If you’re confused about the best method of fabricating a glass block window or wall you’re not alone. In this article you’ll learn about the 3 most popular ways to assemble glass blocks (mortar, silicone and vinyl stack), where to use each method and their advantages and disadvantages.
The mortar system uses either gray or white mortar which is mixed with water and placed between the block joints both vertically and horizontally.
Where to use blocks assembled with mortar – the best place to use the mortar prefabrication method is for frameless windows for basements, bathrooms or garages or for straight glass block walls.
Advantages of Mortar
- Can create different joint sizes on either vertical or horizontal joints (varying from 3/16” to ½”). This can be helpful in custom fitting a window to a masonry opening.
- Very secure – mortared windows are difficult for an intruder to break through.
- Matches well with poured or concrete block foundations.
Disadvantages of Mortar
- Mortar mixtures can vary from batch to batch – causing the joints to potentially vary in color and strength if the person mixing is not careful.
- Window & wall cannot be shipped via common carriers due to the potential of breakage in transit.
The silicone system uses a specialized glass block clear silicone to join the horizontal and vertical joints.
Where to use blocks assembled with silicone – this system is best used in frameless basement, bathroom and garage windows.
Advantages of Silicone
- Creates a clean “all glass” look.
- Can be very time effective to assemble a window.
- Easy to clean.
- Windows can be made smaller sizes (since the blocks are butted together).
Disadvantages of Silicone
- Is the least secure fabrication method (could be easier to break in through if the window is being used for security).
- Should not be used for walls or larger sections.
- The silicone is only placed on the front and back surfaces (it does not go through to the inner cavities of the block).
The vinyl stack system uses preformed vinyl pieces that are siliconed to the inside of the blocks both vertically and horizontally. This system is completed by adding either grout (which should be used for wall projects) or silicone (mostly used in window projects) to the inside and outside surfaces. This final step creates a consistent 1/8” joint between the blocks.
Where to blocks assembled with vinyl stack – this system is the most versatile of the 3 systems. It can be used for framed or unframed glass block basement, bathroom or garage windows and can also be used for straight, angled or curved glass block walls.
Advantages of Vinyl Stack
- Most energy efficient of the 3 systems.
- Provides better strength – this system has been rated to have greater than 400 lb of impact resistance when used in conjunction with a vinyl framed window system.
- Versatile in where it can be used – vinyl stack can be used for framed & unframed windows and even to assemble very large and intricate glass block partition or shower walls.
- Improve water resistance – the vinyl stack and silicone combination provide excellent protection for water infiltration.
- Increased wind load resistance.
Disadvantages of Vinyl Stack
- It’s a more expensive fabrication system than mortar or silicone.
- Uses specialized vinyl connection pieces that are not as readily available as mortar or silicone.
What experience do you have with these 3 systems? Please comment below.
To learn more about glass block fabrication methods or get a free estimate on a glass block window or wall visit or call Innovate Building Solutions on a nationwide basis (877-668-5888) or for a local project their divisions including Columbus Glass Block (614-252-5888), Cleveland Glass Block (216-531-6363) or Mid America Glass Block (513-742-5900) of Cincinnati or Dayton.
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