Do you need planning permission for a garden sauna?

The five rules

A garden sauna falls under Class 3 of the exempted development rules, the same class as sheds, garages and garden rooms. Meet all five rules and you don't need to apply. Miss one and you do.

1. Up to 30 m² in total for every shed, garage, greenhouse, garden room and sauna on the property.
2. At least 25 m² of garden left behind or beside the house after it goes in.
3. Behind the front of the house. Nothing in the front garden.
4. 4 m high with a tiled or slated pitched roof, 3 m otherwise. Most garden saunas have barrel, flat or felted roofs, so 3 m usually applies.
5. Home use only. Not rented out or run as a business.

If the sauna is at the side of the house, its outside finish must match the house. In the back garden, any finish is fine.

The 30 m² total

Garden saunas are small. Even the largest we've recorded, an 8-person cube, has a footprint of about 2.4 × 3.05 m, or 7.3 m². The limit matters only if you already have a large shed, garage or garden room:

A sauna built into a garden room counts as part of that room's floor area.

The 25 m² of garden

In a small garden, this is the rule to check first. Measure the private open space behind and beside the house, take away the sauna's footprint and anything else you're adding, and make sure at least 25 m² is left. A 6 × 5 m back garden (30 m²) leaves room for a sauna of up to 5 m².

Height and flues

Measure the height from ground level to the highest point. For a wood-fired sauna, that can include the flue, so check the stove's flue height against the limit before you buy, and site the sauna so smoke drifts away from houses.

Home use only

The exemption covers buildings used for the enjoyment of your home. Using your sauna with family and friends is fine. Renting it by the hour, selling sessions or opening it to the public is a commercial use that needs planning permission.

When the exemption doesn't apply

• Your house's planning permission removed exemptions. Some estates were granted with conditions that do. Check the original permission.
• Your house is a protected structure, or the sauna would affect its character.
• You live in an apartment. Class 3 applies to houses.

If you're unsure, you can ask your council for a Section 5 declaration, a formal decision on whether your plan is exempt.