Harvia Sauna Stones (Large) 10-15cm

Got it — these are the Harvia Sauna Stones (Large) 10–15 cm, 20 kg. Here's the description following the same format as the 5–10 cm stones:

Harvia Olivine Diabase Sauna Stones 10–15 cm – 20 kg

Best For: Anyone building or maintaining an outdoor sauna with a wood-burning heater, or looking to create a solid, long-lasting base layer in any electric heater with a large stone capacity. Ideal for larger heaters such as the Harvia Symphony and Fort series.

Harvia Olivine Diabase sauna stones in the larger 10–15 cm size are mined from dense, sub-volcanic rock in western Finland — the same traditional material that has been used in Finnish saunas for generations. The larger stone size makes them the perfect choice for the bottom layer of the heater, where they form a solid foundation, promote free air circulation, and provide even, stable heating throughout the stone bed. Their high density means they absorb and hold heat exceptionally well, releasing it slowly and consistently for a soft, lasting steam.

Key Features:

• Stone type: Olivine diabase — traditional Finnish sauna stone
• Size: 10–15 cm (recommended for base layer of wood-burning and large electric heaters)
• Box weight: 20 kg
• Colour: Dark grey
• Split-face surface for efficient heat absorption and steam generation
• Easy to stack with good air circulation between stones
• Excellent heat storage capacity, durability and thermal conductivity
• Safe and free from harmful chemicals
• Mined in Finland
• Compatible with all Harvia wood-burning heaters and large-capacity electric heaters

How To Use Rinse stones before loading to remove dust. Place in the bottom layer of your heater basket, stacking loosely so stones support each other and allow airflow throughout. For electric heaters, finish the upper layers with smaller 5–10 cm stones to maximise steam generation. After loading, heat the sauna and throw a few ladles of water over the stones to disperse any natural stone scent on the first session. Inspect stones annually and replace any that are cracked or crumbling.

The Result A stable, long-lasting stone bed that holds heat evenly and delivers consistent, smooth steam session after session. The larger size is particularly effective in bigger heaters where a solid thermal foundation makes all the difference.