I could say, only in the wet northwest, but will hold back on that in describing this photo. The picture below was taken at a new home that I inspected. Odd as it may seem, the downspout was turned in towards the floor of the deck and drained onto it. So that is odd in itself. But can you guess why there was flooding over the deck, by about two inches, on a new waterfront luxury house? Why was the water not draining between the decking boards? Think about it and the answer is below. By the way, this house had received the final approval from code inspectors -- they saw no problems worth mentioning.
Answer: The TREX deck is up high, built on top of a flat roof. If you read one of my earlier posts, you know that a flat roof should not really be flat -- it needs to drain too. But in this case the flat roof is not draining so there is enough water collected on it to also come up above the decking boards that are above it. If you think about how thick a deck would be, that is one heck of a lot of water and weight. And the structural wood and deck, TREX or not, are not designed to be on the exterior of a submarine -- submerged. Again, this house was brand new. This is another example of why a "common sense" home inspection is important even if a code inspection has been done. They are not the same thing at all!
Thanks for guessing.
Bellingham WA home inspector
Steven L. Smith