Glass handrails are very common in residential and commercial structures. Typical construction methods include a glass pane that rests in a “glass shoe” (typically made from steel or aluminum) that is secured to the structural base material. Generally, the metal shoe is wider than the glass pane allowing for installation flexibility. After the glass is inserted into the shoe, a solid filler is used to embed the glass pane in the shoe. See Figure 1 below, item 3), for typical filler location. Traditionally, poured-in grouts have been used as the solid filler; however, they are typically difficult to install. More and more, glass installers are turning to Hilti’s HIT-Glass Method which uses HIT-HY 270 mortar as the preferred filler solution for embedding the glass panes in the metal shoe. 


Figure 1: Typical cross section of glass handrail with HIT-HY 270 filler material.

Traditional installation of HIT-HY 270 for glass handrails according to the Line Method was a continuous bead of mortar at the top and bottom of the metal shoe on each side of the glass. Hilti has recently performed testing with a method to apply a smaller section of mortar in the form of U- or V-shaped “pucks” spaced a maximum of 18” (457 mm) apart, called the HIT-Glass Method. See Figure 2 below.



Figure 2: Side view of glass pane, shoe, and Hilti HIT-Glass Method with HIT-HY 270.

By injecting and curing HIT-HY 270 mortar between the glass pane and the interior of the metal shoe, the cured “pucks” create a hardened material that acts as a compression block for loads acting perpendicular to the glass pane assembly. HIT-HY 270 does not bond with the metal shoe or glass, and thus does not provide resistance against in-plane motion (e.g. vertical or parallel directions). A top rail or top cap is generally used in conjunction with a structural sealant to resist vertical uplift. However, a top rail or top cap is not required provided that the installer takes additional measures to ensure that uplift of the glass panes will not occur in all installation types (curved, inclined, and/or level), and that sliding of the glass panes will not occur in vertically inclined installations.

Why should I consider using the HIT-Glass Method for glass handrail applications in place of alternative installation methods?

The HIT-Glass Method offers a variety of advantages for the design, installation, and maintenance of glass handrails. 

1. In design, HIT-HY 270 is durable and has been tested to industry standards, including ASTM E935-13, ASTM E2353-16, and DIN 18008-4 Appendix A. 
2. For installers, injection of the mortar is made simpler and cleaner with the dispensing Nozzle HIT-RE 60-Glass mixer attachment for precision placement and a mortar viscosity resistant to dripping, even in applications with inclines up to 30 degrees.
3. Our Insert HIT-Glass EP 9.5 foam and Insert HIT-Glass EP 13 foam rolls provide a continuous profile of material with an adhesive strip on one side that is cut to length by the installer according to the geometry of the installation. These positioning aids are placed on the bottom of each glass pane in a U-shape on either side of each HIT-HY 270 injection location.
4. The positioning aids allow for injection to take place from the protected side of the handrail, providing a faster, safer, and simpler installation. This is possible because the gap created by the aids lets the mortar pass beneath the glass pane and up the other side of the shoe. In addition, the aids offer easier glass adjustability over mechanical wedge systems in curved glass applications.
5. For the long-term maintenance of the handrail assembly, individual glass panes can be removed and replaced with ease because HIT-HY 270 does not bond to the glass or the metal shoe. The installer can easily replace both the damaged glass pane and the required mortar pucks during repair operations.

To learn more about the HIT-Glass Method, check out the HIT-Glass Brochure for reference. You can also watch the HIT-Glass installation how-to video (English and French) by using the QR code below. The HIT-Glass Instructions for Use (IFU) is also linked below.



Calculation Methodology for Minimum Required Pucks to Meet Load Demand

As noted in the Hilti HIT-Glass Brochure, you must install pucks to a certain size and a minimum number of pucks per glass pane with a maximum spacing. The following calculation can be used to determine the number of pucks for a specific glass pane and applied load. Typical handrail design live loads are given in the 2021 IBC, Section 1607.9. The project Engineer of Record (EOR) will need to verify the HIT-HY 270 solution, calculation, and placement is applicable for the project specifications and design codes. The calculation method below is only evaluating the loads on the HIT HY 270 mortar and the EOR is responsible for the design of the handrail, supporting structure, and glass panes. 
For straight and level glass balustrade designs installed according to the HIT-Glass Method in rectangular U-profile shoes (assumption 1 stated below), Hilti has launched a new module in PROFIS Engineering called “Glass Balustrade” to give more peace of mind that glass balustrade specifications will be installed correctly. The module allows the user to enter the balustrade geometries and a service wind load, if required, for the design. The module calculation automatically considers the above referenced live loads from the 2021 IBC. The HIT-Glass Design Report generated by the module provides the project inputs, design calculations, output results, options for Bill of Materials, and HIT-Glass Instructions for Use (IFU). Visit profisengineering.hilti.com for more information. 

Assumptions:


Calculation will require the following variables for your project:




Given parameters:


See the HIT-Glass Brochure for more information.







Calculation Methodology for Volume of Mortar Required

Need additional support?

Please feel free to contact our Engineering Technical Services department for more information or any questions.

Hilti Engineering Technical Services – United States
(877) 749-6337 toll free
hnatechnicalservices@hilti.com

Hilti Engineering Technical Services – Canada
(800) 363-4458 toll free
CATechnicalServices@hilti.com