“There are 2 condo’s in the building, only. I own the upstairs condo. I need to construct an egress stair from my upstairs unit to provide it with a second means of egress as required by the State Building Code.

The downstairs unit owners said they will not allow the rights to the use of the rear yard for the proposed egress stair,

Can the owners override the State Building Code.”

The question is, does the building code override your neighbors’ private property rights. Put that way, the answer is probably no: Imagine a situation with two neighbors, one of whom needs something (like an egress stair) which would fall over the property line. The neighbor is under no obligation to allow this, even if that would mean the upstairs becoming unusable.

However, your situation is different, since the units are condominiums. Normally, there are fairly thick documents setting forth the condo owners’ relative rights and responsibilities, and those documents may very well provide you with some ground for requiring this addition.