I note that should the USofA ever accept the joys of the metric system, then preservation work will become slightly more difficult.  Matching the old grids with metricated materials can be a real pain in the ...

Even though lots of our standard modules are relatively hard conversions, the difference is still significant ... a foot is 305 mm, not 300mm.  So four feet is 1220mm, not 1200mm.  Yet grids for ceiling systems are now typically 1200mm centres, not 1220mm ... and so replacement tiles are really difficult to cope with.

Tends to be more of a problem with interiors than exteriors ... by the time external components are being replaced, the material or component is no longer available, not just the wrong size.

Cheers

david