Shipyard practice explains displacement differences within the Tribal class

Why did Tribal-class destroyers built by different yards have different displacements?

Yards interpreted and built the design differently, and later ships included modifications that affected weight and upgrade potential.

Nominally common plans did not produce perfectly identical Tribal-class destroyers. Different yards interpreted details through their own steel densities, construction practices, and proportions of riveting and welding. Later ships also incorporated changes that made radar upgrades easier. Class data can therefore vary even when ships share the same official design.