It depends on a few factors, including location (e.g., placing the outdoor sauna near a fence), the size, the type of foundation, and the type of heating you’re planning to use. In some instances you will not be required to obtain Planning Permission, however, your Local Planning Authority will have the final word, so it’s a good idea to check in with them sooner rather than later. Until then, do look through our Planning Permission page for a clearer picture, including more technical information.