(6) The work as erected shall meet or exceed the following structural and weather resistance requirements as demonstrated by engineering calculations and mock-up testing. Methods of fabrication and assembly (except as specified herein, or as recommended by the Engineer as a consequence or result of testing) shall be at the discretion of the ontractor provided that the exterior and interior visible architectural effect is not changed, the work of other Contractors not affected and weather tightness and strength qualities as demonstrated by engineering calculations and measured by the results of the tests for performance requirements are not reduced. Remedial measures which may be necessary on the mock-ups or the building shall maintain standards of quality and durability and are subject to approval by the Engineer.