How To Install Glass Block With Silicone

Jessica Stone
by Jessica Stone

Architecturally, glass blocks are very similar to conventional brick materials. Both bricks and glass blocks are used in the same way although, glass blocks can be used in some situations where bricks cannot.

Comparably, both materials are often secured using the same product; mortar. However, to achieve a cleaner look for much less effort, glass block application can be done using silicone. This method is most often used when an all-glass appearance is preferred over visible mortar joints.

Additionally, when installing a glass block window into a wood frame, mortar does not adhere properly. The wood can suck the moisture from the mortar and cause it to flake off or even shrink, resulting in a leaky window. The following is a very simple process for ditching the mortar and installing glass block with silicone.

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Mortar Vs. Silicone

When constructing anything using glass blocks, mortar is often the go-to option. It not only look traditional but also creates the best protective barrier in areas that will come into contact with water, such as a shower. With silicone, if it’s improperly installed, it’s very possible for water to seep in through the joints and loosen the bond.

However, a sleeker look can be achieved by using silicone in the installation of glass blocks. The joints are visibly much smaller, less visible, and allow for more light to pass through when compared to mortar. Silicon is often the preferred choice, and works great in smaller situations such as a bathroom window. Additionally, the application is much easier, as it can be simply applied using a caulking gun.

How to Install Glass Block with Silicone

Now, more than ever, homeowners and contractors are installing glass block windows to provide privacy, security, and energy efficiency in the home. They can also offer a very unique look when installed using silicone. For the purposes outlined below, we will be installing a glass block window into a bathroom wall.

Step 1: Build The Wooden Frame

The first step in installing a glass block using silicone is to build a wooden frame that the silicone can properly adhere to. If the area that you are fitting glass block already has a wooden frame, you can skip building a wooden frame entirely.

Measure the wall hole opening where the glass blocks will be going. To create the insert, you’ll need to build a wooden frame that will fit within this space and around the glass blocks. Cut the lumber to the measured opening and continue to build the frame accordingly.

Step 2: Attach the Glass Block Channels

This next step requires that you purchase glass block installation channels to easily install the glass blocks within the wooden frame. Using a miter-saw, cut the installation channels so that they will fit all the way around the frame.

Once you’ve completed your cuts, you will end up with four pieces of glass block channel. To mount the channels to the frame, screw them in using short screws on each individual side of the wooden frame. In order to blend the screws into the channel, press a bit of paint onto the screws using your fingertip.

Step 3: Assemble the Frame

With the channels installed, you can begin assembling the actual frame to be placed into the wall opening. Take one of the vertical sides and attach it to the bottom frame piecing using wood screws. Drive the screws into the corners to secure.

Step 4: Install the Glass Blocks

Now that part of the frame is attached, you should be able to easily slide the glass blocks into place. Lay the frame out flat and position the first glass block into the bottom channel. Make sure that the block is flush up against the side frame piece.

Install the next glass block, inserting a spacer, or shim, in between the two blocks. The shim will ultimately be filled up with silicone, closing the gap and creating a water-tight barrier. Repeat this step, including the spacer, for however many glass blocks you are installing into the frame.

Step 5: Attach Additional Vertical Frame Piece

With the glass blocks now in place, and the spacers carefully situated between them, your next step is to attach the other vertical side piece onto the rest of the frame. Position the side piece tightly up against the blocks and drive wood screws into the corner to secure.

Step 6: Install the Top of the Wood Frame

Finish off the frame by attaching the top piece to the rest of the frame. Use wooden screws at the corners to effectively fasten in place.

Step 7: Position the Wall Insert

Now that your glass blocks are successfully framed and ready to be placed into the wall opening, you first want to properly position it. Place the entire framed glass block insert into the wall, adjusting it so that it is flush. As needed, use shims along the top and bottom of the frame.

Before proceeding, ensure that the insert is both plumb and level inside the wall opening. Then, secure the insert in the wall by using nails or screws. Drive the nails or screws directly into the shims along the top and bottom of the insert.

Step 8: Attach the Trim or Molding

Depending on your preference, close up the gaps in the wall by attaching a wood trim or molding. Molding can be found in various shapes, sizes, and designs to match your desired look. Measure and cut the trim accordingly to surround the wall insert.

Before attaching to the wall, apply constructive adhesive to the underside of each trim board. Position the trim on the wall, along the insert and attach it with screws or nails.

Step 9: Fill the Gaps with Caulk

The final step, before any of the finishing touches, is to fill up all the gaps. To fill the space between the wood trim and wood frame, use either a latex or paintable acrylic caulk. Either option will suffice. Apply the caulk to all of the gaps, filling up any holes that exist between the frame and the trim.

To seal the holes between the glass blocks and create a sleek, attractive, water-tight barrier, use silicone caulk. Using a caulking gun, run the clear silicone caulk along the blocks, filling any space between them.

Keep in mind that silicone caulk needs to be maintained and removed and reapplied every couple of years. If you are in need of caulk replacement, read more on How To Remove Silicone Caulk From Fiberglass Shower Stall and What Can Be Used To Dissolve Silicone Caulking?

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Related Questions

What type of mortar is used for glass blocks?

If you decide to go the mortar route for your glass block installation, there are types specially designed for this purpose. For example, QUIKRETE Glass Block Mortar can be used to lay glass blocks on both interior and exterior walls. However, glass block manufacturers recommend to use either white Portland cement or white quartzite. Both are free of iron and sand, offering a whiter, more attractive joint fill.

How much does it cost to install glass block in basement windows?

If you’re looking to install glass block windows, you can expect to spend between $400 and $1,100 per window. However, this includes the cost of installation by a professional. If you’d rather purchase pre-built glass block windows and install them yourself, the cost is generally $18 per square glass black or $25 for frosted, privacy squares.

Are glass blocks outdated?

Glass block has been used in homes for decades as a way to open up a space, bring in natural light, and still not compromise privacy. The demand and desire for this material ebbs and flows over the years. Its ability to look “dated” often depends on the year your home was built and the overall architectural design.

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Jessica Stone
Jessica Stone

Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.

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