Hmm, that's interesting. Wood can't be rusty in the literal sense of the word, because "rust" is something that happens to metal.
I would probably be more inclined to think it meant that it was "rust-coloured" (a kind of dark reddish brown). There's nothing else in the short extract you have given us to signpost us to what meaning is meant, but rusty in the sense of "not working, needing repair" is something I associate more with machinery and moving parts than with a house. However, further context might well make that a valid interpretation here.
I'd avoid "old/ancient" as a meaning because something doesn't have to be old to be "rusty".
rusty - definition of rusty by the Free Online Dictionary, Thesaurus and Encyclopedia.
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