Installing an outdoor sauna: foundation, connections and permits

Short answer: an outdoor sauna requires four things from your garden: a level, load-bearing and water-draining surface, a clear spot with the door out of the wind, the right connection (three-phase power for electric, a clear flue gas outlet for wood), and a checked permit situation via your local planning portal. Also arrange crane access in good time, since a complete sauna cabin is always placed with a crane. Below you will find every step in detail.

Step 1: choose the spot

• Wind direction: place the door away from the prevailing wind (in the Netherlands usually south-west). This keeps the cabin temperature stable and prevents a cold gust every time the door opens.
• View: a model with a panoramic window, such as the Q-cube, shows best with a clear view into the garden and the window facing away from the afternoon sun.
• Distance to the house: close by is convenient on winter evenings; further from the house gives more privacy and quiet. Also consider the walking route to a shower or a cold plunge tub.
• Property line and neighbours: keep at least 1 metre from the property line, and preferably more with a wood-fired heater: smoke that drifts towards the neighbours' terrace by default is the fastest route to friction.
• Chimney: the flue gas outlet must vent freely, away from overhanging branches, thatched roofs and roof edges.

Step 2: build the foundation

A sauna cabin with heater, stones and 6 to 8 people quickly weighs more than a small car together. The surface must carry that weight without settling and must drain rainwater, because a sauna standing in water will rot away at the base.

Here is how to build a solid foundation bed:

1. Excavate the spot to around 15 to 20 cm deep, a little larger than the sauna itself.
2. Lay root cloth against weeds and regrowth.
3. Apply a layer of crushed rubble or coarse sand and compact it with a plate compactor.
4. Finish with paving sand and lay tiles or concrete slabs on top, level with a slight fall (around 1 cm per metre) so water runs off.
5. Check the whole surface with a long straightedge or spirit level: the cabin must stand completely level, otherwise the door and window will bind.

An existing, level concrete slab also works. Timber decking only if it is demonstrably rated for the weight.

Step 3: arrange the connections

Electric heater: a sauna heater from around 4.5 kW upwards runs on three-phase power (400 V) and belongs on its own, separately fused circuit with a residual current device. Always have the installation carried out by a qualified electrician and plan this well ahead of the delivery date; waiting times with electricians are often longer than the delivery time of the sauna.

Wood-fired heater: no electricity needed, but a good flue gas outlet is required. Make sure the chimney is tall enough for proper draw, fit a spark arrestor and keep distance from flammable material. Also check local rules on wood burning in your municipality; persistent nuisance complaints can lead a municipality to impose requirements.

How to maintain the heater and stones afterwards is covered in sauna heater and sauna stones maintenance.

Step 4: check the permit

Roughly the same framework applies across the Netherlands: a freestanding outdoor sauna is an "accessory structure", comparable to a garden shed, and in many cases can be placed without a permit if:

• the sauna stands in the back garden area (behind the front facade, not on the street side);
• you stay within the height and surface limits that apply to outbuildings;
• the total built-up area in your back garden stays under the maximum coverage percentage (for smaller gardens, a rule of thumb is a maximum of half the back garden area);
• the sauna stands at least 1 metre from the property line, or the neighbours agree in writing.

Watch for exceptions: for a listed monument, a protected town or village view, a rented home or a homeowners' association, additional or different rules apply. The only way to be certain is the free permit check for your own address on the relevant local planning portal; rules differ by municipality and sometimes by street.

Step 5: prepare for delivery day

An outdoor sauna is delivered as a complete cabin and placed with a crane. That requires some preparation:

• Arrange a setup spot for the crane truck close to the garden.
• Check the route from the street to the garden for obstacles: trees, lampposts, cables and gutters.
• Pass on any particulars in advance (a narrow street, access via the back, a height difference), so these can be taken into account in the planning.

More on the delivery process is in delivery and placement.

Checklist: ready for the sauna

1. Spot chosen: door out of the wind, chimney clear, good view.
2. At least 1 metre from the property line (or the neighbours' agreement).
3. Foundation level, load-bearing and water-draining.
4. Three-phase circuit installed and inspected (for an electric heater).
5. Permit check done on the relevant local planning portal.
6. Crane route and setup spot checked.
7. Neighbours informed; saves questions on delivery day.