Commercial leases usually specify how long you have to wait before you (the tenant) can terminate the lease without penalty due to circumstances (like flood, fire, etc.) that render the space unusable .

Unfortunately, commercial leases are usually written to favor the landlord, so time frames as long as six months are not uncommon.

Note to self: that's why business interruption insurance can be such a handy way of stemming the "red ink" tide should a major disaster--like a flood--occur and disrupt your business.

Review your lease terms with a real estate attorney to determine your options.