modernistmaude Hi moxidigital - love this home and deck. WE are building a similar deck around one side of our pool and also concerned about longevity of deck/timber near the salt water, along with keeping splashed water bouncing back into the pool. This looks like a concrete buffer to me. Its really important to keep the deck well maintained/oiled for longevity. Im definitely not an expert, but usually they would be built on joists. There are the alternative wood look alikes, eg Trex, etc. too which would be much easier to look after, but personally I love the look of timber, despite the maintenance!