Make provisions for a reinforced concrete slab 75 to 100 mm (3 to 4 inches) thick.
Connect the ground lead to the wire mesh.
If the spa is being installed on an existing patio or deck, the patio or deck must be level. Make sure the patio is structurally sound, and able to support the weight of the spa, water and occupants; talk to a structural engineer.
If the spa is being installed on crushed rock, remove grass to 6 inches beyond the sides of the spa and fill the space with crushed rock. Make sure this base is level and well compacted.
Provide a good drainage system for splashing water when filling, draining or using the spa.
Air ventilation in the room (if indoor) will help maintain comfort and minimize building damage.
Check the structure strength on which the spa will be placed.
Make sure mechanical components (motor, water heater, etc.) are easily accessible. Provide extras for maintenance if your spa is not accessible.
Have a licensed electrician hook up your spa and make sure it is GFCI-protected.