It's generally safe to assume people intend to finish what they've started. When parties don't see a project to completion, however, contract law will usually provide remedies. But what if that nonperformance is the result of matters beyond the parties' control? In that case, construction contracts only operate to bail out a nonperforming party if they contain a "force majeure" or similar clause.
Though particular forces of nature can be hard to anticipate, a carefully constructed contract can typically protect the parties' interest no matter the event. You should contact a construction contract attorney who can help to draft a contract that protects your project.
Force majeure clauses operate to provide an excuse for failures to perform caused by matters outside the parties' control. In many other contexts, these matters are limited to "acts of god" or non-human events only. In the construction context, however, force majeure clauses often expand the scope of events to "man-made" events such as strikes, the unavailability of resources, and unexpected enactments of government regulations.
Typically, though force majeure clauses provide an excuse for a failure to perform, they do not operate to cancel the contract entirely. Rather, the performance deadlines are simply extended until the impact of the event no longer impedes on that performance.
What constitutes a force majeure is determined entirely by the contract. This gives parties the power to negotiate for inclusion or exclusion of certain events. You should contact a construction law attorney who is familiar with construction related events, to make sure your force majeure clause has you covered.