Did Your Glass Shower Door Shatter By Itself?

Foot and Shattered Glass
Foot and Shattered Glass. Getty / Renold Zergat

Many readers have written in over the years to report a puzzling phenomenon:  their glass shower doors spontaneously shatter when no one is in the room, and often in the middle of the night.

Is this true?  If so, what is the cause?

"Spontaneously Exploded"

It all began with a reader who claimed that "our upstairs bathroom shower door spontaneously exploded in the middle of the night," I wrote back and asked if, perhaps, the door hadn't actually fallen from the frame and shattered on the floor, giving the impression that it exploded.

  I couldn't believe that this had actually happened.

Keep in mind, shower glass is not supposed to fall from frames.  But even that would be preferable to what actually happened...

The reader provided enough details and photos to convince me that, yes, the door had shattered while in place:

The middle of it blew clean apart leaving glass shards inside the frame.  We were awakened by a very loud explosion upstairs .  It was pretty scary.  My daughter who sleeps upstairs said that she heard two noises.  The first was like a big crack noise.  Minutes or an hour later the thing 'exploded'.

Following are some common themes of this syndrome:

1.  All Too Frequent

This is not a rare, one-off event.  Many owners of glass shower doors report this happening.

2.  "Exploded" and "Blew Up"

Typically, the shower door glass never quietly cracks and mildly "tinkles" on its way down.  The verbiage is always some variation of "exploded."

Retailers have told homeowners that they heard this all wrong.  What they heard, the retailer says, is not an "explosion" but the sound of the glass crashing to the shower floor.  Showers are small spaces and thus amplify sound.  Bathrooms, too, tend to have hard surfaces and little to absorb sound, thus the sound is further amplified.


3.  Happens At Night

Another trend is that this happens at night, often very late or past midnight.  Homeowners are in bed and sometimes are first woken up by an initial crack, followed by the explosion. 

Most happen between midnight and 3:00 am.

Does the temperature change, from warmer to cooler, affect tempered glass?  A Seattle Times article reports contractor Jerry Filgiano as saying that temperature extremes can affect tempered glass, though the slow lowering of temperatures from day to night likely does not count as "extreme." 

The same article says that nicked glass edges caused by a screw or bolt can cause the entire panel to shatter and that framed doors may be less apt to shatter than frameless doors.

4.  Who Is Responsible?

Who is accountable?  Glass people tend to say their door was improperly installed.  Installers say that the glass itself was defective.  Materials blame labor; labor blames materials.

The Consumer Products Safety Commission (CPSC), on its self-reported board Safer Products, lists plenty of instances of shattered shower doors.  One entry regarding a Kohler Clear Glass Bypass Bath Door reads much the same way as the above-mentioned incident.  To its credit, Kohler Co.

does respond to the complaint.

In the specific case of shower doors, all doors are manufactured with tempered glass in compliance with Consumer Product Safety Commission (CPSC) and American National Standards Institute (ANSI) standards. To ensure this is the case, newly tempered glass is fractured and tested on a regular basis every day at our plant. In addition, Kohler voluntarily submits its glass to an independent entity for testing, to ensure consistency with and adherence to these standards.

Although tempered glass in general is stronger than non-tempered glass, especially when it comes to direct impacts to the face of the glass, it can still break. By design, tempered glass completely shatters into thousands of small pieces when stressed beyond its capacity and serves as a safety feature which helps avoid more serious injuries from the larger, sharper shards often seen in non-tempered glass.