How to Install Glass Block Windows Like a Pro

If you’re at all handy around the house, you’ve probably done a few home improvement projects over the years. We’re happy to hear that glass block windows are part of your next project. We’re biased of course, but we think they add beauty and privacy to any home. Today, we’re going to look at how to install glass block windows like a pro. And if you have any questions that we don’t address here, please reach out to us, and we’ll be happy to help.

Important Tips for DIY Glass Block Window Installation

Installing glass block windows in your basement or bathroom isn’t as hard as it sounds. As long as you follow some basic steps, your DIY glass block window installation should go off without a hitch. The following are the basic steps in the process.

Measure your space.

As with any home improvement project, you need to select the right product. In order to do that, you need to first measure your space. Before you can install glass block windows, you have to remove the current window frame, so make sure that you measure down to the masonry or wood and not just the current window frame.


If you are in doubt concerning where the masonry is in relation to the current frame, take several pictures of the window and send them to us, and we can give you a good estimate. And always measure twice. Getting the right dimensions is crucial.

Select the right glass block windows

Check out the types and sizes of glass block windows to determine what pattern and size you want and need. The most economical and easy to install glass block windows are our custom made glass block windows. If yours is a custom opening, be aware that vinyl wrapped quick mount windows will cost more and are only applicable for new build construction projects. The vinyl wrapped quick mount windows come pre-fabricated with a nailing fin. 

If you don’t see windows that match your measurements, please contact us so that we can help you select the right glass block windows for your project. 

Gather the tools and supplies you will need.

You will need:


  • Work Gloves
  • Measuring Tape
  • Carpenter Bar or Pry Bar
  • Glass Block Silicone
  • Shims
  • Level
  • Glass Block Window
  • Utility Knife
  • Bucket
  • Mortar
  • Trowel
  • Damp Sponge

Remove the old window and sash.

Be careful to wear gloves, and if the glass breaks, clean it up. You can use a shop vac to make sure you get all of the shards. In most cases the existing frame can stay. Simply remove the sash and remove any hardware that will get in the way of the new glass block window. 


You may need to use a chisel in some places to tear away some of the frame if it keeps the new glass block window from fitting in properly. (If it is a vinyl framed window, remove the entire frame). Be sure to remove any leftover caulk. You want the opening to be as clear and even as possible before installing the glass block window. 

Install the glass block window.

  1. First, set the shims. Set as many shims as needed on the left and right sides on the bottom of the opening. These will help hold the glass block window in place. Try to estimate the placement of the shims so that when you place the new window, the glass block joints are not directly on top of the shims. This will help avoid unnecessary stress on the joints of the glass block window.
  2. If you are placing the glass block window in masonry, you will use mortar to set the window in place. Apply a thin layer of mortar between the shims to help form a base. Have an assistant help you lift the glass block window and tilt or slide it into place. 
  3. Reset any shims that moved when you placed the window panel. Then, slide additional shims into the top of the window frame until the window is snug. Make sure the window is level and centered before continuing.
  4. Mix mortar to about the consistency of bread dough (follow the directions). Pack the gaps around the shims at the bottom of the window with mortar. Let it set until hard to the touch. From the inside, scrape away any excess mortar with your trowel.
  5. Next, mortar the sides of the window panel. Make sure that the mortar is firmly set before you apply any pressure to the window. Slide all of the shims out once the mortar is set, and finish mortaring the gaps. Let the mortar set for two hours and then smooth it out with a striking tool. 
  6. Finally, fill the top of the glass block window as you did the bottom and sides.  After 24 hours, apply a glass block silicone caulk to seal the top of the block window.  After the first 24 hours, the downward pressure on the glass block could cause a crack at the top of the window that will need to be sealed. Remove any drips of caluk from the glass block window immediately with soapy water. 


For a wood frame opening, check out our blog on how to install a glass block window into a wood frame

Choose From Our Selection of Glass Block Windows

Quality Glass Block and Window offers a wide selection of pre-assembled glass block windows for you to choose from. They are also easy to install and maintain. We only sell Seves glass products to ensure you get the highest quality.  If you need help figuring out how to choose the right glass block windows for your project, we would be happy to help. Just give us a call at (815) 416-1007 with any questions you may have. We are available to help you throughout your project. 


Please keep in mind that for all of our preassembled glass block windows, there will be a certain amount of production time, depending on the product you order. If you don’t see information on the expected production time, please contact us to clarify before placing an order. We want to ensure you know when you will be getting your glass block windows.