Check if your sauna build is set up properly.

It scores six areas out of 100, from size and heater through ventilation, insulation, floor and materials, and names your weakest link. Any sauna, self-builds included.

Intake low near the heater, exhaust high on the opposite wall. Around 150 square centimetres of intake for a 2 by 2 metre room, and a 10 to 15mm gap under the door.

Between 100 and 120cm below it, which is where the heat actually sits. A bench too low is the usual reason a sauna feels lukewarm while the gauge reads hot.

At least 100mm in the walls and 150mm in the ceiling, because heat rises, plus a foil vapour barrier on the warm side behind the cladding.

Usually water with nowhere to go. The floor and ventilation tabs cover drainage, fall and high-level exhaust, and it returns a rot risk. Send us the result for a second view.