I have to go with 'attachment' being a primary problem.
- I looks like the deck collapsed for the outside (railing) end first down towards the house.
- I also looks like the entire system was built as sections. "let's build this one section because the lumber size is easy to handle, then another and another and nail them together". I see this method sometimes on larger decks. It's a good method when covering a roof that may needs servicing at some point but I am absolutely against it in decks as depicted.
- Each deck section tends to 'float' somewhat independently of the others because no one ever properly bolts the sections together to make one continuous run.
- It looks like support and attachment at the railing end are the real culprits here.
- I can't tell what size the joists are from the picture.
How many more news stories do we have to see like this before people stop cheaping out on deck design and maintenance? Every year there's a few.

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Accurate Inspections & Consulting, Inc.
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Markus Keller