Glass Block Basement Windows: 7 Steps to Get It Right the First Time

Glass block basement windows seem simple enough to make: take a few blocks, mortar them together, remove a frame, and then fit them into the opening. However, like most skilled trades, it looks easy when done by a professional who is armed with the tools and tricks of the trade. The key to a successful basement window remodeling project is having a logical process for completing the job.

Learn 7 steps to get this job done right the first time.

Step 1) – Determine what the foundation is made of and take your measurements – Most foundations have masonry openings made of poured concrete or cinder block with occasional openings of wood framing (this is more common in basements where the level bottom is above the ground level of the surrounding terrain). For masonry openings, measure from the top of the sill to the bottom of the head. For a sash opening, measure the area that will exist after the window sash is removed.

Step 2 – Evaluate the need for blocking vents and a dryer vent. It is always best to maximize airflow and ventilation for a healthy, mold-free home. Vinyl framed energy efficient vents can be added to create an operable window within a secure glass block panel. Tumble dryer vents, exhaust fans and fully removable sash windows are also available.

Step 3) Consider Color Blocks and Engravings for Style – Your block window doesn’t have to look like everyone else’s – add style, design, colors and tinted blocks. A project in Alabama used a drop-down color block window instead of stained glass to increase security against high wind loads. Additionally, block faces can now be engraved with custom images or standard patterns to match your personal interests, hobbies, and tastes.

Step 4) Order Precast Glass Block Panel with Mortar or Silicone Grouts – Precast block window assemblies will save you time, money and improve the quality of your finish. The decision between silicone and mortar gaskets is based on personal taste and which processes end up with the window size that best suits your particular window openings. The main advantages of mortar joints are the ability to vary the size of the joint and the traditional look that blends well with brick veneer and block bases. The main advantages of silicone gaskets are that they can be placed in tighter openings and also in the glass aspect of the panel. If you are unsure which will be the best fit for your home or building, call a block window manufacturer with your opening sizes for recommendations on the best joining process.

Step 5) Remove the old window frame and/or sash. On masonry basement windows, remove the casing and window sash. This is best accomplished by first removing the blade and then collapsing, cutting, or grinding the old frame with a pry bar, saw, or grinder. For frame openings, in most cases, you will just remove the sash.

Step 6) Set the window level and plumb and shim it securely in the opening: Position the window in the opening and use a level to ensure proper location. Then use a wooden window wedge to hold the precast panel in place.

Step 7) Secure and seal the window in place: For masonry openings, add water to the pre-mixed block mortar mix (these are available in 50-pound bags), mix with a hoe or trowel and fill the sides, the top and sills (this can be done with a piping bag or a pointed tool). For sash openings, use spray foam insulation between batt panel and window sash, then install wood stops around panel as needed, then install aluminum or PVC-coated coils over wood sash abroad.

If you’re still unsure if you want to tackle installing a glass block basement window, call your specialty contractor for an estimate.