I am building a 20x16 free standing deck attatched to the house, I have 8 footings with 6x6 posts. I was going to go with the composite decking however my customer is wanting a pebble floor. I've seen the floating tiles that just snap in but those do not seem "permanent" and I've done pebble mosaic floors over cement but could I possibly just use pressure treated lumber as my sub floor, then with the right protection, Somehow grout pebbles? I am worried about rot, cracking, etc... Thank you for your consideration and I look forward to hearing from you.