Many people design and build a deck around their hot tub. There are a number of things that should be considered and designed into such a deck. The decking should not run over the top of the tub, but should be flush to the top of the hot tub.
On round hot tubs a small gap should be left between the decking and the hot tub. ¼” to ½” is sufficient. The exception to this is oval hot tubs. In oval hot tubs, over time, the pressure of the water will try to round out the top of the hot tub.
Slight contact between the long side of an oval hot tub and either the decking or deck framing will prevent this. Many people choose to have the top of the deck ¼” to ½” below the top of the hot tub. This helps to prevent dirt and debris on the deck from blowing into the hot tub.
An additional consideration is future access to the exterior of the hot tub. At some point in the future the exterior of the hot tub may need to be accessed for inspection, maintenance or possible for repairs.
Dirt and debris should also be cleared out from around the sides and bottom of the hot tub. If a deck is going to completely seal in the hot tub, screwing down the decking, or providing a trap door or other type of access is advisable.