How to Install Glass Block Windows in Basements

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Most homeowners are not aware of the amount of energy they are losing out of their windows. Up to 25 percent of a home's energy loss is contributed from windows and doors. Glass block windows offer a lot of advantages to homeowners. They allow light to filter in like a normal window but also provide privacy as they are not see through like a normal window.

Things You'll Need

• Scaffolding
• Utility knife
• Flat pry bar
• Hammer
• Level
• Key hole saw
• Speed square
• Cat's paw
• 2 x 4's
• 2 1/2-inch wood screws
• 1 x 6 pine
• 2 1/2-inch finish nails
• Glass blocks
• Framing for glass blocks
• Mortar for glass blocks
• Spacers
• White or clear silicone sealant
• Panel anchors
• Trowel
• Mortar pan
• Drill, driver and bits
• Tin snips
• Measuring tape
• 2 1/4-inch case molding
• Caulk and caulking gun
• Paint and brushes

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Instructions

Remove Existing Window

1. Pry the interior window trim off with a hammer and a pry bar.

2. Remove the exterior window trim that is over the siding in the same manner.

3. Remove the exterior siding, starting with the J-rail along the top of the wall.

4. Use a screw head bit and a drill to remove the screws in the window.

5. Pull the window out.

6. Scrape the old putty tape out and fill all holes with caulk.

Build New Frames & Set Glass Blocks

1. Measure window and remember that the block, mortar joints, expansion foam, and finish trim will also take up some of that space.

2. Frame the side openings of the window with 2 x 4’s and secure them with 2 ½-inch wood screws. Make sure all sides of windows are level before moving on.

3. Cut the interior finish trim out of 1 x 6-inch pine or other trim that matches existing windows after measuring.

4. Place trim flush to the outside wall and mail it in place with 2 1/2-inch finish nails.

5. Prime the bottom sill after all trim is complete.

6. Place a bed of glass block mortar on the window sill.

7. Insert spacers into the grout. Leave room around the edges of the window for expansion foam.

8. Test the blocks to make sure they are level. Take them back out.

9. Mud one side of the block with mortar and press the block into the mortar until it is resting on the spacers. Continue this bottom row.

10. Insert the expansion foam between the block and the trim on the first row.

11. Allow that to dry, then cut off the excess.

12. Spread mortar on top of the first row of blocks.

13. Bend a metal panel anchor at a 90-degree angle and press it into the mortar. Panel anchors will need to be placed ever three rows beginning with the first row.

14. Attach the first anchor to the side of the trim with 1-1/2 inch screws.

15. Insert your second row of blocks following the same procedure beginning at step nine.

16. Call someone over to help you insert the last row as the other person will need to stand outside.

17. Start on one end and switch to the other end, working your way towards the middle of the window. This is the only way to get the top row center block in properly.

18. Insert the expansion foam at the top block, break off the spacer tabs and smooth everything out.

19. Prime the edge of the exterior edge of the frame of the window before caulking the perimeter with glass block sealant. Caulk the interior with the same glass block sealant to allow the window to expand and contract as it will surely do.

Resources

• GrimmBldg.com