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Types of Glass

Wednesday May 10, 2023

Choosing Glass

There are several options when choosing glass.

Different types of laminated glass are available where the interlayer changes for example but there is also several optional extras which customers can choose from. Naturally these have pros and cons which need to be considered.

Image used for header of CPD course description. Show a floor plan on a wooden table

Our technical team are available to provide advice on glass and balustrade designs


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Why toughened glass?

Toughened glass (fully tempered) is far stronger than annealed glass. It is heated up and cooled to harden it. It is not only stronger but when it breaks it goes into very small fragments. These are safer than larger shards of glass.

Toughened glass requires a handrail, this significantly reduces the risk of breakage. However, should a toughened glass panel break, it’s not unheard of for glass fragments to travel over 100m from its original position. Handrail will also reduce the risk of falls should the panel break, by acting as a second barrier.

It should be noted that although a handrail is a second barrier in this occurrence there will still be a big hole between the floor and handrail. This is a safety concern, especially for small children that may not see the handrail or the missing glass panel.

In both instances, should a breakage occur, the area needs to be immediately cordoned off whilst a replacement is sourced.

Heat strengthened glass

This glass goes through a similar process to toughened glass but using lower temperatures. This means the glass is stronger than annealed, however it will break into large chunks. Typically, suppliers will only want to work with toughened glass because of the increased safety.

What is heat soaking?

Glass can have an impurity in it called a nickel sulphide crystal. These cannot be seen by the naked eye. The build ups of nickel sulphide expand in heat at a quicker rate than the rest of the glass and this can lead to spontaneous breakage.

During heat soaking glass panels are placed into a bath and heated up. That means the impurity and breakage are found in the factory, rather than in situ. Reducing mess, and expense for the customer on site.

The disadvantage of heat soaking is that the toughened glass now breaks in larger chunks. This isn’t a problem with laminated glass but with standard toughened it is more dangerous overhead. We always advise laminated glass is used in overhead installations to avoid injuries.

Low Iron

When you look at glass panels side-on you will notice a strong green tinge, this is the iron element. This also affects the clarity of the glass panel, especially with the thicker glass types which are needed in balustrade.

You can request low iron glass, giving you a noticeably clearer glass. From side on this will now look more blue than green. As expected, there are additional costs for this. For increased clarity, you should use an extra strong interlayer.

Why laminate glass?

Building regulations dictate that for a frameless glass installation, toughened laminate glass must be used. This is because when one panel breaks it remains attached to the other. No exploding! The glass would shatter is a spider web fashion and will remain in place until removed.

Should a breakage occur, the area needs to be immediately cordoned off whilst a replacement is sourced.

Different Types of Laminates:

PVB (Poly Vinyl Butyral) 

PVB is the most popular choice for laminate glass in the UK. Made up from a flexible layer of plastic between two sheets of glass. Sandwiched together and placed into an autoclave to bond the glass panels together.

The interlayer is a highly flexible sheet. So, if both glass panels broke the glass would fold over onto the floor. Should one leaf of glass break, over time, the weight would possibly break the second panel.

This is the cheapest option for toughened laminated glass.

PVB is the worst performer for water resistance and can delaminate when water is sat on the interlayer for long periods of time. We advise you to put drainage holes in the base channel to clear standing water and prevent laminate breakdown over time.

ES PVB (Extra Strong/Stiff PVB. DG41 Brand).

These are designed to cross the bridge between PVB and SentryGlas. They are stronger, clearer and more water resistant than standard PVB.

Unfortunately, the cost of this is so close to SentryGlas. It’s often more beneficial for the customer to pay the higher price and gain the far superior performance of the SentryGlas.

EVA (Etyleen Vinyl Acetate) 

Several years ago, EVA was the most common form of laminated glass, and it’s now making a comeback. Like PVB and SG laminates, the interlayer is a flexible sheet. It creates a strong bond between the glass panels. This increases the water resistance on decreases chances of de-lamination. However, this glass is more costly than PVB. Another disadvantage for EVA is that it’s not as strong under force loading, the interlayer can also become discoloured when exposed to UV for long periods of time.

Ionoplast (Most common SentryGlas Brand)

The interlayer used in Ionoplast is a rigid sheet placed between the glass panels. It has a very high tear resistance, making this the strongest type of laminate glass. Even if both sheets of glass broke, they would remain standing and able to withstand force for some time.

SentryGlas has good protection against moisture absorption, delamination will only occur after many years in situ. It also has a strong resistance to UV damage and is not likely to discolour.

The major benefit to SentryGlas is its clarity: providing the clearest interlayer. Combined with a low-iron glass, it’s nearly invisible!

Glass Make-Up Achievable Load Advantages Disadvantages
12mm Tough 12mm 0.36kN. With no fall or used for domestic internal Slim, lightweight, clearer than laminate, cheap. Not as safe on breakage, Handrail required when protecting from fall
13.5mm Toughened PVB laminate

(12.76mm)

6mm/1.52mm/6mm (6mm/0.76mm/6mm) 0.36kN. With no fall or used for domestic internal Slim, safer than toughened, can be frameless (no handrail) Not as clear, the laminate can look thick on such a thin panel
15mm Tough 15mm 0.74kN. Domestic External, Office Internal Strong, Clear Expensive, Handrail Required, not as safe on breakage
17.5mm Toughened PVB laminate

(16.76mm)

8mm/1.52mm/8mm (8mm/0.76mm/8mm) Up to 0.74kN.  Domestic External*, Office Internal Safer than toughened, can be frameless (no handrail), *suits domestic balcony with less than 1500mm run up Expensive, would push to 21.5mm. Doesn’t pass impact loads
19mm Toughened 19mm Up to 1.5kN Very Strong, Clear Very Expensive, breakage not safe
21.5mm Toughened PVB laminate

(20.76mm)

10mm/1.52mm/10mm (10mm/0.76mm/10mm) 0.74kN Domestic External, Office Internal Safe, relatively cheap PVB is least water-resistant interlayer
21.5mm Toughened SentryGlas laminate (20.89mm) 10mm/1.52mm/10mm (10mm/0.89mm/10mm) 1.50kN Light Commercial Very waterproof, clearer than PVB, very strong Very expensive
25.5mm Toughened PVB

(24.76mm)

12mm/1.52mm/12mm (12mm/0.76mm/12mm) 1.50kN Light Commercial/Tall Domestic Cheaper than 21.5mm SG (above). Achieves 2m tall domestic loads Heavy! Some customers don’t like the thickness

Our technical team are available to provide advice on glass and balustrade designs


Contact us

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