How to install glass block windows

This article is about how to install glass block windows. In this step by step project, we show you how to install a window made of glass blocks, as to allow the light to come in, while keeping the intrusive eyes out. In addition, it is a well-known fact that the glass blocks are very good insulators, so if you install them properly you won’t face any issues during winter time. Due to their uniques properties, you can install glass block windows in the basement, bathroom or in stair hallway walls.

Glass blocks come in a large variety of colors and patterns, as you can find easily the ones to fit your tastes and privacy needs. All you have to do is to decide which color match with your house and which pattern will allow the optimum amount of light to get in, as to satisfy your needs.

Installing glass blocks is not difficult nor time-consuming, so it is a good idea to try to do the job by yourself. A contractor has experience and a lot of expertise in the field, so it would do a perfect job, but even a beginner diy-er could pull it through if he uses the right tools and materials. You have to remember that you can save a significant amount of money for a relatively simple job, but you have to assume certain risks.


Made from this plan



In order to install glass block windows, you need the following:


  • Mortar for glass blocks
  • Glass blocks
  • Spacers, sealer, grout



  • Safety gloves, glasses
  • Measuring tape, carpentry pencil, l-square, spirit level
  • Chisel
  • Drill machinery with mixing pad
  • Margin trowel



  • Make sure you prepare the mortar properly



  • A few hours, one person



How to install glass block windows

Window opening

Window opening


First of all you have to measure the window opening, as to calculate the necessary amount of glass blocks. Consequently, use a tape measurement and find out the dimensions of the window opening (both in width and height). This step is essential for the success of your project, so pay attention to this step as to take accurate measurements.

In our case, we had to install only one row of glass blocks, but it is possible to install as many rows as necessary. We also recommend you to check the alignment window opening by using a spirit level, as to check if the sides are plumb and level. If the walls are heavily distorted, then you have to straighten them prior to the installation of the glass blocks.

If you want to replace an old window, you have to remove it by using a carpentry hammer. If the old window cannot be removed from position, you might want to use a crowbar. Nevertheless, make sure you remove the whole window from the opening, as otherwise you won’t be able install the glass blocks.


Preparing mortar for glass blocks

Preparing mortar for glass blocks


Next, you have to prepare the mortar for the glass blocks. This mortar is created for this task, so make sure you buy one designed for this use. Nevertheless, on the market there are mortars which come as powder and pre-mixed mortars. Irrespective of your choice, they will both get the job done, with more or less effort.

If you have bought a powder mortar, you have to mix it by using a drill machinery and a mixing palette. Make sure the mortar has the right consistency; you shouldn’t add too much water, as it should have the consistency of butter.


How to install glass block windows

How to install glass block windows


Before installing the glass block into position, you have to make sure the base surface is perfectly level. Consequently remove all the irregularities and bumps, or add a thin layer of mortar, as to make it level.

Before installing the blocks into the window opening, you have to make a test as to see if there are issues. Consequently, place a piece of cardboard under the first row of glass blocks and install the blocks using the spacers. In this way, you will check there remain large gaps between the glass blocks and the walls. If the gaps are larger than 1/2”, then you have to fill them with plaster mortar, before installing the blocks into position.

Next, you have to apply a thin bed of mortar on the window sill and make it even, by using a margin trowel. Then, you have to apply mortar on the wall of the opening, where you will install the first glass block. In addition, when adding another glass block, make sure you apply mortar on one vertical edge, before laying it down.


Making sure the glass blocks are plumb

Making sure the glass blocks are plumb


After you have installed the first row of glass blocks, you have to use a spirit level to make sure it is level and plumb. This aspect is essential, as after a couple of minutes you won’t be able to align them any more.

Make sure you install spacers between the glass blocks properly, as to make sure the joints will be even. Put another bed of mortar on top of the glass blocks, making sure you fill all the gaps between the glass blocks. Use a wet towel to wipe off the glass blocks, as later will be more difficult to clean them.


Installing glass block windows

Installing glass block windows


Repeat the process until you have laid the last row of glass blocks. Work with patience as to make sure you do a proper job. If the glass blocks move from their position, it means that the consistency of the mortar is wrong. Consequently, add a little more mortar powder and mix it thoroughly.

Clean the excess material by using a wet towel, making sure you don’t move the glass bricks from position.  If you don’t like the color of the mortar, you could apply a colored grout between the glass blocks. In this case, you have to make sure the mortar doesn’t fill totally the visible gaps between the glass blocks.


Glass block window

Glass block window


Last but not least, you have to apply sealant around the glass block window, as to make sure the air won’t get in or out of the room. Consequently, apply a good caulk  sealer around the glass block window, making sure you don’t use too much. After you have applied the sealer along the perimeter of the glass block window, you have to remove the excess by using a putty knife.

Then, you have to clean the glass block window by using a wet towel. Make sure you wipe off all impurities otherwise later you will find it more difficult. Do not try to clean the mortar with an abrasive material, as you risk scratching the glass. As you can see, installing a glass block window is not a difficult job, if you use the right tools and materials.


Glass block window, how to install glass block window

Glass block window


As you can see in this image, you can build a larger window using glass blocks and the same techniques described above. Such window will provide a decent amount of light to a hallway, a bathroom, a stair house or any other room in which you want privacy.

In addition, you can also install a granite window sill, as to add functionality to your glass block window. Caulk the edges of your glass block window, as to make sure you don’t let the outside air to get in.



How to install glass block windows in wood frame opening

Installing glass blocks in a wood frame opening is not more difficult, but there are a few aspects that you have to take into account. Consequently, all the previous steps are available except the following: under any circumstances you shouldn’t put mortar on the wood frame, under the first row of glass blocks. Therefore, you should use a special track in which to lay the glass blocks. Last but not least, seal the gap between the wood frame and the metal track.



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