I had similar leaking roof issues when I lived in San Francisco. My recommendation is to avoid lawyers as much as possible but keep the roofers, or other roofers that the GC engages, coming back until they fix it! In fact, that would be where I would start, by asking the GC to send better roofers to resolve the problem.

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2008 X5 4.8i | Wheels: Summer> style 336 20" RFT; Winter> style 214 Ferric Grey 20" RFT | Aero kit | ESS E-Flash tune | V1 | LCI Rear Tail Lights | Coding completed | Engine replaced at 90K