Sauna Cladding & Bench Slats

Both are genuinely suitable for sauna use, just for different reasons. Thermo Aspen is thermally modified, giving it a pale golden-brown colour and excellent stability. Standard Aspen is kiln dried to low moisture levels specifically for sauna use, keeping its natural white colour, and is more affordable than Thermo Aspen. Which one to choose comes down to look and budget rather than one being better than the other.

Sauna interiors reach 70–110°C in high humidity, with direct skin contact — most timber isn't suited to that combination. Aspen is chosen specifically for its low resin content (so it won't bleed sap when heated) and low thermal conductivity (so it stays comfortable to touch even at full temperature).

No — sauna timber is deliberately left uncoated, whichever finish you choose. A coating would interfere with the timber's heat and moisture performance, which is the opposite of what you want inside a sauna.

Channel Groove is for walls and ceilings — a clean, modern profile with a shadow-gap line between boards. PAR + Rounds is specifically for benches and backrests, with a rounded edge that's genuinely more comfortable to sit on than a square edge, and wears better over repeated use. Both profiles are available in either Thermo Aspen or standard Aspen.

Measure wall and ceiling area separately from bench surface area, since they use different profiles. Allow around 10% extra on top for cutting waste, particularly around door frames and heater cut-outs.

Yes — fitting uses the same principles as standard tongue-and-groove interior cladding, a realistic project for anyone comfortable with general carpentry. Ventilation, heater installation and electrical work are worth having done by a qualified professional regardless of who fits the cladding.