Glass Block Sealants

What are Sealants?
A sealant is a material that is used to fill any joint, crack, or opening in a structure. Sealants are critical for the overall life of any structure or building, as they prevent the entry of fluid and other substances. An effective sealant not only protects the structure from water and moisture, it also protects it from noise, dust, and other unwanted matter. Sealants have three basic functions: fill a gap between two or more surfaces, form a barrier through which substances cannot pass, and maintain sealing properties for the expected lifetime.

A building undergoes many changes over time as it is exposed to a variety of elements and conditions. Joint sealants provide anywhere from 25-50% movement to allow for the natural expansion and contraction of building materials.

Selecting a Sealant
From acrylic resins and expanding foam to polyurethane and silicone, there is a seemingly never-ending selection of sealants to choose from. Depending on its chemical composition, a sealant can have a number of different properties.

The chemical makeup of a sealant is also a good predictor of its overall lifetime and performance. A sealant’s material will ultimately determine how it will react under a variety of conditions, for example, exposure to sunlight or moisture.

When creating a glass block or other type of construction project, it is crucial that the installer carefully choses the correct sealant for the job. Several properties are important considerations for selecting a sealant. These include:

  • Movement tolerance
  • Compatibility with the substrate
  • Paintability or stainability
  • Relative cost
  • Hazardous content

Sealant Maintenance
Determining the life expectancy of a given sealant is not as simple as it may seem, however, periodic maintenance is required to ensure a long and successful lifetime. Without maintenance, cracks in a seal can cause penetration of unwanted moisture and lead to mold. A lack of maintenance can also cause a reduction in the energy efficiency of a structure. A reduction in the sealant’s performance can eventually lead to deterioration of the substrate.

Common Glass Block Joint Sealants
Glass block are commonly assembled using two different sealants: mortar and silicone. Installers rely on these two sealants when building their glass block projects for their sturdiness, durability, and long lifespan. The choice to install with mortar or silicone varies from project to project, but both are suitable for use when installing everything from building facades to partition walls.

Silicone joints tend to have a lifespan of about 15-20 years. Silicone can create smaller, slimmer joints that allow more light through glass block. Silicone is much lighter than traditional mortar, making the shipping of glass block panels and windows easier and more cost effective. For building owners looking to increase the energy efficiency of their house, silicone is a great solution because it provides good insulation.

Mortar is one of the oldest building materials with use dating back as far as 10,000 years. Mortar is the traditional installation method for glass block that typically requires a bit of skill to apply, but provides the opportunity to use various sizes of joint between glass block because it can be applied in a variety of thicknesses. Mortar is also extremely tough and durable, giving it the ability to withstand all types of weather conditions.

Joint Sealant Repair & Maintenance
For designers and builders seeking glass block expertise, GBA Architectural Products + Services offers more than 30 years of industry knowledge and skill. If you are looking for a building material that will last, provide plenty of light, lower energy bills, impart beautiful, ever-changing light effects, and provide superior fire resistance, architectural glass block is the perfect option. The experts at GBA will carefully select the right joint sealant for the job.

For more information about the full range of glass architectural products, visit the GBA website at If you have questions regarding the full range of applications of glass block products, contact the experts at GBA Architectural Products + Services at one of their three regional numbers.

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