Natural light in a basement is a priceless commodity. Home builders of old recognized this and integrated hopper windows in basements. They were normally the size of four standard cement blocks (16" X 32"). Typically, these windows were steel framed and mortared in place. Unfortunately, they also can let in cold air and unwanted guests. Pre-made glass block windows can be installed to retain the valuable natural light and be a beautiful safe solution to the non efficient hoppers.
A good look at the existing window will tell you if you can use a standard 16" X 32"pre-made glass block unit. Measure the length and height of a cement block nearby your project window. The dimensions of a standard cement block have not changed for many years; they are commonly 7 3/4" high 15 3/4" long. The blocks were made this size to accommodate a ½" bed of mortar to make the total measurement 8" X 16". metal window screens Now determine how many blocks the window has displaced. If the opening is 2 blocks high by 2 blocks long or 16" X 32," you're in business.
A 16" X 32" pre-made glass block unit can be purchased at the home improvement center of your choice. Buying a pre-made unit not only saves time and the headache of building one from scratch but also are made square and flush at the factory. Other things to remember at the home improvement center are:
o Tape measure
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 gal. bucket
o Margin trowel
o Access to water
o 4" Glass block "C" channel (commonly found in the glass block aisle)
o 1 ½" screws
o Screw gun
o Safety glasses
o Step ladder
o Torpedo level
o Small piece of batt insulation
o Hand saw
o Plastic sheeting
This home improvement can be done by one person but an extra pair of hands will make this project much easier and is strongly suggested.
To prepare your work area, cut a piece of plastic to fit under the window opening to save vacuuming up a mess. Consider using more plastic to make a barrier to keep mortar chips and dust in a confined area in the basement. Remove the old hopper window sash from the inside. The flat metal arms that the sash hangs on should have an enlarged opening to push the post on the sash up and out. Do the same on the other side and remove the old window away from work area. Now determine the best space (inside, outside) to cold chisel the mortar away from the steel frame. This can be hard work and may require big swings with a hammer, along with a pair of safety glasses. Try chiseling at the bottom of the opening right in the middle. Start near the metal and work your way underneath. Your goal is to make an opening under the metal frame for your pry bar to lift up. Once you have the frame lifted up, use the reciprocating saw or hack saw to cut the frame, and then pry up and out. Now that you have the bottom pried up, the sides should follow, then the top. The opening will now need to be chiseled out to receive the 16" X 32" glass block unit. Measure carefully. If there is concern about a high spot that will give you trouble, now is the time to smooth it out.
You have the hard part out of the way, it's time to install. The board at the top of the opening is called a sill plate. This is where you will screw the "C" channel into. If the "C" channel needs to be cut down to size, it should be done now. The material is a PVC product that is readily cut to size using a hand saw. Care should be taken to position the channel correctly. It is best to position the "C" channel in the center of the opening and flush with the outside wall. It isn't always possible to install flush with the outside wall. That's OK, just try to get it as close as possible. Cut the batt insulation to fit in the "C" channel and to the width of the glass block, (aprox. 4" X 32") and set the shims in a handy place. Two people are needed to set the window up in the "C" channel, insuring that the insulation stays in between the "C" and the window. If the unit contains a window, make sure the window is right side out. The window screen and weeps should be outside and the locking hardware should be inside. Place the shims under the window, keeping the window snug in the channel. The torpedo level is now used to level and plumb the unit. Use the vacuum to remove dust and debris from the opening, and then fill the voids on the sides and bottom with expansion foam. Be careful not to over do it. A little goes a long way, and you do not want to completely fill the void with the foam. As the foam expands, it adds "R" value and helps hold the unit in place. Congratulations! You can now clean up and wait for the expansion foam to do its work overnight.
Upon returning the next morning, cut any excess expansion foam flush with the window. Mix the mortar with water in the 5 gallon bucket to a peanut butter consistency. Mortar is applied over the expansion foam and packed around the perimeter of the glass block with the margin trowel on both sides of the window. This is the strength that holds the unit in place. If the glass block is not flush with the existing wall, the sill must be angled to shed precipitation on both sides of the unit. It will take a little practice to get the mortar right. The less you play with it the more it will do what you want. If the mortar "sags", let it go and come back after its set up but still "green." Shave any excess off with the trowel and smooth the surface. Finally, seal around the "C" channel and the sill plate with silicone at both the interior and exterior for a watertight seal.