By "structurally sound" I mean, "not unsound, structurally."
I don't mean that the engineer who built the house out of playing cards didn't use superglue to hold the house together. I meant that he though any kind of house of playing cards was structurally worth anything other than show.
It doesn't matter that what you have just posted does not make sense. Phrases like "structurally sound" have very specific meanings.
Put it this way - If I was an investor and had that kind of money and was looking at Building 7, no to buying it. It just plain looked kind of shakey.