Glass Block Sizes: 5 Expert Tips to Choosing Wisely

Choosing the right glass block sizes is essential for a glass block project to come together seamlessly. Whether you’re a contractor, homeowner, or designer, knowing how to select the appropriate glass block and the sizes requires careful planning and knowledge. In this article, our experts are shedding light on wisely choosing the right glass block size for your next project. 

Consider Project Outcome Objectives

Before selecting what size and amount of glass block are required for any project, first, know what the project’s outcome objectives are. This information will help narrow down which glass block products are appropriate for the project and, therefore, aid in selecting the correct glass block sizes.


For instance, let’s say a public school in Florida wants to increase daylighting levels in the gymnasium and has selected glass block for this aim because of its durability, low maintenance, and impact-resistant properties. They would have to select a glass block product that meets the following criteria:


  • Hurricane resistant
  • Intended for commercial use
  • Maximum light transmission


To meet this project’s objectives, glass block from the high-performance glass block line from Seves®. This information will eliminate several glass block products and streamline the size selection process. 

Select the Glass Block

Select a glass block collection before determining what block size you will need for your project. Use information gathered from the project’s objectives and then isolate which lines of glass block is appropriate.


When selecting a type of glass block to use, ask yourself the following questions:


  • Is the design for an interior or exterior installation?
  • Are color infused blocks essential to the project’s design?
  • Will the finished project need to be fire-resistant?
  • Is this for a commercial application or a residential project?
  • Will irregularly sized/shaped glass blocks be required?


Answering these questions will help determine the ideal product you should use and direct you to the right glass block size guide.

Know What Installation System Will Be Used

Once the glass block products to be used in a project are chosen, selecting an installation system is the next step in evaluating the glass block sizes. There are two types of glass block installation systems, and each affects a project’s glass block sizing needs differently.


Mortar, the traditional installation method for glass block, has been relied upon for decades by architects, homeowners, and contractors. This tried and true installation method is still very effective and will create gorgeous, low-maintenance results. 


When determining the size of blocks needed and the amount of glass block to purchase for a project, mortar applications will add approximately ¼” between each block. When using mortar as the primary installation method, be sure the right tools and materials are readily available.


Mortarless glass block installation systems use pre-fabricated panels and glass block silicone to bring a new window, shower, or other creation to life. This system allows glass blocks and bricks to sit closer together than if installed using mortar.


When using a mortarless installation system, use the actual size of the glass block for reference and not its reported nominal size.

Understand Nominal Sizing

Nominal sizing is used in the construction and manufacturing industries to convey standard sizing practices of commonly used materials. 


For example, in the lumber industry, a commonly known nominal size is two-by-four. The dimensions of a two-by-four are generally understood to be 2-inches by 4-inches; however, that is the nominal size for the product and not its accurate dimensions. The precise measurements of that piece of wood may range by half an inch in length and width.


This standardization of sizing also exists in the glass block industry. Nominal sizes of a glass block represent the size of space the block will likely consume after it is installed using mortar. Therefore, the exact measurements of glass block are actually smaller than their nominal size.


Know Project Dimensions to Determine Glass Block Sizes

Accurately measure the dimensions of the space where project construction will take place. Then, while taking your installation method into consideration, refer to the sizes of the product line. 


If a mortar installation system is being used, use the nominal size of the product line. When the mortarless method of glass block installation is preferred, use the exact size of the product when planning your project. To find our glass block products' nominal and actual dimensions, refer to the glass block sizing guide.

Consult with Glass Block Sizing Experts

If further assistance with glass block sizing is required, don’t hesitate to reach out to our glass block experts at Quality Glass Block & Window. We’re happy to discuss any design plans you may have and assist with sourcing the best product for your project.


Just give us a call at (815) 416-1007 or use our contact form, and we’ll get back to you as soon as possible.