What is the recommended foundation slab size? It would be best if the slab edge was slightly recessed from the outside face of the sauna walls.

Thank you for your outdoor sauna question. You could choose a slab size depending on the look you want. For example, the sauna exterior is 4? x 6? and then the base trim around the outside would stick out another 5/8? So if you want to basically hide the slab, making it exactly 4? x 6? would be good. A slab that size would be «? bigger than the sauna base frame on all sides. If you want to extend you slab out for some purpose, such as creating a deck area out front, you can create your own look.