Bought a 16 year old house a few weeks back. We're the 3rd owners; original owners were in the house for 6 years, the people we bought from we're here for 10 and did numerous renovations while they owned it. If finding that many of the projects they took on have a sloppy finish or were simply done wrong. This which brings me to the deck/terrace (I'm not sure if it's considered a deck or a terrace)
The house was built with a 20' x 20' "thing" on top of the flat roof garage. My home inspector pointed out that there's quite a bit of standing water on the roof under the deck boards. There's drainage built into the roof to eliminate the water that's bound to end up under the deck boards, but for some reason it's not working.
The deck looks like it was rebuilt a few years ago because the deck boards are in generally fair condition (except they were installed upside down with the crown facing up so they hold water rather than shed it. My curiosity finally got the better of me today so I lifted a few of the deck boards and I was not happy with what I found. They attempted to make a "floating" deck (please no water jokes) by making 5 x 5 frames with deck boards on top and laying them down on the roof. An attempt was make to isolate the wood from the roof (good) by using a waterproof material (also good) and allowing water to pass under the deck (very good!) Unfortunately the material they chose was green drywall (bad). The drywall deteriorated quickly and what I'm left with is a bunch of rotting 2x4's and I believe they're creating a series of dams which keep the water away from the drains.
Long term plan is to fully replace the deck and railings. Short term plan is to fix this mess so I have a functional deck for another 2-3 years. I plan to document the tear down and re-build here to keep all of us northern climate people who may be closing our pools soon entertained.
Feel free to post suggestions on how you'd repair this. I'll post pics tomorrow, I'll start the project next weekend weather permitting.