The rabbit hole: where sauna design principles meet reality

Design notes from the collision between theory and UK reality

Design Notes is a series of reflections we will write as we move through the process of designing and building saunas in the UK. It is not a how-to guide. It is a record of what happens when well understood sauna principles meet real world constraints.

Over the last few years, a growing body of high quality, publicly available material has emerged on how to design a good sauna. Much of it is grounded in Finnish practice and research. Certain principles come up again and again:

Spend enough time with this material and it can start to feel as though the hard work has already been done. On paper, it is possible to sketch something that looks technically excellent.

So why do so many UK saunas not live up to that expectation in practice?

What we are finding is that the answer is rarely ignorance. More often, it is that almost every principle has a deeper layer of constraint beneath it. The rules are real. So is the rabbit hole underneath them.

Feet above the stones: a rule that meets its limits

Feet above the stones is one of the most widely cited sauna design rules. The logic is simple. Heat stratifies. If your feet sit below the level of the stones, you are likely to feel a large temperature difference between your head and your feet. The bigger that difference, the more uncomfortable the experience becomes.

So why do so many UK saunas fail this test?

As we have started designing in earnest, it has become clear that this rule often breaks down not because builders do not know it, but because they have already spent their height budget elsewhere.

A few pressures show up quickly.

Electric and wood-fired stoves behave differently. That affects ventilation strategy, how heat recovers after door openings, and how forgiving the room is when it is busy. In the UK, this is compounded by power constraints. Electric stoves large enough for commercial use often require three-phase supply, which many sites simply do not have. In practice, this pushes operators towards wood. That comes with its own challenges, but in our view, it also brings some real advantages.

Overall building height matters, especially in the UK planning context. Flue height counts. Trailer height counts. Chimneys do not disappear just because the room below them is well designed.

Commercial saunas are often height constrained by planning thresholds, transport limits, or neighbour visibility concerns.

Once the overall envelope height is fixed, something has to give. Bench height, ceiling height, or the distance between them.

The result is predictable. Lower benches lead to colder feet. Colder feet lead to compromised sessions. Once the vertical temperature gradient collapses, the quality of löyly suffers as well. Steam no longer envelops evenly. It dissipates or behaves awkwardly. The rule still holds, but the system no longer allows it to be honoured cleanly.

The theory isn’t wrong. The context is harder.

This pattern repeats across almost every design principle.

Ventilation placement looks straightforward until you factor in winter wind exposure.
Anterooms make obvious sense until you are trying to stay under a planning threshold.
Insulation feels non-negotiable until cost, transport weight, and moisture detailing collide.

Then there are the softer pressures. Finding a viable site. Navigating neighbor objections. Working within tight budgets. Assuming a level of customer knowledge that may not exist.

Taken together, the picture becomes clearer.

Most design compromises do not come from cutting corners. They come from pressure.

Why we’re writing this down

As we move further into designing and building our own saunas, these trade-offs are becoming impossible to ignore. Design Notes exists to document those collisions. Not to claim answers. Not to offer prescriptions. Simply to understand the terrain better.

If there is one thing this early work has made clear, it is that good sauna design is not about knowing the rules. It is about deciding which compromises you are willing to make, and being honest about their consequences.

Further reading

If you want to go deeper into the theory that sits underneath these notes, the following were particularly useful to us:

• Secrets of Finnish Sauna Design by Lassi A. Liikkanen
• Finnish Sauna: Steam, Wood, Stone and How to Build Your Own by Lassi A. Liikkanen
• Trumpkin’s Notes on Building a Sauna
• Craft Your Finnish Sauna by Timo Laakso