Accounting Entries for a new building...

We have an office building and a piece of unused land adjoining the building. The proposal is to partially demolish the existing building and construct a new complex using the land. My question is :- 1. How do I treat the proposed conversion in the books? ie . What are the accounting treatment for this conversion? 2. What accounting standard should I be referring to do my research? Just a high level input would be great. Thank for your time.