Types of Window Glass – What’s Installed in My Window?


When a window needs replacement, the first point of call is to figure out what type of glass was previously installed and what type of window glass the replacement should be. Knowing this will make it easier to make inquiries and get accurate quotes. In this article, I’m going to explain the difference between glass types, and how you can identify them from the different break patterns.

Types of Window Glass

When thinking about glass types, there are three different types that you need to consider.

1. Float Glass

Float glass, or annealed glass, as it’s otherwise called, is just your standard glass. This is the glass that’s installed in any of your aluminium sliding windows or timber double hung windows.

This glass is put onto the truck, and cut on site by the glazier; very easy to install, and very easy to identify. When this glass breaks, it breaks into standard shards that go everywhere. It breaks like regular glass.

2. Laminated Safety Glass

Laminated safety glass is the same as the safety glass that’s in the windscreen of your car. It’s simply two pieces of glass bonded onto a plastic interlayer.

The purpose of the interlayer is to hold the glass together when it breaks. It’s easy to identify this glass type, as it usually cracks off in big spider web pattern, but you won’t see any shards of glass and the glass won’t fall out.

3. Toughened Safety Glass

When toughened glass breaks, it explodes into a million tiny fragments, and it does this because the glass is held under immense tension.

It does this instead of cracking off into shards, so it doesn’t cut you when it breaks. It’s important to know that toughened safety glass is approximately seven times stronger than float glass of the same thickness. It’s great for thermal resistance and impact resistance.

You should note that once this glass is made, it can’t be changed or altered. It can’t be cut, or drilled, or processed. Once that panel is made, nothing else can happen to it. If that panel is wrong, we throw it in the skip and start again.

We’ve considered three glass types today; Float Glass, Laminated Safety Glass, and Toughened Safety Glass. Hopefully, the information here helps when you’re inquiring about a replacement window. You can quickly identify what glass has been installed, and make sure your inquiry process is smooth and simple.

To learn more, download our free guide, or feel free to get in touch.