How to Prepare the Perfect Base for an Outdoor Sauna – Step-by-Step Guide

Before installing your outdoor wooden sauna, preparing a proper and stable ground base is crucial. Many future owners of garden saunas ask us about the best base type and how to prevent water damage and instability. Below you’ll find everything you need to know to ensure a solid, long-lasting sauna foundation.

1️⃣ What to Consider Before Building the Sauna Base

First, decide the exact location where your sauna will stand. Most people start on an unprepared, grass-covered area. Mark out the required space based on your sauna’s size and style — for example, barrel saunas and igloo saunas require slightly different foundations. Always confirm final measurements with our team before beginning construction.

2️⃣ Step-by-Step: Preparing the Ground Base

Step 1 – Remove grass and topsoil (5–10 cm).
Eliminate the grass layer to prevent soft, unstable spots that may block drainage. A well-draining surface is essential because water accumulation under a wooden sauna can lead to fungus, rot, and structural weakness.

Step 2 – Compact and level the soil.
Flatten and compress the soil beneath to provide a stable, even surface. Uneven pressure can cause cracks, distortions, and long-term structural issues. For inspiration on long-term sauna durability, see our post about outdoor sauna maintenance.

Step 3 – Add a drainage layer.
Spread a layer of gravel or crushed stone to allow excess water to flow away from the base. This simple addition protects your wooden frame and keeps humidity low year-round.

These are the most common preparation steps, but every garden is unique. For alternative ideas, check our related article on outdoor sauna problems and solutions — you’ll find useful examples of drainage, foundations, and waterproofing techniques.

3️⃣ Quick Tips for a Durable Sauna Foundation

• Always plan a drainage slope (approx. 1–2%) away from the structure.
• Ensure access for ventilation under the base.
• Use anti-rot treatment or thermowood for wooden foundations.
• Check level again before installation.
• Consult our infrared sauna guide for comparison of heating and space requirements.

Following these steps guarantees that your outdoor sauna base will stay dry, stable, and long-lasting — providing the perfect start to years of wellness and comfort in your own backyard.