(Dear H.K.C.B. Heendeniya - Sorry this is not stacking as a reply under your original comment, but I was unable to get the 'reply' button to appear there.) Since each of the three buildings you described appears to contain more than 1,000 square feet of 'gross floor area', the general rule of thumb would be to treat them each as a separate LEED-certifiable building. Then, the team would have the option of applying one or both of the approaches outlined in the AGMBC (http://www.usgbc.org/Docs/Archive/General/Docs10486.pdf). In particular, the 'group credit' (aka group certification) approach may make sense in a situation like this if all three buildings will be built under a singe construction contract/scope of work.

Occasionally, a different approach might be warranted due to the disposition of integral functions amongst related buildings or other such special circumstances. Teams facing complicated scenarios like this are encouraged to use the Contact form (http://www.gbci.org/org-nav/contact/Contact-Us/Project-Certification-Que...) to explain their situations and obtain feedback directly from USGBC/GBCI before registering their projects as this will help ensure a smoother certification process.