heater.
2. Place them by hand. HUUM’s DROP manual says to lay the stones one at a time, not pour or throw them in. Its HIVE Wood manual says to go one layer at a time.
3. Leave room for air. Harvia says to arrange the stones evenly and sparsely so air can flow between them, and not to wedge stones between the heating elements. Tylö’s US guide says to place them loosely.
4. Cover the elements. HUUM’s DROP manual says the heating elements should not be visible through the stones. Narvi says to lay the stones as tightly as possible round the outside of its Velvet so the elements can’t be seen, and loosely in the middle so air can flow.
5. Mind the shapes. Harvia says elongated stones should stand vertically. For its NC wood heaters, Narvi says to put bigger stones at the bottom and stand flat stones upright.

Stacking affects how the heater works: the troubleshooting in Harvia’s Cilindro Pro manual, for a sauna that heats slowly, lists stones piled too tightly, settled stones and the wrong stone type among the causes.

Sources: Harvia: Sauna heater stones; HUUM: DROP electric heater user manual (EU, 2025), p. 8; HUUM: HIVE Wood stove user manual (EU, v1), p. 8; Tylö (US edition): Sense Sport heater installation and user guide (SSU 5, 7, 8), p. 5; Narvi: Velvet Electric (Flow) heater manual, English section, p. 76; Narvi: NC 16 / 20 / 20 VS / 24 wood-burning heater manual, English section, p. 24; Harvia: Cilindro Pro electric sauna heater, instructions for installation and use (PDF hosted by zoechling-holz.at). Checked between 1 and 3 October 2026.

When to restack and replace sauna stones

Harvia says stones crumble in use and compact in the stone compartment. What each maker says:

Tylö’s US manual for its Luleå saunas adds that the rocks should be taken out once a year for cleaning, and small or crumbled ones replaced.

Sources: Harvia: Sauna heater stones; Harvia Support: How often should the heater stones be changed in a family sauna?; HUUM: DROP electric heater user manual (EU, 2025), p. 9; HUUM: HIVE Wood stove user manual (EU, v1), p. 9; Narvi: Velvet Electric (Flow) heater manual, English section, p. 76; Narvi: NC 16 / 20 / 20 VS / 24 wood-burning heater manual, English section, p. 26; Tylö (US edition): Sense Sport heater installation and user guide (SSU 5, 7, 8), p. 6; Tylö (US edition): Luleå 3 and Luleå 4 outdoor sauna owner's manual, Rev C, p. 38. Checked between 1 and 3 October 2026.

Decorative and cover stones

Two of the listings are decorative stones: white cover stones that Finnmark describes as a decorative top layer, and Harvia’s white marble or red granite at Leisurequip. Check your manual before you use them: HUUM’s DROP manual says not to use decorative stones, because they don’t store enough heat and break easily.

Sources: HUUM: DROP electric heater user manual (EU, 2025), p. 8. Checked 3 October 2026.

Water on the stones

The steam comes from water ladled onto the hot stones. How much the makers say to use, what kind of water and what to pour it with are on sauna buckets and ladles, and the temperatures makers recommend are on sauna temperature.

Scent goes in that water, not on the stones: HUUM’s DROP manual says sauna fragrances and oils can catch fire if poured undiluted directly onto the stones. See sauna scents and how to use essential oils in a sauna.

Sources: HUUM: DROP Electric Sauna Heater installation and operation manual (EU; DROP 4, 6, 7, 9). Checked 3 October 2026.

Sauna stone questions