How many stones does a sauna heater need?

The correct sauna stone capacity is stated in your heater's user manual. The manufacturer specifies the capacity in kilograms and the appropriate stone size. Use this quantity when purchasing stones, but always follow the instructions on filling height and airflow when arranging them.

1. Identify the brand and exact model designation. Check the rating plate, user manual or purchase receipt. Include model suffixes and any product code.
2. Check both stone capacity and stone size. For example, 80 kg and 5–10 cm describe different things: the first is the total stone weight, and the second is the size of individual stones.
3. Consider model variants and accessories. A water tank, stone basket or other structural difference may change the capacity.
4. Calculate the number of bags. Round up to the next whole bag, but keep any unused stones as spares.

Sauna stone capacities by heater model – comparison chart

The tables below cover 34 electric and wood-burning sauna heater models. Click a model name to open its manufacturer's product information or manual. Details were checked on 9 October 2026. The manual supplied for your exact heater version always takes precedence.

The bag count is the calculated minimum using 20 kg bags. It does not include extra stones to account for unusable sizes or damaged pieces. Not every stone type is sold in 20 kg bags. On a phone, scroll the tables horizontally.

Wall-mounted electric sauna heaters

The stone size for Helo Cup was also checked against the Cup STJ installation and user manual (PDF).

Tower and mesh-sided electric sauna heaters

The Pilari-IKI figures apply to models with a separate control unit covered by the linked December 2025 manual. IKI lists maximum stone capacities. Do not automatically apply these figures to an older heater with a similar name or a different output rating.

Wood-burning sauna heaters and large stone capacities

* The figures for IKI wood-burning heaters refer to models covered by the 2025 manual without the optional Plus section. The stated quantities are maximum capacities. For normal use, the manufacturer recommends split sauna stones smaller than 10 cm. This is why 10–15 cm stones are not automatically suitable for every wood-burning heater.

If your heater is not listed, do not estimate capacity based on a similar-looking model. Send Fixmate pictures of the complete heater and a readable rating plate. A photo of the user manual or a product link also helps identify it.

What size and type of sauna stones should you choose?

Stone capacity, stone size and stone material must be considered together. Even the correct total weight will not help if the stones are the wrong size or packed so tightly that air cannot circulate through the stone compartment.

5–10 cm or 10–15 cm?

Many electric sauna heaters use 5–10 cm stones. For several Harvia and Narvi wood-burning heaters, manufacturers specify 10–15 cm. The IKI wood-burning models listed above are an exception. Choose the size specified in the model's manual, not simply by whether it is electric or wood-burning.

Stones that are too small can form a compact layer that blocks airflow. Oversized stones can be difficult to arrange correctly. Stones should fit without bending an electric heater's elements or forcing pieces between them.

Split, rounded and ceramic sauna stones

Split olivine diabase is approved in the manuals of many sauna heaters. Depending on the model, olivine and vulcanite are also used. Check that the packaging identifies the material as suitable for sauna heaters and that it meets the manufacturer's requirements.

Rounded stones, decorative top stones and ceramic stones require separate checks. Some heaters recommend special stones; others restrict their use. Attractive appearance or a high price does not prove compatibility. Do not substitute unknown stones collected from a garden or beach.

Further information about stone types and selection: Harvia's sauna stone guide and IKI manufacturer's instructions.

How many bags of sauna stones do you need?

Divide the recommended stone capacity by the weight of one bag, then round up to the next whole bag. For example, a 90 kg capacity requires five 20 kg bags or six 15 kg bags.

Stone shape and sorting also affect practical requirements. Not every stone in a package will necessarily fit your heater. Obtain a few spares if necessary, but always respect the manufacturer's filling limits. If correctly sized stones fill the compartment before you reach the nominal weight, do not force more stones inside.

For large heaters, plan how to carry the stones. A 300 kg capacity means fifteen 20 kg bags. During a full replacement, the old stones must also be removed from the sauna, so stairs, lifts and access routes affect the work.

How often should sauna heater stones be replaced?

Inspecting and rearranging the stones is not the same as replacing every stone. Harvia advises rearranging stones at least once per year, and more often under heavy use. Remove crumbled material and replace damaged stones at the same time. Whether a complete replacement is needed depends on their condition and the heater's maintenance instructions.

Inspect the stones if fragments collect beneath the heater, the stone bed settles, or pieces crack and crumble when handled. Changes in the quality of steam or unusually slow heating are also reasons to check, although they do not by themselves prove the stones are the cause.

If much of the stone bed has become fragile or its maintenance history is unknown, replacing the complete load may be the most practical solution. In housing-company and other frequently used saunas, maintenance frequency depends on actual use and the manufacturer's instructions.

Maintenance reference: Harvia's instructions for arranging stones in a wall-mounted electric heater.

How to replace and arrange sauna heater stones

Start only when the heater has cooled completely. Disconnect the electric heater's power supply and prevent timed or remote activation. The steps below supplement, rather than replace, the instructions for your own model.

1. Prepare the work area. Protect the floor and use sturdy, manageable containers to carry stones. Wear protective gloves.
2. Remove old stones by hand. Work carefully. Do not bend the heating elements or force stones that are stuck.
3. Remove stone debris. Clean the cooled stone compartment only as permitted by the manufacturer. Do not wet electrical parts or open electrical housings.
4. Inspect visible components. Stop if you notice a damaged heating element or another obvious defect. New stones will not repair a faulty heater.
5. Rinse and sort new stones. Remove stone dust away from the heater and discard broken or incorrectly sized pieces.
6. Place stones individually according to the manual. Leave space for airflow and ensure the heating elements are covered as required. Do not tip an entire bag directly into the heater.
7. Check the fill level. Keep stones within the permitted compartment and avoid an excessive mound above the heater. Follow the manufacturer's commissioning instructions.

With tower heaters, coverage around the sides also matters. Stones must remain securely in place while allowing air to circulate. If a heater is built into the sauna benches, plan in advance how to access the full stone compartment.

Stone replacement does not include repairs to electrical faults. If a problem involving electrical components is discovered during maintenance, arrange the necessary repairs through a qualified electrical professional.

Sauna stone replacement prices in Helsinki, Espoo and Vantaa

Fixmate's indicative pricing is based on stone capacity and the scope of work. The ranges below are those stated on our stone replacement service page on 9 October 2026.

The final estimate depends on the heater's construction, chosen stone type, carrying distance and disposal of old stones. Materials and transportation are confirmed in the quote. For heaters requiring less than 20 kg or amounts between the listed brackets, ask for an individual estimate. See current prices and service details.

Combine stone replacement with other sauna maintenance

You can also request sauna bench oiling and wooden surface treatment. Let us know about all the work you need in advance so we can plan the tasks and time required. Drying times and treatment-product instructions affect when the sauna can be used again.

Explore our complete range of sauna maintenance services.