Glass has cracked but not fallen: how long can it wait?

Work out what the glass is before deciding anything. Laminated, tempered, annealed and insulated units behave completely differently once cracked, and the difference is between a pane that will sit there for a month and one that could let go this afternoon.

Then mark the ends of the crack with a marker and write the date next to it, which answers the only other question that matters.

Identifying the pane

Look for an etched stamp in a corner, which most tempered and laminated panes carry. Failing that, look at the edge of the glass where it enters the frame.

A laminated pane shows a thin dark line through the thickness, which is the interlayer. An insulated unit shows two panes with a spacer bar between them, and the crack will be in one of the two rather than both. Tempered glass looks like ordinary glass at the edge, which is why the stamp matters.

Our article on tempered, laminated or insulated covers what each type is for and where each belongs.

What each type does once it is cracked

Laminated glass cracks and holds. The interlayer keeps the fragments in place, which is the entire point of it, and a cracked laminated pane is usually stable enough to schedule properly. It is still a failed pane and it has lost strength.

Tempered glass normally does not crack, it disintegrates into granules across the whole pane at once. A tempered pane showing a crack that has not released is in an unstable state and should be treated as likely to go.

Annealed glass is the unpredictable one. It can hold a crack for months or drop a long shard with no warning, and the shards are the dangerous kind. Over a footway or a public area, this is the case to act on.

An insulated unit with one cracked pane has lost its seal as well as its strength. It will fog between the panes over the following weeks and it is a replacement rather than a repair.

Reading where the crack started

A crack beginning at an edge and running in a curve is usually thermal or edge stress rather than impact. Thermal cracks follow a cold night after a hot day, or a pane that has become part-shaded by a new sign, awning or partition. Edge damage caused during installation surfaces this way years afterward.

A crack radiating from a point is impact, and the point tells you where. Look for a chip at the center.

Multiple cracks with no impact point, or a pane that has cracked in a frame that also shows distortion, suggests the frame or the structure is loading the glass. That is worth identifying before a replacement pane goes into the same opening and does the same thing.

Whether it can wait

Act now if the pane is annealed or tempered, if it is above or beside a public footway, if it is an exterior pane in a building people are in, or if the crack has grown past your mark since you made it.

It can usually be scheduled if it is laminated, internal, in a secured area, and stable against a dated mark. In that case, waiting for the correct glass to be ordered beats reacting to it.

Either way, keep people from leaning on it, do not clean it, and do not open or close a cracked door pane more than necessary. Movement is what turns a crack into a failure.

What ordering involves

Tempered and laminated panes are cut and processed to order, and insulated units are made up as a sealed assembly, so none of them are stock items. Identifying the type and getting the opening measured early is what stops a stable crack becoming an emergency while the glass is still being made.

Exterior work in Miami-Dade frequently involves impact rated glazing, which brings a permit and a Notice of Acceptance submittal with it. Our article on impact glazing and the NOA covers when that applies, and it adds time that is better spent before the pane fails than after.

Who carries this out

Repairing and re-glazing an existing opening is performed directly by our own technicians, including removing the cracked pane, fitting the replacement and boarding the opening if it lets go first. TrionX carries general liability and workers' compensation on that work.

Replacing the storefront system, altering an opening, or permitted impact rated glazing is coordinated through licensed contractors, because anything requiring a permit is licensed work whatever the trade. If the pane does fail before the replacement arrives, our article on the first hour after a storefront pane breaks covers what to do.