Before selecting wood species, lighting, or accessories, it’s important to get the fundamentals right. The most beautiful sauna in the world won’t perform well if the ceiling height, bench layout, ventilation, and heater placement are incorrect.

These are the design principles we commonly use when designing high-performance custom saunas inspired by Finnish sauna practices and Trumpkin’s recommendations.

Step 1: Build Higher Ceilings

One of the most common mistakes in sauna construction is building the ceiling too low.

Traditional Finnish-inspired sauna design often favors ceilings between 8½ and 9 feet high. Many North American saunas use ceilings closer to 7 feet, which can leave bathers sitting too low within the room’s temperature layers.

Higher ceilings create:

• Better heat distribution
• More comfortable löyly
• Improved bench placement opportunities
• A larger usable hot zone

For most custom saunas, we prefer a finished ceiling height between 8′-0″ and 9′-0″ whenever possible.

Step 2: Position the Benches Correctly

Bench height is arguably the single most important design element in a sauna.

A common rule promoted by Trumpkin is:

The bather’s feet should be at or above the top of the heater stones.

This places the entire body within the hottest portion of the sauna.

Another commonly referenced guideline is the “fist rule,” which recommends approximately one fist width of space between the top of a seated bather’s head and the ceiling.

A typical bench arrangement might look like:

Upper Bench:

• 44″ to 48″ below the finished ceiling

Foot Bench:

• 16″ to 18″ below the upper bench

Lower Step:

• 16″ to 18″ below the foot bench

The exact dimensions may vary depending on the ceiling height and heater selection, but the objective remains the same: keep bathers high within the heat cavity.

Step 3: Select the Proper Heater

The heater is the heart of the sauna.

When selecting a heater, it’s important to consider room volume, glass surfaces, ventilation strategy, and stone capacity—not just the room dimensions.

Many experienced sauna builders prefer heaters with larger stone capacities because they produce softer heat and more satisfying löyly compared to smaller exposed-element heaters.

The goal is not simply reaching a temperature.

The goal is creating a comfortable and enjoyable sauna experience.

Step 4: Install Proper Ventilation

Ventilation is one of the most misunderstood aspects of sauna construction.

Modern mechanical ventilation systems generally provide the most consistent performance.

A common approach includes:

Fresh Air Intake:

• Located near the heater
• Approximately halfway up the heater height if netted or above heater if conventional.
• Connected to fresh outdoor air when possible

Mechanical Exhaust:

• Located beneath the foot bench
• On the wall opposite the heater
• Connected to an inline exhaust fan

This arrangement helps draw fresh air through the room while improving temperature consistency and oxygen levels.

The exact ventilation strategy should always be coordinated with the heater manufacturer and project-specific conditions.

Step 5: Plan for Comfortable Seating

The upper bench should allow bathers to sit comfortably for extended sessions.

We generally recommend:

• Upper bench depth: 24″ to 30″
• Foot bench depth: 16″ to 20″

A deeper upper bench allows bathers to sit upright, stretch out, or recline comfortably during longer sauna sessions.

Step 6: Minimize Excessive Glass

Glass creates a beautiful modern appearance, but it also increases heat loss.

When incorporating glass walls or doors:

• Use tempered glass
• Account for additional heater capacity
• Maintain proper bench-to-heater relationships

Large glass walls can absolutely work when the sauna is properly engineered, but they should be considered during the design phase rather than treated as an afterthought.

Step 7: Design for Löyly

If there’s one word every sauna builder should learn, it’s “löyly.”

Löyly describes the wave of heat and steam created when water is poured over hot sauna stones.

It’s one of the defining characteristics of a traditional sauna experience.

Nearly every design decision—including ceiling height, bench height, heater selection, ventilation, and stone capacity—ultimately affects the quality of the löyly.

That’s why experienced Finnish sauna builders obsess over details that may seem minor at first glance.

They’re not building a hot room.

They’re building an experience.