Swell Sport · Practical guide

Should you oil the inside of a sauna?

Not automatically. Start with the instructions for the cabin and the exact surface. For the supplied Cube 2 manual reviewed here, the answer is clear: oil external faces only, not internal seating, backrests, heater surrounds or internal wall surfaces. ^[1]

Swell Cedar Cube 2 in a home setting.

Use a surface map before buying a product

Draw four boxes: exterior timber; internal walls; seating and backrests; door and trim. Copy the cabin instructions into the relevant boxes. Keep a separate note for any factory-applied finish so a maintenance product is checked against the surface actually present.

For Cube 2 interior seating, backrests, heater surrounds and walls, put “do not oil” on the map. That simple handover note is especially useful when a painter or gardener maintains other outdoor timber at the same property. The exterior treatment instructions do not extend indoors. ^[1]

Why general sauna advice can sound different

Harvia’s general care guidance recommends paraffin oil for sauna benches and says other timber parts do not necessarily require treatment. That is general sauna guidance, not an amendment to the Cube 2 cabin manual. A Harvia heater installed in a cabin does not make every Harvia care recommendation the cabin’s finish specification. ^[2]

If your cabin has a different manufacturer or manual, follow that document’s approved treatment route. For a Cube 2, do not substitute the general recommendation for the express interior restriction. For another Cube version, obtain the care instructions for that version rather than assuming the same treatment schedule.

A practical approval decision tree

First identify the surface and the cabin. If the manual says leave it untreated, stop at cleaning and drying as instructed. If the manual permits a treatment, identify the exact product and current instructions, including preparation, application and when the cabin can return to use.

If the existing finish or product is unknown, send a photograph of the label and the surface to the cabin supplier before application. Ask for a written answer identifying the permitted surface, not a broad statement that the bottle is “for timber”. Keep that answer with the product instructions.

If someone has already applied oil

Stop further application and record the product name, surfaces covered and date. Keep the packaging and take photographs. Ask the supplier for the next step before heating the cabin or attempting a removal process. This preserves a clear account of what was used and avoids layering a second product over an unresolved first application.

Do not try to correct the situation with a generic sanding, solvent or high-heat routine from a different sauna. Ask specifically whether the surface needs inspection or treatment removal and who should carry out that work.

Example: exterior maintenance day

An owner books a contractor to refresh the outside of a Cube 2. The work order includes a marked exterior photograph, the approved exterior product and the instruction “interior seating, backrests, heater surround and walls excluded”. The owner provides the cabin manual before the contractor starts.

At handover, compare the treated areas with the marked photograph. Keep the product label and work date for future maintenance. Interior care remains a separate job: the Cube 2 manual calls for wiping high-use areas once cool and removing wet items after use. ^[1]