Posted by: glassblockblogger | November 5, 2015

All You Need To Know About Installing Glass Block

We frequently get asked how we install our glass block products into both interior and exterior openings. The answer isn’t a “one size fits all” type of answer. There is more than one way to install glass blocks and each way is determined by the size and space of the opening, our designers/installers and of course the customer. Some installation methods might work best in one situation, like installing a basement window, while the same method might not work as well for lets say a glass block shower. This article will help you learn about our different installation methods and products we use to complete each installation we help the customer do or we do ourselves.


The most common way to install glass block is by using mortar. We use a specific mortar mix designed for glass block use that is similar to actual brick laying. There are two ways to install glass blocks using mortar: the mortar I system and the mortar II system.

Mortar I: The mortar I system utilizes Pittsburgh Corning perimeter channels on all four sides of the opening. This method is designed to be used with Pittsburgh Corning Series Glass Block, mainly for panels of 25 sq. ft. or less.

Mortar II: The mortar II system does not utilize Pittsburgh Corning perimeter channels, but instead utilizes expansion strips, panel reinforcing and panel anchors. This method is designed to be used with Pittsburgh Corning Premiere Series (4″ thick) and Thinline Series (3″ thick) glass block. This installation system are for interior and exterior panels that are bigger than 25 sq. ft. and may be framed on two to four sides.

Both methods require our universal mortar spacers and our premixed glass block mortar to make a clean, traditional grid-like pattern holding the project together. Our premixed mortar comes in 50lb bags that only require you to add water and mix together. There are detailed brochures available on our literature downloads page on our website that show step-by-step instructions for all of you DIY-ers out there who want to have a little fun with the project. For everyone else, we got you covered. Our installers have been doing installations daily for over 25 years!

Mortar installations are most commonly seen in exterior windows, basement windows, showers, partitions and glass block bars.

Glass Block Bar Glass Block Partition


Silicone installation methods are most commonly requested when the all glass look is preferred. Mortar installation obviously requires visible joints such as you would see in brick-laying whereas with the silicone there is nothing to see. A benefit of using our structural glazing sealant is that it is a lot easier to put your glass block project together because there are less steps in the process. However, as mentioned before, it is sometimes better to use mortar in some applications and silicone in others. The two main silicone systems are the ProVantage I system and the ProVantage II system.

ProVantage I: The ProVantage I installation system is best utilized when dealing with Pittsburgh Corning Premiere Series (4″ thick) glass blocks. In this system, that glass block panels are installed in perimeter channel. The use of vertical and horizontal spacers are also needed.

ProVantage II: The ProVantage II installation system is used when installing straight and 90 degree angled walls. This method utilizes panel anchors which are secure the glass block panel to the wall and expansion strips. There is also a great brochure explaining in detail the installation process and every other detail you would need if installing on your own.

Glass block basement window with silicone Glass block window with silicone

If you are asking yourself “Well which one is better?”, you’ll be struggling to come up with a simple answer. To help clear up that commonly asked question, here is this. For any glass block project that is being hit by water constantly, like a shower, mortar is recommended because water can creep in between silicone joints if improperly installed. For something like a Hurricane-Resistant glass block panel, then silicone is used. Why? Simple. Silicone would offer the panel a slight give when it comes to withstanding the high-force winds. Silicone allows the panel to “bend” with the winds instead of just staying upright absorbing it all as mortar does. Glass blocks done with either process can be pre-assembled or built on site and both processes can also be assembled with or without a frame.

Has this helped you decide which process is right for you? Let us know! We would be more than happy to help you with a project. If you would like to learn more about mortar and silicone installation, or any other glass block products, call us at 800-635-1226 or email us at We have over 26 years of experience in the industry and our knowledge will attest to that. We look forward to hearing from you!


  1. I am working with a pre-assembled silicone joint shower glass block window. I do not have a frame yet, but I am still researching the care and steps I need to take to prevent water damage and maintain the window based on how I decide to install it. At this time, I am considering using cement board beneath the perimeter channel or an asphalt flashing tape beneath the channel. I would then have bullnose tile kiss the glass blocks above the perimeter channel lip. I’m not sure if I will need to recaulk the silicone joints or how I could do that considering it is a wet application, but I would appreciate input on this. Please comment constructively to help me get my first glass block project right.

  2. I will be installing a glass block panel ( 32×14) to replace my rotting basement windows. Since the blocks come pre assembled, Can I simply bed the whole window in Type N mortar or do I have to use glass block S mortar ??

    • Really any mortar will work for installing a preassembled glass block panel into a masonry opening …. N yes S yes

      • Thank you sir…

  3. What is the way to install glass block without spacer ?

  4. Spacers for installing glass blocks stay between the glass blocks forever …. they are designed so that they are not seen ….. they are also “optional” …. you don’t have to use spacers at all unless you want to … please call 201-803-6440 to discuss further.

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