DIY Guide: How to Install a Glass Block Window

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Glass block windows have graced homes and commercial buildings since the early 1900s. Their unique combination of aesthetics, privacy, and durability makes them an ideal choice for bathrooms, basements, and other areas where discretion is crucial. 

Installing a glass block window can easily be done DIY. Start by selecting your glass blocks from the hardware store and purchasing mortar. Then remove the old window and window frame. Layer the glass blocks, placing mortar and spacers in between as you go. Let it dry and you’re done!

Let’s explore the history of glass block windows and go over measuring, selecting materials, and installing a glass block window.

How to Install a DIY Glass Block Window 

Distorted view of a town seen through glass blocks

Glass block windows, also known as glass bricks, were first used in the early 20th century for industrial and commercial buildings, providing an efficient way to transmit light while maintaining privacy and insulation. 

Over the years, glass block windows have evolved in design and function, making their way into residential homes as an attractive and practical choice for various rooms.

Before You Begin

First, measure the window opening. Then, use a tape measure for width, height, and depth. Double-check these measurements for accuracy. 

Next, visit a home improvement store or shop online to select the right size and style of glass blocks. 

Consider privacy, light transmission, and design to find the perfect blocks. Over the years, glass block designs have expanded. That includes various colors, textures, and patterns, offering a wealth of options for customization. 

Finally, don’t forget to purchase glass block mortar and spacers for a secure installation.

What You’ll Need

Glass Blocks

Glass blocks(on Amazon) are the primary building material for your glass block window project. They offer a unique combination of privacy, light transmission, and design, creating an attractive and functional window solution for any room in your home.

Glass Block Mortar

Glass block mortar(on Amazon) is specifically designed to bond and secure glass blocks. Its unique formulation provides excellent adhesion, resulting in a strong and stable installation that can withstand the test of time.


Spacers are crucial for maintaining consistent gaps between glass blocks during installation. In addition, they ensure proper mortar application and alignment, contributing to the finished window’s overall stability and professional appearance.

Tape Measure

A tape measure(on Amazon) is essential for accurately measuring the window opening. Precise measurements ensure you select the correct size and quantity of glass blocks, avoiding costly mistakes and unnecessary adjustments during installation.


A level is crucial for maintaining even and straight rows of glass blocks. Proper leveling ensures a professional-looking installation and prevents window stability and appearance issues.


A hammer is required to remove fasteners, such as nails, from the old window frame. This tool helps carefully dismantle the existing window to create a clean, debris-free opening for the new glass block window.


A screwdriver is necessary to loosen screws and other hardware from the old window frame. It is vital to safely and efficiently remove the existing window, ensuring minimal damage to surrounding materials.

Caulking Gun

A caulking gun(on Amazon) is required for silicone caulk’s smooth and controlled application. This tool ensures a clean, even bead of caulk around the window perimeter, providing a waterproof seal. 

Silicone Caulk

Silicone caulk is essential for sealing gaps between the glass blocks and the surrounding wall. In addition, it creates a waterproof barrier, preventing moisture infiltration and protecting the integrity of the window installation.


A trowel is necessary for the even application of glass block mortar. This tool ensures a uniform layer of mortar on the support board and between the glass blocks, providing a strong and stable installation.


A bucket is required for mixing the glass block mortar. Mixing the mortar in a clean, dedicated container ensures the proper consistency and helps avoid contamination, resulting in a stronger bond between the blocks.

Safety Goggles

Safety goggles provide vital eye protection during the installation process. In addition, they help prevent injury from debris, dust, and other particles, ensuring a safe and comfortable working environment.


Gloves protect your hands during installation, especially when handling mortar, caulk, and tools. They prevent skin irritation and provide a better grip on materials and tools, ensuring a safe and efficient installation.

Utility Knife

A utility knife is indispensable for cutting through old caulk or adhesive when removing the existing window. This sharp and versatile tool ensures a clean and precise removal, helping to create a debris-free opening for the new glass block window.


Close up four glass blocks

Step 1: Remove the Old Window and Frame

Carefully remove the old window. Loosen screws with a screwdriver, and pry off nails or other fasteners with a hammer. If needed, cut through caulk or adhesive with a utility knife. 

Next, remove the window sash and frame, ensuring a clean, debris-free opening. While removing the old window, be mindful of any surrounding materials, such as tiles or drywall, to avoid unnecessary damage.

Step 2: Attach Temporary Blocks

A temporary support system Place a level, sturdy board across the bottom of the window opening. Secure it using temporary blocks, ensuring the board remains level. 

That provides a stable base for glass block installation. The temporary support system ensures that the glass blocks remain secure during installation.

Step 3: Install the New Glass

Mix glass block mortar per manufacturer’s instructions. Apply a mortar layer on the temporary support board with a trowel. 

Start at one corner and place the first glass block on the mortar. Next, apply mortar to one side of the next block, then press it against the first block. Continue this process, using spacers to ensure even gaps between blocks. 

Proper spacing allows for adequate mortar application and ensures a stable, secure installation.

Complete the first row, apply a mortar layer on top, and create grooves in the mortar with a trowel. That helps the mortar bond to the glass blocks. 

Keep installing rows of blocks, using spacers for consistent spacing. Frequently check the level for proper alignment. If any adjustments are needed, make them before the mortar sets to avoid complications later.

Step 4: Finishing Touches

Allow the mortar to cure for at least 24 hours. This time frame is crucial for the mortar to achieve proper strength and stability. Next, carefully remove excess mortar and spacers to avoid disturbing the newly installed glass blocks. 

Then, apply a silicone caulk bead around the window perimeter, filling gaps between the blocks and the surrounding wall. This step helps create a waterproof seal and prevents moisture infiltration.

Smooth the caulk with a wet finger or caulk-smoothing tool for a clean, professional finish. Then, let the caulk dry according to the manufacturer’s instructions, typically for at least 24 hours. During this time, avoid exposing the caulk to water or moisture to ensure proper curing. Finally, your new glass block window is complete with the caulk dry. 

Glass block windows add aesthetic appeal and improve your home’s energy efficiency thanks to their insulating properties.

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