Glass Block Basement Windows: A Basic Installation Guide


Natural light is a priceless asset in a basement. Homebuilders in the past recognized this and included hopper windows in basements. They were typically four standard cement blocks in size. (16″ X 32″). These windows were typically steel-framed and mortared in place. Unfortunately, they can also let in cold air and undesirable visitors. Pre-made glass block windows can be fitted to retain precious natural light while also providing a stylish and safe alternative to inefficient hoppers. Check out the Best info about Vacuum glass feature.

Closely examining the existing window will reveal whether a conventional 16″ X 32″ pre-made glass block unit may be used. First, take the length and height of a cement block close to your project window. A regular cement block’s dimensions have not altered in many years; they are typically 7 3/4″ high and 15 3/4″ long. The blocks were made this size to accommodate a 12″ bed of mortar, making the overall dimensions 8″ X 16″. Determine how many blocks have been moved by the window. You’re in business if the opening is two blocks high by two blocks long or 16″ X 32.”

A 16″ X 32″ pre-made glass block unit can be obtained at your local home improvement store. Purchasing a pre-made unit saves time and the pain of creating one from scratch, but they are also manufactured square and flush. Other items to keep in mind when visiting a home improvement store are:

o Tape measure

o Hammer

o Cold chisel

o Pry bar

o Reciprocating saw with metal blade or hacksaw

o Shims (composite)

o Expansion foam

o 1 Bag of mortar

o 5 gals. bucket

o Margin trowel

o Access to water

o Silicone

o 4″ Glass block “C” channel (commonly found in the glass block aisle)

o 1 12″ screws

o Screw gun

o Safety glasses

One person can complete this home improvement, but having an extra set of hands makes the project much more accessible and is strongly recommended.

To save time vacuuming a mess, cut a piece of plastic to fit beneath the window opening. Consider using more plastic to create a barrier to keep mortar chips and dust in the basement. Inside, remove the original hopper window sash. The flat metal arms from which the belt hangs should have a giant hole to allow the sash’s post to be pushed up and out. Repeat on the other side, then remove the old window from the work area. Next, choose the finest location (inside or outdoors) to cold-chisel the masonry away from the steel frame.

This can be difficult labor and may necessitate large swings with a hammer and a set of safety glasses. Chisel near the bottom of the opening, right in the center. Begin near the metal and work your way beneath it. The idea is to create an aperture under the metal frame to lift your pry bar. After you’ve elevated the structure, cut it with a reciprocating saw or hacksaw before prying it up and out.

Now that the bottom has been pried up, the sides and top should follow. The opening must now be chiseled to accommodate the 16″ X 32″ glass block unit. Take your time when measuring. If there is a high place that you are concerned about, now is the time to smooth it off.

Now that you’ve completed the difficult portion, it’s time to begin installing. A sill plate is a board at the top of the opening. This is where the “C” channel will be screwed in. If the “C” channel has to be trimmed, it should be done now. The material is made of PVC and is easily cut to size with a handsaw. It is critical to position the channel correctly.

The “C” channel should be installed in the center of the opening, flush with the outside wall. Installing flush with the outer wall is not always possible. That’s fine; try to come as near as you can. Cut the batt insulation to fit in the “C” channel and the width of the glass block (about 4″ X 32″), and position the shims in a convenient location.

It takes two people to install the window in the “C” channel, ensuring the insulation remains between the “C” and the window. If the device has a window, check sure it is right side out. The window screen and weeps should be located outside, while the locking hardware should be inside. Place the shims beneath the window, keeping it snug in the channel.

To level and plumb the unit, a torpedo level is now used. Remove any dust and dirt from the entrance using a vacuum, and then fill the spaces on the sides and bottom with expansion foam. Take care not to overdo it. A little goes a long way; you don’t want the foam to fill the void. As the foam swells, it increases the “R” value and helps to keep the unit in place. Congratulations! You may now tidy up and let the expansion foam operate overnight.

When you return the following morning, trim any excess expansion foam flush with the glass. In a 5-gallon bucket, combine the mortar and water to make a peanut butter-like consistency. On both sides of the window, mortar is spread over the expansion foam and packed around the perimeter of the glass block with the margin trowel. This is the force that keeps the unit in place.

The sill must be inclined to shed precipitation on both sides of the team if the glass block is not flush with the existing wall. It will take some practice to get the mortar just perfect. The less you mess with it, the better it will behave. If the cannon “sags,” let it go and return after it has set but is still “green.” Smooth the surface after removing any excess with the trowel. Finally, use Silicone to seal around the “C” channel and sill plate inside and outside for a watertight seal.

In the next 24 hours, the mortar will build up and solidify. Any extra mortar mistakenly on the glass can be removed with a sponge or a damp rag. All that remains is for you to enjoy the security and beauty of your new glass block window.

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