Trex Decking over Treated Decking
If you don't mind me asking, why do you want to go with this type? If your going to use Trex boards because they are maintenance free, they are not I'm in Destin Fl and you can see them all over. They look good when new but they still have trouble down the road like wood (but no splinters). I've seen many grey decks with trex and they look black and moldy looking. They do not pressure wash clean I've tried this many times. They do not splinter like wood, but at least with wood you can stain and seal wood, but if you insist on buying these I would recommend the brown stain color because I think they wouldnt turn that ugly blackish/moldy color the grey does. Even the brown color will fade and there are many factors about the weight of putting new boards over old boards. It will be a lot of weight, so you have to ask yourself do I have tons of support or just enough. You can also ask a contractor to take a look to be safe. I don't see how anyone can give you an honest answer about the support unless they saw it in person. You can also look at the weight issue like having a ton of friends on the deck at one time - would it hold up - but you are going to have more people on top of that right. I'm sure you can lay any way you want . To be safe just rip the old ones up. Just my opinion and I hope I helped some in sort of way.