Laminated Glass Thickness Chart: 13.52, 17.52 and 21.52 mm Explained

Odd-looking figures such as 13.52 mm and 17.52 mm are not machining tolerances. They are simple sums. A laminated panel is named by adding the thickness of each glass ply to the thickness of the plastic interlayer that bonds them.

How laminated thickness is named

The formula is ply + interlayer + ply:

• 6 + 1.52 + 6 = 13.52 mm
• 8 + 1.52 + 8 = 17.52 mm
• 10 + 1.52 + 10 = 21.52 mm

The common PVB interlayer is made in sheets of 0.38 mm, and laminators stack them. Two sheets give 0.76 mm and four give 1.52 mm, which is why those two numbers keep appearing. Toughened plies are normally laminated with the thicker 1.52 mm interlayer, because toughened glass is never perfectly flat and the extra plastic takes up the waviness between the two panes.

In quotations the decimals are often rounded. "17.5 mm toughened laminated glass" and "17.52 mm" are the same 8 + 1.52 + 8 panel. "Toughened laminated" means each ply was toughened first and the two were then bonded; the difference between the two processes is explained in toughened vs laminated glass.

Toughened laminated glass thickness chart

The glass plies do nearly all the weighing. The interlayer is less than half as dense as glass, so it adds thickness faster than it adds weight. For single-pane figures and the formula behind these numbers, see the toughened glass weight chart.

A quick comparison shows why the number matters on site: a 17.52 mm panel is nearly 40 % heavier than a 12 mm toughened panel of the same size.

PVB vs SGP interlayers

Two interlayer families cover most balustrade glass.

• PVB (polyvinyl butyral) is the standard interlayer. It is soft and flexible, bonds well, holds fragments after a breakage and is the more economical of the two. Because it is soft, a panel with both plies broken tends to sag like a wet blanket unless something holds its top edge.
• Ionoplast, usually sold as SGP, is a much stiffer and tougher interlayer. It makes the two plies act more nearly as one thick pane, and a broken panel is far more likely to stay upright. It also stands up better to moisture at an exposed edge. It costs more and is commonly supplied in 0.89 mm and 1.52 mm thicknesses.

In general terms, PVB is the usual choice where the glass is held in a frame or capped by a handrail that ties the panels together, and SGP is the usual choice where the glass stands free with an exposed top edge. Which one your project needs is an engineering decision for the site, not something a chart can settle. Note that an SGP build-up with a 0.89 mm interlayer gives a different total, for example 8 + 0.89 + 8 = 16.89 mm.

Why laminated glass is used at elevated edges

A single toughened pane breaks into small granules and falls out of its fixing, leaving the edge unguarded. A laminated panel breaks and stays where it is, because the interlayer holds the pieces together. On a balcony, terrace or stair several floors up, that difference is the whole reason for paying more. The wider safety checklist is in is glass railing safe?

Laminated glass has one extra maintenance point: the interlayer is visible at the edge, and long contact with standing water can cloud it over time. Polished edges, drained channels and a cap or handrail over the top edge all help.

Laminated glass thickness for balcony railing

Our glass railing thickness guide sets out which thickness goes with which supported height across the Prince Railing range. In summary:

• 12 mm toughened: supported height up to about 3–3.5 ft. This is the standard for most residential systems.
• 13.52–17.5 mm laminated: up to about 4 ft, for taller balconies, commercial edges and exposed locations, in the heavier profiles.
• Up to 25 mm laminated: the tallest runs, in the heavy-duty continuous profiles.

The same guide recommends laminated-toughened glass for elevated balustrades at any thickness. Treat these as the starting point and confirm the specification for your building against local requirements.

Match the hardware slot to the total thickness

This is the mistake that costs the most. A channel, bracket or spigot is machined for a stated glass thickness, and its gaskets are sized to suit. A 13.52 mm panel does not go into hardware made for 12 mm glass, and a 12 mm panel will sit loose in a slot made for 17.5 mm.

• Most of our continuous profiles and all of our clamp brackets are listed for 12 mm glass.
• The 125 X 70 Mm continuous profile is listed for 17.5 mm glass.
• The 100 X 120 Mm continuous profile is listed for 12 mm to 25 mm glass.

When you order, give the glass processor and the hardware supplier the same full build-up, written out as 8 + 1.52 + 8 and not just "17.5 mm", and name the interlayer. Overseas buyers will find the inch equivalents and the North American names for each part in our glass deck railing hardware guide.

Laminated panels are cut, drilled and toughened before they are bonded, so nothing can be trimmed on site. Fix the hardware choice first, then order the glass to suit. Send us the finished height and location and we will suggest the profile and the glass build-up to match.