Should You Repair or ReplaceYour Window Glass?

Almost every repair-or-replace question resolves the same way once you look at the frame. Glass is a consumable component — it is designed to be replaced, and any competent glazier can swap a lite or a sealed unit in an hour. The frame is the part that is genuinely permanent, and when it fails there is nothing to put good glass into.

So the test is simple. Press a screwdriver into the bottom corners of a wood frame. If it sinks, that is rot and the clock is running. On vinyl, look for corners that have opened at the welds and for a sash that no longer sits square. On aluminum, look for pitting and for a thermal break that has failed. If the frame passes, replace the glass. If it does not, glass is work you will do twice.

Two situations that override the arithmetic

The first is historic review. In DC historic districts, Old Town Alexandria and several Maryland jurisdictions, replacement of street-facing sash is often simply not permitted, and the question becomes how best to restore rather than whether to replace. The second is a whole-house project. If you are doing twenty windows at once, mobilization gets amortized across all of them and the practical calculus shifts toward replacement in a way it never does on a single unit.