It differes by state, this if for California: The Uniform Building Code requirements for plaza decks waterproofed surfaces designed for pedestrian-type occupancy has always been somewhat ambiguous in the past, inviting experts in construction litigation to testify both in defense of and in criticism of architects who have designed decks without slope.
If the deck is properly flashed and the decking is properly spaced and appropriate materials are used for framing and decking, there is no risk of moisture damage. On a closed porch, such as with T and G decking, any slope less than Â¼" per foot is useless and the decking needs to be oriented perpendicular to the house parallel with the slope .
By "step down" what I mean is that there are doors out to the deck that will sit on the low-slope roof. I think I need at least some small step from interior floor to the deck, if they are dead level I will have a problem with melting snow, etc. I don't know how much space I should allocate for this. Prefer not much of a step, but not
My OH says that they should have sloped it slightly so that the rain water would run off the decking, away from the house to the garden to drain away. I have mentioned this to the decking people who say it is "standard practice" to lay decking level and that as it is pressure treated timber, it won't rot.
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