Guide to Designing Glass Floors

Designing a Safe Glass Floor

A glass floor is a glass surface that people will walk on: even the slightest oversight in design can have serious consequences.

This guide is intended as a summary of the key points to consider when designing glass floors.

Topics covered: number of glass layers, choice of heat treatment based on the interlayer, risk of breakage due to impacts from hard objects (hard body impact), risk of falls due to slipperiness, spacer between glass and structure (flexible strip on the perimeter), impact of notches in the glazing, and rigidity of the supporting structure.

STRUCTURAL SAFETY

Redundancy... how to ensure safety in the event of breakage?

Glass is a fragile material with variable mechanical properties. It can therefore break without warning. Unlike a self-supporting glass railing, a glass floor cannot be made of laminated glass consisting of only two layers.

To comply with standards—unless specific testing is conducted—the glass floor must be laminated with at least three layers of glass. If one of the layers breaks, the other two take over the load and prevent a fall or collapse; this is known as redundancy. 

The three layers are generally of equal thickness, since it is difficult to predict which layer might break. The top layer is more susceptible to scratches and impacts, but the bottom layer is subjected to greater bending stress.

MATERIALS & ASSEMBLY

Laminating: Choosing the Right Interlayer

Laminated glass consists of multiple sheets of glass separated by an interlayer that keeps them bonded together even after breakage. However, the choice of interlayer makes all the difference.

Standard PVB (polyvinyl butyral, a viscoelastic polymer) is the most common interlayer, but it is too flexible to use with three layers of fully tempered glass stacked on top of each other: in the event of simultaneous breakage, the glazing could detach and fall... a catastrophic risk for users. In fact, this composition is no longer permitted for guardrails (ref.: CSA A500). It would therefore make no sense to use it horizontally for a glass floor. 

Two potential solutions: 

1. SentryGlas® (an ionoplast interlayer, about a hundred times stiffer than standard PVB) allows three layers of tempered glass to be laminated and used safely in a floor application. 

2. High-strength PVB is also an option, but with one major caveat: its stiffness drops rapidly once temperatures exceed 20 degrees Celsius. It should therefore be avoided in locations where the glazing will be exposed to temperature increases—such as outdoors or near large sun-facing windows.

Note that the interlayer will generally be 1.5 mm (0.060'') thick when combined with heat-treated glass to compensate for “roller waves”—small ripples created on the surface of heat-treated glass during the tempering process.

During the design phase, attention must be paid to the effects of temperature, particularly when glazing is exposed to sunlight or a heat source (such as lighting or other sources). Higher temperatures could affect the thickness of the glass layers. Although SentryGlas® is less sensitive to temperature changes, it is still affected by them.

↑ This type of laminated glass breakage is possible with tempered glass and standard PVB

IMPACT RESISTANCE

The thickness and heat treatment of the top layer vs hard body impact

As mentioned above, the top layer of glass is the one that absorbs impacts: a heel, a stone under a shoe, a falling metal object, etc. 

Although it is not prohibited to use heat-strengthened glass—and although it offers better resistance in the event of breakage—we do not recommend using heat-strengthened glass for the top layer, as it is much less resistant to impacts from hard objects. Fully tempered glass withstands this type of impact much better. 

It should be noted that thickness also plays a role in impact resistance. 

Consequently, even though 6-mm-thick layers of fully tempered glass might be sufficient in some cases for small openings, using this thickness might not provide adequate impact resistance.

USER COMFORT

A non-slip surface

Walking on glass is also a matter of adherence. A ceramic frit pattern (enamel fired directly onto the top surface of the glass) is recommended to create a non-slip texture, especially when exposed to moisture. This has to be decided early on, as it affects both the aesthetics and safety of the floor.

SUPPORT & BRACING

Support Spacers: An Essential Element

The glazing never rests directly on the structure: a perimeter support spacer (continuous strip, with a hardness of 30–45 Shore A) distributes the load and compensates for slight imperfections in the structure. Its width must be calculated based on the loads applicable to the project. Note that for outdoor exposure, neoprene should be avoided. In this case, a continuous silicone support strip is preferable. Certain types of EPDM are also weather-resistant.

1: Perimeter support strip

MANUFACTURING

Effect of notches in the glass

A notch (a localized cut in the contour of a glass panel) made to accommodate a post or fastener creates a stress concentration. These should be avoided as much as possible, as they generally require thicker glass and a generous radius at the internal corners of the notch. This also applies to drill holes.

SUPPORT STRUCTURE

Stricter Tolerances

A glass floor is more sensitive to structural deflection. Given the high rigidity of the glass used in floor glazing designs, excessive structural deflection could cause the glazing to rest on point supports rather than being continuously supported along the perimeter.

For a glass floor, the deflection of the supporting structure must be limited to more restrictive values (generally L/500) than those allowed for a structure supporting elements other than glass (generally L/360).

Stricter tolerances must also be applied regarding the flatness and alignment of the various components. Please contact us for more details.

2: Deflection: L/500 and strict alignment tolerances

IN SUMMARY

🔑 Seven points to consider before designing a glass floor

Safety

At least three layers 

Materials

SentryGlas rather than standard PVB for three layers of fully tempered glass; high-strength PVB is still an option if not exposed to high temperatures.

Impacts

Check the thickness of the top layer of glass 6 mm fully tempered glass may be insufficient, even for a small glazing area.

Comfort

Non-slip sintered ceramic a ceramic frit pattern on the top surface for better traction.

Perimeter Supports

Flexible strip on the perimeter dimensionned for the project... width calculated based on project loads

Manufacturing

No notches if possible otherwise: thicker glass and a generous radius at the internal corners of the notch... to be confirmed by FEA (finite element analysis)

Structure

More restrictive deformation tolerances the support structure must be stiffer and more precise than a standard structure to prevent the transmission of unexpected forces to the glazing.

Every glass floor is a custom project!

The principles above are provided for informational purposes only. Each project must be analyzed by an engineer specializing in structural glass calculations.

Contact us when designing your next glass floor!

© Glaspex Inc., 2026. All rights reserved. Unauthorized reproduction of this article or its contents is prohibited. This article is based on our interpretation of codes and standards. This article and its contents do not constitute professional advice and are provided for informational purposes only. This is an overview that does not necessarily cover all technical aspects and/or special cases. Glaspex, LSVM, or the author of this article will not be held liable for any decisions made in connection with this article. Reuse of this article or its contents for professional purposes, including engineering purposes, is prohibited. Note that each project has specific requirements and must be approved by an engineer. Also note that this applies to all articles published previously and subsequently.